Heat pump, and add on furnace ??

[IndianaTech]

Hey everyone, I'm new to the forum, and new to the wood heating world with a few questions. I spent some time reading through past posts the best I could, but still have some things about my particular setup I would like to run past you all. My house is a 2750' square foot brick ranch with half of that being my unfinished basement. My current heating system consists of a combination of heat pump, and back up resistance coil. My obvious problem is my cost of electricty during the winter months where are lows are generally in the 20's. My house is well insulated since we added blown in insulation at the beginning of 2008. I would like to install a wood burning furnace as an addition to my current heat source. We have access to free, seasoned fire wood on our property so we would not have to pay for fuel for a long time. I have been looking at DAKA's 521FB unit as well as a similar furnace from US Stove called the 1500 hot blast. My questions begin here, since my current heat source is not vented my options for where the flue would go are realitvely limited. I have two windows that are within aproximetly 15' from where the furnace would tie into my plenum. Would having a flue that long cause any issues ? There would only be two 90 degree turns before it was on it's way to the top of the roof line. If this can be done I planned on having the flue bricked into the concrete frame where the window is. Or would it be better to put the furnace closer to the window, and run the two ducts the 15' to the existing furnace ?? My last question is a simple one.... Can this even be done with my current type of heat source ? Another thing I would like to add is that in case of a power outtage I do have two large generators I plan on using for the blower on the furnace if need be. Thanks everyone for taking the time to read through this.

 

[atlarge54]

You'll probably get more help at a different woodburner site, this is boiler oriented information. Personally I'd never attempt to have a 15' horizontal chimney run. You plan to run the chimney from your basement to an outside wall, chimneys that are warm work best and need less cleaning. Happy chimneys are kept warm by the house they're heating.

 

[IndianaTech]

Ok, well thank you for your reply. Do you have any suggestions as to what site may be of more help ?

 

[laynes69]

There are people on here that have installed a woodfurnace with a heatpump setup. There are a few things that come to mind. First in order to install a woodfurnace properly you need clearances to combustibles on your ductwork, which varies from maker to maker depending on how there were tested. Second, having a 15' run of flue on a wood burner isn't a good idea. Both of those furnaces have blowers, therefore you could install then farther away from the heatpump and shorten your fluepipe. If thats the case then you could follow your duct clearances easily so by the time they are at the plenum then theres no worry. Any time you have a woodfurnace and a coil in the ductwork you need to be carefull that the heat from the woodfurnace doesnt cause problems. They can be damaged from the heat. One way to get around it is to install dampers in the ductwork to prevent backflow. A damper ahead of the coil would allow the woodfurnace not to backfeed into the airhandler. And a damper in the woodfurnace ducting also to not allow cold air to feed into the woodfurnace in the summer, which could cause condensation and potentially rust out the woodfurnace. There are better woodfurnaces out there that would use less wood and burn more efficiently but those furnaces should heat just fine. We heated a old victorian for years with a hotblast 1500. If you use the generators, then I would run the blowers on the woodfurnace. With proper backflow dampers in place, getting heat into the house won't be a problem.

 

[rkusek]

My father in law has had a Clayton (now US Stove) tied into with a all electric heat pump for the last 20 yrs. Clayton has it's own blower and thermostat. He has to manually change the damper though which means it's either heat pump or wood furnace. It's not set up for the heat pump to kick on when house is cold and no wood in stove. I've seen some designs here where a spring loaded damper flips which either in one of two directions depending on which blower comes on. I would think that would need to be well balanced however to work reliably. There has to be some type of motorized damper solution out there too I would think. My in laws basically use the wood furnace exclusively through the winter and only flip over the damper for heat pump when out of town. He did have some pipes freeze a couple years ago with 20 below weather and house cooled off enough from the time the morning load ran out until he got home from work at 5PM. I would recommend some type of auto damper to avoid this. The Clayton heats the house very well and has been trouble free for them. I also agree with previous suggestion about placing the furnace near the chimney outlet and running the extra ductwork instead of horizontal flue.

 

[freeburn]

I have this setup. Heatpump with add-on Englander furnace with its own blower. My heatpump is setup to run only when the temp is above 35 degrees, below that natural gas kicks in or wood as I make sure the house is warm enough. I will sometimes turn off my natural gas valve so it doesn't kick in. Once I'm in wood season, then I turn back on in case of emergency.

If I were you I'd put the stove as close to the chimney as possible to minimize elbows and horizontal runs (creates better draft especially in a ranch, which is what I have too by the way). You have to make sure that your heat comes in above your A-coil in your furnace if that is how you are going to duct it in. Another option would be to install separate heating ducts from the wood furnace that are dedicated just to the wood furnace, then you don't have to worry about your existing furnace.

As mentioned already (Laynes69), make sure that if you install into the existing plenum, to have some sort of backflow dampers. What I did was extend my hot air through the plenum so that there is no chance of backblow, that way I can run both blowers at the same time, if needed. I also have the cold air return hooked up to the furnace, that is a big help too in heating more efficiently. May not be an option for you if you are that far away from the furnace. Do you have any ductwork near the windows that you could tap into? Then the only thing you'd need to install would be a backflow damper inside your existing furnace and your wood for air conditioning. Hope this makes sense. Too many things to say all at once. Keep us posted if you need more help and pay attention to installation clearances!

One more thing, if you want a furnace that is going to last, you kind of get what you pay for. DAKA I don't think is known for longevity. I can't speak for US stove but I think there are some tweaks you can make to cause it to burn better as with any.

 

[IndianaTech]

Ok awsome, this was the kind information I was hoping for. My original plan was to put the furnace as close to where the flue would exit as possiable like you all are recommending. There is duct work that is within a few feet from where the furnace will now be going, but it is at the end of the house, if that makes sense. (existing furnace in the middle of the basement, wood furnace would be going at the end on one side). Freeburn if I understand you correctly, are you saying instead of running the duct work the 15' back to the plenum of my existing furnace, I could just run it straight to the closest duct ?? I understand the need for the dampners just fine, and will put them into my plans. Also when you said you extended your hot air through the plenum, what exactly did you do, just run your piping further into the system ? Thanks again guys, you all have already been a huge help !!

 

[freeburn]

Depending on the layout of your ductwork, yes, you could just pipe it into your closest duct as long as you put dampers in the right places, or "Y" into your existing ductwork to get the heat upstairs (If it is close enough to a main living space and would dissipate easily throughout the house. I find that if you can get the heat to go in a straight shot through the ductwork, you get better heat distribution throughout the registers. One problem with this setup is that you can't really use your existing furnace while the wood furnace is going or they will push against each other.

When I said I extended it through the plenum I meant that where I attached my 8x14" or whatever size it is to the side of the furnace plenum my furnace is offset from the main trunk so I was able to extend that 8 x 14 piece through the plenum into the main trunk of the ductwork, thus bypassing the A coil altogether and allowing me to run the furnace fan or even the furnace at the same time as wood. Dont' think that would work in your situation being 15' away anyway.

What would really help is to upload some pictures of where you want to install your furnace (windows, duct runs, furnace and plenum - that kind of thing).

 

[IndianaTech]

Ok sounds like a good idea. I will snap some photo's tonight after work so you all can see the layout I'm dealing with.

 

[IndianaTech]

I did the best I could with the pictures, sorry there not the greatest. I plan on putting the furnace where the tool box is directly under the window above it. I was going to completely remove the window frame, and brick in around the flue. The duct work in front of the tool box is less then 5' away, but is to our back bedrooms, and oppisite to the living room, and kitchen which is one great room with vaulted ceilings. The basement walls, and floor are all concrete, so no combustables are near where the furnace would be, with exception to my things that will be moved.

 

[begreen]

As you look at the tool box, is the return duct on the left? If yes, it looks like there will be an issue with where the supply from the wood furnace ties into the main system supply duct. The main system supply has tapered down near the wood furnace location. Ideally you want to tap the wood furnace supply in closer to the main trunk.

 

[IndianaTech]

Yes, return on the left. Ok, so I guess my only option is to run the ducting from the wood furnace to the plenum of my existing heater. I suppose this will give me more even heat distribution anyway ? Back flow dampners in both my existing unit, and before the wood stove to stop the AC from entering the stove in the summer. Anything else I am missing ??

 

[atlarge54]

IndianaTech if you're a complete newbie to cutting and burning wood you might check out the arboristsite.com. There is a woodburning forum there and good chainsaw tips. I wouldn't be a bit surprised if you find a fellow hoosier nearby that might be of some help. Do you have any wood cut yet for this winter? No matter what you burn it in DRY seasoned wood has no equal. What kind of saws do you run?

 

[Gator eye]

As you look at the tool box, is the return duct on the left? If yes, it looks like there will be an issue with where the supply from the wood furnace ties into the main system supply duct. The main system supply has tapered down near the wood furnace location. Ideally you want to tap the wood furnace supply in closer to the main trunk.

Yes, ideally you would want to hook into the hot air where it is the biggest but the way a wood furnace works with the fan running almost all the time instead of short blast on and off like a gas furnace. I'm betting he would be fine and have plenty of heat hooking into the end of the run because it's not a fast heat it's a slow all day heat. The use of check valves would be a must sense the two furnaces would be facing each other and hooking the cold air return into the wood furnace will improve the stove ablity to heat the house . If there was a question on whether the duct work is big enough you could always replace the duct work where it decreases in size up to the wood furnace so you have the same size run though the whole house

 

[IndianaTech]

IndianaTech if you're a complete newbie to cutting and burning wood you might check out the arboristsite.com. There is a woodburning forum there and good chainsaw tips. I wouldn't be a bit surprised if you find a fellow hoosier nearby that might be of some help. Do you have any wood cut yet for this winter? No matter what you burn it in DRY seasoned wood has no equal. What kind of saws do you run?

In my previous home, we had a wood burning fire place that we used all the time in the winter, so I am familiar with cutting, splitting, and using dry seasoned wood. As of right now I have only cut, split, and stacked a little more then a cord, but I am working on it. We had a hurricane (yes you read that right) come through here in Indiana almost two years ago, and it knocked down quite a few large trees on our property, and that is what I have been using. As of right now I have two Poulan saws that have been getting the job done, and luckily my Father in-law has been kind enough to let me use his hyrdo splitter, so I have not yet had the joy of splitting by hand lol.

 

[begreen]

As you look at the tool box, is the return duct on the left? If yes, it looks like there will be an issue with where the supply from the wood furnace ties into the main system supply duct. The main system supply has tapered down near the wood furnace location. Ideally you want to tap the wood furnace supply in closer to the main trunk.

Yes, ideally you would want to hook into the hot air where it is the biggest but the way a wood furnace works with the fan running almost all the time instead of short blast on and off like a gas furnace. I'm betting he would be fine and have plenty of heat hooking into the end of the run because it's not a fast heat it's a slow all day heat. The use of check valves would be a must sense the two furnaces would be facing each other and hooking the cold air return into the wood furnace will improve the stove ablity to heat the house . If there was a question on whether the duct work is big enough you could always replace the duct work where it decreases in size up to the wood furnace so you have the same size run though the whole house

That depends. The end of the supply appears to be around 8x8". If so, tapping in at that point that will restrict airflow causing too high static pressure in the duct off the furnace. That can cause high temps in the furnace plenum and the fan to race. It's better to tap in at least before the transition to the smaller trunk size, but the ideal for good air distribution (and more even heat) would be to tie into the primary trunk off the plenum. Pay attention to clearances from combustibles for the supply duct as per mfg. directions. Keep the supply duct coming off the wood furnace 6" below the floor joists for the first couple feet.

Indiana, how large is the existing furnace (in btus)? How is it vented? Have you looked at putting it side by side on the opposite side of the current furnace in the unfinished space and venting directly through the wall instead of through the window?

PS: Did you look at the BlazeKing Apex furnace? EPA approved, it gets the $1500 tax credit and should be a lot better in milder weather. If I was putting in a wood furnace I would consider this puppy.
http://www.blazeking.com/furnace-apex.html

PPS: Are the basement walls insulated on the exterior? If not, will they be insulated soon on the interior? That is a source of a lot of heat loss with those uninsulated ducts.

 

[IndianaTech]

I will have to look at the current furnaces btu rating since I do not know of hand. I do not beleive my system is vented since it is heat pump/coil ???? I had thought about putting it next to my existing furnace, but the stairs are right there, and I don't think I will have the clearance I need. I am also in the process of finishing my basement so putting the wood furnace next to the existing would cause more problems with combustibles. I am going to insulate the walls in the near future, as the building progresses.

 

[begreen]

Got it, electric resistance coil backup for the heatpump, correct? Normally a good heat pump system has totally sealed ductwork joints and thorough insulation. This is because the supply air temp is lower than in a conventional furnace system. I don't see either being done in this system which I'm sure is making it much less efficient and more costly to operate. The duct heat loss in an uninsulated basement has to be pretty high. With a helper, the whole basement could be insulated with foam board in a weekend. That is what I would do before anything else.

The reason I asked about size is to get a sense of the heating load. How large is the house? Would a wood stove on the main floor be an option instead of the furnace?

 

[IndianaTech]

While I would love to have a stove upstairs it would be a much more costly endevor in my opinion since I would have to add a hearth, and pipe the chimeny through the roof. My house is 2750 sq upstairs, and down stairs, and since my heat is all electric our average winter electric bill runs right around $300, and sometimes closer to $400. I figured since we have ample access to fuel a wood add on furnace would be a smart move. Another reason I am wanting to install the wood furnace is incase of emergency, we will have heat. There is no way I can heat my home in the winter if we loose power since I would have to have a large standby generator which I cannot afford right now to say the least. The basement in my house never gets colder then about 60-65 degrees in the dead of winter. Now that may be due to heat loss through my unisulated duct work, but I am not sure. So, do you think the wood furnace would not do what I expect it to do ?

 

[laynes69]

Also you need to be careful closing off the room too much. I wouldn't want a woodfurnace in a little room in a house. They need combustion air and the returns have to be setup properly so if both units would need to work together in extreme cases they can. A woodfurnace will put off a good amount of radiant heat when operating which in return will heat in that aspect also. With your ductwork not being sealed, go to a homedepot get a container of duct mastic and brush it on all the connections after they are wiped clean. You'll be suprised how many leaks you will have in a system. When I seen the pics of the ductwork, I also wondered about going against the layout of the ductwork. It may work, but there won't be any airflow on the other end of the ducting where its larger. If that ductwork is modified, then its no longer designed for the heat pump cooling load or heat at that matter and the efficiency of the unit will be decreased dramatically. My caddy has a 1300 cfm blower thats more than enough to push the heat through ductwork. With the hotblast 1500 those 2 outlets can only produce 400cfm total. Ideally you want a woodfurnace with a plenum opening with a larger fan for better heat distribution.

 

[begreen]

Nope, you can make a furnace work. It's just my nature to explore all options. I like a woodstove because it is easier to control smaller fires in the shoulder seasons. And you get to enjoy the fire view. Wood furnaces can be trickier in low burn situations. But at that time of year, maybe using the heat pump would make more sense.

I appreciate that you are trying to stay within a budget. Just be sure to add in the tax credit when looking at both options. Unless this is an EPA furnace, no credit. An EPA woodstove + flue will qualify on the credit for the entire installation. So lets say that the basement furnace installation cost $1400 for the furnace, $1500 for the flue and $200 for the ductwork or about $3100 with no credit. Then compare to a stove like the Englander 30NC (~1000) + flue (1800) + hearth (~200). That would be less costly ($3000) plus half would come back as a credit.

 

[IndianaTech]

That has me thinking a bit..... Do you think a stove such as the Englander would heat my entire house ? My concern is getting the heat to the back bedrooms, if the stove would be in the main living area. I didn't realize the cost of the flue would be so high with a wood furnace setup. I do have an area in my kitchen that would work well for a stove since the flue could go straight out the wall, and would only have to go up about 4' to be 3' above the roof line. As far as the hearth goes, I assume I would have to have a brick base, and the walls behind the furnace would need to be brick as well ? Money is certainly a issue, but if I am going to spend it one way or the other I want it to work for me in the best possiable way. The Hot Blast furnace is not an EPA furnace, and will not count for the credit so I would be loosing out there. I am open to all options, and I really appreciate everyones input thus far.

 

[laynes69]

There are clearances you need to follow for furnaces. Depending on the model go on the website and you can look over manuals to give you an idea. I'll say this. I seen a huge difference going from a old unit to a EPA unit. If you can make a good EPA stove work instead of a basic woodfurnace you are by far ahead. Cleaner burning, more heat, less wood. With the tax credits in place it would be a no brainer. Is your house 2750 total? Alot of people heat their homes with woodstoves. Depending on your layout it may work for you. Plus power outages aren't a concern like with a woodfurnace.

 

[begreen]

An exterior flue will need a tee, brackets and brace, extra pipe lengths and a thimble that add to the cost. If at all possible consider running the flue straight up. It can be enclosed in a chase on the second floor. This will look and function 100% better than an exterior flue.

Start another thread in the main hearth forum on the topic for more opinions and perspective. If money was tight for me, I would be looking hard at the Englander. Yes, it will heat the whole place, especially if it is correctly located. Currently Overstockstoves.com has them on sale for $980 and that includes freight to the nearest loading dock near you. No need for a brick wall behind it as long as clearances to combustibles are honored. The 30NC can be as close as 5" to the wall as long as it has the side and rear shields and a double wall connector. The hearth needs more insulative value than just brick if it is to be installed on a wood floor. But if you like that look a hearth can be made with a brick veneer on top of a sheet of insulation board like micore and then a layer of cement board. Lots of options here.

In your new thread, include more info on the first floor plan, house style, concerns, etc. If you can post a sketch of the 1st floor that would be a big help.

 

[oldspark]

Sounds like he would have a very short chimney if he puts it on the main floor.