Hello, I have been following these boards for quite a while now. Hoping the hive-mind can help me get the new Kuuma running to its full potential. I upgraded to the Kuuma this past September from a 1960’s era Shenandoah wood furnace. The shoulder season through New Years was awesome with the Kuuma, but this week we’ve been hit by a real cold spell (single digits) and I’m struggling. Through New Years, the Kuuma was keeping the first floor of my house at 72-73 degrees consistently on two loadings per day. With this cold snap, I’m struggling to maintain 66-67 degrees. I believe the furnace is working properly and based on my reading of the forums, my setup is the likely culprit. Any advice will be much appreciated, so here goes:
With the Shenandoah, I was going through 9-10 cord in a season, constantly loading and manually adjusting a thermo-spring air intake damper. I was aiming to keep the house at 68, but would’ve preferred 70.
I got the Kuuma hooked up in September, using the same ductwork. The ductwork has a roughly 25’ long trunk with 8 registers into the first floor. The ductwork also services a propane furnace/heat pump. There are two cold air returns from upstairs, but only one effectively services the Kuuma. My installer set up the return ducting to cover the bottom half of the Kuuma, while the top half of the Kuuma is open to the basement. The basement door has a grate to allow return air. I have had better luck blocking off the top half of the Kuuma.
The furnace is located in a block-wall basement, unfinished and below ground. The furnace is located at one end of the house. The chimney is an 8” flue, brick with terracotta liner, located on the exterior of the house. I’ve never had a problem with draft (even had to slow it down with the Shenandoah), but I don’t have a manometer. One is arriving today and I will measure the draft. The 6 inch exhaust from the Kuuma is ”necked-up” to 8 inches at the wall. I am considering a chimney liner, but draft seems to be okay (pending manometer reading). The barometric damper is set at the lowest setting and it flaps only slightly. Any higher of a setting and it will not move. There is a clean out door in the chimney below the thimble. I will usually start a draft for the first burn by lighting a small fire at the bottom of the clean out. Once going, the draft sounds like a freight train with that door open.
The house is 1980s construction, R-19 insulation in 2x6 walls. Conditioned space is 2400 sq. feet (1200 each floor). I had cellulose blown in the attic this year over top of the fiberglass batts that were there. It is two stories above the basement. The furnace and ductwork only service the first floor. There is an electric heat pump located in the attic to heat and cool the second floor. In the past, I relied on the furnace downstairs to heat the whole house with the upstairs being 3-4 degrees cooler than downstairs. Over the past year, I have worked on buttoning up the house pretty good. I have one door with a small air leak that I’m working on and another door with barely anything of a leak. New windows throughout the home.
We did an addition on the first floor this year, 800 sq. feet with a 13 foot cathedral ceiling. I did not bring any ductwork into that space as it’s full width is open to the first floor anyway. I will install a Fisher wood stove in there for space heating and ambience, not intended for primary heat of the house. The walls and ceiling of the addition were insulated with closed cell foam. The floor of the addition is not yet insulated and it is built on a crawl space foundation. Insulators couldn’t do the floor on the day they did the walls due to a moisture issue, but they are set to finish that this week. I am hopeful that insulating the floor will make a big difference, but I’m finding it hard to imagine quite this much heat loss or additional heat load from that floor.
For example, I left the house this morning with a full load in the Kuuma and it was on “c.” The computer is set on Medium. Until this week, it lived on Low. I brought the home up to 68 degrees using the propane furnace and re-loaded the Kuuma. When I left, my Nest thermostat read 67 degrees. Less than an hour later, it’s reading 66. Upstairs is reading 65. Based on yesterday, I anticipate it will drop to 64 within the next two hours, but the Kuuma will still be doing “c-1-c-1.” Up to New Years, a full load of wood in the morning would still be burning when I return home at 5pm. The propane furnace will kick on at 62 degrees. Last night, I did a full load at 11pm. At 7am, the propane furnace was on and the Kuuma was at “3.”
Using a laser thermometer, the single wall flue pipe out of the back of the Kuuma is reading about 200-225 surface temp. I have the low-limit fan switch currently set at 115F. Prior to New Years, it was set at 105F. The plenum is warm to the touch and the fan is no longer running constantly through the burn. The registers closest to the furnace upstairs will show a supply temp of about 100 degrees, dropping to 90 or less within 3-4 minutes of the fan kicking on.
I am burning mixed hardwoods that were seasoned for over a year in log length, then cut-split-stacked this past spring. Moisture on a fresh split reads about 21%. I should have 2-3 cords left over from this stack going into next season, so hopefully much dryer by next October.
My thoughts on what to do next:
1) Insulate the floor of the addition
2) Measure the draft and adjust as necessary. Chimney liner possible.
3) Change the return air setup
4) Increase the low-limit switch to 120-125.
5) ?
It seems to me the supply temps are too low and the plenum should be much warmer on a fire that gets to “c” as quickly as it does. Wondering if I’m losing a lot of heat up the chimney, but don’t know how to stop that.
Long post, thanks for reading. Any tips, hints, advice much appreciated.
With the Shenandoah, I was going through 9-10 cord in a season, constantly loading and manually adjusting a thermo-spring air intake damper. I was aiming to keep the house at 68, but would’ve preferred 70.
I got the Kuuma hooked up in September, using the same ductwork. The ductwork has a roughly 25’ long trunk with 8 registers into the first floor. The ductwork also services a propane furnace/heat pump. There are two cold air returns from upstairs, but only one effectively services the Kuuma. My installer set up the return ducting to cover the bottom half of the Kuuma, while the top half of the Kuuma is open to the basement. The basement door has a grate to allow return air. I have had better luck blocking off the top half of the Kuuma.
The furnace is located in a block-wall basement, unfinished and below ground. The furnace is located at one end of the house. The chimney is an 8” flue, brick with terracotta liner, located on the exterior of the house. I’ve never had a problem with draft (even had to slow it down with the Shenandoah), but I don’t have a manometer. One is arriving today and I will measure the draft. The 6 inch exhaust from the Kuuma is ”necked-up” to 8 inches at the wall. I am considering a chimney liner, but draft seems to be okay (pending manometer reading). The barometric damper is set at the lowest setting and it flaps only slightly. Any higher of a setting and it will not move. There is a clean out door in the chimney below the thimble. I will usually start a draft for the first burn by lighting a small fire at the bottom of the clean out. Once going, the draft sounds like a freight train with that door open.
The house is 1980s construction, R-19 insulation in 2x6 walls. Conditioned space is 2400 sq. feet (1200 each floor). I had cellulose blown in the attic this year over top of the fiberglass batts that were there. It is two stories above the basement. The furnace and ductwork only service the first floor. There is an electric heat pump located in the attic to heat and cool the second floor. In the past, I relied on the furnace downstairs to heat the whole house with the upstairs being 3-4 degrees cooler than downstairs. Over the past year, I have worked on buttoning up the house pretty good. I have one door with a small air leak that I’m working on and another door with barely anything of a leak. New windows throughout the home.
We did an addition on the first floor this year, 800 sq. feet with a 13 foot cathedral ceiling. I did not bring any ductwork into that space as it’s full width is open to the first floor anyway. I will install a Fisher wood stove in there for space heating and ambience, not intended for primary heat of the house. The walls and ceiling of the addition were insulated with closed cell foam. The floor of the addition is not yet insulated and it is built on a crawl space foundation. Insulators couldn’t do the floor on the day they did the walls due to a moisture issue, but they are set to finish that this week. I am hopeful that insulating the floor will make a big difference, but I’m finding it hard to imagine quite this much heat loss or additional heat load from that floor.
For example, I left the house this morning with a full load in the Kuuma and it was on “c.” The computer is set on Medium. Until this week, it lived on Low. I brought the home up to 68 degrees using the propane furnace and re-loaded the Kuuma. When I left, my Nest thermostat read 67 degrees. Less than an hour later, it’s reading 66. Upstairs is reading 65. Based on yesterday, I anticipate it will drop to 64 within the next two hours, but the Kuuma will still be doing “c-1-c-1.” Up to New Years, a full load of wood in the morning would still be burning when I return home at 5pm. The propane furnace will kick on at 62 degrees. Last night, I did a full load at 11pm. At 7am, the propane furnace was on and the Kuuma was at “3.”
Using a laser thermometer, the single wall flue pipe out of the back of the Kuuma is reading about 200-225 surface temp. I have the low-limit fan switch currently set at 115F. Prior to New Years, it was set at 105F. The plenum is warm to the touch and the fan is no longer running constantly through the burn. The registers closest to the furnace upstairs will show a supply temp of about 100 degrees, dropping to 90 or less within 3-4 minutes of the fan kicking on.
I am burning mixed hardwoods that were seasoned for over a year in log length, then cut-split-stacked this past spring. Moisture on a fresh split reads about 21%. I should have 2-3 cords left over from this stack going into next season, so hopefully much dryer by next October.
My thoughts on what to do next:
1) Insulate the floor of the addition
2) Measure the draft and adjust as necessary. Chimney liner possible.
3) Change the return air setup
4) Increase the low-limit switch to 120-125.
5) ?
It seems to me the supply temps are too low and the plenum should be much warmer on a fire that gets to “c” as quickly as it does. Wondering if I’m losing a lot of heat up the chimney, but don’t know how to stop that.
Long post, thanks for reading. Any tips, hints, advice much appreciated.
