New Harman 300i Not Throwing Out Enough Heat

Feb 17, 2015
74
Baltimore
Hello fellow Hearth members,

I recently had a wood burning insert installed in my family room, which is about 15'x20' with vaulted ceiling. It's not the ideal room design, so I chose the Harman 300i since it is designed for larger sized living space. I have a 2 level colonial with 3620 sq ft. living space with an additional 1500 sq ft. of finished basement. I'm looking to heat the main area of the living space on the first floor, which is roughly 1700 sq ft. The area connected to the family room is open space kitchen and I've been running the insert and medium-high for past 4-5 hours, yet the thermostat on the other side still read a chilly 60 degrees. The outside temperature is about 18 degrees.

I've been following the instruction on how to properly start a fire and maintaining a hot coal bed. I close the damper and let the AB kick-in. After 5 minutes, I looked outside my chimney and no smoke visible, so I know that my AB is working, but still my insert is not throwing out a lot of heat. I can stand a few feet in front of the blower vent and not feeling too hot, while across the family room about 15 feet away is still chilly. My firewood is dry and seasoned oak/locust, which is measured at about 8-12% moisture. It's been season at least a year and 1/2. The chimney is 28' tall and was connected via SS liner, it appears that I have proper draft and plenty of ventilation.

I've read a few Harman owners stating that they can heat their entire house of 2000 sq ft. of space with external temperature at lower than single digits and they couldn't be in the same room with the stove/insert. I'm wondering if there is something I'm doing wrong or perhaps there is a defect in the equipment or installation.

Any advice is greatly appreciated. Thank you. A New Harman Owner Trying to Stay Warm
 
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begreen

Mooderator
Staff member
Nov 18, 2005
78,033
South Puget Sound, WA
Welcome. Is this an exterior chimney? Is yes, did they install a proper, insulated block-off plate in the damper area?

Tell us a bit about the wood being burned. When was it split and stacked? What species wood?
 
Feb 17, 2015
74
Baltimore
Welcome. Is this an exterior chimney? Is yes, did they install a proper, insulated block-off plate in the damper area?

Tell us a bit about the wood being burned. When was it split and stacked? What species wood?
The chimney is partially inside the room, with part of it exterior. With regard to install a proper insulated block-off plate in the damper area, I'm not certain if that was done, but I do know that they capped it at the top of the chimney; whereas, I used to feel cold draft coming down from the fireplace when fire is not lit, but no longer the case.

The wood being burned is seasoned Oak/Locust, split about a year and half ago and stacked.

I'll upload a picture of the fireplace/insert along with exterior shortly. And I'll also upload a picture of the wood as well.

Thanks for your help.
A new Harman owner trying to stay warm
 
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begreen

Mooderator
Staff member
Nov 18, 2005
78,033
South Puget Sound, WA
An insulated block-off plate will make a difference. It will keep the heat around the stove instead up the chimney. That will reduce heat loss from the convection jacket surrounding the insert. It would be good to test some of the wood for moisture with a moisture meter. The wood should be room temp and tested on a freshly exposed face of the wood, not end grain. If you don't have a tester, resplit some of the thicker pieces of wood and put the freshly exposed surface of the split up against your cheek. If it feels cool and damp, it is. If you have a moisture meter, the wood should be reading less than 20% moisture.
 
Feb 17, 2015
74
Baltimore
An insulated block-off plate will make a difference. It will keep the heat around the stove instead up the chimney. That will reduce heat loss from the convection jacket surrounding the insert. It would be good to test some of the wood for moisture with a moisture meter. The wood should be room temp and tested on a freshly exposed face of the wood, not end grain. If you don't have a tester, resplit some of the thicker pieces of wood and put the freshly exposed surface of the split up against your cheek. If it feels cool and damp, it is. If you have a moisture meter, the wood should be reading less than 20% moisture.
I'll verify the insulated block-off plate with the installation people/company. With regard to the wood, I do use the moisture meter regularly to test the wood on both end and face of the wood. And from time to time, I would split a piece of larger wood to test the moisture content of the wood as well. I think I trust the wood more so than I do with the installation or perhaps my own operational knowledge, but based on given evidence, the lack of smoke in the chimney and relatively long burn time of the wood. I think the AB is working properly. The only lacking is all that heat I am suppose to get.

Any other thoughts are greatly appreciated
A new Harman owner trying to stay warm.
 

branchburner

Minister of Fire
Sep 27, 2008
2,755
southern NH
I've been running the insert medium-high for past 4-5 hours
In addition to the possibility of masonry heat loss via an exterior chimney (or up a chimney with no block-off) you could be losing a lot of heat up the flue by running the stove with lots of primary air. Do you have a way of measuring flue temps?

When it is extremely cold out, my system drafts very well. After a reload, before I close the bypass, internal flue temps run over 1000f. They quickly drop when I close the bypass, then drop further when I step back the primary air to about 1/4. My external flue temps might then run 200-300f for hours measured a foot up from the stove (meaning internal of 350-500f?).

But if I leave the primary air 1/2 open or more, external flue temps might then run 300-500f (meaning internal of 500-900f?). That's a hot flue, with a lot of heat loss.

These stoves run hot and draft hard when its cold out. I suspect sometimes when I see no smoke but have very high flue temps I am not actually getting an ideally efficient secondary burn in the AB chamber. The stove is efficient in terms of particulate, but not in terms of heat transfer to the house.

Consider, you can also burn virtually smoke-free if you leave the bypass open and overfire the stove! The fire would be very smoky on startup, but soon become so hot that it produced very little smoke. I've been there, done that (by accident), and while the stove was certainly throwing some heat into the room it was also pushing a ton of it up the flue. I'm not saying this is what you are doing, just using as an example of a very hot stove that fails to heat the house.

I suspect you probably have a combination of running the stove with too much air AND losing some heat lo your masonry. BTW, are you loading the stove pretty full, and what kind of burn times do you get with a full load?
 

begreen

Mooderator
Staff member
Nov 18, 2005
78,033
South Puget Sound, WA
We have seen a lot of inserts that have greatly improved their heat output with a proper block off plates. Installers rarely install them because they are time consuming and therefore costly. But they don't pay the heating bills for the house, right?
 

branchburner

Minister of Fire
Sep 27, 2008
2,755
southern NH
I'll verify the insulated block-off plate with the installation people/company. With regard to the wood, I do use the moisture meter
The other question BeGreen posed could be critical: is the chimney on an exterior wall and exposed to the outdoors, or in the interior, fully contained within the house?
 

begreen

Mooderator
Staff member
Nov 18, 2005
78,033
South Puget Sound, WA
Sounds like an exterior wall chimney. Pics are coming.
 
Feb 17, 2015
74
Baltimore
So here is the picture of chimney inside.
 

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prezes13

Minister of Fire
Jan 12, 2014
910
Connecticut
The other thing is when you get the stove going is the house warm or cold? It takes a while for the stove to establish. If it's really cold and house was cold to begin with it might take 2-3 burn cycles to warm everything up.
 

branchburner

Minister of Fire
Sep 27, 2008
2,755
southern NH
is the chimney on an exterior wall and exposed to the outdoors, or in the interior, fully contained within the house?
Sorry for repeating the question after you answered... you post hasn't shown up on my screen when I was typing.

Looking at your pic, I am guessing all the brick expose to the outside cold is acting as a giant heat exchanger, helping transfer heat produced by the insert to the great outdoors. This could be a factor even with a block-off plate, but would be MUCH worse without one.

In addition to asking about the block-off (I assume there is none) ask if there is any insulation of the fireplace itself, behind the stove. One thing worth noting about Harmans is that the secondary burn takes place in the rear of the stove, so their inserts really depend on the blower moving that heat out. Obviously whatever heat is being lost to the masonry/outdoors cannot be transferred by the blower.

I'm not saying this to be cruel, just honest, but if you had a free-standing Harman sitting on an extended hearth out in the living space, you'd be very toasty.
 

branchburner

Minister of Fire
Sep 27, 2008
2,755
southern NH
That wood looks great, should be heating you up. I fear it is the installation that's the problem.
 
Feb 17, 2015
74
Baltimore
I'm not saying this to be cruel, just honest, but if you had a free-standing Harman sitting on an extended hearth out in the living space, you'd be very toasty.
The problem with that is I have two young daughters, 5 and 2, which I don't feel safe to have a free standing stove in an area where they play. It's just a personal preference thing.
 
Feb 17, 2015
74
Baltimore
The other thing is when you get the stove going is the house warm or cold? It takes a while for the stove to establish. If it's really cold and house was cold to begin with it might take 2-3 burn cycles to warm everything up.
The house was warm, about 70 degrees with outside temperature at about 18-22 degrees. The insert itself was brand new installed on the 16th, so I would say it is cold stove.
A New Harman Owner trying to stay warm
 

begreen

Mooderator
Staff member
Nov 18, 2005
78,033
South Puget Sound, WA
That's a large mass of masonry exposed to the outdoors. An insulated block-off plate will raise the output temperature significantly. If there is room, slipping some non-combustible insulation board behind the insert will also help.

The other issue is the room design. Get on a ladder and measure the temp up high near the peak. I think that is where a lot of the heat is. Do you have a ceiling fan running in reverse in this room?
 
Feb 17, 2015
74
Baltimore
That's a large mass of masonry exposed to the outdoors. An insulated block-off plate will raise the output temperature significantly. If there is room, slipping some non-combustible insulation board behind the insert will also help.

The other issue is the room design. Get on a ladder and measure the temp up high near the peak. I think that is where a lot of the heat is. Do you have a ceiling fan running in reverse in this room?
So pardon my ignorance, but where would the insulated block-off plate be placed? I'll check with the installers to see if there is room in the back for non-combustable insulation board, but can't tell right now given the current installation.

With regard to the temperature, even with the fan running, I'm not getting any heat at the sofa 15' directly in front of the blow, I'm not sure that overall heat output is there, which is what I fear.
A New Harman Owner trying to stay warm
 
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begreen

Mooderator
Staff member
Nov 18, 2005
78,033
South Puget Sound, WA
We saw this same issue with the same type ceiling just a few weeks back. Heat was pocketing up high. Is there a ceiling fan running in the room?

A block-off plate will help improve stove output. Here's a wiki article on block-off plates with thread links at the end.
https://www.hearth.com/talk/wiki/why-damper-seal-is-needed/
 
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prezes13

Minister of Fire
Jan 12, 2014
910
Connecticut
If you stand right in front of the stove with the blower fan on do you feel a stream of hot air going up?
 
Feb 17, 2015
74
Baltimore
If you stand right in front of the stove with the blower fan on do you feel a stream of hot air going up?
I can literately stand a foot or two away from the blower and not have to shy away due to heat, even though I have a have a full hot bed of ember and three large pieces of dry locust wood in it. I am not sure where is the heat going in an enclosed insert. I'll check the masonry at the outside of the house, but I doubt that the heat would be trapped there.

Quite lost at this time.
 

bluedogz

Minister of Fire
Oct 9, 2011
1,247
NE Maryland
Just for kicks, I live in North East... wouldn't mind popping over there to point out what they're talking about. You buy the coffee.
 
Feb 17, 2015
74
Baltimore
The ceiling fan is running along with any other fan I can think of to circulate the air.

Just for kicks, I live in North East... wouldn't mind popping over there to point out what they're talking about. You buy the coffee.
Sure, stop by anytime. Although it's a long drive from where you are.

On a side note, I put up a picture of how the chimney looks from outside, and there is a wrought iron grate, which I can open and look within, which is the back of firebox itself. I reached in and felt the bricks are slightly warm to the touch. Not sure what that indicates, but something interesting.