Question for automatic damper furnace owners...

[taken]

So, I'm thinking I've decided on the new wood furnace for the home I am building in the spring. I was sure it would be a Harmon or an Englander but after reading here and getting a point in the right direction, I found the Caddy. Seems to have everything I'm after with the auto damper, glass door, and the ability to connect in series. High efficiency doesn't hurt either. Coming from an Avalon insert, I have a few questions about the auto damper. (I think the Englander would be very similar to run to my Avalon.) So, you all with auto dampers on a wood furnace, here goes. I will have a new house that's very well insulated. About 2200 square feet, two story center hall colonial, in MA. My worry about the auto damper is it will be shut down too often and build creosote. I am thinking this because the home will be so well insulated and I tend to get warm easily and usually keep the house at about 69-71 tops. I will have a new 2100 degree metal chimney with an insulated chase. Will I have a problem with creosote build up considering my setup? I also intend to run two ducts to my three car garage. Not to keep it up to house temp, just to take the edge off. I imagine this might help with the furnace output not being too much for the house. I was also thinking that I could open a duct or two to the basement if I needed to. Would be nice to have warm floors on the first level. My concern about the furnace being at idle too long comes from my longtime chimney sweep. He has been in business for 30 years and also worked for many years for the local high end fireplace and stove center doing installations and repairs so I trust his opinion. He told me that having too big a system has resulted in bad buildup because of being at idle too often. This fear makes some part of me want to stick with what I know like the Englander but I'm probably over analyzing. Thoughts?

 

[laynes69]

The Caddy is meant to burn cleanly even if the damper closes. It operates the same as a EPA woodstove except you have a secondary heat exchanger, and a servo on the damper attached to a thermostat. We run our furnace probably 90% of the time right now with the damper closed and we get either nothing from the chimney, or a light steam. They burn hot and they burn for hours. Its a night and day difference from a standard furnace. They really do operate like they claim. Alot of people that remember furnaces or had them they were wood hogs and burned dirty. Thats why we upgraded our old one and it was well worth it. The one thing I will say though is you need seasoned wood for them to operate properly. With it being EPA certified it won't shut down fully to smother the fire.

 

[taken]

Thanks again Laynes. I guess I'm reading too much into it. Are you keeping your house very warm or can I maintain 70 +/- without choking the fire?

 

[Gooserider]

Both Layne's and the sweep are right - in different ways.... The Caddy as an EPA approved unit should burn cleaner than an equivalent sized non-EPA unit in the same installation, assuming the same everything else...

However, ANY unit will make more deposits when idling than when burning flat out, EPA or not, so if the Caddy is oversized, it could be a problem... The other issue that may arise, is that because the Caddy doesn't do as full of a shutdown as a non-EPA unit, it WILL keep making some heat as long as it's burning, and that heat will have to be sent somewhere - possibly into your house making it warmer than you might otherwise want...

This is why we keep harping on the need to do heat load calculations to avoid oversizing.

(I will say that I would not be looking at a furnace and forced air system if I were building new - far as I'm concerned, forced air for heating is a hack at best when compared to what can be done with a hydronic setup - If I were building I'd be putting radiant floor in everywhere, and doing a boiler + storage system - far more efficient, gives me "free" DHW as part of the deal, and only needs to burn every few days during shoulder season, which is fairly lengthy in MA... If I felt that AC was needed, I'd then put in a separate mini-split or equivalent system...)

Gooserider

 

[laynes69]

You will have far less of a heating demand than I have so you will probably be closed down most of the time with the furnace set at 70. Its not like a gas furnace, as long as there is wood in the firebox, heat will be pumped through the home. You can control your heat output with smaller loads until its cold. You should easily maintain 70+ with the furnace operating without the damper open on a call for heat. It won't fully shut down, so it burns cleaner than a conventional furnace.

 

[laynes69]

I'd agree 100% with a hydronic setup. A constant comfort, DHW, etc. For us its was a cost issue. It would be wise like gooserider said and get a heating demand calculation for the home. If you had a heat pump then you wouldn't need to operate a woodfurnace until it got cold out which would help.

 

[taken]

Both Layne's and the sweep are right - in different ways.... The Caddy as an EPA approved unit should burn cleaner than an equivalent sized non-EPA unit in the same installation, assuming the same everything else...

However, ANY unit will make more deposits when idling than when burning flat out, EPA or not, so if the Caddy is oversized, it could be a problem... The other issue that may arise, is that because the Caddy doesn't do as full of a shutdown as a non-EPA unit, it WILL keep making some heat as long as it's burning, and that heat will have to be sent somewhere - possibly into your house making it warmer than you might otherwise want...

This is why we keep harping on the need to do heat load calculations to avoid oversizing.

(I will say that I would not be looking at a furnace and forced air system if I were building new - far as I'm concerned, forced air for heating is a hack at best when compared to what can be done with a hydronic setup - If I were building I'd be putting radiant floor in everywhere, and doing a boiler + storage system - far more efficient, gives me "free" DHW as part of the deal, and only needs to burn every few days during shoulder season, which is fairly lengthy in MA... If I felt that AC was needed, I'd then put in a separate mini-split or equivalent system...)

Gooserider

Interesting info. How would I do a heat load calculation for my home? Do you think heating the basement and garage will prevent the Caddy from being over-sized for my application? As for radiant floor, I agree and would love to go that route. But, with the added installation expense and added expense of adding my central ac, it's a bit much. Plus I can do a hot water coil with the forced air system if I really want. Not sure about the cost to return ratio as the direct vent units are so efficient these days. To clarify one point, the house will also have a 96% gas furnace and when the outside temp is above 40, I will just run that so I'm not too concerned about the transitional seasons.

 

[laynes69]

You will get radiant heat from the furnace so it will heat the basement. The garage you could probably keep it as warm as you wanted to. They make a smaller version of the caddy called the mini-caddy, but you are better off having something thats a little big than too small. The Caddy is Phase 1 certified. Building smaller fires is a good way to lessen the heat output of the furnace.

 

[taken]

I guess damping down the Caddy will be better than roasting with an uncontrollable Englander right? I'm used to running a stove like the Englander with my Avalon insert, BUT it is a little undersized for the house. So, keeping a roaring hot fire is just what I need to keep my house at 70. Must be a good design as I still get 8 hours overnight without a problem. I'll just have to tackle the learning curve head on with whatever I decide on. Leaning toward the Caddy and most people who advise me, here and offline, agree.

 

[taken]

One thing I just figured out about the Caddy is that it is NOT rated at 140,000 BTU's output. This is actually good for me as I don't need nearly that much. It is rated at 140k btu's max INPUT from your exsisting furnace when installed in series. It is rated at an average 69,160 BTU's output with a max of 106,400. Much better numbers for my application.

 

[laynes69]

With the Caddy, I can go to bed, and wake up in the middle of the night to see hells inferno in the furnace. As the wood outgasses into the burn, the furnace produces more heat into the burn. I guess using the term idle is bunk because the furnace is just burning at a lower output. It still throws alot of heat when shut down, but spreads the heat over a period of hours. A furnace can and will raise a house temperature fairly quick. Its a whole different animal than a stove where it may take hours for heat to radiate through a home, it could take minutes to start raising the temperature. But the benefit is a whole home thats warm. There are things to do to help with the heat output. Not running the furnace when its mild out will help.

 

[taken]

Thanks again Laynes for all your input. My decision is made and Caddy it is. Now on to the next. I never realized how many things I would need to analyze and how many decisions I would need to make before even breaking ground. The good part is this is fun for me. Next choice is finding a decorative gas fireplace for the LR. I guess a question in a different forum area is in order. Thanks again everyone for your input.

 

[Gooserider]

There are a variety of programs and websites that will allow you to do a heat load calculation. All essentially look at the areas of your outside exposed wall surfaces, and calculate how many BTU's / hr you will lose based on the wall construction, size, direction, etc, including things like the areas of doors and windows, and so on... Since the house isn't built yet, you would use your plans for all the relevant details... (Which offers some advantages to those of us in previously owned homes where we can't always be sure about the construction details) You also plug in the local area data for "design day" which is the coldest weather you will have. (There is also an identical set of calcs for cooling that is used for sizing your AC, but we don't talk about that much here - but it's worth doing both)

This will do a few things for you -

1. It will answer all your questions above about whether or not the addition of basement and garage loads will be helpful

2. It will give you the exact info you need to get properly sized heating and cooling systems.

3. (and this one is a biggy) It will allow you to do some very precise "what if" experiments to see what changes and paybacks there can be for playing with options on construction techniques and materials - i.e. adding additional / different insulation, and so on - How much extra does it cost or save, what is the impact on the heating bill?

Note that a lot of energy efficiency improvements are easily done, and relatively cheap at build time, but difficult and expensive later... Also I have heard that there are programs out there that will help cover the costs, including ones that cause your bank to allow a larger amount on the mortgage to cover the extra cost, on the theory that you can afford a bigger monthly house payment if your utility bill is a corresponding amount less...

Gooserider