Mr. Heater F260550 Big Maxx MHU50NG Natural Gas Unit Heater

My garage was reaching near freezing temperatures and I found it not very fun to be working in the garage having to wear a winter coat and gloves. I wanted to install a garage heater, but wasn’t sure which route to take: natural gas, propane, or electric. Electric units were cheaper and easier to install (running electrical wire is trivial compared to LP/NG) but would cost more to run because electricity is more expensive per BTU in my area. I could run propane, but I would need to install a tank outside my house and get it filled when empty. This left me with NG. From everything I read online I should fear NG like a loaded gun ready to go off in my face at any second, throwing my house up into the air and leaving a crater the size of a large comet in the ground.

I decided I would be able to teach myself how to run NG by mitigating the risks through education. I consulted with my NG provider, laying out my plan and asking for advice. From his reaction what I had in store was mostly above and beyond the requirements laid out by Indiana code. The gas meter was on the same side of the house as the garage. I ran the NG line along the outside of the house.

The first issue was the NG meter. It was old, rusted, and the shut-off valve on the supplier’s side leaked. After a quick call to the provider they came out and explained that a little bubbling leak was “no big deal”. Quite the contrary to what I had read online, where even one molecule of gas leaving would cause the gates of hell to open and consume me.

I found my suppliers request documents for getting a new meter put in. I stated that i would need a new one anyone on the account of the old meter only supplying 175 CF/H when I am eventually upgrading everything in the house to NG. They responded after a few days and put me on their schedule for an upgrade.

After some research I decided on the Mr. Heater F260550. Based on the size of the garage (12’x12’x8′) and the insulation present online calculators said this would be adequate. I found a seller with some refurbished units and went with them instead of a new unit. In hindsight, my local Menards sold this same unit, and with a 11% rebate the price would have been worth it given the refurbished unit only had a 90-day warranty.

I used 3/8″ rod with nuts and washers to suspend the heater from the ceiling. the heater requires a 1″ clearance on all sides from combustibles.

I didn’t like the look of screws the heater straight into the drywall, so it was suspended from the rafters in the attic. I had to add a cross section between two of the joists to get the heater supported from 4 points.

After the heater was suspended I slowly screwed the nuts up the threaded rods until the unit was nice and high.

I ran the electrical through the ceiling and into protective conduit to the heater. This unit doesn’t have an outlet plug and needed to be wired directly to the circuit.

Then I ran the thermostat wire up into the ceiling and down by the door into the house. This location was out of the direct path of the heater and would give an accurate temperature reading from this spot. I couldn’t find any information on running a low voltage wire through the same conduit box as high voltage. Everything I read said if the low voltage line is carrying digital information the signal could be interfered with by the high voltage, but a thermostat wire doesn’t do this. I ran the wire outside the flexible conduit but fed it into the same conduit box as the electrical.

I had an old thermostat laying around I installed the system with.

Once the heater was suspended I set out to acquire the needed supplies for running the NG. The pipe coming out of my meter was 1″. For the 30′ run I would need to the heater and the BTU requirements (50,000), charts online stated I would need a 1/2″ pipe to satisfy the demand of the heater. I decided to stick with 1″ the whole way because the price was about the same and bigger is better, right? In the future I might do some beer brewing in the garage, and having a large pipe for that would be nice.

I laid out the pipe to see what I needed to do to get it lined up against the side of the wall. I planned on attaching it to the foundation of the house to keep it from moving.

I used unistrut to secure the pipe running up the siding to the attic at the top and the bottom. The NG line was attached to the strut with clamps.

The line then went into the attic and after a foot straight down through the drywall into the garage.

I placed shutoff valves at both the source at the gas meter and at the heater end. I turned off the gas at the shutoff valve, and bled the gas out of the line by turning the furnace on for a few seconds. I tee’d into the gas line going into the house by cutting it with a reciprocating saw. To my surprise and dismay of the online community I didn’t explode and nothing caught on fire. I added a tee, shutoff valve, and a union to put the pieces back together. To my surprise, NONE of the pipe I undid had pipe dope anywhere on them, including the 3 adapters the original installer used to get the 1″ pipe down to 1/2″ before it went into the house. My confidence in my ability to do the job correctly continued to rise. I used pipe dope all around while assembling the pipe and made everything nice and tight with pipe wrenches and a little muscle. I attached the gas pipe to the foundation using concrete screws and 1″ metal brackets. Once secured I could jump up and down on the pipe without it budging. After assembling I turned the gas on and went looking for leaks. With my homemade leak detector (squirt bottle with soapy water) I sprayed everything down without a single problem.

Next up was the exhaust. The heater isn’t a high efficiency unit, and according to the manual I needed to use Type B gas vent to protect combustibles in the attic from combusting.

According to national code when a vent penetrates a roof the top of the vent has to be 2′ taller than anything else on the roof 12′ away. Since my heater was at the edge of the garage this meant it would have to be pretty tall to overcome this rule. I could have run the exhaust up through the attic towards the top of the roof to have a shorter pipe, but the manual stated if the exhaust pipe was longer than 5′ it had to be insulated the entire length to prevent flu gases from condensing and falling back down the exhaust pipe.

I went a little overboard attaching the exhaust to the roof. The flashing went under 2 courses of shingles and was nailed down at the bottom by 4 roofing nails. I used roofing sealant to water proof everything. I put a storm collar on over the flashing and sealed that as well. I was surprised with how expensive Type B vent was. It was nearly $90 for all of the pipe.

I still need to install some plates over the holes to make things look nice, but the fire stop is in place and everything should be up to code at this point.

Inside I got the gas hooked up using some flexible appliance gas line and took the heater on a test run.

It lit on the first try!

The next week the gas provider came out and replaced the meter with a brand new 450 CF/H meter! The installers took a look at my work and said it looked good to them. They said the shutoff valve I had at the source wasn’t necessary (I did it so the rest of the house could still have gas while I assembled the new section of line) but everything else looked well done. They asked if I had a NG generator in the garage because the line was so big. They scratched their heads when I told them it as just a little heater.

Behind the meter you can see the new pipe, tee, and shut off valve I added to run the gas to the garage.

The heater can bring the garage from 40 to 60 degrees in about 20 minutes. It uses a spark ignition, which can get a little annoying when it turns on, as it runs until the unit senses heat coming from the lit burners. I like the glow igniter, like the one my house furnace uses which is silent, more than this. It takes the air coming out of the unit about 3 minutes to get to it’s peak temperature. I measured the heat tubes at around 350 degrees right at the tips of where the flames reach inside. The exhaust vent never goes above 60 degrees, meaning it’s doing it’s job correctly. I wish there were a way to get the unit to operate more efficiently, it seems like a big waste venting 100 degree exhaust outside the house.

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