Understanding stove efficiency ratings

[mariohere]

I've read several articles about efficiency ratings - EPA, Real-world, etc.. But I can't find a real simple definition besides the amount of heat that ends up in your home as compared to the potential of the fuel (pellets in this case) that was burned.

Sooo... my question is: Can we look at an efficiency rating as simply the amount of heat that goes into your house vs out the chimney? For example, if a stove has an efficiency rating of 75% then does that mean that roughly 25% of the heat goes out the chimney?

 

[Pelleting In NJ]

yes, a 75% efficient stove sends 25% of the heat out through the exhaust, and 75% of the heat into your home.

 

[JRemington]

You want to look at the HHV which is the high heating value for the heat you get into your home.

 

[Highbeam]

Beware of crooked marketing departments that try and invent irrelevant efficiency figures. My favorite is the useless “combustion efficiency” which is of no value. You want to use the total efficiency because heat delivered to the home vs. fuel expended is all that matters.

Now be careful when comparing the total efficiency of your pellet stove to a ducted furnace because the furnace efficiency rating can not and does not account for duct losses which can be 20%! Subtract that 20% from the 95% efficient gas condensing furnace and now you’ve only gotten 75% or less of that energy delivered to your home.

 

[mariohere]

Thank you everyone!

 

[rickwai]

Beware of crooked marketing departments that try and invent irrelevant efficiency figures. My favorite is the useless “combustion efficiency” which is of no value. You want to use the total efficiency because heat delivered to the home vs. fuel expended is all that matters.

Now be careful when comparing the total efficiency of your pellet stove to a ducted furnace because the furnace efficiency rating can not and does not account for duct losses which can be 20%! Subtract that 20% from the 95% efficient gas condensing furnace and now you’ve only gotten 75% or less of that energy delivered to your home.

As long as the ducts are in conditioned space (basement, interior walls ect.) then theoretically there is 0% duct lose, is that right?

 

[Highbeam]

As long as the ducts are in conditioned space (basement, interior walls ect.) then theoretically there is 0% duct lose, is that right?

I would say yes. There is the issue of electrical consumption to pump the air through those ducts but that may be minor and all energy lost to pumping is returned as heat if the ducts are inside.

 

[Panthera]

I have another question on efficiency, more directly related to the pellet stoves. I recently installed a Pel Pro PP60 (cheapest one at Menards) to heat the basement. It works fine, just having it in low mode continuously keeps the basement at 70+ degrees. The stove is not equipped for an external thermostat, but looking at the schematics, it would be very easy to modify it for using one. If modified, It would actually shut down completely when the temps are warm enough, and start up on the thermostat going into high heat mode.

The question would be do pellet stoves generally run more efficient in a low burn mode, or in a higher burn rate mode? I realize some heat get expended out the venting, but as a percentage of available heat, it may actually be less in high mode. In addition, the fans and such would not be running full time with the thermostat option.

Does anyone have any links, or other information for this?

Thanks in advance
Panth

 

[Ssyko]

It would be easyer on the igniter if it ran in high-low mode but your economy might be in on and off mode. Usually stoves set up for a tstat have a secondary program mode to adjust fans for such settings. But yours doesn’t have this ability. So im curious on how you plan to do this.

 

[Panthera]

It would be easyer on the igniter if it ran in high-low mode but your economy might be in on and off mode. Usually stoves set up for a tstat have a secondary program mode to adjust fans for such settings. But yours doesn’t have this ability. So im curious on how you plan to do this.

The control on this is a three wire potentiometer that feeds into the control board. By interrupting the middle wire, the control board will see it as being put into the off mode, and goes into the cool down/shut down cycle. When the thermostat closes, the control board will then see the actual setting on the control potentiometer, and start up again.

You are right, it will utilize the igniter a bunch more this way, as currently it gets used once a day after cleanup. What sort of life does everyone get from igniters?

 

[Pelleting In NJ]

Pellet stoves typically have a higher efficiency when burning at higher burn rates.