Strange question about wood heat as compared to electric heat pump

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Aug 12, 2020
86
Parkers Lake, KY
We've been using a Hardy H2 here at "the bunk house" to heat the property since we've moved in as caretakers. It's a new experience for us; learning about wood, building fires, feeding the furnace etc. I like the concept but have never had the opportunity to heat with wood before. This practical application of self reliance resonates strongly with me on many levels that the amount of labor required equals the motivation to save money and being independant.

However, we have experienced something that I consider very strange so I wanted to come here to y'all whom I consider experts ask my question. When we moved in, we immediately set the thermostat on the electric heat pump system to warm the house and went about cleaning and wood gathering. That was months ago and we've managed to amass a wood pile that included oak, pine, hemlock, maple etc. Some of our wood is running about 21% moisture content on my moisture meter and we've burned through all that was below 20% MC.

Here's the thing: once we fired the Hardy, both my wife and I, separately from each other thought privately that the wood heat feels warmer. The is the strange thing because the Outside Wood Burner is using the same forced air fan system to deliver the heat and the same thermostat setting to regulate the temperature. We've discussed this concept of feeling warmer while the wood is burning and agreed between us, much to our surprise, that we both thought the wood heat "felt" warmer. Let me clarify that I'm not talking about how fast the heat is delivered or the identical thermostat setting but the sense of feeling warmer on your bare toes while sitting in front of the television.

This situation was the focus of discussion again this morning. Last evening I decided to "idle" the OWB and let the fire go out. We switched the heat pump on and turned the circuit breaker off for the OWB, expecting the the fire would go out and I could complete a major cleaning sometime in the next week or two. This morning, I was standing over a vent feeling the cool air on my feet being pumped into the house from the heat pump. While standing there looking out the window at the last vestiges of snow in shadow of the trees and the new frost on the ground from our over night temperature of 25°, I noticed that there was still smoke puffing from the exhaust stack of the Hardy. "WTF" I turned that thing off. Why was it still smoking? More importantly, how was it still smoking? I flipped the breaker back on, reset the thermostats to call for heat from the OWB and the smoke started rolling out of the stack in a big way! The fire was still burning and the air from the vent IMMEDIATELY felt much warmer on my feet. I went outside to check the fire box to find the bed of coals still smoldering and I stirred the remaining wood in the burn chamber and added another new piece of oak and AWAAAAAY she goes; burning in a big bright energetic flaming fire. I was amazed and the Hardy was ablazed.

So, we're back on the OWB but I wanted to ask, WHY does this "feel" warmer? Same fan, same thermostat setting, same ductwork...I just can't figure out why it would feel different.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,642
central pa
We've been using a Hardy H2 here at "the bunk house" to heat the property since we've moved in as caretakers. It's a new experience for us; learning about wood, building fires, feeding the furnace etc. I like the concept but have never had the opportunity to heat with wood before. This practical application of self reliance resonates strongly with me on many levels that the amount of labor required equals the motivation to save money and being independant.

However, we have experienced something that I consider very strange so I wanted to come here to y'all whom I consider experts ask my question. When we moved in, we immediately set the thermostat on the electric heat pump system to warm the house and went about cleaning and wood gathering. That was months ago and we've managed to amass a wood pile that included oak, pine, hemlock, maple etc. Some of our wood is running about 21% moisture content on my moisture meter and we've burned through all that was below 20% MC.

Here's the thing: once we fired the Hardy, both my wife and I, separately from each other thought privately that the wood heat feels warmer. The is the strange thing because the Outside Wood Burner is using the same forced air fan system to deliver the heat and the same thermostat setting to regulate the temperature. We've discussed this concept of feeling warmer while the wood is burning and agreed between us, much to our surprise, that we both thought the wood heat "felt" warmer. Let me clarify that I'm not talking about how fast the heat is delivered or the identical thermostat setting but the sense of feeling warmer on your bare toes while sitting in front of the television.

This situation was the focus of discussion again this morning. Last evening I decided to "idle" the OWB and let the fire go out. We switched the heat pump on and turned the circuit breaker off for the OWB, expecting the the fire would go out and I could complete a major cleaning sometime in the next week or two. This morning, I was standing over a vent feeling the cool air on my feet being pumped into the house from the heat pump. While standing there looking out the window at the last vestiges of snow in shadow of the trees and the new frost on the ground from our over night temperature of 25°, I noticed that there was still smoke puffing from the exhaust stack of the Hardy. "WTF" I turned that thing off. Why was it still smoking? More importantly, how was it still smoking? I flipped the breaker back on, reset the thermostats to call for heat from the OWB and the smoke started rolling out of the stack in a big way! The fire was still burning and the air from the vent IMMEDIATELY felt much warmer on my feet. I went outside to check the fire box to find the bed of coals still smoldering and I stirred the remaining wood in the burn chamber and added another new piece of oak and AWAAAAAY she goes; burning in a big bright energetic flaming fire. I was amazed and the Hardy was ablazed.

So, we're back on the OWB but I wanted to ask, WHY does this "feel" warmer? Same fan, same thermostat setting, same ductwork...I just can't figure out why it would feel different.
My guess is the vent temps run higher with the owb than with the heat pump. Ultimately the room will get to the same temp. But the air moving will be warmer so it will feel different.
 
  • Like
Reactions: tabner

jetsam

Minister of Fire
Dec 12, 2015
5,283
Long Island, NY
youtu.be
It probably IS a lot warmer. A heat pump (if it's in heat pump mode and not using its resistive elements) is going to have a hot side heat exchanger temp of 140°F on a good day. The OWB's is probably a lot hotter when the fire is going.

You then have line loss going inside, so you may see much lower temps than the hot side heat exchanger is at (especially if the lines are just buried without insulation)- but I bet it's still significantly higher than 140 on the indoor side.

If the heat pump gives up and kicks in its resistive mode, it's more of an even match, though, depending how big that heater is.

So that's totally normal, but it's not actually anything to do with burning wood versus electrons, it more speaks to the common perception that heat pumps "blow out cold air" because they have a lower exchanger temp than other traditional heaters.
 
Last edited:
  • Like
Reactions: LiamFitzpatrick

begreen

Mooderator
Staff member
Nov 18, 2005
89,761
South Puget Sound, WA
Add to the above, the out of the register temps with our heatpump system ranges from about 105-125º. Even if the warmed air was only 90ºcoming from the registers, it would still warm up a room, just slower. Now, if the registers are wall-mounted and blow into the room, across the floor instead of floor registers on the outside perimeter blowing upward, you will definitely feel a difference. We just set it and forget it. If we are away for the day and the fire has gone out, when we come into the house it feels warm at 72º. Resistive heat kicks in at 25ºF outside.
 

electrathon

Minister of Fire
Sep 17, 2015
570
Gresham, OR
Dry heat feels warmer. When you get out of the shower and the room is 70 degrees the moisture makes you feel cold. Wood heat is generally more dry than heat pump heat. High moisture in the air makes you feel cooler, the moisture transfers the heat away from your skin faster than the dryness does.
 
  • Like
Reactions: Grizzerbear