Alpha CD20S loosing pressure
Worcester 30 CDI – failed pump
Baxi Solo 3 PFL 40 – Boiler completely dead.
Potterton Promax 15 HE – Intermittent ignition lockout.
Ideal Isar HE 24 boiler dead – faulty printed circuit board
Worcester 24i Junior ignition lockout – faulty pressure switch
Vaillant ecoTEC Pro 28 – F75 fault code
Baxi 105e Instant fan or flue fault – melted venturi
Glowworm Swift-flow 75 – Fan stuck
Potterton Promax 15 HE seemingly dead – faulty flow switch
Gas leak – screw through gas pipe
Alpha CB24X leaking not holding pressure – faulty expansion vessel
Potterton Promax 15/2 explosive ignition – burner failed
Vokera Linea heating on constantly – faulty diverter valve
Ideal Mini C32 no ignition – faulty printed circuit board
Remeha Avanta Plus 24C – leaking from expansion vessel
Vokera Compact 25 poor hot water losing pressure
Baxi Platinum HE28 E168 error code, poor hot water losing pressure
Glowworm Betacom poor flow from hot water tap
Potterton Suprima 30L intermittent lockout – faulty printed circuit board
Worcester 28CDI hot water not working – faulty diverter valve
Worcester 15Ri seemingly dead – transformer burnt out
Procombi 85HE leaking, not holding pressure
Halstead Ace High intermittent hot water – faulty PCB
Baxi Combi 105e Instant Losing pressure rapidly
Glowworm Hot Water Express – intermittent hot water
Vaillant ecoTEC Plus 624 ignition lockout, lossing pressure.
Worcester ZWB 7-30 – EA fault code, no heating, no hot water.
Thorn House Warmer S no heating no hot water – burner sooted up
Alpha CD20S loosing pressure
The Alpha CD20 S is a system boiler. This customer uses it to heat his koi pond during the winter. The boiler had started to lose pressure when it was on, which was due to a flat expansion vessel. The boiler was well overdue a thorough service as well.
Worcester 30 CDI – No heating, no hot water, failed pump
This boiler would just overheat when you put a demand on it. The pump had failed altogether, this boiler has a special pump with variable speed control on it. It is not usual for a pump to just burn out completely, often the impeller gets jammed for whatever reason. This one needed to be replaced entirely though.
When these boilers overheat they often display a U code, like U9 for example, which goes down slowly. This can be mistaken as a fault code, but when the temperature exceeds 100 degrees centigrade the display reads U which means it is over 100 degrees.
Baxi Solo 3 PFL 40 – Boiler completely dead.
This boiler was completely dead and had tripped one of the circuit breakers in the house. It turns out the printed circuit board had gone with a bit of a bang which had caused a short and caused the breaker to trip. You can see on the photo the black mark that was left on the board. The PCB is a component on a boiler that cannot be serviced, this one had just come to the end of its life and had given up. After having replaced the PCB the boiler was back in working order.
Potterton Promax 15 HE – Intermittent ignition lockout.
This boiler would work for sometime and then need to be reset. It got to the point where it needed to be reset after every 5 minutes or so. This turned out to be a faulty ignition printed circuit board. You can see in the photo that the resistors on the board were starting to discolour, which is usually an indication that a circuit board will need to be replaced at some point if it isn’t faulty already.
Tom & Sally, S64
Ideal Isar HE24 – Seemingly dead heating would stay on constantly before it died
A very common problem on the Ideal Isar and Icos is a faulty printed circuit board. Usually the transformer burns out and melts the plastic of the housing slightly as can be seem in the photo. the photo was taken from an Icos which uses the same PCB.
Another problem with the Isar is a faulty diverter valve. The Isar has a permanent preheat function which keep the water inside the heat exchanger hot for better hot water delivery. When the temperature in the heat exchanger drops below a certain temperature the boiler assumes a tap must be running and fires up for the hot water. When the valve goes faulty the boiler can’t get up to temperature as all the heat goes down the flow pipe and warms the radiators up first until the heating return pipe gets up to temperature.
This can make it seem as though the heating is stuck on. This is quite common on boilers with a preheat function, but most can be turned off. On the Isar it cannot be turned off.
Worcester 24i Junior – Boiler failing to ignite ignition lockout
On a lot of older boilers you have a pressure switch which checks to make sure there water in the system before the boiler will fire up. Often these get blocked up which can make then stick on or off. Sometimes they just stop working altogether and need to be replaced.
This boiler would spark for a second then go to ignition lockout, which can mislead you into thinking that its a faulty printed circuit board.
Vaillant ecoTEC Pro 28 – Boiler failing to ignite F75 fault code.
No sudden change in pressure detected on turning on pump.
The pressure sensor on most boilers detects the static pressure in the system, but also detects the small rise in pressure created when the pump runs. Apart from insufficient pressure, the F75 fault code is usually caused by a blocked or faulty pressure sensor. It can also be caused by a faulty pump which is not uncommon on these older Vaillant ecoTEC models. I keep replacement pressure sensors as stock as they are quite a common problem.
The problem on this particular boiler was that the pump was failing, but the pressure sensor was going faulty so we ended up replacing that as well before it failed completely. The pump shown below is the one that comes with the original ecoTEC models. I have replaced quite a few of these pumps and I suspect they must have had some sort of design flaw which causes them to fail prematurely. The replacement pump is manufactured by Grundfos.
Baxi Combi 105e Instant – Ignition lockout, fan or flue fault.
On these older boilers they have a small plastic venturi or venturi’s housed inside the fan assembly. These venturi(s) create a small pressure which is used to activate the air pressure switch which tells the boiler that the fan is running and it is safe to fire up. Sometimes the venturi(s) are made of metal but are usually plastic, on this particular boiler the venturi had melted which stopped the appliance from working altogether.
Apparently the exact same thing had happened 12 months earlier. This fault is caused by the flue gases being too hot and it is a very rare fault which doesn’t happen very often. All checks confirmed that the boiler was operating safely, using the right amount of gas and operating at the right temperature. Whether the melted venturi happened suddenly or over a period of time could not be determined, but the boiler is still working ok at the moment.
Glowworm Swiftflow – fan stuck
This customer had just purchased and property and wanted to have the boiler checked over to make sure it was working safely. This boiler must be close to 20 years old, although I’m not sure exactly. It was in a pretty condition although the fan had stuck and had not been working properly for sometime, however the boiler seemed to still work ok even when the fan wasn’t running, so it must have been working like a balanced flued appliance. I lubricated the fan with some of my ‘special’ spray which is a high temperature lubricant which solved the problem.
Potterton Promax 15HE – Boiler not working seemingly dead
This was a relatively straight forward diagnosis and a slightly more time consuming repair.
On these appliances they have safety device in the form of a flow switch, which detects when the pump is running. These switches almost always leak at some point and need to be replaced.
This is probably the first one I have come across where the switch is just faulty and needs replacing. This requires draining down the whole system, unless the boilers upstairs.
Gas Leak – Screw through gas pipe.
I was called to this to locate and repair a gas leak, which was urgent as they had called the National Grid who had capped off their gas supply.
I located and repaired a gas leak in cupboard which housed the gas meter, but they still had a leak somewhere else.
They had been renovating their house and were replacing the bathroom at the same time. They were told to place a solid board down in the bathroom so that it could be tiled properly. A screw had been put through the floorboard which coincidentally had the gas pipe running underneath it….
So I had to remove what seemed like 1000 screws and remove the board to get access to the gas pipe.
Alpha CB24X – Boiler leaking.
This boiler was leaking badly from the expansion vessel, which regulates the pressure in the system. The expansion vessel had split at the seam which meant it had to be replaced. Sometimes if an expansion vessel with a weak seam gets too much pressure in it then it will leak. if you reinflate the inner tube it sometimes fixes the problem.
The problem with a lot of boilers is that the internal expansion vessel is located right at the back of the boiler which can make it difficult to replace. If the flue runs out of the back of the boiler or if there isn’t enough room above the boiler, then you often have to remove the boiler from the wall to replace the internal vessel. Sometimes it is better to fit an external vessel in a suitable place.
Fortunately whoever installed this particular boiler didn’t seal the flue in properly, so removal of the flue was relatively easy and a lot less painful than taking the boiler off the wall.
Potterton Promax 15/2 HE Plus – Boiler making loud banging noises.
The boiler would makes several loud bangs then fire up. this is known as “explosive ignition”. Usually there is a single explosion but on this appliance it was making several which is very unusual. I have not come across this before or since. It was caused by the burner which had failed. Quite a common fault with these appliances. The burner has since been replaced.
Vokera Linea 24 – Heating on constantly, poor domestic hot water.
This problem turned out to be related to the diverter valve. On these boilers there is a ‘preheat’ function which keeps the water inside the heat exchanger warm as to deliver hot water faster when you run a hot tap.
When the diverter valve doesn’t function properly the boiler tries to warm the heat exchanger up but the heat slips past the diverter valve into the central heating circuit, warming the radiators up. So the heat exchanger won’t get up to temperature until the whole house does, the central heating will seemingly come on without a request for it.
At the same time when you run a tap, all the heat that should be going to the water ends up slipping down into the central heating flow pipe instead of back around the boiler. This means that unless you’ve had the heating on for some time, the water coming out of the tap won’t be very warm.
You will usually notice this problem get progressively worse. Early warning signs are one or two radiators upstairs getting warm when you have a shower or run a bath.
The diverter valve service kit for one of these costs around £30 – £40.
Ideal Mini C32 – Boiler cycling on and off when. No heating etc.
A very common fault on these appliances. The boiler will cycle on and off when trying to fire up. This turned out to be the ignition Printed Circuit Board(PCB). The ignition PCB on these appliances costs between £100 and £200 depending on the model. Some of these boilers only have one PCB whilst most usually have two. Unfortunately there is no amount of preventative maintenance you can do to prolong the life of a PCB, this boiler was around 10 years old.
Comparing the old board to the new board, you can tell by the colour of the resistors that it was tired. There were a couple of dry joints on the back as well.
Remeha Avanta Plus 24C – Boiler losing pressure, leaking and wouldn’t hold pressure.
The expansion vessel on this appliance was flat and needed to be repressurised. The customer had tried to fill the system back up when the boiler stopped working and it was leaking from the seam on the expansion vessel. The pressure gauge wasnt working. So I repressurised the expansion vessel. Removed and cleaned the pressure relief valve. Removed the pressure gauge and blocked this also.
Whenever the power if turned off this boiler goes through a purge cycle which lasts several minutes. Once I had carried out the repair and reinstated the power the boiler kept locking out with the E10 fault code relating to the pressure(despite there being enough pressure and the pressure switch activated). Sometimes you can upset certain appliances when you turn the power off. Fortunately after several attempts it decided to work again.
These boilers aren’t very common. I believe they are expensive to buy and replacement parts are very expensive. I definitely wouldn’t install one and would avoid this make of boiler at all costs.
Vokera Compact 25 Combi – Intermittent hot water, losing pressure.
This boiler is essentially the same as the Procombi CT25. Another engineer has looked at this boiler before myself and apparently broke something relating to the diverter valve then replaced it at the customers expense. The part he broke and replaced wasn’t even related to the issue anyway. He said he wasn’t entirely sure about the hot water issue and left.
The hot water was intermittent due to the Domestic hot water thermistor sensor being out out of range and needing replacement. Fortunately this was a relatively cheap part and cost less than £10. The boiler was losing pressure as the expansion vessel which regulates system pressure was flat and needed to be repressurised. This turned out to be a relatively straight forward repair in the end. Interestingly their 2 year warranty had just expired shortly before the issue. These boilers aren’t built to last.
I know that British Gas refuse to insure these as they fall apart, are problematic and can be expensive to repair.
The customer said –
“Fantastic service, really happy with thorough check, diagnosis and repair. Will use again and will recommend to all”
Peter & Kerry, DN5
Baxi PLatinum HE28 Combi – Intermittent hot water, losing pressure, intermittent E168 error code.
This boiler turned out to be fraught with problems. Nothing on which couldn’t be rectified. I was called to look at this one when another engineer had let them down.
The boiler had a flat expansion vessel(this regulates system pressure on a sealed system), a leak from the dhw thermistor(sensor), the plate to plate heat exchanger for the hot water was blocked which would cause the boiler to ramp up and down delivering inconsistent hot water. The E168 error code would show itself intermittently, which is usually indicative of a Printed Circuit Board(PCB) fault on these boilers.
So I recharged the expansion vessel to 0.8 bar. Repaired the leak on the thermistor. Removed the plate heat exchanger and flushed it out with acid. Replaced the PCB, then tested the appliance. Most engineers would have replaced the plate heat exchanger in this case but in most cases you can flush them out with acid. Its not very often I have to replace a plate heat exchanger due to a problem like this. This obviously saves my customers money as some of these heat exchangers can cost well over £100 to replace depending on the make of boiler.
Needless to say the boiler is operating as it should now, all is well. The Baxi Platinum is quite a good boiler in my opinion and I think it was worth trying to salvage this one.
Glowworm Betacom 30 – Poor flow from hot water tap.
It can be hard to believe that something so small can cause such a big problem.
On these boilers there is a non-adjustable flow restrictor in the hydraulic block, which is designed to restrict the maximum flow of water going to the hot taps to a set rate.
The problem is that there is a tiny rubber O-ring inside the restrictor which swells up and increase in size over a number of years. This causes the flow of water to be further restricted, which eventually gets to the point where there is not much more than a trickle of water coming from the hot taps.
The flow restrictor on these boilers is in an awkward place and usually the best way to fix the problem is to break the restrictor with a screwdriver and remove the pieces.
Potterton Suprima 30L – Intermittent lockout, would sometimes take a few attempts to reset the boiler and then it would work for a period of time before locking out again.
Nicola was quoted several hundred pounds to power flush her central heating system, as they were told the appliance was overheating and a power flush would fix the problem.
However the system did not need a power flush and it turned out to be a problem with the Printed Circuit Board(PCB). These boilers had a problem with the original PCB’s that were supplied with the boiler. I could tell straight away that it was still on the ‘original’ PCB and that it needed to be replaced. I dont come across that many of these issues relating to the PCB, as most have already failed and been replaced. There are still one or two out there on the original board though.
It wasn’t a cheap fix as the PCB’s are around the £200 mark, but needless to say the problem has now been resolved and Nicola has saved a lot of time and money by letting someone who knows what they are doing have a look. If you’ve been told that your system needs a power flush, then due to the average cost of such a service it would make sense to get a second opinion.
The customer said-
“Excellent service, came quickly and at a time to suit us, carried out the required service and also provided advice on other issues we were having and helped to fix them. Would recommend to others”
Worcester 28CDI Combi – Hot water not working. Pressure gauge broken.
This one was relatively straight forward, albeit in an awkward little cupboard. The diaphragm in the diverter valve had split which stopped the hot water from working. There is a service kit you can get to replace the diaphragm, but in my experience its more cost effective to replace the whole diverter valve so this is what I did. The expansion vessel was flat so I recharged this to 0.75 bar, cleaned the pressure relief valve and replaced the broken pressure gauge.
I like these older Worcester boilers, they seem to have a well thought out design, are built well and seemingly were built to last. Which is a lot more than I can say for a lot of other boilers. Things like the diverter valve go wrong at some point on these boilers, but this is just general wear and tear. If I had one of these I wouldn’t be in a hurry to replace it.
Worcester 15Ri – Boiler seemingly dead would not work.
This was quite a straightforward fix. The Printed Circuit Board was blowing fuses when you turned the power on. On most Worcester boilers they have a transformer on the PCB which can be removed. Once I had removed the transformer I could tell straight away that something wasn’t right. A quick double check with my multimeter confirmed this.
I think the replacement transformer cost less than £15. These are good little boilers though, as far as I know they don’t go wrong very often.
Procombi 85HE Combi – Boiler leaking, not holding pressure.
This repair turned out to be a very expensive repair indeed(not for me thankfully).
This boiler is essentially a derivative of a Vokera Syntesi with one or two small differences. The Syntesi started off as a Vokera Linea I beleive. Vokera retrofitted a secondary heat exchanger(economizer) to the Linea and turned it into a condensing high efficiency boiler.
Anyway the coil inside the economizer(top left hand side of boiler) had popped which caused it to leak, hence it wouldn’t hold pressure. These boilers have never been very good. The cost of a new economizer was around £430 I think. This boiler should have been scrapped but the repair was done through a letting agency of some sort and they ended up paying the bill. I’m glad it wasn’t me. These boilers aren’t made to last. They are very cheap to buy but when they go wrong(and they will) the parts aren’t cheap. Its generally more cost effective to replace one of these when they start to go wrong. Most self respecting installers who care about their customers will not install one of these.
I have seen one of these boilers literally fall apart at the seams within less than two weeks.
Halstead Ace High Combi – Intermittent hot water.
This turned out to be an issue with the Printed Circuit Board(PCB).
The switch which told the boiler to come on for hot water was doing its job, so I narrowed it down to a PCB fault. Upon closer inspection the signs were clear that the PCB was getting tired…
The brown marks around the resistors on a PCB is usually a clear indication that it will need to be replaced at some point. You can see the difference in colour between the old board and the new one. This is generally something I check for on a service.
The customer said-
“Richard was professional and pleasant came on time talked me through what the problem was with my boiler and how much it would be then ordered the part what was needed came back as per arrangement and fixed it”
“I couldn’t recommend this young man high enough he is professional he had to come back to my boiler a couple of times,as soon as I called him he came out no probs eventually he sorted it he even contacted me to ask if it was ok and working ok now a couple of days later very nice young man”
Baxi Combi 105 Instant – Losing pressure rapidly.
Some boilers were retrofitted with a secondary heat exchanger called an economiser. This essentially increases the efficiency, turning a non condensing appliance into a condensing one.
On this particular boiler the inner coil on its economiser had developed a small hole through it, which was causing the boiler to lose pressure constantly and very rapidly. This rapid loss of pressure can be difficult to identify for homeowners and inexperienced engineers alike, as the water coming out of the coil goes straight down into the condensate trap and into the drain leaving no obvious signs of a “leak”.
Glow Worm Hot Water EXPRESS 100 Combi – Losing pressure, intermittent hot water.
This is probably one of the oldest Combi boilers I have ever worked on. I think I have only ever come across two of them. It was losing pressure due to a flat expansion vessel and the hot water was working intermittently.
So i recharged the expansion vessel to 0.75 bar, cleaned the pressure relief valve and replaced the domestic hot water flow switch, which was responsible for the hot water issue. I think I ended up replacing the thermocouple as well. The flow switch wasn’t cheap (around £80 – £100 I think) but everything else worked OK and the general condition of the boiler was good, so it was a repair worth doing. So overall I would have to say this is a very good little boiler, I think it was at least 20 years old but I’m not entirely sure.
My general advice is that if you’ve got an old boiler that is working OK, not causing any issues and not costing you an arm and a leg, then keep it as long as you can. This is a good example of one such boiler.
Vaillant Ecotec Plus 624 – Boiler wouldn’t fire up and had been losing pressure for some time before it stopped working.
There was an issue with some Vaillant and Glow worm boilers where the burner gasket(or burner door seal as they like to refer to it as) would fail and cause heat from the heat exchanger to escape and cause damage.
The damage in this instance was that the air intake/filter had completely melted which stopped the appliance from sucking in any air and stopped it from working. I think it also melted the wires which lead to the overheat stat on the heat exchanger. Another issue was that the rubber tube inside the expansion vessel had popped and the vessel needed to be replaced.
All in all it wasn’t a cheap fix, but after replacing the necessary bits the issue was resolved and now the boiler is working as it should. I don’t encounter this type of problem as much anymore as most of the boilers with this issue have had their gaskets replaced. I believe Vaillant recommend replacing the gasket every five years, I’m assuming Glow worm have the same recommendation.
Worcester ZWB 7-30 – EA fault code, no heating, no hot water.
I don’t come across that many of this particular model of boiler. On this particular boiler the spark electrode assembly needs to be replaced every so often. There is a piece on the assembly which detects if there is a flame present and this generally degrades over time needing replacement. When they wear out the boiler can’t detect if there is a flame present so goes to ignition lockout showing the EA fault code. Also if the assembly is not cleaned on a service they tend to get fouled up and stop working.
A while ago
Thorn House Warmer S Back-boiler – Heating not working.
I came across this one some time ago when I was still working for a company doing insurance work. I cant remember exactly when or where it was but the customer said his heating wasn’t working. The appliance was an old Thorn House Warmer S Back-boiler, which was installed in 1971. The first Back-boiler was launched by Baxi around 1966 I believe. This is one of the oldest(if not the oldest) appliances I have ever come across.
The appliance had seemingly not been serviced for some time and had completely sooted up. I think it needed new burner pads as well. I ended up turning it off and never went back to it so I’m not sure what the outcome was.
On the images you can see where the flame had been coming out, licking the front of the boiler, leaving a black sooty mark. It looked as though someone had carried out some sort of dodgy repair with tinfoil on the electrical cable going to the gas valve. I’m not sure what this was for, but it appeared as some sort of heat shield and I’m guessing maybe someone did that to stop the flame from melting the cable or something. I’m not sure. I come across this issue every so often.
If you have one of these old open-flued appliances, then an annual safety check and service is paramount. These old appliances don’t have the same safety devices as modern appliances and can become very unsafe very quickly if maintenance is neglected.