Heat Ratings

[StackedLumber]

If my current NG forced air furnace is rated at 100,000 btu how does this translate to a boiler set up? As in, if I install a wood boiler rated at 112,000 btu and a heat exchanger that is a 129,000 btu exchanger will this work comparably?

Basically is there a big difference in output rating for btu's between a forced air set up and a boiler/heat exchanger set up?

 

[webbie]

Depends on the boiler.

High efficiency forced draft boilers (EKO, Tarm, Etc.) can usually actually produce the stated output, while one which uses natural draft might only produce 1/2 or less of the stated output much of the time.

Either way, the heat exchanger should work out fine.....it's just that at lower outputs the fan might cycle more, etc.....or you can set up the controls to blow more mild air (less on-off).

 

[StackedLumber]

How much will a thermostatically controlled squirrel cage blower mounted in the manual draft opening help in raising the btu capability of the furnace?

Also, had someone tell me that an induction draft set up burns-in their words-a "significant amount more" wood than manual draft boilers-is this true?

 

[flyingcow]

This is the way i did my sizing. Got lucky, but it worked. I have a 80,000btu weil mclain oil boiler with an amtrol set up. this has heated the house about right. Didn't short cycle too much, run really steady in the mid january cold. So, basically worked about right.
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I put in a 100,000btu +/- wood boiler in. My main goal was to burn the least amount of wood possible. With the help of this site, I decided to put in a gassifier. This has a draft fan. They are a little more pricey, but in the long run, since I'll burn less wood, it'll pay for itself. I may burn up the wood quicker, but this is designed to do that. Because of the storage, than I use the heat from the storage for the rest of the day after the fire goes out. My burn lasts about 3 to 3 1/2 hours. That is "signifigantly faster" than no fan boilers, but as Webmaster pointed out, my fan driven unit was at full output for those 3 or so hours.
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Don't know if this helped, I usually get off topic or just confuse things. But i do it well. I noticed you're in P.I. I live on the southern end of the county. I'm heating (+ yr round DHW) an 1800 sq/ft 2 story hse, on a windy hill, with 2 adults and 3 kids(that shower too long). I'm doing this on about 6 1/2 to 7 cord of wood.

 

[flyingcow]

Just noticed you're in PI Michigan, not Maine. But similiar climate, i think.

 

[webbie]

How much will a thermostatically controlled squirrel cage blower mounted in the manual draft opening help in raising the btu capability of the furnace?

Also, had someone tell me that an induction draft set up burns-in their words-a "significant amount more" wood than manual draft boilers-is this true?

Unless the unit is manufactured and tested with a draft induction blower, you should not mount one.

 

[StackedLumber]

how big is your storage capacity?

 

[btuser]

If my current NG forced air furnace is rated at 100,000 btu how does this translate to a boiler set up? As in, if I install a wood boiler rated at 112,000 btu and a heat exchanger that is a 129,000 btu exchanger will this work comparably?

Basically is there a big difference in output rating for btu's between a forced air set up and a boiler/heat exchanger set up?

What really matters is the temperature of the air coming off the coil or out of the heat exchanger. Have you done a heat loss calculation?

 

[StackedLumber]

You know, i tried using one of those heat loss calculators, but it lost me. Thought I was smarter than it, but I guess I wasn't . . . plus the one I used on the net really didn't tell me what to do with or understand the data it was giving me. Soooo having said all that, I'm all ears to be educated!

 

[flyingcow]

820 gals. My routine is start a fire about 4 to 6 pm. Been getting down to the 20's at night. 40's daytime. Fill the boiler about 2/3 full. This will get me thru until next day. When we get into the deep of winter, start about the same time, fill the firebox full, may refill a few hours later, just depends on what i figure I need. Still learning. My house is r-19 in walls and 30 in attic. Should be thicker. I have baseboard in most of the hse, and rad flr in my kitchen. Summer time i was able to go 5 days, at least, on one firing of boiler, to supply DHW to the 5 of us.
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Oh yeah, from when i light boiler off, it'll send 165 soon to be 180/190 degree water to my house in about 40 minutes. Been very consistent.

 

[StackedLumber]

so here's my "newbie" question . . . .the unit i'm looking at is has just a 20 gallon storage capacity. What am I up against? I figure that I'll need to throw wood on the fire at least 3 time a day or so-am I wrong in my thinking? Am I really going to go through the wood like crazy w/ only a 20 gallon capacity?

 

[Gooserider]

so here's my "newbie" question . . . .the unit i'm looking at is has just a 20 gallon storage capacity. What am I up against? I figure that I'll need to throw wood on the fire at least 3 time a day or so-am I wrong in my thinking? Am I really going to go through the wood like crazy w/ only a 20 gallon capacity?

That really isn't "storage" capacity, it is just the amount that the boiler uses as it's working volume to heat, if you have a circ pump going, that water will only be in the boiler for about a minute...

If you run a gasser without storage, it will work, but you will spend a considerable amount of time idling, which makes more smoke and is less efficient... Essentially you will have to have a fire going 24/7 since you have no storage, but much of that time will be spent idling... If at all possible you really should try to get 500-1,000 gallons of storage, or possibly a bit more, as that will let you burn flat out at maximum efficiency while charging the storage, and then feed your house loads off the storage until it cools down, and then build another fire... With properly sized storage you will probably build 1-2 fires / day during your peak heating season, but during off peak maybe one fire every 2-3 days. During non-heating season, many get their DHW from solar or other fuels, and shut the wood boiler down, but those that do fire find once a week or so is typical.

Gooserider

 

[jebatty]

I would use 75% of rated output as an approximate average for a gasification boiler output over the burn period. As to the hx, capacity is based on rated gpm flow: just make sure you are sizing your plumbing and circ appropriately to get the rated gpm through the hx.

 

[StackedLumber]

the boiler i'm planning on using has a taco pump for circulation and is not a gasification boiler-don't have the $$$ to spill on one of those right now. It's just a simple Menominee wood buring boiler.