I'm buying a 1500 sq foot shop 12ft high eve. Looking to see how many tons that would require. Can you do this or will you just be clogging the filter all the time?
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I'm buying a 1500 sq foot shop 12ft high eve. Looking to see how many tons that would require. Can you do this or will you just be clogging the filter all the time?
Moderator
Many of us have added Mini Split systems to our shops...they are uber-efficient and easy to keep clean. You really need to consult with a local HVAC resource to get the calculations for your geography, also considering the level of insulation, what your sun exposures are, etc.
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The most expensive tool is the one you buy "cheaply" and often...
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Around 4 tons, but we need more details.
Like, building construction, insulation, doors,windows, equipment.
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A typical US dwelling, this size and moderately code compliant, would need around 3 tons (36,000 BTU/hr) in the Houston area.Originally Posted by Travis Conner
However, lots of things influence tonnage - High ceilings (not sure what to tell you there). What amount and quality of insulation? How many door/window penetrations? What size? How often are they open (expected traffic)? Since its a shop, do you let it get heat soaked, and then want to cool it quickly and get to work? (Might need 2x the normal capacity.) Or, will you condition the space 24/7? Overall shape? Any partitions?
I'd probably mount the evaporator horizontally and up high to eliminate the 'footprint' on the floor - and build a large primary filter array (maybe 4 ea. 24x24 filters = 16sqft). These could be cheap throw-a-ways, then put a somewhat-larger-than-normal high-performance filter downstream of that - and finally flow into the evaporator. ...Kind of a Frankenfilter housing.
Mini-split is an easy install option, but consider some means to distribute the air? Maybe multi-zone with one air handler (evaporator) in each end? Or just one air handler and a big ceiling fan!
...Guessing you can skip the heat unit.
Last edited by Malcolm McLeod; 08-22-2020 at 9:53 PM. Reason: clarity
[OP]
Member
Building has no insulation. I don't think an hvac system would work well without any so that would need to be installed. I believe 6in on the ceiling and 3 on the walls is standard.
[OP]
Member
How much would a heater be?
Moderator
No need for it to be separate...typical HVAC units, whether conventional or mini split are heat pumps which can provide both cooling and heating as needed. The latter are more efficient and use less energy. But the former can often be obtained "used" for things like workshops.
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The most expensive tool is the one you buy "cheaply" and often...
Contributor
Are you talking about closed cell spray foam or fiberglass batt or ?
Way too thin for anything but closed cell spray foam. Even that would benefit from additional 6" fiberglass in the walls and 20"+ blown in ceiling
Good Luck
Ron
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Member
I'm not sure the correct terminology, but yes fiberglass batt would probably be the correct term. You see it in warehouses on the walls and ceiling,
it's white.
Moderator
Ron, the insulation specifications for Houston are likely different than for here in the north and this is also not a residential structure. R15 fiberglass in the walls wouldn't be unusual I would think. R21 in the ceiling (6") would be light to my preference, but might be ok in that geography, at least relative to cold. But insulation isn't just for cold...it's also to keep "hot" out...
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The most expensive tool is the one you buy "cheaply" and often...
Contributor
Our 1750 sf house in Florida is happy with 2 tons but it's built like a house. You have a very different situation. I researched it extensively when we replaced our system and learned 1) bigger is not better than big enough, it's worse and 2) it's difficult to get someone who thinks he already knows all the answers to take the time to work up your specific situation. I got 2 tons against the advice of everyone who gave me an estimate - they all advised 2 1/2 or 3 - and after 3 years it's clearly the right size.
If you Google "Manual J" you will find some information on how it's calculated and links to DIY sites for running the numbers yourself based on your location. Some have very detailed selections about insulation, etc. If you use reasonable numbers and change insulation values, you might get an idea what you want.
Last edited by Alan Rutherford; 08-23-2020 at 10:14 PM.
[OP]
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Yeah indont know What insulation is more effective for. Heat or cold. My guess would be cold. It doesn't get below 50 very often down here.
Member
If you give me the layout, R-values, equipment, windows, and doors I can give you the BTUs.
That's normal insulation for a "butler" building. Usually the insulation is between the siding/ roof and perlins.
Guessing I get 37,500 BTU's. 3 ton condenser and 3 1/2 ton coil. I'd probably bump that up to 3 1/2 and
4 ton.
How much duct? 1 room? I'd make a return plenum and cut filter grilles right into it. I'd also use a standard return filter.
It's a good heat pump application.
There's nothing efficient about butler buildings.
Remember, hot goes towards cold, insulation is generally ignorant in regards to this.
We could turn the building into a meat locker, but it would cost a fortune (and sweat like a pig).
Member
Manual J is residential. It's not relevant to a tin can.
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Member
Let me guess 3 tons probably wouldn't run long enough to condition the air and the smaller 2 ton would run more, but it would be a wash power usage wise since it's a smaller unit.
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