Baxi WM No Heating

I was left a message on my answerphone because a customer of mine had no central heating and asked me to attend the next day. He had told me that he could see that the pilot light was lit on his Baxi WM boiler and that the thermostat was turned up. He though it may be the pump as he had a pump seize before.

I attended in the morning, but unfortunately for myself the central heating had come on with the timer and had been working as it should be. The timer had switched off before I arrived and so I switched the heating on and the thermostat up. Everything was working with no obvious issues. I put the hot water on and tested the motorised valve to ensure that it was switching between heating and hot water as it should be. There appeared to be nothing wrong with the system.

The customer asked me to look at something unrelated which I did, and then went back to do a final test before leaving. On the final test I switched the heating on and the motorised valve began to move over but did not open fully enough to activate the micro-switch. I waited a few seconds longer but it still did not cause the boiler and pump to run. I put some pressure on the lever of the motorised valve and it moved further before activating the boiler an pump. I drained the system and replaced the motorised valve and everything has been working well since.

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 WM 30/4 RS No Hot Water

I was called to look at a Baxi Solo WM 30/4 RS which was not working and the lady had ran out of hot water. Immediately I could see that the pilot was not lit and attempted to relight the pilot light. It would not stay lit and being the SS version had an overheat thermostat interrupting the pilot thermocouple at the gas valve. Once I had reset the overheat thermostat I was able to relight the pilot light and the boiler was able to fire for the hot water.

As soon as the main burner came on I could hear that the boiler was unusually noisy and so checked the burner pressure which was as it should be. The pump which was adjacent to the boiler was fairly old and didn't quite sound as if it was running at the correct speed. I replace the pump and refired the system and the boiler was running a lot more quietly and didn't sound so scaled up.

After the boiler ran for about five minutes it started to crash and bang before cutting out on the overheat thermostat. I used my flue and gas analyser to measure the flow and return temperatures to find that the flow temperature was exceeding what it should have been and the boiler thermostat was not cutting off the boiler until the overheat thermostat kicked in. I replaced the Ranco C77P0135 thermostat and the system was working well 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.

Baxi Combi 80e No Heating or Hot Water

A retired gentleman called me to look at his Baxi Combi 80e because he had neither heating or hot water. Unfortunately, being elderly he is unable to get into the loft to check on the boiler. Contrary to Building Regulations the loft does not have fixed access, although it is lit and boarded. Regardless  of this, the poor old boy would not be able to ascend or descend a ladder and calls me regularly.

As soon as I looked at the boiler I could see that the water pressure in the system was very low and the 'pump' warning light was flashing to indicate that there was no circulation. This is the 60 degree light. I refilled the system to 1.5 bar using the filling loop, set the heating on and tested the hot water. The hot water was working again fine, but when I returned to the loft I could see that the water pressure in the system had increased significantly, and so turned the heating back off.

I fetched my hose and pump out of the van. I connected the hose to the system and let the pressure out leaving the drain-off cock open. I then connected my pump to the Schrader valve on the pressure vessel and the gauge on my pump was showing zero pressure. I preceded to pump up the pressure in the pressure vessel until the pressure was steady at 0.8 bar. I then turned off the drain-off cock and refilled the system to 1.5 bar. This time when I ran the system, the radiators got hot and there was a normal increase in system pressure.

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 80e Dead No Lights

Was called by a customer today as their Baxi Combi 80e was not working for either central heating or hot water. I expected to find that there was not enough water pressure in the boiler, but this was not the case. There was no lights lit on the front of the boiler so I checked that the fused spur was switched on and that the fuse was ok. The fuse was ok but a 13 amp fuse, so I swapped it for a 3 amp fuse.

I removed the cover on the boiler for the electrical connection and tested for power there. There was 240v across live-neutral and live-earth, and nothing untoward between earth-neutral. There was no power on the boiler side of the 2 amp fuse so this had obviously blown. Removing the PCB cover completely I could smell that the PCB had burnt out, and there was some black staining in the cover. Removing the PCB there was considerable damage to the underside of the PCB as can be seen below.

After replacing the internal fuse and PCB 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.

Baxi 105e Combi Lights Flashing No Hot Water

I was called by a customer who regularly calls me because his Baxi 105e Combi boiler stops working. The boiler is installed in the loft and contrary to building regulations does not have a means of fixed access which makes it impossible for the elderly gentleman to attend to the boiler.

The boiler had gone into a fault mode and one of the LED's on the front panel was flashing. The symbol above the flashing led was an upside triangle which is the pump symbol. In the manual it suggests there is an issue with circulation, which there was. The pressure gauge was showing zero pressure and hence there was not enough water in the system.

I opened the filling loop, filling the system to 1.5 bar before switching the boiler off an on to reset it. The boiler ran and I topped up the water as necessary due to the air being expelled through the automatic air vent. Once again the boiler was 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.

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.

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.

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.

Keston Boiler Replacement

Had the pleasure of replacing a Keston K60 boiler which had provided thirteen years of disobedient service today. The design of the boiler looks good and easy to work on, it it is a shame that it has been unreliable.

Fitted a Baxi Solo 24 HE boiler to replace it. The existing boiler was undersized and the customer had got fed up with calling British Gas out to repair it.

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.