Rheem Gas Fired Heater - Possible Purchase or Keep Looking?

[danieldd]

I have a 36x42 shop fully insulated (ceiling & walls)with closed cell foam. Walls are 12 foot high with an open ceiling at the moment. Immediate plan is to install a tin ceiling with R30 batts above the tin. Walls will at some point be covered with either drywall or some type of wood product. I called a local HVAC contractor to have them quote intersecting the existing gas line (runs up in the ceiling trusses) and bringing the gas line down so I can install forced air heat later on.

While getting a price for the gas line I asked his recommendation for shop heat and he recommended a Rheem Gas furnace 70K unit. It has a 92% efficiency, which I do like..

Link here: https://www.rheem.com/product/r92t-rfma-r92ta0701317msa

It sits on the floor and has a relatively small footprint. I like the size as it doesn't take up much room, but it still takes up valuable floor space. What I am concerned about is the forced air is out the top of the unit. Not sure how that will effectively heat the shop. Warranty is 10 years on parts and 1 year on labor. Installation price is around $3300.00. I guess I should continue looking at other alternatives...

 

[Bert_]

It's a furnace, it needs a plenum and some sort of ducting.

 

[naturalgas]

You will need to deal with condensate and some kind of duct work. Will also need bumper post protection that will take up more space. Get a ceiling hung unit (hot dog) or look into Rinnai direct vent space heaters.


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[isb cornbinder]

I bought and installed a horizontal furnace. I made some ducting to better control the hot air. This has worked well for over 30 years.

 

[Jim greengo]

I bought and installed a horizontal furnace. I made some ducting to better control the hot air. This has worked well for over 30 years.

Looks good to me.

 

[Showkey]

In shop/garage the furnace mentioned should mounted off the floor by 18” ( or what local code says) away from flammable fumes.

The duct work could be as simple as a Plenum and two vent off the plenum. At $3300 suspect the quote includes a small amount of duct work.

A ceiling mounted garage heater like Mr Heater Big Max or Modine Hot Dawg would be about $500 plus install. It would be 80% not 92%, no condensate line needed, vented with B vent up or CATIII out the side or end wall. The home furnace is likely better quality over 15 years.......but.......garage heat is just heat.

https://www.northerntool.com/shop/tools/product_200577751_200577751

 

[danieldd]

In shop/garage the furnace mentioned should mounted off the floor by 18” ( or what local code says) away from flammable fumes.

The duct work could be as simple as a Plenum and two vent off the plenum. At $3300 suspect the quote includes a small amount of duct work.

A ceiling mounted garage heater like Mr Heater Big Max or Modine Hot Dawg would be about $500 plus install. It would be 80% not 92%, no condensate line needed, vented with B vent up or CATIII out the side or end wall. The home furnace is likely better quality over 15 years.......but.......garage heat is just heat.

https://www.northerntool.com/shop/tools/product_200577751_200577751

Good points indeed!

 

[Sawlog]

Just hang the furnace horizontally at the ceiling and run pvc vent thru the side wall. Won't take up any floor space.
As far as the condensate drain goes, pipe it to a sink or floor drain. The one in the shop at work is piped to a 8 gallon bucket that gets dumped twice a week. Not the most friendly deal but has been that way for years

 

[danieldd]

There is a guy here locally that has a larger shop than mine that is running a Rheem unit. Going to try to see if I can see his installation before I decide what to do. Agree on having it off the floor, though...

The Hot Dawg unit has an 80% efficiency whereas the Rheem unit has a 92% efficiency. Don't know if the cost differential of Rheem has any appreciable payback over the life of the unit compared to the Hot Dawg. Gotta keep reminding myself this is for heating a shop, not my house...

 

[finn]

The condensate line is the biggest problem. You will have to heat the building 24/7 in a northern climate to avoid freezing the condensate line and any traps in your floor drain.

You can’t just run the line out the wall, as it will freeze solid and the condensate will back up.

A conventional hanging shop fester, although not as efficient, has no condensate line to deal with.

 

[allinon72]

Hard to imagine a 12% increase in efficiently being worth it, especially since you probably won’t even achieve 12% in the real world. There’s a reason unit heaters exist - for fairly quick and easy way to heat large spaces cheaply and without the complexity of duct work.

 

[Showkey]

Hard to imagine a 12% increase in efficiently being worth it, especially since you probably won’t even achieve 12% in the real world. There’s a reason unit heaters exist - for fairly quick and easy way to heat large spaces cheaply and without the complexity of duct work.

12% is real world plus high efficiency is going above 12% differential plus to have outside combustion. So cold outside is not coming into the the building. Typical 90 plus unit Exhaust temperatures for 80-100*

If there’s any blue sky in the number the 80% heat unit is likely place to look for not being real world. Exhaust temperature of 250-300*.

Obviously any payback or ROI a would be based on fuel cost, climate, full time or partial use. I would never ever install a 80% in a modern home. Number of years back replaced two 125k btu units 20 plus year old (80% on good day) with two 80k units 96% ......NAT gas fuel cost dropped 40%.

80k ceiling mount 80% is $500 plus install

80,000 BTU Furnace, 80% Efficiency, Single-Stage Burner, $762 plus install

80k 95% furnace can be purchased for $1294

So agree:
$500 to $1294 differential is going to be stretch on payback for garage/shop at current low NAT gas prices.

Wind card is on the install.....long or difficult vent could easily double or triple the install cost. Where 90- plus is PVC about the side wall and done.