S Plan with Stove + Controls

[aesmith]

The valves and stats don't seem to be in the same locations, if I follow correctly.

The design decision for the OP is whether the stove, or the boiler takes precedence. Then the right interlocks need to be in place.

In particular that N/O valve in the gravity circuit return is a concern, it needs to be open any time the stove's burning irrespective of what the rest of the system is doing. So that can't just be closed when the boiler's running. Nor do I think it can be controlled by the stat on the return, unless that is set really low - in which case it wouldn't be correct to inhibit the heating pump until the gravity circuit's up to temperature. I'm thinking you may need a separate stat for the purpose, and it would need to be somewhere where pumped flow from the boiler wouldn't influence it.

 

[Hants-Spark]

Thanks again for the info, it is pretty much the same as I'd drawn with minor changes to suit the system I'm doing so hopefully it should be ok, you've both been a great help, cheers.

 

[Hants-Spark]

The valves and stats don't seem to be in the same locations, if I follow correctly.

The design decision for the OP is whether the stove, or the boiler takes precedence. Then the right interlocks need to be in place.

In particular that N/O valve in the gravity circuit return is a concern, it needs to be open any time the stove's burning irrespective of what the rest of the system is doing. So that can't just be closed when the boiler's running. Nor do I think it can be controlled by the stat on the return, unless that is set really low - in which case it wouldn't be correct to inhibit the heating pump until the gravity circuit's up to temperature. I'm thinking you may need a separate stat for the purpose, and it would need to be somewhere where pumped flow from the boiler wouldn't influence it.

From what the heating engineer has said, the valve needs to be open at all times unless the boiler is running, except when the low level stat operates and closes it to prevent cool water being pumped through the stove. Does this go along with what your thinking??

 

[aesmith]

From what the heating engineer has said, the valve needs to be open at all times unless the boiler is running, except when the low level stat operates and closes it to prevent cool water being pumped through the stove. Does this go along with what your thinking??

Not quite. If this was a pure solid fuel system, the low level stat on the return would inhibit the heating pump, but not the gravity circuit. The gravity circuit is needed any time the stove's lit, otherwise there's no where for the heat to go, and without flow I'm not sure you could rely on the stat on the return closing.

 

[Hants-Spark]

If I'm understanding you correctly the high level will deal with any heat build up, once the h/l stat operates it shuts the boiler off, if running, opens the heating valve and runs the pump or am I misunderstanding you?

 

[aesmith]

I think I see what you mean. If I understand you correctly the sequence would be ... heating running from boiler, so the N/O valve is closed by the interlock from the boiler controls. Now someone lights the stove. There's no gravity circulation because that valve's closed, so heat builds up in the stove boiler. If your high level stat is close enough to the stove it will receive this heat as well, and close. This breaks the link to the low level N/O valve which then opens and allows circulation through the stove.

That could work as long as that high level stat does in fact sense the stove boiler temperature when there's no flow.

Solid fuel operation only you want the pump be operate only when the gravity return (low level stat) is up to temperature.

 

[Hants-Spark]

You've got it in one, thanks for all the input its been a great help.

 

[PEG]

I think I see what you mean. If I understand you correctly the sequence would be ... heating running from boiler, so the N/O valve is closed by the interlock from the boiler controls. Now someone lights the stove. There's no gravity circulation because that valve's closed, so heat builds up in the stove boiler. If your high level stat is close enough to the stove it will receive this heat as well, and close. This breaks the link to the low level N/O valve which then opens and allows circulation through the stove.

That could work as long as that high level stat does in fact sense the stove boiler temperature when there's no flow.

Solid fuel operation only you want the pump be operate only when the gravity return (low level stat) is up to temperature.

Hi,just crossing the tees'...just ensure that NO valving,manual or electric ,restricts circulation. This can be assisted or biased,but never restricted.

The default position,regardless of setting,malfunction or electrical mishap,should always allow gravity operation and dumping of output.

I have come across many systems,where boiler stoves have been shoe'd in,and things are groovy,till a fuse blows,or a pump/valve fails...and then it's thunder time...:tounge_smile:

 

[Hants-Spark]

Thanks for the input PEG