Garage Heater / BBQ Pit

[DonPowers]

I built a 32 x 48 garage and put pex in the floor for radiant heat. Currently, I don’t have a heat source in place or any controls and the pex has the gear used for the air test still in place. (There are six three hundred ft loops of half inch PEX, which I plan to use as one zone using two or three pumps.)

The plan was to build solar panels for my primary heat source and I haven’t nailed down a secondary source. There are plenty of options including an artisan well that produces a pretty good flow of 45 deg water year around, heat pumps, wood and many more.

I also want to build a wood fired BBQ / Smoker with stacked or rotating racks.

During one of my sitting in the garage thinking sessions I got the bright idea of combining an outdoor wood-burning furnace to heat water and a BBQ pit. We will call this combination The Contraption.

Still don’t know if I will build it yet but someone may take the idea and run with it. In any event, I figured that writing it down will put it in the continue to think about it pile of all the other things I want to do and by posting it, good feedback will help fine tune the plan.

Possible Uses For Hot Water:

• Heat first floor garage slab.
• Heat garage rooms upstairs with baseboard hot water heaters.
• Controlled snow removal from roof with a Modine type hot water heater with blower in the attic.
• Heat driveway in front of the garage doors, as required, to prevent ice buildup.
• Heat for future greenhouse.

The Concept:

I have a three bay wood shed which I already have plans to move to a new location. The bays are 10ft x 10ft. The shed is modular and it’s relatively easy to reconfigure the bay lengths and overall height. The only thing that’s fixed is the depth, but that could be adjusted if another foot or two is required.

In the shed’s new location, pour a concrete slab for the bay that will contain the contraption. Place 2” blue board under the entire shed to mitigate frost movement and place several inches of crushed stone in the bays containing firewood.

Make the main firebox from steel with firebrick on the inside and a removable ashtray under the grates. A large steel used wood stove could also serve as the firebox.

Make a steel cavity around the firebox with a copper tube heat exchanger and fill the cavity with sand.

Insulate around the cavity and install a sheet metal outer skin.

On one side of the firebox, build the BBQ / Smoker.

Fabricate a flue, for the firebox, with a damper that can proportionally direct smoke outside or through the smoker for BBQ temperature control. Fabricate another flue for the smoker with an additional damper.

Install a stack sensor on the firebox flue to detect a fire and turn on a circulator pump.

Install pressure relief valve(s) on the heat exchanger pipe, just outside the firebox.

Install a water storage tank, size and location to be determined.

Control type and logic to be determined.

Number and size of pumps to be determined.

Number of heating zones to be determined.

Design of smoker to be determined.

Comments and suggestions welcome.

 

[DonPowers]

Here are a couple photos of the wood shed.

This photo the shed is in its original location with two 6x10 ft bays and one 10x10 ft bay.

View media item 48358
This photo is relocating it to its current location with three 10x10 ft bays. Also beefed up the center beam from 4x4 to 6x6 and the front beam from 4x4 to 4x6.

View media item 48359

 

[DonPowers]

Here is a photo from the wood shed roof of the PEX, just prior to placing concrete. You can also see the well on the left side of the photo. Overflow from the well currently runs into a ditch and does not freeze, even with temperatures bottoming in the 20 below range for days on end.

View media item 45819

 

[dw1]

Q # 1- are you going to fill system with water or glycol, if water, will it have a chance of freezing ? or will this system be in operation 24/7?
You could use a line voltage T-Stat to turn your circ pump on. I think this would be a great project. I actually did something like this for my buddy, but he had a heat exchanger attached to a portable incinerator that he had, we used a water heater tank just for storage. I think he did fill the system witha glycol mixture so it wouldnt freeze when not in use.

 

[DonPowers]

Q # 1- are you going to fill system with water or glycol, if water, will it have a chance of freezing ? or will this system be in operation 24/7?
You could use a line voltage T-Stat to turn your circ pump on. I think this would be a great project. I actually did something like this for my buddy, but he had a heat exchanger attached to a portable incinerator that he had, we used a water heater tank just for storage. I think he did fill the system witha glycol mixture so it wouldnt freeze when not in use.

The system would definitely be filled with glycol. If I have the solar setup, the contraption may run intermittently in the spring and fall and most likely full time in the winter. Was also considering a hot water tank for storage, preferably a propane one.

The line voltage T Stat is a good option, thanks.

The driveway heat has two purposes, one for melting ice and the other for dumping excess heat.

 

[dw1]

Is the driveway a zone by itself? you could always have another Line Voltage T-Stat come on at a higher temp to open a solenoid and allow heat to flow to driveway zone

 

[DonPowers]

Is the driveway a zone by itself? you could always have another Line Voltage T-Stat come on at a higher temp to open a solenoid and allow heat to flow to driveway zone

Yes dw1, the driveway would be on its own zone. Current thought is manual initiation for ice melting and some sort of logic for heat dump. Something like, if no zones calling for heat and storage tank approaching a set point temperature.

I expect that during the summer, solar panels would generate more heat than what is required and additional heat would be generated when using the BBQ/Smoker function. If it were to become a problem, could always cover the solar panels during the summer.

A line voltage T stat could be used as a backup to controller logic, similar to a Hi Hi alarm function and start dumping heat somewhere else to protect the system.

A friend who has radiant heat with a solar panel array and wood fired indoor boiler uses a modine heater for his heat dump.

 

[dw1]

So now you have my full attention on this project, what do the solar panels tie to in this system. I have my gravel pad, I will go 30x48 or 50. I hope to do something soon building wise!! Do you think 3-100' rolls of Pex will work? can you put regular Pex under concrete? or is it rated different? This is a cool project.

 

[DonPowers]

Thanks dw1

The solar panels will most likely go to a hot water storage tank with the various zones pulling from the tank or tanks.

You should use PEX that is rated for hydronic heating, which can be placed under concrete. Mine was purchased, installed and tested by a plumbing contractor, who knew it would be a few years from installation to system operation. The PEX did have to be tied down to prevent it from floating up when pouring the concrete.

With regard to amount, your needs in KY will be considerably different than in northern Maine. The plumber used 1 ft spacing with 6" spacing near the overhead doors, which consumed 1,800 feet of PEX, which translates to six 300 ft loops. Don't know how he figured the amount required or established the pattern. I was working out of town at the time and the General Contractor that I hired to do the slab and close in the building hired him.

If you can't find something on line for density requirements for your area, check with some local heating supply people.

There is a lot of good stuff on this site, check out the Glitch & Fix stuff. John Siegenthaler is the guru for hydronic heating and has a few books on the subject, which I need to get before building anything. Right now I'm only in the conceptual phase and once the concept is nailed down the real work begins.

http://www.radiantandhydronics.com/topics/2652-the-glitch-the-fix

Now that I'm mostly retired, there is more time to get in trouble. If I was still working full time doing projects on the road, would probably just buy the stuff and have someone put it in, but that takes all the fun out of it.

Like I mentioned in a previous thread. I want to be the crazy old fart down the road with weird contraptions in his back yard. My overall goal is to keep my heating and utility cost as low as reasonably achievable during my retirement years.

Other wish list energy projects include:
A grid tie photovoltaic system to power the stuff.
Walk in cooler/root cellar using water from my well for cooling.
Making solar stuff with parabolic reflectors and or fresnel lenses.
Solar powered rankine engine using refrigerant to run a generator.

 

[dw1]

Thanks for the info, I will check it out. I bought a 1.5 acre lot and 115 Y.O farm house about a mile down from my house. This had been in disrepair, foreclosed, and untouched for about 10 years, I cleared the whole lot, took about 40 tri axle loads of debris out and about 18 tri axle loads of dirt in to re-direct the water issue there ( a near and dear friend owns an excavating company, we trade favors) I have a gravel drive and pad in right now, just waiting to start my building. I cleaned the farm house out, I will do something with it later, down the road. I am going to put bathroom in and now want to at least put the Pex under the floor. (Next call will be to my other buddy that owns mechanical contracting co.) There is no way I could have done this by myself, it would have taken me 5 years to clear the lot, plus people were dumping stuff back there, now its wide open, and I just got done with new 4 board fence and gate.

 

[DonPowers]

Its nice to have good contacts. I ended up buying an excavator and 16' dump trailer to do the earthwork. Spent a couple years doing it on weekends that I was home. At least I have a sub base and drainage that I'm happy with. Any problems, only myself to blame.

Something else to consider before pouring concrete, put in a couple spare 4" PVC pipes for future use. I put two, one on the north wall and another on the west wall. They go down and under the footing then extend out a couple feet. Plan to bring my outdoor hot water pipes through one of them.

Your Mechanical guy should have a pretty good idea on setting up your PEX, if not, he probably knows someone that does.

I hope you plan on starting a build thread.

 

[dw1]

I will start a thread when the time comes and will be following yours, the more I read the radiant floor heat, the more I am interested in it. I will do all the mechanix myself, I do want my buddies help on laying out the bathroom.
Thanks for the info and good luck, we just got about 10" of snow and now its suppose to get really cold.