Boiler High/Low Temp Control

[Kelster]

Hello,
I'm wondering if anyone has come up with an elegant way to stop/start a boiler fan/pump when the fire has expired? I'm thinking that I can save a lot of heat by disabling the fan when the water temperature drops to say be low 120F.

The way the fan control works now if the boiler is on and not up to set-point (180F), then the fan is enabled. So you build a fire, the fan cycles on/off in response to high limit setpoint, then the fire eventually goes out, but the fan continues to blow cool air through the firebox and cooling the water.

I was thinking I could install a dual setpoint controller with an override button by the front door, so that when you reload the boiler or start a new fire the fan starts and runs until you reach setpoint.

Yes, I'm aware of the obvious safety concerns, but it should be able to be idiot-proofed. I'm Not thinking of winging it here - a Honeywell L8124 dual aquastat or Johnson A350 set-up or similar with an override relay or timer should do the trick.

Any thoughts would be appreciated.

 

[maple1]

My boiler came with a flue stat that starts & stops my loading unit pump. Not sure where you can get them, it's European I think. But you could check with the dealers that advertise on here. My whole boiler setup came from Smokeless Heat - not sure if they sell those stats separately, but you could ask them. Or the other dealers.

I actually added more control to it, by running the loading unit power through a L4006 aquastat first. It has an A side & B side. Forget the specifics, but normal use is say the A side - which goes through the flu stat for control. But then if the boiler gets up to the aquastat set point (say 195), it switches to the B side which is direct to the loading unit. That would start the circ if something bad happened to the flue stat & it didn't happen to start the circ & the boiler got too hot. I'm controlling a circ, and you're controlling a fan, so there's some differences, but a flue stat should help. Might be other ideas coming from others....

 

[mustash29]

A few folks did this a few years ago. Search around for "end of burn draft fan shutdown" etc.

https://www.hearth.com/talk/threads/snap-disk-to-cut-off-fan.135530/

https://www.hearth.com/talk/threads/end-of-burn-draft-fan-shutdown-control.73405/