Thermostat for stove back boiler

bbam

Hi guys..
Quick question on setting a stove thermostat..

We have a backboiler stove as part of our heating system. Runs through one of the triple coils in our tank - fairly standard setup.

I have a question on setting the thermostat for the circulating pump. I currently set it by trial and error, moving a bit further up and trying, went to a stage where you could just hear water boiling in stove before it kicked in.. dialled it back a bit from that. So it works well, light a fire - stove heats up - pump kicks in and heats water and rads..

My problem is with the cool down phase.. I find that the pump runs quite a long time after the fire has gone out and the water is cooling. The problem is it tends to drain back the heat in the hot water into the circulating water in rads..

the result is that the morning after the stove is lit there is less hot water than if I'd had the oil heating on or after a sunny day with the solar runing.

Its a type of over run I suppose... I know another person with a similar problem..

Sorry for long description of the problem...

There seems to be too wide a band between the on & off setting in the thermostat, and it doesnt seem adjustable.

Any ideas how to prevent this over run on the circulating pump ?

dugger

bbam wrote: »

Hi guys..
Quick question on setting a stove thermostat..

We have a backboiler stove as part of our heating system. Runs through one of the triple coils in our tank - fairly standard setup.

I have a question on setting the thermostat for the circulating pump. I currently set it by trial and error, moving a bit further up and trying, went to a stage where you could just hear water boiling in stove before it kicked in.. dialled it back a bit from that. So it works well, light a fire - stove heats up - pump kicks in and heats water and rads..

My problem is with the cool down phase.. I find that the pump runs quite a long time after the fire has gone out and the water is cooling. The problem is it tends to drain back the heat in the hot water into the circulating water in rads..

the result is that the morning after the stove is lit there is less hot water than if I'd had the oil heating on or after a sunny day with the solar runing.

Its a type of over run I suppose... I know another person with a similar problem..

Sorry for long description of the problem...

There seems to be too wide a band between the on & off setting in the thermostat, and it doesnt seem adjustable.

Any ideas how to prevent this over run on the circulating pump ?

I have 2 thermostats on the pipe coming out of boiler, 1 operates the pump and the other operates a motorised non-return valve, If you set the non-return valve slightly lower then it opens before the pump kicks in and when fire is out it shuts keeping most of the heat in the rads

bbam

dugger wrote: »

I have 2 thermostats on the pipe coming out of boiler, 1 operates the pump and the other operates a motorised non-return valve, If you set the non-return valve slightly lower then it opens before the pump kicks in and when fire is out it shuts keeping most of the heat in the rads

Thanks..
Is there not a danger if you have a power failure that the non-return closes and serious pressure builds up in the system..

I doubt I'll go to the bother of installing it now.. problem isn't serious, more of an irritation.

Iderown

Maybe the best that you can do is to be certain that the stove is heating the lowest internal coil in the hot water cylinder. With that arrangement the bulk of the heated water in the cylinder will be above the stove heating coil.

Dtp1979

bbam wrote: »

Thanks..
Is there not a danger if you have a power failure that the non-return closes and serious pressure builds up in the system..

I doubt I'll go to the bother of installing it now.. problem isn't serious, more of an irritation.

Where exactly is your stat located?
What temp have you it set to?

bbam

Dtp1979 wrote: »

Where exactly is your stat located?
What temp have you it set to?

Two feet from stove. Quite a distance from tank.
Can't remember actual temp but it's just low enough so the water doesn't boil in the stove. If I turn it any higher the water will bubble in the stove boiler and I've been told that isn't good long term.

Dtp1979

bbam wrote: »

Two feet from stove. Quite a distance from tank.
Can't remember actual temp but it's just low enough so the water doesn't boil in the stove. If I turn it any higher the water will bubble in the stove boiler and I've been told that isn't good long term.

For a start the water shouldn't boil in your stove unless maybe all the rads are really hot and the air damper is open too much. Is the top pipe in your stove rising continuously to the cylinder.? This very important

bbam

Nope.
Seems it goes up two floors to the attic and droops back down into the hotpress upstairs where the cylinder is.

The thermostat at the stove is set at 60 degrees.

Dtp1979

bbam wrote: »

Nope.
Seems it goes up two floors to the attic and droops back down into the hotpress upstairs where the cylinder is.

The thermostat at the stove is set at 60 degrees.

And where does the bottom pipe from your stove go?

gctest50

bbam wrote: »

Two feet from stove. Quite a distance from tank.
Can't remember actual temp but it's just low enough so the water doesn't boil in the stove. If I turn it any higher the water will bubble in the stove boiler and I've been told that isn't good long term.

A stat to turn it off when it gets too low needed as well ?

http://www.ebay.co.uk/itm/Honeywell-L641B1004-Low-Limit-Pipe-Control-Thermostat-/180411507840

bbam

Dtp1979 wrote: »

And where does the bottom pipe from your stove go?

Down from cylinder different route to hot from stove. . Under ground floor and back up near stove and then into stove.

whizbang

You need a differential thermostat. Two probes, one inlet, one outlet, Switches pump on only when out higher than in.

But you might have another problem with the plumbing. Maybe a NRV will help anyway.

bbam

whizbang wrote: »

You need a differential thermostat. Two probes, one inlet, one outlet, Switches pump on only when out higher than in.

But you might have another problem with the plumbing. Maybe a NRV will help anyway.

thanks..
Ill check that out..

Panel mac

bbam wrote: »

thanks..
Ill check that out..

Hey. Jus wonder on did u get this sorted I hav same problem. Not much hot water on the mornin. And my pump seems 2 be runnin wen the fire is gone out.