potterton boiler with honeywell st6400c


Postby shanfu » Sat Jan 03, 2009 7:15 pm

hi, i have a potterton floorstanding boiler with a honeywell st6400c controller - it has been working fine but lately there is no hw/ch - the boiler fires up for a minute or so and then goes off - even when the lights are on for ch/hw, the boiler does not fire - it makes a noise as if it would fire but then stops dead - i put the timer to on all the time, set the thermostat to highest but still nothing - the other night it lit and stayed on on the whole night, even when there was no on light on the timer - it worked for 1 whole night but swiched off during the day and wont start again - what could it be??????
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Postby stoneyboy » Mon Jan 05, 2009 5:01 pm

shanfu,
Bit confused "the boiler fires up for a minute or so and then goes off" and "even when the lights are on for ch/hw, the boiler does not fire" so does the boiler fire or not? is it gas or oil? have you got a froststat fitted?
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Postby shanfu » Tue Jan 06, 2009 12:16 am

hi, as i said earlier, the boiler actually fires up for about a minute or so add then dies out - about 20 minutes later it will fire up again for another minute or so and then die out - it goes on like this all the time - it wants to start up but something is making it stop - maybe the pump or maybe an air lock?
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Postby plumbbob » Tue Jan 06, 2009 4:55 pm

You have not really given enough info to diagnose a fault but the first thing I would check is to see if the pump is running.
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Postby stoneyboy » Tue Jan 06, 2009 6:39 pm

shanfu,
The fact that the boiler fired overnight would indicate that you have a froststat. These normally bypass all other controls. Try to find it and turn the temperature up (temporary solution)
If you can get at the pump remove the screw on the end and see if the shaft is turning with CH/W on (is it turning?). If you can find a motorised valve try pushing the lever to the open position with CH/W on (is there any resistance?).
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Postby TheDoctor5 » Thu Jan 29, 2009 1:20 pm

If you type the key words of your question into our search box to the left of the site you may find the answer is already posted or is in the DIY projects section of the website. Every post goes through a monitoring process and using the search box may speed up your answer.
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