Puma 100e Frost Thermostat Problem

28 Mar 2003
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United Kingdom
My Puma 100e is fitted in the garage and when the temperatue drops low enough the boiler comes on and stays on. I read the manual which says that it should run until the system water has been raised by 10C but mine just seems to run and run until i switch the power off. This happened a few weeks ago when we had a cold few days but was ok again when the weather improved. Yesterday it has started doing it again.
Do I need a new frost thermostat or is there another answer.
Thanks for your help.
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How does a frost stat know the water temperature has raised 10 degrees?, it measures the air temperature same as a room stat.
The frost stat should be sited very close to the boiler and slightly above it
also check setting of stat (many of these are set far to high)

You could try fitting a low limit pipe stat on flow pipe. This is then wired in series with the frost stat. The frost stat will still bring the boiler on when it falls below the set temperature but when the boiler warms up the pipe stat will detect a rise in temperature and will turn boiler off a lot quicker than frost stat on its own.
honeywell make frost protection kit K42008628-001
I thought the frost stat was inside the boiler - I don't think I have an external one. I might just replace it (about £6) and see if it helps.
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i have that potty boiler the frost stat is inside (look at page 17 of manual)
sorry but I took it that you had an external frost stat :confused:
I agree it does sound like faulty internal frost stat
you could try disconnecting one of connections on the stat when it next occurs just to confirm

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