Assuming both are gassifying, is one more efficient than the other?
I can see advantages in both ways of heating a house.
I can see advantages in both ways of heating a house.
Boiler vs. Furnace
- Thread starter velvetfoot
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JRHAWK9
Minister of Fire
The furnace should be more efficient at transferring heat from the fire to the room since the heat is being transferred to a cooler 70 degree load than the hotter water of a boiler. A bigger delta. Then after those btus make it to the hot air duct you can lose it to duct losses if you ducts are not in the right place.
Assuming both are being run at optimum output (not idling), and both use the same technology (gasser, or?) then I would expect nearly identical efficiencies. You can cool the exhaust from either firebox down to low levels with either water or air.
Assuming both are being run at optimum output (not idling), and both use the same technology (gasser, or?) then I would expect nearly identical efficiencies. You can cool the exhaust from either firebox down to low levels with either water or air.
The huge advantage with a boiler is the ability to "store" the heat generated by the fire. Provided one has a storage based hydronic system in the first place that is.
Air is a very poor storage and heat transfer medium when you get down to the physics of it.
If you operate a furnace at a steady state condition it would be at least as good if not better than a boiler because of the
T provided by 65-70* room air temp coming across the heat exchanger. The fact of the matter though is that a wood fired furnace cannot be designed to take full advantage of that factor. It would turn into a blob of creosote and condensation if it were operated under anything less than ideal conditions.
When it comes to burning wood, the boiler definitely has the advantage.
Air is a very poor storage and heat transfer medium when you get down to the physics of it.
If you operate a furnace at a steady state condition it would be at least as good if not better than a boiler because of the
T provided by 65-70* room air temp coming across the heat exchanger. The fact of the matter though is that a wood fired furnace cannot be designed to take full advantage of that factor. It would turn into a blob of creosote and condensation if it were operated under anything less than ideal conditions. When it comes to burning wood, the boiler definitely has the advantage.
BadgerBoilerMN
Member
Water is 3500 times more efficient than air at transferring heat. Add this to the radiant comfort factor and storage is just icing on the cake.
BadgerBoilerMN
Member
No. Both can have the same flue temps and efficiencies. You'll get the same energy into the room per log with both.
The efficiency differences come from the delivery side and are either zero or they can be significant depending on how ideal your setup is.
Buzz Saw
Minister of Fire
Thermal Storage is the reason I'm going to make the conversation to a boiler(won't happen for a few more years though). I've always burned with a wood furnace and I'm looking forward to not having a fan turning on and off causing warm and cold cycles in the house. One minute there is a chill on the air, the next your sweating.
GS7
Member
Thermal storage and clean burns pushed me into going the gasification boiler route as well...Last winter marked my first burn season. No regrets whatsoever. In fact it still amazes me quite a bit.
BoilerMan
Minister of Fire
Furnaces have the advantage of not freezing, and being fast to respond. Fast response is really a disadvantage especially with wood. Think HOT...cold....HOT....cold with a blower cycling. In theory (on paper) both being gasification efficiencies are the same.
Forced Hot air (FHA) or scorched air as we in the trade call it, is dirty, moves dirty air and dust around a house. But has the advantage of electrostatic filters and central A/C. This is why the VAST majority of residential homes in the southern states have FHA.
In two identical buildings one with FHW and one with FHA the water will have more room due to lack of duct-work and be cheaper to operate due to lack of blower to move (force) air. Think about a 20"x20" duct coming from a furnace compared to an 1-1/4" pipe from a boiler. Even a typical wet rotor circulator uses 85W an typical 1/2HP blower motor is 600W.
A camp would benefit from FHA but a house would benefit from FHW and storage! Zoning is also much easier with water than with air and dampers.
TS
Forced Hot air (FHA) or scorched air as we in the trade call it, is dirty, moves dirty air and dust around a house. But has the advantage of electrostatic filters and central A/C. This is why the VAST majority of residential homes in the southern states have FHA.
In two identical buildings one with FHW and one with FHA the water will have more room due to lack of duct-work and be cheaper to operate due to lack of blower to move (force) air. Think about a 20"x20" duct coming from a furnace compared to an 1-1/4" pipe from a boiler. Even a typical wet rotor circulator uses 85W an typical 1/2HP blower motor is 600W.
A camp would benefit from FHA but a house would benefit from FHW and storage! Zoning is also much easier with water than with air and dampers.
TS
hot air rises, so the warmest temperatures are typically where you are not 
So if the delivery is via air, count on stratification.
Easy to hear DHW pools, snowmelt, etc with a boiler.
FA gives you the ability to heat, cool and add or subtract humidity as well air filtration.
So if the delivery is via air, count on stratification.Easy to hear DHW pools, snowmelt, etc with a boiler.
FA gives you the ability to heat, cool and add or subtract humidity as well air filtration.
Huge price difference. Boiler system reported here at over 15 thousand dollars which includes some hookup costs. The best wood furnace is what? 4000$ with lots of clean burners much lower.
BoilerMan
Minister of Fire
This is not apples to apples here. If we are looking at the appliance only then a boiler is around 2K more. If we step back and look at the whole system as I said above with ductwork compaired to pipes then the picture comes in a bit different. Of course a house that already has ductwork it would be cheaper to get a quality wood furnace like Kumma, or Caddy.
But with new construction the decision is a bit more blurred.
TS
Well now, you don't need ducts for a furnace but you need some sort of radiation for a boiler right?
BoilerMan
Minister of Fire
Ok so one ginormous radiator in one location is the same as a furnace with no ductwork?
The place already has ductwork so a furnace it is for the OP.
TS
You would have a stove unlike any other stove. It would have a huge firebox, huge blower, high output, and some sort of thermostatic control. Lots and lots of folks have a big stove in the basement or in a big shop building. Switching to a furnace, even without ductwork, can be superior to the stove.
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