Contributor
In my climate humidity is not a problem in summer so I oversized my ac in the house. This way I only run it on low for quieter operation. If humidity get over 35% we feel swampy here and it does not rain for 8 months or so. I still have not seen dew in the morning since April or so.
Bill D
Contributor
Stick a pin in the 5 ton “contractors” card and burn it on a full moon. As pointed out, if you had a 5 ton unit in a 2.5-3 ton building you will be cold, wet & po’d.
Member
This question was asked before. I'd be happy to run the numbers. I would need a lot more information: crack and R value for walls, ceiling, windows, doors; wall, floor and ceiling treatments; exhaust numbers, motor sizes, and occupancy load just for starters.
Those "calculators" aren't always accurate, they round numbers, which can compound.
For a comparison, up here 25 BTUs per sq ft is a close guess. This is for an 8.5 ft ceiling.
For a 1500 sq ft house I get 37500 BTU. (3 ton condenser and 3.5 ton evaporator) If I had 12 ft ceilings, I'd be at 54,000 BTU. 5 tons. This is only a quick example.
Keep in mind the calculation, whether digital or manual, only gives BTUs. It does not size the equipment.
I would guess that 5 ton "guess" is correct. I would consider 2 stage. This is normally a good idea if you anticipate large swings in load, like that garage door.
Always get 3 quotes, always understand the job, and always compare apples to apples.
Stan
[OP]
Member
Yeah but I also don't want to run into a situation where it won't cool either. My brother had that issue in his house where everyday 4pm it wouldn't even keep it at 80 degrees upstairs. The solution for that was add more insulation. Of course that's an attic, so that's fairly simple to fix. The insulation for a steel building is kind of hard to add more later down the line.
[OP]
Member
Possibly. I know my 60 gallon air compressor heated up my bathroom (sound enclose) a few degrees after just one cycle. Honestly I don't know much about that stuff. My biggest motors are 5hp.Originally Posted by Dave Mills
Member
I didn’t read all the replies so maybe this is a repeat.
You didn’t say if the system was a heat pump. If so you need a bigger unit for heating than cooling sometimes. But not 5 tons. Windows matter too, lots of heat gain in summer and heat loss in winter. If on a concrete slab it will take less tonnage to cool.
The tall ceiling is what’s causing the larger quote. I would say 3.5 to 4 tons for cooling assuming good insulation and a slab. If heat pump it would be 4 to 5 tons. Heat pumps can keep up with cold weather if undersized but the electric strips come on more which costs way more per BTU than straight heat pump operation.
[OP]
Member
Aren't the heat pumps more efficient than the heat strips? I'd probably go the heat pump rout. I have a heat strip system in my house and it the heating bill is outrageous compared to the cooling bill in the 100 degree summer heat.
Contributor
Travis, for reference-a loaded 5hp motor is worth roughly 1 ton of ac.
Moderator
Any form of resistance heating is going to drink power. Heat pumps sometimes have that feature for supplemental heat when the outside air temperature drops below a certain point (my minispilt is -5ºF as the lower limit for it working effectively) but heat pumps work by extracting heat from one space and exchanging it into another space; ie, inside and outside and vice versa. It's very doubtful that any supplemental heat would ever be needed in your area, so for operating costs, which will generally be skewed toward AC for you, higher efficiency (SEER) is going to impact your energy bill in a positive way. Of course, the trade-off there is higher initial cost for higher efficiency units. Again, I'll point out that right now in the market, Minisplits offer the highest efficiency for any cooling solution.
--
The most expensive tool is the one you buy "cheaply" and often...
Member
One other factor is that when calculations are made on a 1500sf house the actual air volume is much less due to the thickness of the walls. An open building of 1500 is actually about 250sf larger than the same size house. I’m thinking that for TX the 5ton is probably the right size.
Contributor
Echoing Jim and other's comments, I'm a huge fan of mini-splits for workshops at least in moderate climates. I had one in my former garage workshop and now in my dedicated shop. They are super-efficient and have actually been less maintenance than traditional systems in my house, despite operating in a much "dirtier" environment.
There is a very fine line between “hobby” and “mental illness.” - Dave Barry
Contributor
I believe that the calculation is called a "manual J". That's what tells them x windows/doors this type of insulated wall.
Member
Do you guys with mini splits just have the one "head" in the room? Or do you run a couple heads to different areas? The ones I'm familiar with can be run both ways, and I assume these don't have ducts. I just wonder how evenly the room is conditioned if you only have one source for cool/warm air.
Member
Resistance heat is 100% efficient, meaning that there is not any energy wasted. It is all converted to heat. It is also the most expensive way to heat a space. A heat pump is much more economical to run. It uses less electricity.
I don't think Manual J will have any useful information. Who ever is supplying the building should be able to give you the thermal coefficients, same with the doors and windows.
Keep in mind a 1500 sq ft building with 12 ft ceilings has a lot more volume than a home. 30% more cubic feet? 30% more cooling.
Is the ceiling flat or is it pitched? (Is it really only 12 ft?)
If the building is 30x 50 with a 12/4 pitch, you add another 3750 cu ft. We are getting close to a 3000 sq ft house.
A dust collector will also add significant heat.
Stan
Contributor
Running my dust collector is the same a having a 3000W - 5000W (depending on which blast gates are open) electric heater running. After even half an hour the shop warms up significantly.
Posting Permissions
Reply With Quote