Safety Thermostat Fault - Potterton Promax Combi HE Plus

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Hi there, looking for some help diagnosing a fault on my Mothers boiler and not sure if it might be the condenser pipe or not?

System is a Potterton Promax Combi HE plus and fault code displayed is E110 - Safety Thermostat. Have poured three kettles of boiling water over outside brass condenser outlet pipe and reset three times but system sparks up then shuts down seconds later with water pressure going high to 3 bar.

Very noisy on ignition as though water is trying to get through.

Not sure if this is symptomatic of the condenser outlet being frozen or not and can also hear pressure valve on top of the system hissing on reset so don't want to try again and risk further damage or worse.

82 year old Mother in sunny Scotland just now, so any advice would be gratefully appreciated!
 
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The condensate pipework is usually plastic pipe ,not brass ?? If blocked its not likely that burner would ignite at all.sounds more like an overheating problem thru lack of circulation to me. Does the temperature of the flow pipe exiting boiler get hot at all when burner ignites ? What is the pressure when cold ,before it rises to 3 bar ?
 
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Thanks Terry - I know most condensate pipes are plastic but this one seems to be copper. The only pipes at the back of it going outside are that one, the water drain valve and the exhaust from the burner so can't see there being one I'm missing.

The pressure when off is sitting at 1 bar and the flow pipe does seem to warm but only for a second or two before it shuts down.

Cheers and thanks again for your help!
 
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Condensate pipe should go to drain ,pressure relief pipe is usually terminated to a visible and safe position ,as very hot water can expel from it. I think you are going to need an engineer ,the boiler is firing ,generating heat ,but the heat is not dispersing ,pressure goes up ,overheat stat intervenes and boiler locks out. Not diy fix really.possible expansion vessel problem as well as other issues
 
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Thanks Terry - I've just sussed that the condensate pipe is going to drain on the inside of the house at the sink waste so doubt it can be that, that was frozen. Apologies should've picked that up before posting. The one I was looking at earlier is the pressure relief right enough. D'oh!

Can you shed any light on the pressure that is expelling from the valve on the top of the boiler?
 
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If you are referring to the PRV ,which is connected to the pipe outside ,that valve will open at around 3 bar ,to relieve the excess pressure ,by allowing water out ,via the pipe to outside. Its doing its job . your issue is what is causing pressure to rise from 1 bar to 3 bar ,in a very short time ,and why is heat rising in boiler in a very short time that is not being distributed through the flow / radiators .a problem with the expansion vessel may contribute to the pressure rise. It may not. The main issue is why is heat not being dispersed. And that needs on site ,skilled diagnosis

Edit ,is the boiler or any central heating pipes in a cellar or other place where freezing is likely near the boiler ? Frozen pipe would prevent circulation
 
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Thanks again Terry - managed to get an engineer so will see what comes next. The central heating pipes are internal with no cellar but are against the outside wall so inlet water pipe is very cold but don't think it's frozen.

Here's hoping something straightforward!
 
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Engineer just away - circulation issue right enough and turns out it was the pump, which they bled & adjusted and now working fine again.

Got a good price for them to replace if necessary and will monitor for now.

Thanks again for taking the time to help! Really appreciate it
 
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Glad your sorted ,really lucky getting an engineer that quick. I am a bit tired now ,so I will e mail my invoice to you tomorrow :LOL::LOL: . by the way if you don't mind me asking ,how much is quote to supply and fit a new pump in Scotland ?
 
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Nice one Cash price for mates, I hope?

Quote was £220 all in parts & labour. How does that stack up with you?
 
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Not bad . British Gas do 200 quid inclusive ,if job can be done in less than 2 hours ,which is ample to fit a pump.that's a one off repair ,no contract and don't have to be a customer of theirs . just to Give you an idea .but they will probably tell you it needs a powerflush !!!!
 
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