Flue thermostat switch

[Central]

We have a log gasification boiler and are trying to eliminate some unnecessary heat losses.

 

The problem is as follows.

 

Boiler runs and heats accumulator tanks to 90C.

 

Boiler runs out of wood and heat demand in the house drops overnight.

 

The pump between the boiler and the tanks keeps running, dumping the heat from the tanks back to the cooling boiler and hence the outside world, until the pump switches off.

 

So we would like to fit a flue fan switch to cut the pump between the boiler and the tanks once the boiler has ran out of fuel or dropped into slumber mode.

 

Are there any negatives to doing this and can someone please let me know the spec of what I need to do it and ideally a parts list, if you have done this yourself already.

 

Thanks in advance

[billt]

I fitted an earlier version of this Laddomat Flue Thermostat for activation of loading valve when I installed my system. (Other makes are available.)

 

No doubt you could make your own with a suitably high temperature sensor, but it's not worth the effort and time.

 

No downsides, but the temperature setting needs to be done carefully.

[openspaceman]

We have a log gasification boiler and are trying to eliminate some unnecessary heat losses.

 

The problem is as follows.

 

Boiler runs and heats accumulator tanks to 90C.

 

Boiler runs out of wood and heat demand in the house drops overnight.

 

The pump between the boiler and the tanks keeps running, dumping the heat from the tanks back to the cooling boiler and hence the outside world, until the pump switches off.

 

So we would like to fit a flue fan switch to cut the pump between the boiler and the tanks once the boiler has ran out of fuel or dropped into slumber mode.

 

Are there any negatives to doing this and can someone please let me know the spec of what I need to do it and ideally a parts list, if you have done this yourself already.

 

Thanks in advance

 

My boiler cuts the fans 10 mins after flue temperature drops below 50C, pump to accumulator cuts out at 60C (this should be modified so that it stops if accumulator is hotter than boiler water I guess), circulation to building cuts out at 40C. My guess is it all can be done with an omron escn-r2mt-500 but I've never mastered the programming manual. Logic would be IF boiler off and boiler water temp < accumulator temp cut pump else continue pumping.

 

This is something my old boss was good at up in Yorkshire.

[hardtop110]

Laddomat Flue stat here too - works a treat.

 

 

50-300C FLUE THERMOSTAT LADDOMAT BIOMASS LOG PELLET BOILER WOOD STOVE | eBay

 

[hardtop110]

Or you could use one of these - placing the sensor on the flow pipe at the tank end.

 

All-purpose Digital temperature controller with Sensor thermostat 2 Relay | eBay

 

 

I use one to switch on the ch pump and open the valves when the top of the accumulator tank gets to within 5 degrees of the TPR valve opening.

 

Probably worth a punt at only £18

Edited November 25, 2013 by hardtop110
typos

[tcar]

Laddomat Flue stat here too - works a treat.

 

 

50-300C FLUE THERMOSTAT LADDOMAT BIOMASS LOG PELLET BOILER WOOD STOVE | eBay

 

 

I'd second that...it works well on our system.

[New Forest DEAN]

I have an ESBE load unit on my Clearview stove, connecting to a thermal heat store (250ltr accumulator). It won't start to load the tank until the water is the required temperature, which makes for a more efficient, long lasting system.

 

The problem is that it doesn't stop thermo-syphing the wrong way - as the stove cools over night, heat leaks from the tank down the back boiler and is then lost (warm lounge but cool tank). It is controlled by a flue stat.

 

In short, I haven't found the load unit to be very good at controlling this.

 

High or low temperature valves are apparently a better idea?

 

Not sure if this helps, but all info' is good!

[hardtop110]

NFD - have you considered changing the stat in the ESBE load unit? If the syphoning is through the load unit, then a higher temp one may help reduce it. The highest temp stat available is 75 degrees, which may help.

[New Forest DEAN]

Thanks Hardtop (sorry to hijack the thread!)

 

The syphoning tends to drop the tank store by about 20 degs C regardless of where its starts - i.e. tank at 70 last thing at night will be 50 in the morning, 60 down to 40, and so on.

 

I believe the load unit has the 60 deg C setting, which is standard for domestic.

 

Should I change it? presumably this will affect loading the tank as well? - the stove typically on produces hot water at 58 / 60 deg C.

 

Cheers - DEAN

[hardtop110]

Dean - I'm not sure, but they cost peanuts and are easy to change without draining the system, so it might be worth trying a 75 deg C one.