Frost Thermostat Causing Heating To Run All Night

Throughout the last couple of winters I've had numerous customers complaining that their central heating has bee running excessively throughout the night even though the central heating is turned off. The usual cause of this  is their boiler being in the garage is protected by a frost thermostat. Frost thermostats are installed to protect vulnerable parts of the heating system from freezing and can be set to come on usually between 3 and 20 degrees. It is likely that if the temperature drops below freezing outside and the garage also drops to this temperature that the frost thermostat will run until the location has warmed up.

The frost thermostat should be wired to override all time and temperature controls. In the case of a three-port motorised valve system the boiler will then supply heat to the valves last position. So if the central heating has been on until late in the evening but goes of at bedtime, and then the temperature outside drops overnight, the central heating will come on.

One solution to this problem is to fit a pipe thermostat such as the Honeywell L641B. This can be wired in conjunction with the frost thermostat. If the temperature in the garage drops below the set temperature of the frost thermostat the boiler will come on until the temperature on the pipe thermostat is satisfied. Therefore, the pipes will be protected but the boiler should not run excessively throughout the night on particularly cold nights as we have been having the last few winters.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Ideal Classic FF No Heating Or Hot Water

Was asked to look at an Ideal Classic which was not working for either heating or hot water. Looking at the boiler I could see an orange glow coming from inside the control box and so I knew it was receiving demand. Feeling the case I could feel some warmth even thought the boiler had not been working. I removed the case and could smell that the fan was overheating from trying to turn.

I replaced the fan with the correct version and the boiler was working fine again.

There are two different fans for different versions of the boiler which look similar. The obvious difference between the fans being the terminal positions. On one version the terminals are both on the left hand side of the fan motor and the wiring loom is shorter for these terminals. On the other version, the terminals are on opposing sides of the fan motor as you look at the fan motor from the front and the grey wires are longer in this case. There are other fans for other versions of the Ideal Classic as well such as the NF30-80.

It is also important to remember to slide the flue back together correctly. If the inner flue is not connected back up the boiler will baffle out when it lights and the boiler will cycle on and off.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Glowworm Energysaver 2 Combi 100 Faulty Hot Water

Another engineer asked me to look at a Glowworm Energysaver 2 Combi 100, the boiler was fairly old, but had only been installed three years ago. Asking if I'd seen one before, I told him that I'd replaced one once, and fortunately I had kept the instruction book in my van.

The customer had been using the boiler with the front case removed as this seemed to help the boiler to work. When the boiler was in operation there was quite a strong smell of fumes, and it felt as if there was heat coming back out of the fan inlet. After the boiler had run for a couple of minutes and started to ramp down there was a loud vibrating noise that continued until the flame went out. There were no error codes displayed on the boiler.

I suggested that the noise and smell were due to poor combustion, and that the engineer should get hold of the necessary seals before carrying out a full strip down service. It may be that the combustion just needs adjusting, but due to lack of servicing it could be that the heat exchanger is partially blocked. This would explain why the boiler worked better with the casing off. In the interests of safety the boiler was disconnected from the gas supply so it could not be used before a service was carried out.

We asked in Parts Center about a some seals for the heat exchanger that may need to be replaced on the boiler during servicing and we were told that the lower seal was still available, but the upper seal only comes with the heat exchanger that cost over £500+VAT. As we were not 100% confident at being able to fix the boiler without replacing the heat exchanger and there were other parts also required to fix the boiler, the customer decide to have a replacement boiler fitted.

Protherm 40-50 Ci Overheating

I had to look at a Protherm 40-50 Ci boiler which was regularly overheating. The button on the overheat thermostat had clicked out a few times over the last few days.

This can be quite common on this boiler especially if the boiler thermostat is in it's maximum position as I expect the temperature difference between the overheat thermostat and boiler thermostat maximum is not that great. Reducing the burner pressure from it's maximum can help to reduce the overheating as can turning down the thermostat from it's maximum. Sometimes it can be caused by interruptions to the power supply whilst the boiler is running,

In the case of this system the fault was due to the hot water zone valve. The microswitch had failed and was permanently demanding heat from the boiler even when the controls were turned off. Because of this the boiler was coming on and there was nowhere for the heat to go as a bypass was not installed. The zone valve opens when power is supplied to to brown wire of the valve. There is power permanently applied to the grey wire which is connected to the microswitch and when the valve opens the microswitch 'makes' and power comes out through the orange wire to power the boiler.

I diagnosed which of the zone valves was causing the issue by removing both of the orange wires with the power off and testing for continuity between the 'grey' terminal and each of the orange wires. The hot water zone valve had continuity across the grey and orange and deemed the faulty valve. Replacing the hot water zone valve solved the issue.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Cold Radiators Downstairs

I looked at a system today and the complaint was that not all the radiators downstairs were not heating. One of the smaller radiators was heating but the bigger double radiators were only hot at the pipes to the radiator but the radiator was not actually getting hot. All of the upstairs radiators were heating correctly.

I checked that the upstairs radiators were balanced down as they should be. I also looked at the pump which was set to it's fastest setting. I replaced the pump and all the radiators were working well.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Gledhill Boilermate 2 Buzzing Loudly

Had to look at another common issue today with a Gledhill Boilermate 2. The customer was complaining of a loud buzzing noise coming from the airing cupboard which had woken her up and she was unable to stop.

I removed the front panel on the cylinder which houses the thermostat, electrics and PCBs. I could hear the buzzing was coming from the pump delay timer PCB. I turned off the power and replaced this little circuit board. However, when I turned the power back on the pump drive PCB began to buzz intermittently. It was not as loud as the original buzzing but annoying nonetheless. I replaced the pump drive PCB also and all is working well.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Ravenheat CSi Primary Boiler Cycling Fan

I had a look at a Ravenheat CSI Primary boiler today which was not working properly. When the boiler was coming on for the heating and hot water sometimes it would work fine other times it would come on and off frequently. The fan would start up and burner light, running at full power for 30 seconds or so before the fan and burner would cut out. Then the process would start over again, occasionally going to low flame after the initial high flame. Sometimes the fan would only run for a few seconds before cutting out.

This is quite a common issue on these boilers and not the first time the fan control PCB has been replaced. I replaced the fan control PCB which has solved the problem.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Glow-worm Ultimate not lighting

Glow-worm Ultimate not lighting every attempt. Sometimes it lights straight away, other times it sparks for a long time before lighting. A common problem on these models, the pilot jets get blocked quite easily reducing the size of the pilot flame. This can prevent enough gas getting through for it to light the pilot flame, or the flame is too small and the boiler fails to rectify the flame.

To rectify this, the pilot injector is removed from the pilot assembly. This injector is unusual in  that there are two holes in the injector for gas to pass through. Both these holes need to be clean and unobstructed. A simple way to clean the through is to put some water into the injector and force it through. Once the holes are clear of any obstructions the boiler can be re-assembled and relit. This time the pilot lights first attempt with a good flame, and crosslights the burner.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Worcester Bosch 24CDi not working

Worcester Bosch 24CDi combination boiler not working for heating or hot water. Boiler starts to run on demand, pump and fan starts. Ignition spark can be heard but not lighting at the burner.

I remove the combustion casing so I can see the ignition electrodes, and demand heating from the boiler. Again it runs, and tries to light. There is a good spark at the electrodes, but still not lighting the burner. I replace the cover and undo the gas inlet test nipple to ensure there is gas supply to the boiler. There is a smell of gas and my manometer is registering approximately 20 mbar pressure. Firing the boiler has no effect on the gas supply pressure, so it is looking like the gas valve is not opening. The boiler manual tells me to check the resistance on the two purple and two brown wires to the gas valve, it should be less than 100 ohms. one of the wires is showing 24 kohms. I check the cable for continuity, which is fine on all four wires. The manual suggests the problem definitely is the gas valve.

After replacing the gas valve, I create hot water demand, setting the burner pressure to maximum on the rear of the PCB housing. Using a 2mm allen key I adjust the burner pressure to 13.2 mbar. I check the minimum burner pressure setting, again by adjusting the setting on the rear of the PCB housing. The burner pressure is 1.8 mbar and does not require adjusting using a 3mm allen key. I reset the burner pressure to normal on the rear of the PCB housing and put all the casing back on the boiler.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Potterton Promax System HE Plus E133 Error

Went to loot at a Potterton Promax System boiler which had gone to lockout and was displaying the error code E133. "Interruption of gas supply or flame failure."

Assumeing the gas supply had not been interrupted, I removed the ignition electrodes to find that the two probes were almost touching each other, and there was a bit of carbon bridging the gap. They had obviously bent together with their prolonged exposure to high temperatures. Bending them back to their correct gap would have been a wast of time, as they would soon bend in the heat again. Replacing the electrodes was the only long-term solution to the problem.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Broken Towel Rail Brackets

I got asked to look at a chrome towel radiator which was in danger of falling off the wall today. The brackets were unusual in that they clamped round the rails rather than between the rails. As can be seen from the picture below the nearest bracket is intact, but the claw of the furthest bracket has broken.

I have tried to find a supplier of these brackets, and not knowing who manufactured the towel rail or where it came from has made it impossible. I have found one solution though, you can buy the alternative style radiator bracket from B&Q. They sell brackets for both straight, curved and Kudox towel rails both in chrome and white.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Ideal Classic Sealed System Not Working

I got called to look at an Ideal Classic Sealed System boiler which was not working for the central heating. The hot water was heated by an immersion element only, and the boiler is only used for the central heating.

I ensured the programer was on and the room thermostat turned up to call for heat. I also ensured the boiler was switched on. I could hear that the pump was running but there was no noise from the boiler. I removed the case and could smell that the fan had been overheating. I checked to make sure there was 240 volts at the fan which there was.

I replaced the fan and the boiler was working fine again.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Myson Apollo 30Si Not Lighting

Had to look at a Myson Apollo 30Si that was not always lighting. Another engineer had looked at the boiler and replaced the PCB and sleeving to the spark electrode lead but this had not solved the problem.

The boiler was lighting intermittently. Sometimes it was lighting within a few sparks other times it would spark for ages before lighting if it lit at all. When the pilot flame lit it looked adequate but maybe a little on the small side. I stripped the pilot assembly down and cleaned the pilot injector out as thoroughly as possible as I could not remove the injector from the pilot assembly.

I re-assembled the boiler and the pilot flame was larger and lighting quicker which looks like it solved the problem.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Baxi Solo HE Leaking

I had to look at a Baxi Solo HE which was leaking. I had been to look at this boiler for leaks in the past so was quite concerned  to be looking at it again. Before we looked after it there was signs that it had been leaking from the flowswitch. The rubber seal on the heat exchanger manifold also failed. Replacing the seal was not successful due to corrosion on the main heat exchanger which also had to be replaced as a consequence. There had also been a leak from the connection to the condensate trap where the overflow pipe connects. To solve this the nut was undone and slid back, as was the shaped rubber seal. Wrapping PTFE tape around this shaped rubber seal helps to seal this leak.

On this visit the leak was also coming from the area of the condense trap. Opening the case there was some water sitting in the bottom of the case. To reveal where the leak was coming from I poured water in through the flue outlet to simulate condensate production. The leak was coming from the condense trap, but could not be seen. I could not feel any dampness around the connection onto the bottom of the heat exchanger. I removed the trap and there was a tiny split in the condense trap on the rear corner.

I fitted a new condensate trap which stopped the leak.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Glowworm Flexicom 15HX F1 Fault Lighting With A Bang

I was called to look at a Glowworm Flexicom 15HX which a customer was concerned about. The boiler was just over two years old and had been serviced six months ago. The boiler had occasionally been lighting with a bang for some time but not every time it lights. This was occuring prior to the service but the engineer was unable to establish a cause.

I checked the gas inlet pressure, and the combustion performance which were both perfect. I removed the electrode and there was slight distortion to the probes and some darkness to the tips. I replaced the electrodes and the boiler is lighting a lot better and the problem should hopefully be solved.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Ideal W2000 No Central Heating

I went to have a look at a system where the central heating was not working.

The system was a three-port motorised valve set-up, so I checked the wiring in the junction box . There was power on the white wire and the grey wire but the motorised valve was not opening.

I drained the heating system and replaced the valve, and heat tested the central heating.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Potterton Netaheat No Hot Water

I went to have a look at a customer's system who wasn't getting any hot water. The customer said that the water was not working at all, and had been working irregularly fora week. Sometimes, he would have plenty of hot water, other times none, and sometimes only lukewarm.

I switched the hot water on at the programmer, and ensured the hot water thermostat was turned up fully as the immersion heater had been on earlier. The system was had two zone valves and I checked the voltages at the junction box. There was power at the grey wire and the brown wire, but no power on the orange wire. The Honeywell V4043H zone valve was partially open looking at the manual lever but not fully. I removed the head from the body and felt the spindle. The spindle was not moveable by hand, and the cause of the problem.

Fortunately I could isolate the zone valve by switching off the pump valve, bypass valve and gate valve on the hot water return. Due to the location of the zone valve it would have been awkward to replace the whole valve, and so I removed the 'paddle' plate by undoing the four bolts. I replaced the o-ring and 'paddle' plate before opening all the valves isolating the zone valve. I wired in a new valve head before fitting it to the 'new' body. I tested the hot water system and it was all working well.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Protherm 40-50 CI Heat Exchanger

A friend of a friend has a Protherm 40-50 CI boiler which has started dripping from the heat exchanger. I was unsure whether the heat exchangers would still be available for these boilers although they are essentially a rebadged Glowworm Ultimate.

A quick Google and I find them available from Total Boiler Spares for £235.70+VAT although it says they are out of stock, it does deliver a lot of parts direct from the manufacturer. The website also gives me the part number S801382, although searching under this part number also leads to a Saunier Duval part. I telephoned Total Boiler Spares and they said the part was available in 4-6 working days direct from the manufacturer.

I also asked at my local Parts Center and was given a retail price of £550+VAT, although as an account holder I would pay a lot less than this but they did not have one in stock or available from their main warehouse.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Another Glowworm Ultimate With No Hot Water

Went to have a look at another Glowworm Ultimate as the customer was complaining that there was no hot water. The overheat thermostat had not operated on the control panel, and there was no orange glow from any LEDs on the PCB.

I looked at the programmer, heating and hot water were both set to be on, and the red lights illuminated for both. I went to the airing cupboard and the system was a two-port set up. Removing the cover to the electrics in the airing cupboard I checked out the voltages at various terminals. There was no power at the orange, but there was power on the grey wires. There was power on the supply to the cylinder thermostat and brown wire to the hot water two-port, but the valve was not opening. I also checked that there was no power across the neutral and the earth.

Manually opening the valve caused the pump to start running so I knew that the microswitch was ok, but the motor in the valve was not operating. I drained the system and replaced the two-port zone valve on the hot water side. Testing the valve after it's replacement and the hot water was heating successfully.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Glowworm Ultimate No Hot Water

Went to have a look at a Glowworm Ultimate as the customer was complaining that the pilot light had gone out, and there was no hot water. The boiler was a fan-flued model and so did not have a permanent pilot. The overheat thermostat had not operated on the control panel either, and there was no orange glow from any LEDs on the PCB.

I looked at the programmer, heating and hot water were both set to be on, and the red lights illuminated for both. I went to the airing cupboard and the system was a three-port set up. Removing the cover to the electrics in the airing cupboard I checked out the voltages at various terminals. There was no power at the orange or the hot water connection from the programmer, but there was power on the grey wire. Disconnecting the wires that were connected into the same terminal as the grey, the power was coming from the hot water off of the programmer even though the hot water was set to be on at the programmer.

The existing Danfoss FP975 programmer was on a standard backplate, so replacing this with a Drayton LP241 was straightforward. I would have preferred to fit another Danfoss programmer, but only had the Drayton in my van stock which is a perfectly good programmer. Replacing the programmer solved the problem and the hot water and heating are both working correctly again.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Thermostatic Radiator Valve (TRV) Buying Guide

It is commonly said that you get what you pay for and in the case of thermostatic radiator valves (TRVs). I have found that the cheapest radiator valves often need replacement first and should be avoided in most cases. Another sign of a TRV that is not going to cause too much trouble is the size of the pin. The valves with the smallest pin often get stuck and need replacing or un-sticking. Although the Myson TRV 2-Way have a reasonable size pin and constantly get stuck.

There are many different TRVs on sale from B&Q, Wickes, etc., but they tend to be of the cheap variety to avoid or overpriced in comparison to the online retailers.

Danfoss RAS-C2	I don't mind these TRVs
Danfoss RAS-D2	A more expensive version of the above
Drayton RT212	Can be quite difficult to turn, and not that reliable
Drayton RT414	Hopefully an improvement on the RT212
Drayton TRV4	One of the original TRVs which look good, but better valves can be had for less
Honeywell VT117E	One of my preferred valves
Honeywell VT15EG	Slight improvements on the above but could be styled better
Myson TRV 2-Way	Troublesome valves which often leak from the pin casing them to seize or a mess
Pegler Terrier II	A reliable, low-cost valve
Siemens MTN51GB	Nice looking valve, would be happy to fit these

I do not know every TRV and if you would like to fill in the gaps I would be more than grateful.

One thing I have found with the Honeywell TRV's lateley is that you are given some strange shaped brass olives to use with the valves and the are difficult to tighten correctly on the tails. I had fitted a pair of straight Honeywell vlaves to a towel rail I fitted and it was leaking on the copper pipe as it entered the valve and so had to tighten the nut further after installation. Then two days later the nut is leaking where it connects to the radiator tail so I tighten this up, which loosened the tail itself. I had to take the towel rail off and replace the olives on the tails with copper ones and re-taped the tails whilst I was at it. In the future I shall be replacing these brass olives with some softer copper ones.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Heating Working Upstairs But Not Downstairs

A nice simple job for a change, the customer was complaining that the hot water was working fine and the central heating upstairs, but none of the radiators downstairs. The boiler, Potterton Netaheat, was running fine and not making any unusual noises.

Looking in the airing cupboard at the pump, it was very hot and didn't sound as if it was running very quickly. I replaced the pump, and the radiators downstairs were soon working again.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Central Heating Not Working Properly

I had to look at room thermostat that had been replaced by another engineer recently. The customer was complaining that the heating would come on, get up to temperature, but not come back on in the same time period when the room cooled back down.

The engineer had installed a Honeywell T6360B room thermostat which is a basic and simple-to-use room thermostat and in my opinion a good room thermostat. According to the installation instructions you should always connect a neutral wire to the room thermostat on systems less than 6 amps, which is not always done. Many installations have a cable to terminals 1 (supply) and 3 (load) and no neutral connected to terminal 2. In this scenario the wires work as a switch either way around. With the neutral wire connected to terminal 2 it works as an anticipator.

The wires in this case were the wrong way around, so the supply was in 3, the load in 1, and neutral in 2. Had the neutral not been connected the thermostat would have worked correctly (although installed incorrectly). Switching the wires around in the thermostat so that they were in the correct terminals solved this problem.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Glowworm Ultimate Failing To Light

I was called to look at a Glowworm Ultimate which was failing to light today. Upon arrival it was still attempting to light as I could hear it sparking. Sometimes the ignition lead wears through at the point where it passes through the casing, but insulating this with electrical tape usually solves this problem as was already the case with this boiler.

After removing the case the spark could be seen at the ignition electrode and there was a tiny flame but not big enough for rectification to occur. I turned the boiler off and stripped out the pilot injector. Holding it up to the light there should be two holes clearly visible. In this case there was only one hole partially visible. I ran it under the tap and blew through the injector forcing the water through until both holes were clear.

After replacing the injector and case, I lit the boiler which ignited first time, solving the issue.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Broag Remeha Avanta Plus 39C Combi E4 Error

Was called by a customer today to look at a Broag Remeha Avanta Plus 39C combination boiler which was not working and displaying the code E4. The error code E4 is when there are more than 5 start attempts without any flame formation.

Earlier in the week the customer was able to reset the boiler and it would work fine again for a while. I checked the electrode initially which I had replaced on a previous visit with the updated electrode. The gap was fine and there wasn't a lot of accumulation on the tip. I reset the boiler and plugged my laptop in which has there software enabling me to communicate with the boiler. From this I can see the previous lockouts, their codes and the boiler's status when the occurred. I can also see live readouts of the boilers statistics such as flow and return temperatures, ionisation and whether the gas valve and other mechanical parts are open or closed.

The boiler fired up to pre-heat some hot water and it took three ignition attempts to light. I set the boiler to it's high rate and checked the ionisation at the electrode which was close to 9, and on it's low rate around 6 which is more or less the correct reading.

Using my flue gas analyser (fga) I checked the combustion readings at both the high and low rate. At both rates the CO2 reading was at 9.3% which is above what it should be set to. I adjusted the gas valve to the correct readings. Following this adjustment the boiler was igniting on the first attempt.

From my experience the E4 code can also be caused by the gas valve failing to open, the ignition transformer not working and most commonly the earlier ignition electrodes bending out of shape. There are other reasons for the E4 code appearing such as the gas being turned off, incorrect gas pressure, air in the gas supply, flue faults and faulty seals in the boiler (combustion door seal, burner seal or flue connection seal).

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Glowworm Micron 50FF Lights Flashing

Was asked to look at a Glowworm Micron 50FF because the lights were flashing and the heating was not working. Upon arrival I could hear a slight hum from the boiler which felt warm, but not as noisy as usual when running. Both the burner light and the reset light were flashing as this boiler had the latest board fitted which displays fault diagnostics through the green LEDs as opposed to the original PCB with orange LEDs.

I had a look at my chart to diagnose the fault.

The reset LED was flashing fast, and the burner light flashing slow which tells me it is related to the fan or APS (air pressure switch). From the slight hum I could hear I had already assumed that the fan was seized. Removing the case I could smell the motor where it had been trying to rotate the fan, and there was some scorching to the motor windings. The fan motor was also red hot. Fortunately I isolated the power whilst I went to pick up a replacement fan which helped it to cool down.

I replaced the fan, and is running well.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Potterton Suprima Orange Light Flashing

My sister asked me to look at her boiler, a Potterton Suprima, because it had been clicking on and off frequently and failed to heat the house properly on one day.

The boiler is the earlier Potterton Suprima but had the PCB upgrade kit 5111603 which replaces part number 407750 the troublesome PCB found on most Potterton Suprimas. The original PCB had two LEDs (red and green) which could be used to diagnose faults. The new PCB has a single LED which is able to produce three colours (Green, orange and red) and will flash various colours at various rates depending upon the boilers status.

The boiler was set to be on when I arrived, and had been on as the radiators were warm. When I looked at the boiler the orange light was coming on, there would be a click, the light would go out and kept cycling in this fashion at a slow pace. I checked the voltage at live and switched live which were both at 240v and steady. Looking at the fault finding guide which comes with the PCB upgrade kit, a flashing orange light on the PCB indicates that there is a problem with the temperature control and suggests to check the temperature control on the boiler is switched up which it was.

I checked the resistance of the thermistor on the yellow wires and it was within the range of 20k ohms to 4M ohms after unplugging it from the PCB. Testing it at the connector to the PCB tests the resistance of both the component and the cable at the same time. I wanted to check the resistance of the yellow wires as when the PCB was upgraded the engineer neglected to run the cables to the thermistor and overheat thermostat through the hole behind the fan housing which keeps them off any hot surfaces.

The flashing combined with the clicking from the PCB had led me to assume that the PCB was at fault rather than any other component, but wanted to check everything to be sure as they are not cheap. Replacing the PCB has solved the problem.

LED Indication Status	LED
Mains Off	Off
Mains On No Ext. Call for Heat	Continuous Orange
Ext. Call for Heat ( Temp. Control set to Off)	Flashing Orange
Air Proving & Ignition	Flashing Orange/Green
Burner On	Continuous Green
Boiler Temperature Control Satisfied	Flashing Green
LED Indicators Fault Modes Status	LED
Thermister Fault	Flashing Red every 5 sec
Wiring Harness Fault	Flashing Red/Orange 3 times/sec
Incoming Voltage <180V	Flashing Red/Orange once/sec
False Flame	Flashing Red/Orange every 5 sec
APS or Flow Switch Fault	Flashing Red 3 times/sec
PCB Fault	Continuous Red
Lockout	Flashing Red once/sec 5 flashes = Overheat 2 flashes = Ignition Failure
To establish cause press reset button for more
than 10 seconds. LED will flash Orange
once then Red, count number of Red flashes

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Central Heating Not Working

I was asked to have a look at a central heating system that was not working correctly. The initial complaint was that a few times the central heating had not been coming on. To get the heating to come on the lady was resetting the boiler, a Glowworm Micron, and the central heating would come on.

At the time of the faults the timer was set to be on as they leave it on 24 hours a day, the room thermostat was turned up, but there was no lights on at the boiler and no noise coming from the boiler. Initially I suspected that it was either the thermistor or PCB causing the fault. I had a PCB but suspected it was more likely to be the thermistor so would return with one in a few days.

On my return the customer told me that the heating had come on at the weekend, and would not go off. The usual cause off this problem is the motorised valve getting stuck, fully or partially, in the central heating position whilst the hot water is calling for heat. Therefore, I replaced the motorised valve on the assumption that this was causing both problems. I may be wrong and it may be the room thermostat that is the problem.

I still cannot explain why the customer was able to get the central heating going by resetting the boiler. The boiler had the newer PCB on it which has a diagnostic sequence built into the two display lights, which should show a fault if resetting is required. If anything changes I shall update you.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Baxi Combi 105e Losing Pressure

Went to have a look at a Baxi Combi 105e which was losing pressure regularly, the customer noticed that the pressured drops rapidly when the pump kicks in. He was also having to top it up regularly and there was a small leak coming from the underneath.

After removing the cover, I could see that there was some staining from the pin on top that activates the pump proving micro-switch. There was also water leaking from where the differential pressure diaphragm housing sits in the diverter valve. These were only minor leaks and did not fully explain the pressure loss.

I switched the heating on and the pressure dropped on the gauge, but I explained this is quite common on these particular boilers at the pressure fluctuations are due to the gauges proximity to the pump and the force of the pump affects the reading. The water pressure in the heating system was beginning to rise as the boiler was running, and I checked at the pressure relief valve outlet to see if there were any signs of water. There was no staining or running water, but a few droplets of water indicating that the PRV was not passing water continuously but had released some water which led me to suspect the pressure vessel was low on pressure.

I turned off the mains water to the boiler and opened the hot tap to drain off the water side of the boiler. I switched off the isolating valves on the flow and return to the boiler, and drained the boiler from it's drain point. I then undid the nuts on the differential pressure diaphragm housing which are 10mm, and released it from the diverter valve by undoing the grub screws which hold it onto the diverter valve. This could be removed and the leak could be seen from where the spindle exits the diverter valve to act upon the water differential pressure diaphragm. I removed both microswitches from the diverter valve body by undoing the single screw which holds each one on. I then undid, the nut underneath, nut the nut right hand side, the pressure gauge connection, removed the clip from the rear pipe and the pipe on the rear of the diverter valve which is held in by an 8mm nut. There is also a screw which holds the diverter valve in from underneath which I removed. The valve should then slide forward out of the plate heat exchanger and the pipe at the rear.

I then re-assembled the boiler with a new diverter valve in reverse adding some silicone grease to the o-rings and replacing the 3/4" fibre washers on the unions to the bottom and left hand side. When re-fitting the micro-switches it is important to replace them the correct way round or the boiler will fail to work properly. The pump proving micro-switch is connected to red wires and sits on top of the diverter valve. The hot water flow micro-switch sits in front of the differential pressure diaphragm housing and has red wires. Whilst the boiler was still  drained and the system was open I recharged the pressure in the pressure vessel which had lost the majority of it's pressure. After filling and testing everything looks to be working well again.

I have been led to understand that the pressure vessels on these boilers struggle to maintain their pressure because of the design of the boiler. This may be related to the fluctuating pressure when the boiler operates. I have been told that not using the hot water pre-heat extends the life of the pressure vessels.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Room Temperature Control

The use of a room thermostat can help you save money when using your central heating system. According to the Energy Saving Trust installing a room thermostat can save you £70 per year. A basic wired room thermostat such as the Danfoss RMT230 cost as little £7.21 from Screwfix. The difficulty with adding a wired thermostat to your system if you don't already have one is that installing the wiring to the optimum position is not always possible without disruption to the décor.

To overcome the difficulty of installing a wired thermostat there are a number of wireless room thermostats available. As a basic room thermostat my recommendation would be a simple and neat digital thermostat like the Honeywell DT92E avalaible for £74.68.

When installing a wireless (RF) room thermostat it is always my recommendation to install a programmable room thermostat, as they provide a much greater flexibility in the control of the room temperature and the cost difference is not that great. The Energy Saving Trust suggest that lowering your room temperature by one degree may save you £55 per year. Therefore, if you can set your room temperature lower when you need it then a programmable room thermostat will soon pay for itself. My favourite RF programmable room thermostat  is the Honeywell CM927 available for £110.04. They are simple to install and simple to operate, the display clearly shows what is going on at all times. The Honeywell CM927 allows you to set different temperatures at different time periods throughout the day and for every day of the week as well as having a host of other features.

If you have a wired room thermostat and wish to replace it with a programmable thermostat, the above Honeywell thermostat also comes in a wired version the Honeywell CM907 which works in exactly the same way as the Honeywell CM927 but is not wireless. However, it is only £62.81 which is quite a saving over the RF version.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Hot Water Too Hot

A nice simple job for a change, the customer was complaining that their hot water was too hot when coming out of the taps. My first port of call was the Danfoss Randall hot water cylinder thermostat, which was set to 70 degrees celsius. It is quite common for these to get knocked and set to the wrong temperature as the temperature dial is quite exposed. I reduced the temperature that the cylinder thermostat was set to and recommended that the customer takes more care to avoid knocking it in the future.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Baxi Solo HE Incorrect Combustion

I fitted a brand new Baxi Solo 18HE today, and when I went to commission it the combustion was not correct. The CO level was around the 200ppm mark, so I left it to run for a while hoping that it may just be burning off some of the oils from production but this did not solve the problem. Rechecking the combustion the CO2 was at 10.3% which is higher than it should be. I checked the gas rate and the meter was passing one cubic foot in approximately 45 seconds, which when referring to the tables is an input of 24kW. The working pressure was 20 Mbar at the meter and 18.5 Mbar at the boiler inlet.

I spoke to Baxi's technical department who suggested it may be something to do with the plugs on the PCB and asked me to check them. On the second plug from the bottom, there are two links, the colours and number of which depend on the boiler output. The links are actually resistors which alter the fan speed settings according to the boiler output. The links on the 18kW model are yellow and grey. They also suggested it was caused by the difference in gas pressure over the pipework or that the flue may not have been incorrectly assembled. All valid suggestions but not in this case. We tried another PCB, but that made no difference.

The solution was to replace the gas valve with a new one. This gave us CO of 40ppm, and CO2 of 8.5% which is within the manufacturers tolerance of 9% +/-1%. Not what you want when fitting a brand new boiler on a Friday.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Honeywell ST6400C Playing Up

I got asked to look at a Honeywell ST6400C programmer which had been playing up recently. This programmer is a two-channel programmer with lights for both heating and hot water. The programmer had been set to come on automatically for heating and water and various time throughout the day. However, the heating had not always been coming on or going off at the times. The heating light was coming on and off, but not in line with the times set.

I decided to replace the programmer, and used a Danfoss Randall FP715 Si programmer. Using the industry standard backplate makes it simple to replace many programmers, and future replacement of the programmer itself. A permanent backlit display is also handy for the 'darker' installations. Automatic summer/winter time change also is a useful feature.

The programmer can be set up in a variety of ways to suit the end user, the time can be set to be displayed as AM/PM or 24 hour time-clock. The programmes can be configured to provide either 2 or 3 on/off settings. The programmer can also be set for a fully-pumped or gravity system. For the installer the biggest benefit is the ability to configure it either as a 24 hour, 5/2 day or 7 day programmer as the customer desires. This programmer genuinely suits the majority of installations and is currently one of my favoured programmers to be kept as van stock.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Leaking Hot Water Cylinder

A customer had called out his home insurance company as he had a leak in the airing cupboard. They found the leak was coming from the hot water cylinder and would need replacing.

I visited to look at the cylinder, and after removing some of the foam lagging could see that the leak was coming from the backnut on the coil and could be repaired. I partially drained the central heating system and hot water cylinder, removing the pipe between the three-port valve and cylinder. I then loosened off the backnut, and wound some PTFE tape into the gap as can be seen in the picture below. I then tightened the nut onto the PTFE tape sealing the cylinder. I re-connected the pipework and re-filled the system and the leak was successfully solved

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.

Honeywell DT92E Wireless Room Thermostat

Was asked to look at a Baxi Platinum Combi with a built-in digital timeclock which was not working. I replaced the digital timeclock with the simpler analogue timeclock, and also fitted a Honeywell DT92E wireless room thermostat as there was no room thermostat connected to the boiler.

The Honeywell DT92E wireless room thermostat is quick and easy to add on to a combination boiler wiring. For me a system without a temperature interlock is not a good system, just using thermostatic radiator valves and a timeclock doesn't stop the heating from coming on during warm days. A wireless room thermostat is the best solution to the problem, as a room thermostat can be installed without disturbing any décor.

When converting a system over to a combination boiler my favourite time and temperature control is the excellent Honeywell CM927 Wireless Room Thermostat. Using these means you don't have to use the over-priced and unreliable built-in timers or external single channel timeclocks. They can be used as a basic room thermostat or as an advanced heating control to set different temperatures at different times of the day.

Disclaimer: The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem. Work should only be carried out by persons qualified and competent to do so.