Installing a Garage Heater

By CrowWinger Follow

I have wanted a garage heater basically forever. and one day during the middle of COVID before winter started, I was walking through Northern Tool and saw them on sale. Without much forethought, I pulled the trigger on a whim and found myself with a big box on the garage floor without a plan.

I'm not an expert, just a DIYer and the intention of this Instructable is a high-level overview of this process with things to consider for your own project. including overall cost, which could be significantly higher than the sticker price on the heater.

All things considered, I had fun and learned a lot installing the heater. in hindsight it was a great decision and I have gotten tons of enjoyment out of it already in only a few months.

This install was done using an 80k BTU Mr. Heater Big Maxx unit for a 3-stall insulated garage.

Supplies

There were other miscellaneous items and tools used, but this gives a baseline on full project cost. noting that material costs for installation are actually more than the heater itself.

Area Item Total
Unit Big Maxx 80k BTU (Norther Tool) 10/5/2020 $410 Venting 4" Z-Vent 10x10" Wall Thimble (Adj from 5-10") $38 Venting 4" Z-Vent Termination Hood 2SVSHTX04 $42 Venting 4" Z-Vent 45 degree Elbow 2SVEEWCF0445 $42 Venting 4" x 18" Z-Vent pipe 2SVEPWCF0401.5 $32 Venting 4" x 12" Z-Vent pipe 2SVEPWCF0401 $20 Venting 4" Z-Vent Universal Adapter w/ backflow 2ZVB04 $33 Venting Silicon Caulk $5 Venting Vinyl J-Channel $5 Gas 60' 1/2" Type L Copper Tubing $99 Gas Copper straps (bag) $1 Gas 1/2" Black pipe for heater sediment trap assemb $7 Gas TFE Tape (instead of pipe dope) $3 Gas Leak detector $3 Gas 1/2" FLX/FIP Gas Valve $9 Gas 1/2" Forged Flare Nut 2 pack (Qty = 2) $13 Gas 1/2"x1/2"x1/2" Flare Tee $7 Electric 14-2 25' Wire $12 Electric Double junction box $1 Electric 15A toggle switch $1 Electric 15A outlet $1 Electric Outlet/switch wall plate $1 Electric Thermostat (ICM Controls FS1500L Garage Stat) $20 Electric 18-5 50' Termostat Wire $15 Tools Hang 'Em High Hoist (Used for hoisting heater) $22 Tools 4 pack of 10' Cambuckle Straps (used to hang) $12 Tools Screw Eyes (used to hang heater) - Qty 4 $4 Tools Flaring tool (for copper gas line) $14 Tools Pipe Wrench - 14" $7 Total Cost: $879.91

Step 1: Positioning

Ideally, you would want to position the heater in the coldest location in the garage at a 45 degree angle aimed at the garage door.

I had limited options, but my one open spot met both criteria - which was a corner with 2 outside walls (coldest) and I positioned to angle directly to the middle of the 3-stall garage door wall.

Other considerations
If you have multiple location options, it would be wise to also factor in accessibility for the electrical and gas runs. Although I didn't have multiple options, this was certainly assessed to ensure it could be done.

In my case, that garage "attic" allowed me full access to the ceiling.

Step 2: Mounting

Because I'm stubborn, I decided to hang the heater myself one night. It was probably stupid and would have been safer with another person, but here's how I did it (and I think this would work good even if you had another set of hands):

Mounting Preparation
Due to mounting position being angular to the ceiling joists, I first mounted 2x6 boards that were long enough to hit 2 studs at the desired angle (using lag bolts). Then I mounted the front and back of the heater to the 2x6 boards. The heater weighs about 80 lbs, so this should be more than sufficient to support it.

Hanging
For this, I used: Eye Hooks, a Pully, ratchet straps, & cambuckle straps.

1. Eye Hooks: Install some heavy duty eye hooks into the joists on the ceiling positioned on either side of where the heater will be mounted. These will be used for:
   1. Supporting the pulley for the initial lift of the heater
   2. Cambuckles that will be used for the final support of the heater when attaching lag bolts.
   1. Hang the pulley from one of the eye hooks attached in step 1.
   2. Wrap 2 ratchet straps around from bottom to top of the heater. These are the camo straps you can see in the photo.
   3. Attach the bottom of the pulley to both ratchet straps at the top of the heater.
   4. Raise the heater with the pulley as high as possible (with the pulley I had, this was not nearly as high as I would have wished).
   1. Position a solid ladder that will allow you be directly under the final location of heater.
   2. Attach 2 cambuckles to the eye hooks mounted in step 1 and loop under the suspended heater. These are the bright green straps you see in the photo.
   1. With the heater now fully supported by the Cambuckles attached to the ceiling, remove the pulley and the ratchet straps.
   2. Position yourself on the ladder such that you can raise the heater upwards. I used my shoulder and one free hand to raise it until there was slack in the cambuckle straps. Use your other hand to pull the loose end of the strap and tighten until all the slack is removed (you're now a couple inches closer to your final destination).
   3. Repeat the previous step until you have the heater as tight as possible to the 2x6 boards.

   
   Hindsight Thoughts:
   I actually mounted my heater prior to spending much time in the attic (this came later). But I wish I would have instead placed support boards over the top of the joists in the attic and dropped rods from them to the heater. Although not a huge deal, it would have given a cleaner look.

   Step 3: Electrical

   I won't get too much into the wiring, just highlighting my approach.

   I added a dual junction box in the ceiling next to the heater that will contain an outlet and a switch. I ran power to this box and hard-wired the heater up through the ceiling and into this box. The outlet is always powered and the switch can be used in the summer to ensure the heater is always off (switched on in the winter and off in the summer).

   Step 4: Thermostat

   This is a pretty straight forward step and I had run the thermostat wire will doing the electric. I went up into the attic from the heater and down the wall next to the door into the house.

   After the thermostat is connected, you can now do a quick test of the heater. When the thermostat calls for heat, the heater will engage the fan for a short period to clear fumes. If that happens as expected, you're at a milestone.

   Hindsight Thoughts on Thermostat:
   I made a point in trying to find a "cold" thermostat that was capable of having a temperature set down to 35 degrees (most house thermostats do not go that low - maybe 45 at the lowest). My garage is well insulated and have found that it rarely goes below 45 degrees except on sub-zero stretches.

   The decision to get this type of thermostat eliminated smart thermostat options. I wish I had one and will likely switch as some point. and not because I want the ability to turn it on remotely (it heats up so fast, that it has never been a problem turning it on right when I go out), but to be able to automate turning it down (kids, forgetting, etc).

   Step 5: Ventilation

   This was mentally the most challenging part for me. go vertical and cut a hole in the roof, or go horizontal and cut a hole in the wall?

   • Vertical: Cheaper materials (you can use Type-B venting vs. Category III for horizontal)
   • Horizontal: One less hole in the roof & likely easier

   Ultimately, I chose to go horizontal and will outline that process. After measuring 15 times and cutting a hole in the wall, this was a pretty easy procedure.

   Materials
   I put this in during COVID and I think everyone in my state bought a garage heater and was installing right before winter. I could not find local materials. everything was sold out and due to shortages there was no assurance when inventory would be replenished. So I had to buy on-line, which made my measurements more critical to get right the first time. Happily, all was good with one shipment - I order from SupplyHouse.com and would highly recommend them.

   Reference the supply list for the pieces I used (my heater called for 4" pipe). I was unable to buy the kit because I required a 45 degree elbow vs. the 90 degree in the kit.

   But you basically want to measure material that will go from the heater exhaust and through the wall until it extends at least 1 foot from the wall (this will prevent exhaust moisture from entering the attic through the soffits). In addition, horizontal venting requires a wall thimble.

   The wall thimble has 2 pieces that connect together on each side of the wall. The diameter of the thimble pipe that passes through the wall is wider than the actual exhaust venting and provides a heat barrier between the hot vent and combustible wall material.

   Cut the Hole

   1. Semi-assembled venting to determine the wall hole location (see image that shows 45 degree elbow right next to the wall) by drawing a circle around the vent where it would exit the wall. Make sure you are exiting between studs!
   2. Drill a hole directly in the center of your circle all the way through the exterior wall (this requires a long drill bit & I happened to have an old concrete bit that worked). You can see this "pilot" hole in the image after I had cut the vinyl.
   3. Use a section of your wall thimble and position it centered over the pilot hole and draw another circle on the exterior wall.
   4. Carefully cut the vinyl if applicable (I tried doing this with a utility blade and it was very difficult, so switched to some tin snips I had and it worked great). I then used a utility knife to cut the white barrier paper.
   5. Use a saw (I used a jigsaw) to cut the wallboard and sheet rock. Gently tuck loose insulation back in place. You now have a clear hole through the wall for venting.

   Install the Wall Thimble
   Wear gloves for a lot of the remaining vent work since the venting is really sharp.

   1. Push the exterior side of the thimble through the wall from outside and again trace the perimeter of the square facing on the siding.
   2. Trim the vinyl using snips to allow the thimble facing to rest directly against the wallboard (you can see a photo of this prior to adding the trim).
   3. Install the interior side of the thimble and mate the pieces. Pull them together until tight against both walls (I was able to just stick my arm through the hole to pull one side and push the other.
   4. Configure and cut J-Channel trim for the square you cut. I included a little diagram on how I tabbed the pieces, but search a video on how to trim this since it is critical to get right for proper water run-off.
      * Menards stocked tons of colors and was able to find a close match without a special order.
   5. Apply Silicon caulk all around the interior of the J-channel "frame" and the corners. The outside of frame should be good if trimmed right.

   Assemble the Venting
   You're now ready to complete the venting by simply connecting the pieces. The Category III venting is rubber sealed on each end to support the positive pressure of horizontal venting. So no caulking is required along the joints, one end of each piece will have a clamp to secure the rubber seal. But the pieces can fit very tightly and silicon lubricant can be used to help slide the male pieces into the rubber gaskets.

   Since the thimble hole is slightly bigger than the exhaust vent, there is a small gap that allows for air flow. I didn't want cold air coming in though that gap, so I also added silicon caulk around the exhaust pipe where it exists the outside thimble facing (see image).

   Congratulations, another milestone!

   Step 6: Natural Gas

   This is likely the most intimidating part of this project for most and I'm not going to detail this process in extent since codes vary by your location. I actually was going to hire this out, but estimates were coming in at a minimum of $800 and I couldn't justify it. If you are comfortable with plumbing and wiring, this isn't far off in terms of difficultly. this may take a little fear out of it:

   Do your math
   I sized my gas lines by calculating the distance of all appliance runs and BTUs consumed to determine if I could supply my heater on a serial run vs. a new dedicated line from the mainline manifold. This was important to me due to simplicity in running the line if I could branch.
   I determined that I had an existing line in proximity to the garage that could support another 80k BTUs in a serial run. I branched off of this line and ran it through the attic, dropping down directly above the heater.

   This took some research time and there is a lot of sources for this information to help, but it is a good exercise and necessary to stay in code. Search "longest length method" for detail on these calculations. It seems over whelming at first, but math doesn't lie and becomes clear once you're done.

   I saved at least $700 doing this myself and would never hesitate to do it again. It was definitely more mentally difficult to commit to it than to actually do it.

   Step 7: Conclusion

   Power on the heater, turn on the gas & raise the temperature on the thermometer!

   This is one of the best things I've done in a long time. I never seem to have time for projects in the summer and in the winter I'm dying to get out there and do things. I only regret not doing this sooner.

   Step 8: Appendix 1: Z-flex Universal Adapter

   The Z-flex Universal Adapter I used for this heater was technically not the correct one.

   I had initially sent an email request to Mr. Heater, but due to delay I called and was told that the Universal Appliance Adapter (2ZVB04) would work - so I place my material order.
   I then got the email response later and it contradicted the advisement saying that the appliance adapter will not work and I should instead order 2SVSRHA040, which appeared to be a pretty hard item to find (on back order a month out).

   My order is already shipped and was planning to complete that weekend, so decided to proceed. After received the Z-flex the Universal Appliance Adapter (2ZVB04), I could see why I was later informed that it "wouldn't work" from Mr. Heater.

   I'm attaching 2 photos:

   1. Side profile showing depth alignment of the adapter and the flue transition on the heater. The raised ring on the adapter is where the red rubber gasket is housed. You can see that this overlaps only slightly on the short flue transition attached to the heater.

   2. Looking inside the attached adapter to the heater. Here you can still see the red rubber gasket exposed because you can't fully push the adapter onto the transition. However, the main reason you can push it on further is because of the clamp screw that you can see towards the top of the 2nd photo (there is a clamp on both sides of the adapter).

   I made 2ZVB04 work by removing the clamp from the heater side and push it on further until the rubber gasket was fully onto the flue transition. It is very tight fitting and does not move at all.