Can the Garn handle a Canadian winter -40's

[Scott from Canada]

Hello all, I have been researching boilers for a couple of years now. I want to do this once and do it right. I am hoping to tap into
the great wealth of knowledge on this forum. I would like to heat a 1600 sq ft house with a combination of floor heat and HX in my electric forced air furnace, a 2000sq ft shop with a combination of floor heat and HX, and a 16x 26 pool. Temps here can be in the -40s. There are boiler manufacturers here but I seem to be drawn to WoodGun and now more so the Garn. I welcome any and all input to help me finalize my decision. If what I am hearing on the forum is true, I'm glad I didn't buy into the GreenWood gasifier.

 

[Como]

I am a long way south of Canada, we hit -44F last winter. I think when you get down to these figures there is not much difference between C and F.

Both come in different sizes, it all depends on you heat load and which system best meets your individual circumstance.

In my case the Wood Gun has the advantage of dual feed and Stainless Steel. The Garn built in storage and horizontal chimney.

 

[Scott from Canada]

That is the one thing that I wish the Garn had was the ability to say switch to autofeed pellets. I have a small saw mill so I seem to be able to come across an abundance of cord wood for now.You have hit I believe the to main points to weigh, WoodGun dual feed vs Garn water storage. From what I read both these units have been time tested and have proven to be strong. If I have it right the water/heat storage of the Garn should = less burns. Could I get some comments from folks who have operated these units in -30s . Will I get away with 1 burn per day with the Garn? It has been estimated my heat load is 300,000btu.

 

[Rick Stanley]

I think that is gonna depend on what we have for radiation. I've been told that with the old cast iron radiators I have here, that I will be able to draw the garn storage temp down to 140* or so. With fin tube convectors I guess it's up around 180* with radiant floor making the best use of the stored energy by being to get usable heat from water as cool as 90*....................

 

[Como]

I think you would need two 2,000's to have one burn a day. Cheaper than one 3200. I am probably going for a 2,000 but leave space for a another if I need it.

 

[Scott from Canada]

I believe the 1500 is around 300,000 btu if it takes a burn in the morning and one at night on the coldest days I can live with that. They are always saying that the boiler should not be over or under sized so the 1500 should do. I hope so because the boiler is one part of this project, the distribution system will also be a significant cost.

Thanks keep the info coming, I know there are alot of Garn experts out there.

 

[TCaldwell]

Scott, the 300kbtu you refer to, what time frame is that referenced to, hr, 24hr day?

 

[Scott from Canada]

I believe thats BTU/hr. I ran my building info through a BTU calculator. It may have been on the WoodGun sight. I'm not sure how accurately it is because the shop and house came out at 138kBtu and the pool was 103k BTU. Total of 241k btu but of course the pool won't be heated in the winter when the shop will. suggestions on how to figure this out accurately? Thanks

 

[karl]

300,000 btu/hr is insane. The average house in the States has a heat load of 35,000-40,000 btu/hr. All in all that maybe right for you since you're heating a pool and shop. If it really is 300k youre going to need to buy your own forest too. You're going to be burning a cord every two and half days.

 

[Como]

My load is 405,000btu

5,500 sq ft

Colorado

But we get Solar Gain, and it gets really cold for usually no more than 4 days at a time.

I estimate 30 cords.

 

[heaterman]

300,000 btu/hr is insane. The average house in the States has a heat load of 35,000-40,000 btu/hr. All in all that maybe right for you since you're heating a pool and shop. If it really is 300k youre going to need to buy your own forest too. You're going to be burning a cord every two and half days.

Wrong on all counts. The burn rate for a 1500 is about 350,000 per hour. The other part (regarding matching output to load) is a common misconception about a Garn and I'll try to put this as clearly as I can. With a huge storage capacity such as a Garn contains, the burn rate is immaterial until you reach a point where you are actually using all those btu's as they are produced. As an extreme example, a person could have a Garn 1500 connected to a load of only 10,000 btu's. And it would work wonderfully, consuming very little wood while it provides heat for the structure. This is because the burn rate or fire if you will is not heating the space, the heat is coming from stored energy in the 1500 gallons of hot water. You see, how fast you burn the wood doesn't matter because you are storing all the heat for use as it is needed. The rate of burn does matter when it comes to emissions and efficiency. The hotter and faster you can burn without cycling the fire, the better both become. The Garn contains no rocket science combustion process, just a continuous clean burn that is connected to a very good heat exchanger. As an example, if you start with a 1500 at 200* water temp and use heat out of it until the water temp is down to 120*, you have extracted about 750,000 btu's from it. This can be done with no fire in the Garn at all. However, that heat is still available for use because of the storage integral in the Garn.

To answer the first poster, yes a Garn can handle 40 below. The burn rate is more than adequate. How often you have to fire depends entirely on your load. Consider what i said about the 750,000 btu draw down in light of your proposed load of 300,000 per hour. If that is truly the case you would need to fire the Garn about every 2-1/2 hours. A 2000 would give you another hour of "off" time. Now if you connect a a typical wood burner with no storage capability to that load, you would need to maintain a continuous fire in it that would meet that demand. Storage is the key, burn rate, not so much.

 

[Scott from Canada]

Thanks for replying , just trying to learn from you that know. From what you say , I sure hope that calculation is wrong. Is there someone at Garn that can do an BTU calaulation for me? So the water storage is key, the more you have the more reserve you have and time between burns.. correct?

 

[Jim K in PA]

Scott - Heaterman is correct, and so are you (now). The storage is key to how long a draw period you have between burns. The GARN is a "batch burn" unit for most applications. That is, you perform a burn when the storage temp drops to your low limit, and recharge the tank. Then the fire goes out, but you continue to draw off the stored heat. If you are drawing at a rate that drops the off-burn time to less than 2 hours, you need more storage capacity (IMO). This method is what allows the GARN to burn efficiently every burn, for the whole burn. No idle time or throttling, and no worries about overheat unless you ignore the temperature gauges and light it when you don't need to.

Take your time and do your heat load calculations. GARN may be able to help you with some estimates, but you can download a freeware load calculator from Slantfin.com. The pool losses should be available from any pool heater manufacturer.

You are now beginning to see the difference between a GARN and just about every other unit. Other gassifiers can be set up to function like a GARN by adding an equivalent amount of storage, but then you need a seperate heat exchanger to get the tanks charged, which introduces an efficiency loss.

Heaterman has installed more GARNs than anyone I know. His advice is sound, so take heed!

Best of luck with whatever you choose, and welcome to the Boiler Room!

 

[Scott from Canada]

Thanks very much for all your advice. I'll redo the calculations, something doesn't seem right. If the total is 240k I will only be heating the pool and domestic hot in the summer est. 103k for the pool. That would leave 140k ish for the house and shop in the winter. I may be making this more difficult than it is. I'm going to redo my heat calculations. I have heard folks here burning 15 cords a winter in the old boilers so I can't see it with a gasifying Garn.

 

[Gooserider]

Thanks very much for all your advice. I'll redo the calculations, something doesn't seem right. If the total is 240k I will only be heating the pool and domestic hot in the summer est. 103k for the pool. That would leave 140k ish for the house and shop in the winter. I may be making this more difficult than it is. I'm going to redo my heat calculations. I have heard folks here burning 15 cords a winter in the old boilers so I can't see it with a gasifying Garn.

Loads that aren't being heated at the same time shouldn't be added to make a total... Your total load will be JUST the house and shop in the winter, or JUST the pool and DHW in the summer. It is possible that you might have points where you are heating everything, but I'd expect one demand or the other to be much less than peak at all times... IOW, I would estimate that your peak load would be on the order of 140K for the house and shop based on your numbers...

Gooserider

 

[heaterman]

Thanks for replying , just trying to learn from you that know. From what you say , I sure hope that calculation is wrong. Is there someone at Garn that can do an BTU calaulation for me? So the water storage is key, the more you have the more reserve you have and time between burns.. correct?

Now you have it. If your actual winter heating load is say...100,000, using the scenario I gave above, 200-120* you would have about 7-1/2 hours of no burn before refiring.

Tell me a little bit about your house. insulation, window amount/size, sq ft. etc.

 

[Scott from Canada]

Sure since you ask , the house is 1700sqft, R26 walls, R 50 attic , R28 basement, 8' ceiling, 345sqft of windows, 2-doors. The shop is 2000sqft, R20, arch rib design, 12x12 door. The pool is 16x26 x4' deep.

I just ran the numbers through a heat loss program and this is what I came up with:

House-67k Btu/hr

Shop 90k Btu/hr if I was to heat the entire thing.

Pool- 150k Btu/hr based on ambient temp of 70F - final temp of 85F at 1 degree/ hr rate.

As we discussed earlier the shop and house will be heated in the winter and the pool and domestic hto in the summer.

Thanks everyone for your input. This a large cash venture, so it has to be right and feasible.

 

[TCaldwell]

As heaterman states the btu storage capacity between 120degf and 200degf, that is dependant upon the useable supply temp for your emitters. I think you stated infloor heat, if you are refering to radiant , then your useable supply temp might be lower than 120degf, thus increasing your storage capacity per burn, also a fan coil for forced air might require a much higher supply temp, thus reducing the storage capacity.

 

[heaterman]

Sure since you ask , the house is 1700sqft, R26 walls, R 50 attic , R28 basement, 8' ceiling, 345sqft of windows, 2-doors. The shop is 2000sqft, R20, arch rib design, 12x12 door. The pool is 16x26 x4' deep.

I just ran the numbers through a heat loss program and this is what I came up with:

House-67k Btu/hr

Shop 90k Btu/hr if I was to heat the entire thing.

Pool- 150k Btu/hr based on ambient temp of 70F - final temp of 85F at 1 degree/ hr rate.

As we discussed earlier the shop and house will be heated in the winter and the pool and domestic hto in the summer.

Thanks everyone for your input. This a large cash venture, so it has to be right and feasible.

OK. There's some numbers to work with. All the decisions from type of wood burner to size of tube and circs start with the heat loss. BRAVO!!

So..........Assuming those numbers are for your design temp of -40*C, and assuming that we use the water in the Garn from 200-120* here's what you can expect. With a 1500 capable of delivering 750,000 btu's and your shop/house heat loss at 157,000 you would get roughly 5 hours of heat, with absolutely no fire in the Garn. If you stack a big load of wood in there you could probably expect to raise the temp back to the 170-180 level on one load, while simultaneously heating both buildings. You would probably have to add another medium sized load after 2-3 hours to top it back off at 200*. From there the cycle would repeat. Now, the question I always pose to people is how many days do you actually spend at design temps during the winter. If you are like most places you'll see 2 maybe three weeks of worst case weather and the rest of the winter is milder. That means your heat loss is not as severe and that 750,000 btu drawdown will happen over a longer period of time. Let's say it's maybe only -10*C or maybe even 0*C. That same 750,000 btu storage will now last for 8-10 hours between firing.

All that being said, if you can tolerate a few more frequent firings in the dead of winter, a 1500 Garn will probably heat your place just fine.

Making any sense?

 

[fabguy01]

sorry not to hijack the thread but tought this might be good info for scott being a potential Garn owner like myself.
Heaterman, so what hapens when the Garn either reaches its high limit or the timer kicks off? will it sit there and smolder like a OWB? Or will it cut the air supply enough to to put the fire out? Will the Garn turn off the blower if there is no fire left in the box and it has'nt reached temp? Or is it going to continue running the blower and radiating heat from the Garn to the outdoors?

 

[heaterman]

sorry not to hijack the thread but tought this might be good info for scott being a potential Garn owner like myself.
Heaterman, so what hapens when the Garn either reaches its high limit or the timer kicks off? will it sit there and smolder like a OWB? Or will it cut the air supply enough to to put the fire out? Will the Garn turn off the blower if there is no fire left in the box and it has'nt reached temp? Or is it going to continue running the blower and radiating heat from the Garn to the outdoors?

There is no high limit. Being an open system it just boils and you evaporate a little water. Ever see/hear 2000 gallons of water boiling ? :O (makes a very abrupt learning curve)
All the Garn owners I have worked with seem to very quickly develop a sense of how much wood and how much time is needed to reach a desired temp. This pretty much eliminates blower shut down before the wood is pyrolized or after it is completely consumed. Stack loss at idle in a Garn is about nonexistent as it has virtually no draft until the blower runs.

I do know that Martin is tossing around a cost/benefit analysis of a variable speed draft motor "governed" by a flue mounted O2 sensor. That would be a mighty interesting piece of equipment. Probably a couple years out unless the customers really clamor for it. The unit doesn't need it to meet efficiency or emissions standards.

Just as info to all here, I heard today that testing on the Garn 1500 showed efficiency of 85%+ on the "low" heating value test. Emissions have never been an issue. There will be something about the test posted at www.garn.com within a week or so.

 

[fabguy01]

Maybee they could also look at a thermocouple in the first pass of the flue to shut the blower off as soon as the fire is out

 

[heaterman]

Maybee they could also look at a thermocouple in the first pass of the flue to shut the blower off as soon as the fire is out

The O2 sensor would monitor the excess oxygen in the flue gas and ramp the VFD draft motor up and down accordingly. As the fire is building it would ramp up the speed supplying the correct amount of air and then drop the rpm as it died down. The thing is, for a unit that's already starting out at 85% there's really not a lot of added benefit to be gained from a cost standpoint.

 

[SolarAndWood]

Pool- 150k Btu/hr based on ambient temp of 70F - final temp of 85F at 1 degree/ hr rate.

Have you looked at one of the simple solar heaters for this? That is a lot of wood during a period of the year that you have a lot of sunlight.

 

[RowCropRenegade]

whenever I hear the word, sensor, I cringe. 2 02 sensors in chevy truck cost 240.00 The simplicy of the Garn is what made me buy one. It needs to improve efficiency at least 5-10% to justify the headaches that come with "sensors" JMHO.