overheat stat
- Thread starter gk
- Start date
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gk said:
It stops the boiler from functioning in the event of the boiler overheating
Many different methods of operation, depending on the boiler. If there's a permanent pilot light, overheat usually knocks it off, thus ensuring the boiler won't relight. With electroninc ignition it gets a bit more difficult, because the boiler PCB usually has little memory of past events. In some cases, the O-H stat just acts as a backup to the main one (and by being positioned often on the heat exchanger rather than on the internal plumbing is useful for sensing pump not working or other causes of no circulation of water). In these examples, once the boiler has cooled it will try to restart - and of course overheat again.
The relentless and depressing stream of postings in this forum talking about boilers 'banging' or 'sizzling' are most often cases of overheating, where the OH stat is actually preventing the thing going BANG, VERY LOUDLY. It never ceases to amaze me that people are not alarmed by these noises, turn it off and get if properly fixed!
The relentless and depressing stream of postings in this forum talking about boilers 'banging' or 'sizzling' are most often cases of overheating, where the OH stat is actually preventing the thing going BANG, VERY LOUDLY. It never ceases to amaze me that people are not alarmed by these noises, turn it off and get if properly fixed!
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Hi Croydon'
I have come across many installations that use only radiator stats, no room stats. Consequently when the radiators shut down and reduce the circulation the boiler overheats and its stat operates. It irritates me when at my brother in laws to listen to the constant cycling of the boiler on/off.
He tells me that "the man said" is the way it should work now that thermostats have been fitted on all the rads! Personaly I dont like rad' stats' They do stick, and there are are quite a number to keep an eye on. Can't beat a room stat IMHO Regards Flounder
I have come across many installations that use only radiator stats, no room stats. Consequently when the radiators shut down and reduce the circulation the boiler overheats and its stat operates. It irritates me when at my brother in laws to listen to the constant cycling of the boiler on/off.
He tells me that "the man said" is the way it should work now that thermostats have been fitted on all the rads! Personaly I dont like rad' stats' They do stick, and there are are quite a number to keep an eye on. Can't beat a room stat IMHO Regards Flounder
if theres stats on all the rads there should be a bypass on the system
What purpose the bypass? If the rads shut down there is no didipation therefore the mad hot water goes back to the jacket which relies on the overheat stat. hence the constant cycling on/off. IMHO Flounder
IMHO Flounder
the boiler dosent cycle on the overheat stat it cycles on the boiler stat
overheat stat is there if the service stat fails
usually needs a manual reset
overheat stat is there if the service stat fails
usually needs a manual reset
Wrong assumption.
Boiler requires circulation of water to operate properly. For a start, in many combis the CH temp sensor is on a pipe some distance from the heat exchanger. So if there's insufficient circulation, the boiler will overheat before the electronics get any signal to modulate the burner down or switch it off altogether.
So all rad valves shut = no circulation = overheat.
All the bypass does is provide an alternative path. Commnly, it used to be provided by a partly-open gate valve on a fixed pipe between flow and return. Latest regs require pressure-operated valve which only opens when bypass flow is needed. Some boilers include an internal bypass which may require an adjustment.
Boiler requires circulation of water to operate properly. For a start, in many combis the CH temp sensor is on a pipe some distance from the heat exchanger. So if there's insufficient circulation, the boiler will overheat before the electronics get any signal to modulate the burner down or switch it off altogether.
So all rad valves shut = no circulation = overheat.
All the bypass does is provide an alternative path. Commnly, it used to be provided by a partly-open gate valve on a fixed pipe between flow and return. Latest regs require pressure-operated valve which only opens when bypass flow is needed. Some boilers include an internal bypass which may require an adjustment.
fair comment cc but the boiler wont cycle it shuts down
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