Add-On Storage Tank Design for a Englander 28-3500 Wood Furnace

Hi!
This is my first time posting on here! So hello to you all!

We are now the happy owners of a Englander 28-3500 wood furnace Good bye oil !!!!!

Anyway, being that it's rated for 3000sqr feet and our house is about 1900sqr feet we do have some excess capacity, it's a hot air furnace, so whatever storage that we would add on would be a diy thing most likely. now the furnace is intended as an add-on since it's burn time is 8hrs max, but as we get into our maine winter I don't know if that's going to go down as we run it harder. It's all manually controlled draft, not even a bimetal damper so sometimes we're hot and sometimes we're running downstairs to give it another turn or two. I'm not complaining , just thinking about improving it further.

Now I've only had this idea since this morning, and my head's been fogged up with a cold, so feel free to tell me i'm an idiot

If I were to build an insulated metal frame in the basement (the only way down into the basement is by a narrow set of steps that was a tight fit for our furnace) and put in a bladder tank -500gals a bare minimum?- and then take a clean truck radiator (research showed that they're rated 80k-200k btus) of at least 100k BTU rating and construct the ducting so that when the blower on the furnace came on a pump would circulate the water through the radiator. and when the furnace was let to go out during warmer times, we could grab some heat from the tank.

Questions:

1. Am I an idiot?

2. Am I the good kind of idiot or the bad kind? Or should I just take more NyQuil and leave you all alone?

3. Would it work at all?

4. How large a tank would we need for just evening out times so we could extend it to 12hr+ heating times?

5. How long could the the tank keep it's heat if it was insulated with at least 3" of foam?

6. Is there a better way of storing heat from this furnace?

Now unless we do improve this furnace, several years down the road we'l probably get a longer burning more automated furnace. We went with this because the furnace was only $1200 from home depot, and it'll pay for it'self real quick with oil $3.00+ a gallon and tree length wood at $130 a cord

Anyway, let me know what you think!

Nothing wrong with your thinking. I don't think very practical though. Too expensive.

That's the thought behind what are called Russian fireplaces; A large mass of masonry to store heat which allows a short very hot fire to burn clean with the masonry storing that heat.

Solar heating people have used large masses of gravel to store heat. Water of course will store the most but is the most inconvenient.

This place has a lot of heat storage stuff, tanks, controls, calculations, etc. Check it out.
https://www.hearth.com/talk/

Theres really nothing that can be done with the excess heat. A forced air woodfurnace is a bit different than a boiler. You won't pull enough heat from the furnace for any storage tanks. There are some that run a stainless coil and get free hot water, but thats about it. The only option is to get a smaller furnace, or build smaller fires. We heat with a EPA certified furnace and it does well for our home, but its quite bigger. You may find that 8 hours is pushing it. Down the road consider a woodstove to replace the furnace if all the heat isn't needed. Otherwise cracking a window will help ease the heat. Feels good not to have a oil/propane bill.

Welcome to the Forum. Do remember that you have come to a coal burners forum, so you may not be among the most knowledgeable people when it comes to burning wood. That being said. Many of us did burn wood before we learned about coal.

If you can get the radiator & bladder tank for close to free, have fun! See what you can come up with, but, if you're paying retail for all the parts.... I dunno. I don't think you'll get nearly enough heat exchange to heat the water in the tank. Then, the truck radiator... I don't think the 100,000 BTU rating is going to work backwards....maybe, maybe not. That rating is to give off heat from water in it at 195 degrees. Hoping to reverse the process.... hard to guess, but I'd guess it's just not going to transfer all that much heat. If you are paying retail, my gut says you'd be dollars ahead to skip the radiator and trade for a boiler. But, again, if your uncle Milton was a trucker & there's a giant radiator sitting behind the barn, give it a go! Get a $30 kids swimming pool & see if you can melt it down. If you can, then give Tom Gozee from the Saturday morning radio show a call & see about a lined tank. It's fun to play!

PS. Tree length may not be the cheapest way to buy wood. I would insist on buying it by the weight. One crooked tree & you can lose a cord of wood. If you can get 8 foot it's usually a better deal. Remember, the most wood you can have in one cord of wood is one piece of wood, four feet round and eight feet long. ANY other size & length will have more air spaces and less wood. When you buy tree length, you buy the most air and the least wood.

Thanks for the input

Yeah, I know that paying all retail would be a rather foolish endeavor. I'm actually leaning toward 10 55gal plastic barrels ($5 ea) instead of a bladder now, wouldn't have to build much of a frame, can still move it downstairs piece by piece, and won't have 550gals in the basement all at once if there is a tank failure.
I didn't think that it made a difference as to which way the radiator functioned, but I'm only familiar with them working as a heat dump. I looked on ebay and big radiators are gong for $100 shipped if one's not picky about the brand, but I'd research to make sure that it wouldn't be undersized.

We got a 8 cord load of tree length, and lost count of the half cord loads we've moved already, but I think we're still on target. I'll definitely keep your advice in mind though!

Tseeker wrote:I didn't think that it made a difference as to which way the radiator functioned

Think about it...you have a radiator filled with 180 degree water with room temperature air blowing through it...probably a 100 degree delta between the two. Or...you can have a radiator filled with room temperature water, and blow 110-120 degree air from the furnace through it. Which do you think will transfer more BTU's to/from the water?

OK. Now I think I understand what you mean, sorry about that.

The thermostat for the blower on the stove is adjustable, I think it's current factory setting to turn on, as you said, at 110 and shut off at 95. the upper limit on the stat is 250, so would it work better, with a room temp of 72ish, to run it at say 175 on and 160 off to achive a better delta?

Thanks for your patience, I've used wood stoves some before but never a whole house furnace.

I think you would get a lot more temperature fluctuation in your house with the higher air temperatures.

True, but it would be turned up so the radiator could soak the heat up more effectively, the hot air after going through the radiator would then be at a lower more comfortable range for circulating through the house.

Or would it not work like that?