my first point was this, please explain as i am trying to understand !! - say the stat has just failed of its own accord, no scale, etc - how would it get to 100 and pump over, wouldn't the room stat break the circuit before boiler stat temp anyway, hence the point of a room stat??
Boiler stat failure? how?
- Thread starter reneel
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i meant what agile was saying about having the pressure set higher at the burner pressure than was required, range rated boilers.No, a boiler stat failure is quite simply a boiler stat that's failed.
There's many reasons the water will boil and vent to atmosphere, (it doesn't pump over when it boils)
Scale, pump, mv, closed circuit, and even no by-pass valve can cause boiling.
The room stat has nothing directly to do with the boiler temperature, it senses the room temperature, and shuts the system down at a set temperature, to do that the radiators have to loose heat into the room first, in the meantime the poor boiler is roaring away uncontrolled.
ok thanks for your help. sorry for sounding annoying.
when water boils though in an o/v system it does usually pump over, a classic sign, and then the cold feed replaces lost water, and in 5 mins or so, the process repeats itself in a cycle.
when water boils though in an o/v system it does usually pump over, a classic sign, and then the cold feed replaces lost water, and in 5 mins or so, the process repeats itself in a cycle.
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Nothing to do with the operation of the boiler stat.
Some larger industrial boilers, require a shunt pump to dissipate the heat quicker, or they will lock out through over heating, but that is not connected to the boiler stat, but simply a case of not being able to get the heat away quick enough.
that's what i meant anyway, same thing really though.
Can i just say though: when the room stat is making and calling for heat, the boiler stat at that time is close/making too, and when the room stat (if set at he usualy 21 etc, breaks (is satisfied) the boiler stat is still closed (making) as it set higher. so even if the boiler stat was stuck in the on position, it wouldn't be noticed/make any difference surely... as the room stat breaks the switched live to it anyhow.
Can i just say though: when the room stat is making and calling for heat, the boiler stat at that time is close/making too, and when the room stat (if set at he usualy 21 etc, breaks (is satisfied) the boiler stat is still closed (making) as it set higher. so even if the boiler stat was stuck in the on position, it wouldn't be noticed/make any difference surely... as the room stat breaks the switched live to it anyhow.
You still don't understand.
Lets say it takes the radiator 60minutes to heat the room enough for the room stat to shut the boiler down.
By the same token it will take the boiler to cut out with its stat maybe 6minutes, and another minute to boil if it doesn't.
Lets say it takes the radiator 60minutes to heat the room enough for the room stat to shut the boiler down.
By the same token it will take the boiler to cut out with its stat maybe 6minutes, and another minute to boil if it doesn't.
ok, sorry about this, i'm not doing it on purpose i promise.
so basically, for example, the room stat say takes an hour to heat up the room to temp, but during this hour, the boiler stat will reach temp and shut down/main solenoid in gas valve close, etc and re-open quite afew times.... and hence if stuck in the on/closed position, boiling will occur? is this why you hear the boiler's gas valve main solenoid open and close, like a clikcing noise, quite often with the htg/hw on??
so basically, for example, the room stat say takes an hour to heat up the room to temp, but during this hour, the boiler stat will reach temp and shut down/main solenoid in gas valve close, etc and re-open quite afew times.... and hence if stuck in the on/closed position, boiling will occur? is this why you hear the boiler's gas valve main solenoid open and close, like a clikcing noise, quite often with the htg/hw on??
Yes, the boiler will reach temperature and turn off, as the return water cools the boiler it will fire up again, and keep repeating the cycle.
Picture a 3Kw rad heating the room stat, V a 30 Kw boiler heating a boiler stat, which would you imagine would win.
Picture a 3Kw rad heating the room stat, V a 30 Kw boiler heating a boiler stat, which would you imagine would win.
thanks for your help. i feel embarrased now for not knowing this of course a boiler stat can fail without another system fault!! it's so basic!! i'm just trying to learn about boilers as they interest me. i've done some basic jobs in my house and for family, and diagnosed faults using a multi-meter, etc on mv's/pumps/cyl stats/programmers/trvs etc but never a boiler, as you probably have gathered
thanks again for your help.
of course a boiler stat can fail without another system fault!! it's so basic!! i'm just trying to learn about boilers as they interest me. i've done some basic jobs in my house and for family, and diagnosed faults using a multi-meter, etc on mv's/pumps/cyl stats/programmers/trvs etc but never a boiler, as you probably have gathered thanks again for your help.
sorry, one more boiler stat question whilst i'm thinking of it
there are 2 wires to the stat phial, the sl in and the return to the main solenoid correct?
when you turn the dial/knob to increase/decrease the boiler stat setting/range, how does this open/close the contacts closer/further apart in the phial? is there a 3rd lead to it from the dial?
there are 2 wires to the stat phial, the sl in and the return to the main solenoid correct?
when you turn the dial/knob to increase/decrease the boiler stat setting/range, how does this open/close the contacts closer/further apart in the phial? is there a 3rd lead to it from the dial?
No, only sometimes always.
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