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Hints and Tips for Heating, Gas and Boiler Engineers from VanCert Academy

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5 Common Boiler Problems (and lesser known solutions)

At VanCert we earned our stripes fitting and servicing boilers. We have trained up budding young engineers, we have done the legwork and along the way we have come up against every common boiler problem and error code there is.

So, to help our men out there on the front line, we are sharing the knowledge, experience and general tricks of the trade that we have accumulated over the past 20 years.

We have created these hints and tips for Heating, Gas and Boiler engineers. If you like them please share them, and comment below – we want to hear your tricks of the trade too!

boiler fix

$   1.       Potterton Promax He

An engineer arrives at the boiler and it is displaying a fault code of E168. This fault code does not exist within the manufactures literature. This is a PCB fault and it needs to be replaced.

$   2.       Potterton Suprema HE / system boiler

An engineer arrives at the boiler and it is displaying a fault that in the manufactures literature indicates that the air pressure switch or fan is faulty. However, make sure to check the condensate pipework first, as if it is blocked the boiler will also indicate this fault code.

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$   3.       Baxi 105e

An engineer arrives at the boiler and it is displaying a fault code. You then reset the boiler and it fires up ok. What should be checked next? Turn off the power and remove the fuse (safety first). Remove the boiler casing and PCB casing and if it smells of TCP, the joints on the PCB have burnt out (or are on the way out). It may reset a few times but you will end up fitting a new PCB.

     4.       Common Boiler Problem when a new kitchen or bathroom has been fitted

An engineer arrives at a property and the client is not getting any hot water. They take the casing off the combination boiler and notice that the diverter is motoring over fine, and diagnose an issue with the domestic hot water flow switch. Before jumping to this conclusion though, go and flush the toilet and stand by the boiler. If you can hear water flowing through the boiler, the hot and cold water pipework is crossed.

$   5.       Common Boiler Problem when visiting properties fitted with a TMV / domestic blending valves.

An engineer arrives at a property and the overflow from the domestic cold water storage tank is overflowing. If the ballcock valve if fine, this could be that the hot and cold water pipework has been crossed, or the non-return valve in the TMV has failed. This means the pressure of the mains cold water is greater than the tanked water, and it is pushing back into the tank causing it to overflow.

Look out for our next week’s tips.


  • Bob W Harris ST10 GAS Saturday, 06 February 2016

    Top tips

  • Dave Wilson Monday, 08 February 2016

    Thanks Bob - we're glad you agree. There are plenty more to come so stay tuned!!

  • Vic Wheeler Wednesday, 22 June 2016

    Some good ones in there Dave!

  • Aaron Monday, 19 September 2016

    While the Baxi megaflow, duotec and promax e168 does poss mean a pcb it's also a earth fault.

  • Debbie Boden Tuesday, 20 September 2016

    Thanks Aaron - we will pop that one in our next top tips!

  • Mark David Sunday, 04 December 2016

    Some of the best tips you have shared with us. Thank you.

  • o dang Wednesday, 18 April 2018

    Thank you for sharing such great information. It's a pleasure to visit here. You can also visit us in BOILER-INSTALLATION-BEXHILL | SAME DAY BOILER-REPAIRS .

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