My 10 year old gas CH system has gone on the blink.
The boiler fires up fine on the Hot water mode, but does nothing when I try run the CH. Any clues as to what this utter novice should attempt next TIA
My 10 year old gas CH system has gone on the blink.
The boiler fires up fine on the Hot water mode, but does nothing when I try run the CH. Any clues as to what this utter novice should attempt next TIA
JP explained on 25/12/2006 :
If you have a two port valve, that being stuck would be the most likely cause. If it is an old type room thermostat, check that clicks over at the appropriate temperature. Check the time clock is showing on for heating.
the damn thing has started working! Mystified but happy
>
An awful lot depends on the design of the system, and exactly what components it has in it.
But, seeing as it's Christmas, I'll take a flyer and go for the most likely cause. I'm going to guess that you've got a fully pumped Y-Plan system with a 3-port mid-position motorised valve which directs the hot water from the boiler either to the indirect coil in the HW cylinder or to the radiators or to both at the same time. If I'm right, you have a problem with the valve - or more likely with the actuator (the electrical bit) - which is failing to move away from the HW position. Once the HW demand is satisfied, if the valve doesn't move to either the mid or CH position, the boiler won't come on because it's a microswitch in the actuator which actually switches it on. So, my diagnosis - starting with the most likely - but based on very little information(!) is:
Clearly, you'll have to sort out the valve and/or stat, but to get some heat in the meantime do the following:
The system will then run and will attempt to heat the HW to the cyl stat setting - which it won't be able to do - BUT the radiators will get hot - albeit not quite so hot as usual.
JP presented the following explanation :
Sticking valve it is then :-)
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