Garn 2000 for house and shop

Grigg

Member
Jan 7, 2015
21
Lexington, VA
After a lot of research on wood boilers and particularly Garn a few years ago we're finally making plans to install one in the coming weeks/months.

Timing was favorable to pick one up on a trip with some friends and family to Wisconsin a few weeks ago.

Just poured the slab this Monday and will unload it next Monday. It'll be in a mechanical room as part of a shop addition.

Radiant heat in new slab. Forced air in part of the existing shop. Still considering options but likely radiant floor in part of house, radiators or baseboard in other parts and part of new shop space.

Expect I'll have plenty of questions along the way. We have hired a local hydronic heating contractor to help with the application part but they haven't been around a Garn before, not that it makes much difference where hot water comes from.
I've been doing the research and work to get the thing physically installed.

Obviously had hoped to have it in service about now but things didn't quite fall in place to start the project in time.
 

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JohnDolz

Minister of Fire
Dec 29, 2015
524
Burlington, CT
After a lot of research on wood boilers and particularly Garn a few years ago we're finally making plans to install one in the coming weeks/months.

Timing was favorable to pick one up on a trip with some friends and family to Wisconsin a few weeks ago.

Just poured the slab this Monday and will unload it next Monday. It'll be in a mechanical room as part of a shop addition.

Radiant heat in new slab. Forced air in part of the existing shop. Still considering options but likely radiant floor in part of house, radiators or baseboard in other parts and part of new shop space.

Expect I'll have plenty of questions along the way. We have hired a local hydronic heating contractor to help with the application part but they haven't been around a Garn before, not that it makes much difference where hot water comes from.
I've been doing the research and work to get the thing physically installed.

Obviously had hoped to have it in service about now but things didn't quite fall in place to start the project in time.
Congrats, exciting stuff! It might make a difference where the hot water comes from. Some hydronic folks only know 185 degree water coming out of a boiler being run through large circulators. I would think you want someone that is very comfortable with the different water temps that best fit each type of emitter - you mention quite a mix: radiant, forced air, baseboard, etc. I'm a fan of Outdoor Reset so I would look for someone that is knowledgeable on that as well. Heating the water is 1 task, using the stored BTU's in the most efficient manner is another. Not suggesting the person you chose is not knowledgeable/fully capable.
 

Bad LP

Minister of Fire
Nov 28, 2014
1,118
Northern Maine
Utilizing various emitters that requires different design temps gets tricky.
I’m doing it and not 100% thrilled.
Hard to make 180 water in a tank with 140 water.
RFH wanting 120 water is a non issue.
Heating BR’s with BB that were designed for 180 isn’t efficient.

I’m guilty of changing my mind on a heating source after the fact. I’ll continue to make the needed changes:
A) Put domestic HW back on the LP boiler.
B) Remove the BB heaters and install panels.
C) Add a CI radiator to a currently unheated space. I might add electric RFH if I remove the current w/w carpet with tile. Plans are in the air at this time.

LESSON. Retrofitting is twice the cost.
 

Grigg

Member
Jan 7, 2015
21
Lexington, VA
Thanks for the feedback. I think we've picked the right folks and are familiar with their good work on my parents house about 18 or 20 years ago. A good friend is also knowledgeable in this and has offered to advise if needed and for his own curiosity. First I'll listen to the folks we've hired trusting they know what's going on. I'll be sure to understand the system and options as they develop.

Few pictures of the in floor tubing.
6" of foam under the slab.
Also 6" up the stem wall which will overlap the 6" SIP walls to come and make a sort of shelf all the way around the room. Seemed like a good way to deal with the under slab to wall insulation transition.
6" slab. We ended up replacing the bricks with pieces of cinder block to get the tubing a little lower. Even so the concrete guy was afraid to cut any more than the one control joint at the inside corner (no tubes in the vicinity).

The Garn sits over the Garn sized lack of tubing.
We've provided two 4" pieces of conduit with long sweeping elbows to get insulated hot water to and from the house basement, about 30-40' run from the back of the Garn.
 

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Grigg

Member
Jan 7, 2015
21
Lexington, VA
The first floor will be two main rooms each with a thermostat. We did put in tubes for in slab temp sensors if desired.

Much of the new space (pictured earlier) will have a second floor. Undecided at this point how to heat it, or if it'll even need much heat if the first floor is kept warm. Only 5 small to medium size windows in the 1500 sq ft second floor with 12" insulated roof panels.
Investigated radiant heat built in to the second floor subfloor but that didn't seem cost effective.
Right now thinking of a few radiator panels under those windows but still open to options.

In the existing shop about the only realistic option is a heat exchanger in the existing AC system. It currently has no heat or provisions for heat other than a traditional wood stove that will be removed.

The existing house (very small) will likely get staple up radiant heat under the bedroom and the bathroom floor.
Right now hot water baseboard or the flat radiator panels sound like good options for the living room and kitchen. They have old thick wood floors and also wouldn't be real easy to install radiant floor heat underneath. (bed and bath have newer floor systems and less going on under them)

Also want to use the Garn to supplement the gas hot water heater in the house. Still looking into options and listening to ideas from our radiant heat guys on that.
 
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Grigg

Member
Jan 7, 2015
21
Lexington, VA
Back to the Garn.
They have a technical service bulletin dated Feb 20 2019 that came inserted in the paper manual with my unit. Bulletin not yet on the website but that's the link if it is.
They are now suggesting you can use the bottom of the tank for hot water supply and return to the upper fitting, this is opposite of how they originally intended you to plumb them.
Sounds like the newer models now have a 2" female pipe fitting for both ports and they supply a piece of 1.5" pipe a few feet long that can be inserted and screwed in to either port you choose to be the hot water return.

They say a number of owners have tried reverse flow in the past. I think they must have used the 1.5" pipe (welded in) as the suction, they now/still want you to have 2" suction wherever it is.
Benefits of the reversed flow are increased useable thermal storage and reduce or eliminate pump suction boiling.

They don't list any downside to using the lower tank fitting as the hot water supply so long as it is 2".

Any thoughts on, or experience with, this?
 

jebatty

Minister of Fire
Jan 1, 2008
5,734
Northern MN
The Garn is a good boiler. My experience is with the 3200. Keep in mind that the Garn is not pressurized and elevations of your various emitters in relation to the Garn will be an important design consideration. If a pressurized, closed system is needed, you probably will need a water to water heat exchanger to isolate the Garn from the pressurized system. Also, the Garn is intended to be a batch burner, not burn with storage, and not burn continuously. Let us all know you your design/install progresses.
 

maple1

Minister of Fire
Sep 15, 2011
10,382
Nova Scotia
Make sure your emitters are sized for lower supply temps. Or else you won't be able to utilize the batch burning & storage capabilities anything close to fully.

That would likely mean oversizing your W-A Hx way more than what someone used to conventional heat sources would normally size at. Baseboards as well. It's easy to mix down hot water to a lower supply temp for say in-floor, but if your HX & baseboards get sized for 160 or above, that will likely lead to disappointing system performance.
 

Grigg

Member
Jan 7, 2015
21
Lexington, VA
I understand lower temp the better for efficiency, within reason, and not high enough then 2000 gallons won't be enough storage for infrequent burns given the heating demands.

What's a good or average water temp to use for those emitter sizing calculations?
 

Bad LP

Minister of Fire
Nov 28, 2014
1,118
Northern Maine
I understand lower temp the better for efficiency, within reason, and not high enough then 2000 gallons won't be enough storage for infrequent burns given the heating demands.

What's a good or average water temp to use for those emitter sizing calculations?
It really depends on the finish floors. I was told not to exceed 105 on my wood floors in the DR and LR. My tile areas will take whatever you can stand but they too are on the same water temp due to using a Taco Radiant Floor Mixing Block. It has outdoor reset with program min/max parameters built in. I think it works very well knowing they are rarely used these days.
 

jebatty

Minister of Fire
Jan 1, 2008
5,734
Northern MN
If my recollection is correct, the Garn will work best on supply temps of 140F and less. In other words, burn the Garn to a high temp, mix down to 140 or less, and use the Garn as your storage supply above 140F and to your lowest level of water temp needed. After the high temp burn, let the Garn burn down to low coals or "out." Empty ash/coals if they are accumulating. Then another batch burn as needed.
 

TCaldwell

Minister of Fire
When I first installed my garn in 2006, the manual suggested supply at the bottom and return To the top. I believe this was primarily due to over firing ( water temp too high) that exacerbated cavitation ( npsh) due to poor install practices, mainly the circ being too high in elevation.
At that time there wasn’t any internal or recommended diffusers, tank temps tended to be more homogeneous, with not much thermocline.
Some time after the the dip tubes came into play advocating supply from the top, thermocline and reduced cavitation.
I believe the single temp gage originally supplied and installed At the same height as the high supply port was confusing to most regardless of what they read in manual that did state not to fire if over 185. Not that this was wrong but it totally dependent as to the result of how your garn is piped. Supply from the top and you have 3/4 of the tank to heat up, supply from the bottom is more homogeneous, requiring less wood to reach the target temp., based on that one thermometer. Unfortunately this all required a learning curve not to over fire.
At this point low temp emitters And thermocline are the key, as the longer you can wait to fire the garn the more efficiency you gain.
I’m piped from the top, return to the bottom, using 4 equally spaced thermocouples to monitor tank temps. It’s not uncommon to see a 60 plus differential from top to bottom, really leveraging that top 1/4 of storage to lengthen times between burns.
I average the 4 temps subtracting that sum from my target temp, then multiplying that by 3 ( it will take you roughly 3 lbs wood to raise your 2000 gal garn one degree)
So if my averaged temp is 140, my target is 180 = 40 deg diff. 40 x 3= 120 lbs wood required to get you there, you’ll need to weigh your wood.
For this to work properly you’ll need to mix the tank only as it’s firing So as the tank is fully charged ( same temp top to bottom).
 

maple1

Minister of Fire
Sep 15, 2011
10,382
Nova Scotia
It really depends on the finish floors. I was told not to exceed 105 on my wood floors in the DR and LR. My tile areas will take whatever you can stand but they too are on the same water temp due to using a Taco Radiant Floor Mixing Block. It has outdoor reset with program min/max parameters built in. I think it works very well knowing they are rarely used these days.
I think what he was asking related to supply temp to use for size calcing other emitters, and not floor heat. Baseboards, etc. Hotter can always be mixed down for in floor.

I think I would maybe use 140 supply temps for baseboard or W-A Hx sizing calcs. See what that says, and then even add more if you have room for it. Don't think more can hurt anything. Then there may also be some spots in your house & system layout you could throw in a cast iron rad or the like to pull out more heat. If on the same zone as baseboard, I would put that at the end of zone after the baseboard. Assuming a commonly accepted dT through emitters/zones of 20°, that would mean 120° returning to boiler. The longer you can keep the coolest water possible returning to the boiler, the more efficient it should be in pulling heat out of the exhaust before it gets exhausted. And the better stratification (thermocline) will be.
 

Bad LP

Minister of Fire
Nov 28, 2014
1,118
Northern Maine
Agreed. All I know is every room in my house is zoned and the cooler the tank storage gets the more the BB zones do not stop asking for heat. This lower heat also pulls the heat out of hot water storage trying to satisfy that set temp.

I'm 100% sure that if I changed out the BB for panels I would still remain warm and be able to use my lower temps in storage more effectively.
 

JohnDolz

Minister of Fire
Dec 29, 2015
524
Burlington, CT
Agreed. All I know is every room in my house is zoned and the cooler the tank storage gets the more the BB zones do not stop asking for heat. This lower heat also pulls the heat out of hot water storage trying to satisfy that set temp.

I'm 100% sure that if I changed out the BB for panels I would still remain warm and be able to use my lower temps in storage more effectively.
"I'm 100% sure that if I changed out the BB for panels I would still remain warm and be able to use my lower temps in storage more effectively." - Absolutely.

"All I know is every room in my house is zoned and the cooler the tank storage gets the more the BB zones do not stop asking for heat. This lower heat also pulls the heat out of hot water storage trying to satisfy that set temp." - I leverage Outdoor Reset and use a design curve that never gets me to the point that my thermostats stop calling. My objective is to run the circs 24x7 with a minimal flow at the lowest temperature possible. I have BB heat and manage to keep my house near 72 using very low water temps - of course it would be more efficient with emitters designed for lower temps. Granted this is a theory and doesn't actually work this way - circs end up going on and off due to thermal gain, etc.
 

Grigg

Member
Jan 7, 2015
21
Lexington, VA
We have a roof over it now and I'm closer to getting it set in its final resting place.
Building the rest of the system will start in the new year.

I'm hearing that it's desirable to mix the tank while firing, which I understand.
Earlier I was thinking supply for heating from the bottom per the recent technical service bulletin. This has a few advantages as mentioned earlier, increased useable thermal storage being one. Does mixing while firing do as much or more in that regard?

Not yet sure if the main circulator pump will be used for mixing. If not, what size pump would be desirable as a stand alone for mixing?

Thanks,
Grigg
 

eauzonedan

Member
Jan 21, 2011
95
Bayfield Co. Wi
Based upon the layout of the of the internal piping within the storage area I suspect Martin spent a lot of time to optimize uniform water heating without need for a dedicated mixing pump. That being said everyone’s pumping rates, return water temps etc will be different and anything we can do to optimize the mix on recharge is good. Garn recommends the addition of their filter system which I retro fitted and plugged into the control box so it cycles with the fan. It’s piped the opposite of my supply pump and located on the front of the unit which I believe sets up a flow pattern within the tank. My 3 submerged sensors tell me 50+ degrees of stratification before the burn is under a degree after the burn and includes the recommended filtering. So the combination of Martins design, the rear supply pump for heat to the system and the “counter flow” filter pump gets me near a 100% mix during a burn. Please note relying solely on Garn’s single internal temp measurement will not give you the whole story on your storage temps.
Dan
 

hedge wood

Member
Mar 1, 2009
102
Eastern NE
Dan
How old is your Garn? Mine is 10 years old this year. I added a stainless housing filter to my Garn after having mine down this summer repairing the weld that failed were the heating chamber is welded to the front of the unit. I am pulling out the front on the bottom drain port and putting back in my piping that goes to the top of mine were the water is pulled from for heating the exchanger's I was down May to Aug and have had the pump for the filter running 24/7 since then. First couple months was changing filter every two weeks down to a month now. I think later I will wire mine like yours that the pump for the filter only runs when the blower is running.
 

eauzonedan

Member
Jan 21, 2011
95
Bayfield Co. Wi
my serial is 2812. It’s been in service 5 years but sat in the pole barn a few years before it got piped up. It was of the first ones to get the electronic control module. I suspect yours has the old egg timer and may not allow a direct plug in of the filter pump.?? The new controller has a duplex outlet for the fan motor and also room for the pump to be just plugged in. The Garn guys said there was enough capacity in the relay to handle both fan and pump. My well water sucks and after the initial chemical dump it creates a heavy flock It takes daily filter changes for a few weeks to clean things up. Mike at precision says some form of iron. Ya don’t want that crap to settle to the bottom of the tank as it will become a sludge that will block the chemicals from protecting the steel. I added a couple hose bibs in the filter loop to allow me to roust the nooks and crannies to keep things in solution and allow the filter to do its thing. Good news is that once it’s gone.... it’s gone and I cycle with the fan for maintainence . Filters now last months. Dan
 

Grigg

Member
Jan 7, 2015
21
Lexington, VA
We're finally making progress on the Garn after working on the building first (and still).

Set the Garn on 8" of foam to get the air inlet up high enough to clear the masonry wall. Still feels like a comfortable loading/operating height otherwise would have trimmed the wall if lower was necessary.

Piping is well under way. I haven't fully grasped the system design but as I do learn parts it makes sense and seems logical. Glad to have folks doing this that have done it for decades, I'd be at it for months were I to figure it all out and install the piping myself.

Their is a large heat exchanger separating the Garn from the rest of the system. The circulator in the primary loop, suction from bottom of tank, will run when called for and also run when the blower is on for mixing while firing.

Two pump flanges on top are for two different rooms, one gets coil in air handler and other a unit heater hanging from ceiling.

Pump flange on left with a mixing valve is for radiant slab and will benefit from outdoor reset.

Pump at bottom right is for a loop to the house for heat and hot water. Indirect tank heater for the domestic hot water uses whatever temp is coming from the Garn and then output of that feeds through existing gas water heater, and likely a thermostatic mixing valve. House heat still undecided, either radiant under floor or radiators.

If all goes well they'll have the primary loop and bypass filter connected today or tomorrow and I'll get it filled and running this week.

Grigg
 

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hwater85

New Member
Jan 22, 2020
10
Virgilina, Va
We're finally making progress on the Garn after working on the building first (and still).

Set the Garn on 8" of foam to get the air inlet up high enough to clear the masonry wall. Still feels like a comfortable loading/operating height otherwise would have trimmed the wall if lower was necessary.

Piping is well under way. I haven't fully grasped the system design but as I do learn parts it makes sense and seems logical. Glad to have folks doing this that have done it for decades, I'd be at it for months were I to figure it all out and install the piping myself.

Their is a large heat exchanger separating the Garn from the rest of the system. The circulator in the primary loop, suction from bottom of tank, will run when called for and also run when the blower is on for mixing while firing.

Two pump flanges on top are for two different rooms, one gets coil in air handler and other a unit heater hanging from ceiling.

Pump flange on left with a mixing valve is for radiant slab and will benefit from outdoor reset.

Pump at bottom right is for a loop to the house for heat and hot water. Indirect tank heater for the domestic hot water uses whatever temp is coming from the Garn and then output of that feeds through existing gas water heater, and likely a thermostatic mixing valve. House heat still undecided, either radiant under floor or radiators.

If all goes well they'll have the primary loop and bypass filter connected today or tomorrow and I'll get it filled and running this week.

Grigg
Nice to see someone else is from Virginia.
Do you have to unit just resting on top of foam?
Adam
 

Grigg

Member
Jan 7, 2015
21
Lexington, VA
I know of two other Garns in our county, one I've seen and one I haven't. You're not that far away, do you have one as well?

Yes, it is sitting on Dow Thermax Polyisocyanurate Insulation which has a compressive strength of 25 psi. The boiler full of water and given the runner area only applies 8.3 psi, so although it seems counter intuitive the foam is more than adequate to support the weight.

Grigg