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My Potterton 80e often doesn't start up anyone know why?

My Potterton 80e gas central heating and hot water boiler often won't fire up on its own .

We tend to have the Honeywell timer control set to Continuous in winter, and run the hall thermostat at 20degress, and turn it down when we go to bed to about 16 degrees; until a couple of weeks ago, the boiler would turn itself off and on, as it should, but recently it stopped firing up during the night, with the reseult that the house was cold when we got up at around 7 a.m. The hot water timer is set to come on at 0630, and this also isn't working.

The boiler starts when I press the reset/manual startup (?) button underneath it, and generally works and gets the heating up to temperature, but once it's got there (and it doesn't get there every time), it often won't start up again on its own, when the temperature drops below the 20 degrees (or 16 at night). Hot water is fine too when I do a manual start up.

Initially I thought it might be an overheat problem, we found some coolspots on some radiators and have flushed and balanced the rads, so that when the boiler is working, the rads are ok. But I don't think it can be an overheating problem as the boiler fails to start at night or during the day when the room temperature drops below the temp set on the hall thermostat, and its clear that the boiler hasn't run for hours overnight - probably since turning the hall stat down from 20 to 16.

Anyone got any ideas please?

Many thanks in advance - Neil
Neil, March 2010
Hi Peccavi
Many thanks for your answer and clarification of my term "reset switch".
I will pass on your suggestions to my engineer.
Thanks again - Neil

Neil, March 2010
Hi Peccavi
Many thanks for your answer and clarification of my term "reset switch".
I will pass on your suggestions to my engineer.
Thanks again - Neil

Neil, March 2010
its time to put on make up, its time to light the lights, its time to meet the muppets on the muppet show tonight, combi systems are not as prone to sludge as open vented systems, so provided it was cleaned before installation i would go straight for a new pump to solve this problem

kermit, March 2010
I am an unqualified muppet with respect to boilers so my advice is useless.

On my Potterton Profile 100e the button you refer to as the "reset/manual startup" is the Overheat Thermostat which may trip-off if the pump is not moving water from the heat exchanger quickly enough.

Your boiler seems also to have another fault - when there is no call for H/W and just a requirement for C/H (during the night) the boiler fails to fire up. In this specific condition the signal to turn the boiler on (call for heat / switched live) comes from a microswitch in the Motorised Valve (Mid Position Valve) on the orange wire. The switch may be defective - it happens on my own system from time to time.

http://www.gasheating.co.uk/Mid-Position-Valve.html

But again I must stress that I know nothing - your heating engineer will be able to help you better than I can.

Good luck...

Peccavi, March 2010
link Click here to see other fixes for Potterton.