Which Big Maxx -50k or 80k?

[VeemanOH]

Hey all... The new shop is almost done and want to make the final choice on the hanging gas heater. The shop is 32 x 44 x 12 and will be fully insulated with R19 walls and R30 in the ceiling, two overhead doors at one end and three windows along one wall.

From what I've been reading, the Mr.Heater Big Maxx seems like a good way to go and I know they have a 50k btu and a 80k btu model.

The 50k says it's good to 1500 sq. feet of insulated space.
The 80k says it'll do 2500 sq feet of insulated space.

Since I have 1400 sq. feet under roof, will the 50k work for my Ohio winters? Or since I have 12' walls, should I attempt to get the bigger model (the "more is better" outlook)? I'll probably keep the thermostat low (45 degrees maybe?) during the day while I'm at work and when I need to use it, crank it up to 60 or so.

Any been there / done that experience with these? Thanks!

 

[benjamintmiller]

The 50 kbtu model should be plenty. The 80 kbtu model would likely short cycle, which is hard on equipment and leads to large temperature swings.

I have a larger barn than you -- 36x56x13, and I did manual j and manual s calculations today and determined I need about 56,000 btu's of heating capacity.

Just for fun, I entered your numbers into the calculator assuming northern exposure for the windows and longest wall, and east/west exposure for the gable ends. Here is what it says:

Cooling - Minimum: 9439 btu's
Cooling - Maximum: 10855 btu's
Heating - Minimum: 29998 btu's
Heating - Maximum: 41997 btu's

You can enter more accurate numbers with the calculator at www.loadcalc.net and see what you get, but I bet it will be very close to 40,000 btu's needed.

 

[benjamintmiller]

I guess I should note that the calculations I suggested above assume you'll keep the building at a constant temperature. If you need it to warm up quickly when you want to work in it, you may need a larger heater.

Myself, I would rather turn the heat up the night before so that my tools aren't all icicles.

 

[VeemanOH]

I guess I should note that the calculations I suggested above assume you'll keep the building at a constant temperature. If you need it to warm up quickly when you want to work in it, you may need a larger heater.

Myself, I would rather turn the heat up the night before so that my tools aren't all icicles.

Thanks for the reply and the calculations! I hear what you're saying about short cycles and I don't want that...

I would imagine I'll keep the shop around 45 degrees or whatever then crank it up when I go to work out there. In the previous house, I had a small torpedo heater that I'd use to knock the chill off, so maybe that's a possibility while the Big Maxx is running initially. After it's up to 55-60 degrees, the Big Maxx can maintain.

 

[Showkey]

45 is a little low..........most heater manufacturers have a recommended low heat setting no lower 50*. Below 50* causes excessive rust and corrosion on the heater components.

 

[Pruittx2]

I'm 48x28x10 no windows and 2 doors, Only have 2in spray foam on 60% of walls and nothing yet in ceiling. Mid Michigan. I went with the 80k. I'll only be a weekend warrior, and will Not be keeping it up to temp all the time.
Northern tools has the best prices, I got my 80 on sale for $30 more that the 50k was, on sale. I paid $380 Shipping was $55 but a membership for 1 year was like 32 and that gave me free shipping on heater + members only pricing on some items and free shipping for a year.

 

[wesst]

I would recommend the 80 due to the subjectively low delta between the purchase price of the two models. It appears it is possible to reduce the output of the 80 by blocking a single orfice if needed as well.

To put it into perspective, when I purchased my 80, it was $50 more than the 50 at Menards.

Just food for thought...

 

[Unhdsm]

Both Mr Heater and Northern Tool will tell you either will work, it's just matter of how quickly you want to heat it up. I'm inclined to agree. I talked to everyone and researched everything out there, and landed on the 80k for 1120 sqft with 10 ft ceilings, R19 and R30 fiberglass in VT. I don't heat 24/7 so I went 80k. I'm happy with my decision.

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[Showkey]

1000 sqft well insulated.......I went the other way had a 60k go bad..........replaced it witha 45k. Saw no difference in performance or the cost.

 

[jameslinn83]

I have a 50000 btu in my 24 x 36 I wouldn't want any smaller. I have 2 over had doors and a window. I would go 80 if I were you

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[biggziff]

80K. You can de-rate a bigger unit, you cannot up-rate a smaller unit. I bought the 80K and fully expect to de-rate it to around 50K once I'm insulated. Until then I have more than enough BTU to keep the shop warm and recover from opening a 14' overhead.

 

[R.Beans]

Following

 

[FreddiFiche]

80K. You can de-rate a bigger unit, you cannot up-rate a smaller unit. I bought the 80K and fully expect to de-rate it to around 50K once I'm insulated. Until then I have more than enough BTU to keep the shop warm and recover from opening a 14' overhead.

This. So much this.

Run it at 80K, and see if it works for you. (probably will) if it does short cycle, pinch a burner off. (4 burners instead of 5) If you go with the 50K, you can't add a burner, and it ight take alot longer than you want to heat up your space.

 

[u3b3rg33k]

the larger heater being only slightly more $ is the reason most people have furnaces that are too big.

45 is a little low..........most heater manufacturers have a recommended low heat setting no lower 50*. Below 50* causes excessive rust and corrosion on the heater components.

given that - corrosion is less likely with a lower BTU output (higher average flue gas temp)

This. So much this.

Run it at 80K, and see if it works for you. (probably will) if it does short cycle, pinch a burner off. (4 burners instead of 5) If you go with the 50K, you can't add a burner, and it ight take alot longer than you want to heat up your space.

running longer is GOOD though - it takes time to heat up your tools. air heats up fast, stuff does not. I have seen two installs of 60k 80% Modines, both in 3 bay insulated garages, and once they've gotten up from 40F to 65F (about 10 min), they run 3 min on cycles after that (6 min off time). I'd call that "short" cycling.

 

[D45]

I vote 80k

I have a 75k in my 1,000 ft shop and love it, especially the longer heat throw with the larger fan

 

[Showkey]

80k with decent insulation and insulated garage door is twice as BIG as it needs to be for 1000 sqft shop/garage. It’s not uncommon to find 80k furnace in 2000 sqft home.

As for pinching off one burner tube............the exhaust blower is sized to carry the hot exhaust out. Pinched burner is now 15-20% lower heat with the blower running the heated exhaust out at the same rate for 80k. Sounds like a waste and sure way to knock the efficiency off by a fair amount ?

When it comes to heat and AC .......BIGGER .........is rarely better.

 

[toyotadriver]

Remember, you aren't getting 50k BTUs OUT of it. It's 81% efficient so you only get about 40k BTUs of actual heat.

I live in a slightly warmer climate. I have a 30x40x10 shop. Well insulated but also have two windows and two 9 ft insulated garage doors and a walk through door. I had a 45k Mr Heater in there and while it would heat it, I don't heat full time so I wanted to be able to walk out there, turn it on, and be working in a short period of time. The 45k would heat it but took too long. I put an 80k BTU heater in it and it's perfect. A 60k would also work fine but Mr. Heater doesn't make a 60k.

The doors and ceiling height will require more BTUs.

Buy the 80k.

 

[mygarageone]

I laugh every time I see answers like above. No one has yet figured out why you want your heater at the proper btu rating. Bigger is Not better . Good luck.

 

[biggziff]

I laugh every time I see answers like above. No one has yet figured out why you want your heater at the proper btu rating. Bigger is Not better . Good luck.

sigh...one in every crowd.

 

[finn]

More is better, I guess. It’s the American Way.

10k vs 7k trailers, 6” vs 4” slab, Cummins dually to commute or go to HD.....

 

[Showkey]

More is better, I guess. It’s the American Way.

10k vs 7k trailers, 6” vs 4” slab, Cummins dually to commute or go to HD.....

The other ones are 7.5 HP compressor , $400 Fluke meter or 5 HP cabinet saw for the casual DIY guy.

 

[u3b3rg33k]

Heck, the 120K heaters on craigslist are the same price. go big or go home!

 

[Unhdsm]

sigh...one in every crowd.

In this case they are both within spec. The 80k isn't too big.

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[mygarageone]

In this case they are both within spec. The 80k isn't too big.

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Define with in spec ? Are you a professional installer ?

A pc of heating equipment works best when it is sized as close to the heat loss as possible. There are several reasons for that . Comfort is much higher when a furnace is properly sized , wear and tear is reduced , fuel usage is reduced .
Bigger has never been better , it’s a deterrement to a qualty installation.
The only time a furnace should be over sized is if and when there needs to be a lot of fresh air required. Or maybe the house or garage will have an addition in the near future or the doors will be open a lot.

 

[biggziff]

Define with in spec ? Are you a professional installer ?

A pc of heating equipment works best when it is sized as close to the heat loss as possible. There are several reasons for that . Comfort is much higher when a furnace is properly sized , wear and tear is reduced , fuel usage is reduced .
Bigger has never been better , it’s a deterrement to a qualty installation.
The only time a furnace should be over sized is if and when there needs to be a lot of fresh air required. Or maybe the house or garage will have an addition in the near future or the doors will be open a lot.

You've never seen the forum personalities threads I assume...

 

[shaggyant]

Define with in spec ? Are you a professional installer ?

A pc of heating equipment works best when it is sized as close to the heat loss as possible. There are several reasons for that . Comfort is much higher when a furnace is properly sized , wear and tear is reduced , fuel usage is reduced .
Bigger has never been better , it’s a deterrement to a qualty installation.
The only time a furnace should be over sized is if and when there needs to be a lot of fresh air required. Or maybe the house or garage will have an addition in the near future or the doors will be open a lot.

I think it’s a legitimate reason to oversize if the space is only intermittently heated and the temperature needs to be raised quickly instead of taking what could end up being several hours.

 

[mygarageone]

You've never seen the forum personalities threads I assume...

I see from your profile your well qualified to give heating advice . I should hire you.

 

[Pruittx2]

what would your recommendations be for a(28x48) 1344 sq ft, 10 foot ceilings, no windows, 2 8x9 insulated doors, OSB lids with no insulation?

 

[mygarageone]

what would your recommendations be for a(28x48) 1344 sq ft, 10 foot ceilings, no windows, 2 8x9 insulated doors, OSB lids with no insulation?

Well what’s your heat loss ? My shop is just your size with 1 window , 1 service door , 2 garage doors and 10 foot ceiling , my heat load was less than 30,000
Btu’s .
But the floor is insulated , foundation walls insulated , 6” walls and 18” ceiling insulation.
I live in Michigan’s U.P where it’s cold in the winter. I keep my heat on all the time and it’s shirt sleeve comfortable all the time .
I have a 40,000 btu heater in there , 80% er
The thing is most heat load calculations have fudge built in , so most times your heat load is higher than it should be.
The other thing , your location makes a big difference , you TD makes a difference.
Systems should be designed on building usage and comfort desires. Not if 50,000 is right go bigger just because it no more money.
Just this week , we removed an 80,000 btus 90% furnace and installed a 70,000 unit because the old one was over sized and burnt out.

Arm chair heating guys haven’t a flipping clue as to what you should have . Good luck.

 

[Pruittx2]

I'm down by Grand Rapids,, Pole barn non insulated slab, no insulation in ceiling, and only spray foam on 60% of the walls. I will only heat on weekends for projects. Not all the time. output on furnace is 64kbtu. should heat up pretty quick,, keep comfortable for 4-6 hrs at a time. I'm sure I didn't make the most informed decision for my setup, but feel I should be fine. Any arm chair anything, generally don't have a clue, that's why guy's join this and many forums to get the help in areas they need. Auto Collision was my biz for 30yrs, I've seen some things non car guys do,, as you have non hvac guys have done.

 

[Showkey]

^^^^^^One issue with no or low ceiling insulation besides the increased cost of heating..........snow and ice melt and ice dams forming on the roof causing leaks. You can end up with 10-12” of ice on the roof edge.

Next problem with a poorly sealed building is condensation.

Depending on the pole barn size with poor insulation 64k is going to struggle to heat that space. Guys with pole barns and no insulation often use a large torpedo heater 100-200k.

 

[Pruittx2]

Big Maxx 80k has an output of 64k. I"ll do some blown in,, when I get the funds and time.

It's better that the 55k reddy heater torpedo blowing at me with no osb ceiling. that I've had in the past.

 

[scottybk]

I also vote for the 80 K, nothing beats being able to "crank her up" and get that place warm fast.

I don't believe in going crazy with insulation, better off to just oversize the heater and be done with it.

 

[Unhdsm]

Define with in spec ? Are you a professional installer ?

A pc of heating equipment works best when it is sized as close to the heat loss as possible. There are several reasons for that . Comfort is much higher when a furnace is properly sized , wear and tear is reduced , fuel usage is reduced .
Bigger has never been better , it’s a deterrement to a qualty installation.
The only time a furnace should be over sized is if and when there needs to be a lot of fresh air required. Or maybe the house or garage will have an addition in the near future or the doors will be open a lot.

I have almost the same garage and insulation in a similer climate (maybe slightly colder) and that's what the engineers that designed it at Mr. Heater told me when I talked with them. *shrug*. Whatever- he can pay for a professional to come out. It's no difference to my wallet.

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[TractorJeff]

In the new Shop I am heating a 1000sqft and 12 foot ceilings (R19 walls, R38 ceiling) with a 15,000 btu radiant heater. I get up at 5am, pour coffee, decide to work in there I put a coat on and walk out to turn on the heater. By the time I get out there at 8:30am its 50 degrees. Sweatshirt weather
This is my decision to get a 50k Heater that could be set to hold 50 degrees all winter.
I don't want to spend a TON of money on gas for convenience!
BTW they are currently on Menards webpage for $355 and free shipping to the store!