New hydronic heating system in stages; advice?

[Downeast Farmer]

So, here I am envisioning a replacement for my forced-air wood furnace with oil backup for my 3,300 sf house in Maine, the system that has me up every 3 hours all night if the temperature drops below 10F or so.

I've been considering a gasification boiler with storage, either a Garn or another boiler with external storage, and using this to drive radiant floor heating. Trouble is, that's a bit too big a chunk of time and money to commit for one year. Thus, I'm wondering how to split the project into two or more years.

Would it be reasonable to get the boiler and storage in the first year and use a heat exchanger in the forced air plenum to supply heat while I go about installing radiant tubes? The problem with this, as I understand it, is that the heat exchanger must run at 140F or so, thus robbing me of much of the benefit of storage, as I'll only be able to draw the storage down from 180F to 140F and thus have to make fires frequently.

Is there some better way to conceive of this? Some better way to install the new system over a couple of years?

 

[kod198707]

I'm building my system much the same way you just discribed. I'm located up north in NY. about 25 min from Canada. At the moment I have no heat storage, but this last week of -0 temps I was able to sleep from 11pm to 7 am. I'm heating a circa 1842 victorian at about 4000sqft. Heating off a 200k BTU hydronic heat exchanger, and a poorly designed duct system.Something else I got when I purchased this "labor of love" some day we'll call a home.

 

[Downeast Farmer]

Welcome to you, kod198707!

So, you're system works ok then? What drives the hx, a wood boiler or something fossil-fueled?

 

[mikefrommaine]

Do you need to replace the hot air ductwork. Or do you just want radiant floors to take advantage of storage?
You could always add more storage instead of going through the expenses of radiant floors. And keep the hot air with a coil.

To break up the financial hit I used my boiler without storage for 1 year and then slowly added storage to my system.

 

[Downeast Farmer]

I mainly want to end up with a system that needs less tending and that is as efficient as I can make it. Am I right in thinking that the storage is of less value if I'm working with the narrower temperature requirements of a heat exchanger?

 

[kod198707]

I have a biomass 60 with a thermo pride furnace that moves the air. it works better than the 35 yo wood furnace I replaced.I will be adding about 2000 gal of storage.

 

[Downeast Farmer]

And you'll keep the arrangement of the heat exchanger in the plenum of the thermopride?

 

[kod198707]

Yes, until i to have my radiant installed

 

[kod198707]

1000 gallons of water. supplying a 200k hx for 8 hrs will have a temp drop of 10.5 degrees. If my mathis right.

 

[Downeast Farmer]

Won't your hx take 200kBTU/hr * 8hr = 1,600,000 BTU?

To raise 1,000 gallons of water 1 degree = 1,000g * 8.34 BTU/g/degree = 8,340 BTU/degree

For your 200kBTU/hr hx: 200,000BTU/hr / 8,340 BTU/degree = about 24 degree/hr loss from your 1,0000 g storage.

That's my math.

 

[Downeast Farmer]

But then you're probably only burning at 150,000 BTU/hr (assuming you load up with 150 lbs or wood, which would yield 8000 BTU/lb, which is about 1,200,000 BTUs, which is you exhausted the load between 11pm and 7am, would mean you burned 150,000 BTU/hr for 8 hours).

 

[kod198707]

Your math is obviously better then mine.I stand corrected. Thats an example of how heat storage will extend your heat time . I have'nt weighed what a load of wood is, but I'm guessing thats close.I know for me 8 hrs of sleep is better then the 4 or so I was getting from the old wood furnace.

 

[maple1]

I know for me 8 hrs of sleep is better then the 4 or so I was getting from the old wood furnace.

That right there is the kind of thing that is quite often underestimated in all of this.

I was literally exhausted & seriously sleep deprived by the end of last heating season (likely made worse by also compounding with just simply getting older) - for the last time. Now I load up on the way to bed (most times around 10pm), and don't even think about checking temps or making another fire until late afternoon the next day (no, I don't sleep till then ) , or noon worst case so far (and this has been quite the cold snap). I'm also kind of light on storage compared to what others have - I'd have more if I had the right space.

 

[mikefrommaine]

And of course it gets better on non design days. Could easily go Much longer on storage. I don't know about coil in hot air systems but I think you could oversize the coil to get a bigger range of useable storage temps.

 

[flyingcow]

I would think the cost of installing a hx for the existing hot air system wouldn't be too much would it?

Storage early on? Be a plus yes, but with your heat load (3300sq/ft in Maine) would eat up a lot of storage. But do as Maple1 is doing. Fill it at bedtime and should be all set for a 12/18 hour period.

If you don't go with a Garn, get a gasser a little big and than you have the bigger firebox? Tie that in with a set back T-stat and it will probably work.

How's your house envelope? Insulated at the R-19 norm? drafty?

You want a DHW from wood? How many people in house?

Do you have set back T-stats? For my household those help. Many a times I've gotten up early am and the T-stat was set at 74. Come home in the afternoon, nobody home all day, T-stat at 73/75. Now i use set backs. About 10pm it will set back to 62. Never gets that low, maybe 66/67, but it's helped with keeping storage. Weekdays it sets back from 7am to 3pm.

I like you idea of doing the HX and the rest as time allows. I've got staple up in my kitchen floor, and Base board thru the rest of house. I like the BB and in floor combo. I can get behind in my storage and fire up boiler, i will have 180+ running thru the BB in 45 minutes. The staple up works great in the shoulder seasons.

Oh yeah, will your existing oil furnace heat the house by itself? How many btu's is it?

 

[Downeast Farmer]

This is great. This figuring of how to simultaneously get a warm house and enough sleep has eluded me for quite some time, but I feel I'm getting to the nub of it now with all your help here.

 

[ihookem]

I have a HX above my furnace. It works good but I don't like it. It's loud, sucks lots of heat out of the water and forced air isn't all that comfortable. So, a month ago I put 250' 1/2" pex under my family room floor. It raises the floor temp about 5 degrees but feels a lot warmer on my feet. We have foam under the very fluffy carpet. Some say it doesn't work under carpet well but the heat has to go somewhere if it is installed properly. My wife likes it too when she takes her electric blanket and lays on the floor. It gets her toasty warm. I have a new ranch so 2 pex tubes between the joists was easy. I just stapled it up and took some scrap aluminum coil from window trim coils about 2' long and stapled it up instead of buying it. We are going to put it under the kitchen floor next and will be another 250' of 1/2" pex. Also, Is 1/2" pex good or should I go bigger or smaller? ANother observation, when it's 35 degrees or so the furnace doesn't run When the furnace is set @ 66 Degrees. The hydronic heat is enough to heat the house. We have a super insulated house though.

 

[maple1]

Pex is great stuff - all kinds of things you can do with it that are a bit outside the typical box. Very DIY friendly and relatively cheap.

3/4 is a lot harder to handle & bend around tight spaces than 1/2 - I'm also thinking that for under floors in a pressurized system you'd want O2 barrier? Sounds like the first room was a success - I'd say go for it, everywhere you can get it into. Warm water circulating around the living space in winter is all good.

 

[dogwood]

Downeast Farmer, have you looked into the Kuuma VaporFire Units. They are wood gasification forced hot air units. I think they might go a lot longer between burns. Maybe you could simply substitute one of these for your current unit and avoid all the extra expense and time of converting to a bolier. I'd find you the link but I'm at work.

Mike

 

[Downeast Farmer]

Thanks, Mike. I've been considering the Vaporfire as the easier, cheaper alternative that would be light years ahead of what I now have. I think I'm suffering storage envy--all those guys with their reports of that once-a-day fire tending having me longing for a similar experience. I'm planning the 30-year system, though I may not have the budget for it....

 

[dogwood]

I'm not so sure very many get down to one burn a day even with storage except in the shoulder seasons. Good thing to shoot for though.

Mike

 

[maple1]

Some things get mixed up in terminology sometimes.

I do one burn a day in the evening but it's a longish one since I usually reload the firebox 4 hours or so after lighting. One lighting, one burn, two loads?

 

[kod198707]

Thats were I'm trying to get when i have my storage in. I'm planing a 2000 gal. open storage with a drain back solar panel. hopefully I can get enough out of the solar that I wont have to burn in the shoulder months.

 

[Tennman]

This is our 4th season with the BioMass and just now adding storage. ROI for us was ~3 years since we heated a pretty big place with propane. So yes many here do it in stages. I'm very glad I didn't do storage right away not so much because of spreading the expense (although that's nice), but it was a simpler system to debug that first year as the DIY'r installer. FYIW, I love having only hot water coming into our home. Work through the decision of what you prefer; your wood appliance in the home or in a separate building. That will somewhat focus your path and help you decide if you can do a wood furnace. I think the concensus is a Garn has disadvantages if you must have forced air. I think that has to do with a radiant system still being efficient at lower temps. I actually kicked around a Garn upgrade vs adding storage but since I'm stuck with ductwork I'm better off with the separate system. Hopefully others will chime in about forced air and the Garn. But if you need financially to split the project up many here do it and I'm one of them. One thing's for sure, I've never read about a unhappy Garn owner. But lots of very happy EKO and BioMass folks here too (less expensive gassers). Enjoy the research, your at the right place. Welcome.

One other thing, there are some really amazing newer U.S. and European boilers coming out. Since I have about $5500 in the boiler component of my system, it's not out of the question down the road to upgrade to a.... Vigas, Varm, Tarm, whatever since it would be essentially just a boiler swap in my total system. That way I'm able to see my system as a 50+ year system... at which time I'll be 110 and probably not too concerned about my boiler.