Stove fans and exit gas temps

[rashomon]

I've been dialing in my fan speeds to hopefully use the most efficient amount of heat from my stove instead of sending it up the chimney. I don't have a stove top thermometer, but I do have an Flueguard exit gas thermometer the proper height up my double walled pipe from the stove, and my stove came with a catalyst thermometer.

I have a Green Mountain 60 and been aiming for ~400 exit gas temps (on the lower end of the optimal operation temp). My chimney goes straight up double walled the whole way (more info in signature).

The fan noise becomes annoying, but I'm hoping this is the best way to get the most heat from my stove. We had a subzero few days recently and had it cranked as hot as I could but had to fall back on my home furnace to keep us warm.

I do notice the flue gases will dip to ~300+ and into the "too cool" region but my catalyst temps are 1/2 - 3/4 up to "too hot", so I often lower the fan speeds to compensate. I'm surprised my catalyst temps are that hot when the exit gas temps are read barely 2 feet directly above that catalyst?!

Firstly, am I correct in my method using the fan? Regarding having "too cool" flue temps while my catalyst reads over 1/2 way in the optimum zone, does a stove pull that much heat off the flue flange? Or maybe I'm just reading too much into everything.

 

[begreen]

Sounds like you are doing things right. Running a stove is a balancing act sometimes, especially in extreme cold like the Denver area recently saw. Having to run the furnace occasionally during these very cold events is not a bad thing.

 

[rashomon]

Thanks! And so I guess the low flue temps when the catalyst is hot just goes to show the efficiency of the fan pulling away the heat before it escapes the flue collar.

Definitely overthinking but it seems I learn new stuff here everyday!

 

[danrclem]

I just got my new stove and fan not too long ago and using an EPA stove is a lot different than using my old Fisher that didn't have a fan. The temps have raised a lot over the last few days so I tried not using the fan and it seems to help keep the stove hotter with smaller loads.

 

[rashomon]

I just got my new stove and fan not too long ago and using an EPA stove is a lot different than using my old Fisher that didn't have a fan. The temps have raised a lot over the last few days so I tried not using the fan and it seems to help keep the stove hotter with smaller loads.

Would you say your new EPA stove without the fan performs as well as your old Fisher?

 

[danrclem]

Would you say your new EPA stove without the fan performs as well as your old Fisher?

It's really hard to say because the weather was mild when I turned the fan off. In mild weather I'd say that the heating performance was as good as the Fisher. When it was down in single digits and below zero the fan was always running and it did a good job then.

The Fisher Grandpa Bear kept the house warm but I'm pretty sure that it was using more wood.

 

[EbS-P]

So when you run the stove harder with the fan higher to get more heat you need to run flue temps hotter. During the coldest 4-7 days a year efficiency is not a big concern.

 

[stoveliker]

A hotter flue does not necessarily mean a lower efficiency.
Yes, the number of BTUs going up the flue per hour is larger, but the number of BTUs going into your room is too. The ratio of that is the efficiency, and that may stay the same.
(Testing shows it does so for my (cat) stove, and I think that for a tube stove that would even be more the case.)

 

[danrclem]

I do whatever it takes to keep the house warm unless it means not being safe.