Circulating pump over running when system cooling down

_Brian

Our Solid fuel back boiler stove heats the hot water in the tank and the rads in the house, heating wise it works well..

When the fire dies down the stat is staying on far too long and essentially running the hot water cool again, its very frustrating loosing a tank of hot water.

If I turn the stat higher the water will boil in the stove before the pump kicks in as there is no gravity loop from the stove to the tank.

The band in the stat seems very wide, I know its not an exact science but can I adjust the band in the stat so it switches off quicker on cool down. I appreciate an ammount of a band is good to stop the pump flicking off/on quickly. Do any/all stats allow adjustment inside??

I've discounted puting a second stat on the return line as I think this needs a gravity loop to operate properly..

Any opinions appreciated

jimf

how close to the boiler is your stat fitted

_Brian

jimf wrote: »

how close to the boiler is your stat fitted

10 inches

agusta

_Brian wrote: »

Our Solid fuel back boiler stove heats the hot water in the tank and the rads in the house, heating wise it works well..

When the fire dies down the stat is staying on far too long and essentially running the hot water cool again, its very frustrating loosing a tank of hot water.

If I turn the stat higher the water will boil in the stove before the pump kicks in as there is no gravity loop from the stove to the tank.

The band in the stat seems very wide, I know its not an exact science but can I adjust the band in the stat so it switches off quicker on cool down. I appreciate an ammount of a band is good to stop the pump flicking off/on quickly. Do any/all stats allow adjustment inside??

I've discounted puting a second stat on the return line as I think this needs a gravity loop to operate properly..

Any opinions appreciated

What would happen if you had a big fire on in the stove and then you had a power cut.If it were my stove i would be fitting the gravity loop to the copper cylinder.this would cure your hot water issues too.I know it would cost abit but it would be far safer

_Brian

agusta wrote: »

What would happen if you had a big fire on in the stove and then you had a power cut.If it were my stove i would be fitting the gravity loop to the copper cylinder.this would cure your hot water issues too.I know it would cost abit but it would be far safer

This is one solution, but I'm not ripping through the house for this. The hotpress and stove aren't in any way conveniently located to make this a possibility.

gctest50

_Brian wrote: »

........

If I turn the stat higher the water will boil in the stove before the pump kicks in as there is no gravity loop from the stove to the tank.
...........

best would be to put in a suitable buffer tank or you need to move the tank or the very least, a yoke like this :

http://systemlink.ie/products-59/heat-genie.html

or this will happen sooner or later

_Brian

Lets not loose the run of ourselves... the stove loop has an expansion tank in the loft, small ~5g black tank in the event of power failure the pressure will be released there..

I'm looking for a solution to a nusience problem..

gctest50

put a thermostat on the flue ,


leave the pipe thermostat connected as some effort at fail safe

_Brian

gctest50 wrote: »

put a thermostat on the flue ,


leave the pipe thermostat connected as some effort at fail safe

Thanks..
I'll investigate the idea of the second stat on the flue/similar location, I presume the idea being that when this is cold the fire has gone out and so the pump can be shut off.. when its hot, enable the regular pump/stat combination to pump to the system..

Food for thought..

gctest50

http://www.stovecentre.ie/product.php?id_product=473

jimf

gctest50 wrote: »

put a thermostat on the flue ,


leave the pipe thermostat connected as some effort at fail safe

how would the stat on flue be wired and to achieve what

_Brian

jimf wrote: »

how would the stat on flue be wired and to achieve what

Wired in series with the existing stat would work.
Then only when both stats are "hot" could the pump run.

John T Carroll

_Brian wrote: »

Our Solid fuel back boiler stove heats the hot water in the tank and the rads in the house, heating wise it works well..

When the fire dies down the stat is staying on far too long and essentially running the hot water cool again, its very frustrating loosing a tank of hot water.

If I turn the stat higher the water will boil in the stove before the pump kicks in as there is no gravity loop from the stove to the tank.

The band in the stat seems very wide, I know its not an exact science but can I adjust the band in the stat so it switches off quicker on cool down. I appreciate an ammount of a band is good to stop the pump flicking off/on quickly. Do any/all stats allow adjustment inside??

I've discounted puting a second stat on the return line as I think this needs a gravity loop to operate properly..

Any opinions appreciated

This may sort out your problem. http://www.honeywelluk.com/products/Thermostats/Pipe-Cylinder-Thermostats/L6190/

_Brian

John T Carroll wrote: »

This may sort out your problem. http://www.honeywelluk.com/products/Thermostats/Pipe-Cylinder-Thermostats/L6190/

Interesting.
How do you see this working.

John T Carroll

_Brian wrote: »

Interesting.
How do you see this working.

Because you have an adjustable hysteresis (band), you can move the pump switch off point closer to the switch on point, you dont need the overtemp facility, you may find your local heating suppliers have a simpler and cheaper version just with the adjustable band.
I suppose its nothing as daft as a faulty pipestat, the normal hysteresis on these is probaby around a fixed 5C t0 10C which should be fine for most applications, you can get an idea of this by turning the dial down until it clicks on and turning it up until it clicks off and noting the dialled temperature differences but I assume you have already tried all that jazz.

After re reading your post a few more thoughts.
quote "If I turn the stat higher the water will boil in the stove before the pump kicks in as there is no gravity loop from the stove to the tank."
Because of the above it may be the case that you have to set the stat cut out to a relatively low setting of say 45 to 50C as there is very little water circulating with the pump off so the heat is being transferred by conduction only and even with an actual relatively high stove water temperature of 80 or 90C you are still only seeing 45 to 50c at the stat., if this is the case you would need to have the pump cut out set higher than the cut in which is the opposite to the normal thermostat operation, this could probably be achieved with a couple of NO/NC relays but would need a bit of thought. The first thing that I would suggest is to determine the actual temperature in the pipe at the thermostat location at the cut in point, you can then have a harder think re the proper solution.