Heating & Cooling New Shop

Concrete Block construction building. Steel roof. We will be insulating the roof and sealing entry/exits. The main building will be 2500ft². The secondary building will be 1600ft², but not going to do this one right away.

So, 2500ft² CBS construction, steel roof, in SouthEast Wisconsin, having two machining centers, two turning centers ( hydraulic pumps ), various manual machines, ( mill, lathe, cylindrical and flat grinders, Gear Hobs, Gear Shapers, blah, blah, blah, etc... ) General rule of thumb for sizing a cooling/heating unit?

My Google-Fu is weakened by fatigue and overuse, but I'm coming up with approximately 6T for the size. Does this sound right? If someone has done this recently, was there one approach that worked better than another? Gotchas to watch out for? Split Package units? What about the DIY Pre-Charged units?

Thanks.

Get a few quotes from local HVAC outfits. They don't cut gears do they? just giving you a bad time. Dan

Dan from Oakland said:

Get a few quotes from local HVAC outfits. They don't cut gears do they? just giving you a bad time. Dan

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Your'e not completely wrong to, either.

Truth is, I have two calls out, already. But I'm more looking for the experiences and input of owners/managers that may have gone through this semi-recently. ( probably should have put it in the owner/manager sub forum, too LOL )

Besides, honest ribbing from others sharing similar shoes and roads traveled is to be expected.

If your running tighter temp control be sure to ask what the deadband of the thermostat is they've got listed. One of our heatpump units has a 2 degree deadband, works great. New fancy multizone/wifi/do-all thermostat on our new unit is a 4 degree deadband and it drives me nuts, haven't found one yet to replace it with but haven't looked to hard either.

Are you allowed to build with no wall insulation?
Bill D

Well, there is FIRE.
And then there is ELECTRONS.

Pick one......

RTU will be most cost-effective option. Curbs can be difficult to seal on metal roof. 6t unit sounds a bit light. You should get an accurate load calc done to be sure. Rule of thumb is 600 sq ft/ton for residential and around half that for commercial. Free spreadsheets are available online but you need to look up numbers to input into cells. So there is heat gain on building itself, roof ,walls, windows and doors. Gain from ventillation. People load. Lights. Machines, motors. All commercial projects in WI must go through State plan approval and plans must be submitted by a licensed professional. Builder usually handles all details.

Bill D said:

Are you allowed to build with no wall insulation?
Bill D

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I wondered about that as well. No wall insulation at all, or just not mentioned?

rbent said:

If your running tighter temp control be sure to ask what the deadband of the thermostat is they've got listed. One of our heatpump units has a 2 degree deadband, works great. New fancy multizone/wifi/do-all thermostat on our new unit is a 4 degree deadband and it drives me nuts, haven't found one yet to replace it with but haven't looked to hard either.

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Thank you. That's a gem I would never have known until it bit me.

deltap said:

RTU will be most cost-effective option. Curbs can be difficult to seal on metal roof. 6t unit sounds a bit light. You should get an accurate load calc done to be sure. Rule of thumb is 600 sq ft/ton for residential and around half that for commercial. Free spreadsheets are available online but you need to look up numbers to input into cells. So there is heat gain on building itself, roof ,walls, windows and doors. Gain from ventillation. People load. Lights. Machines, motors. All commercial projects in WI must go through State plan approval and plans must be submitted by a licensed professional. Builder usually handles all details.

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Thank you for the info. I need to adjust my calculations.

Zahnrad Kopf said:

Concrete Block construction building. Steel roof. We will be insulating the roof and sealing entry/exits.

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Bill D said:

Are you allowed to build with no wall insulation?
Bill D

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AND

awake said:

I wondered about that as well. No wall insulation at all, or just not mentioned?

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< shrug > I thought I was clear. The roof is ( was ) not insulated. The walls are CBS. Aside from the filling of the cavities, I've never seen a mandate that insulation be attached to the walls. Have I led a sheltered life?

Either way, it's a non starter at this point. Got out there to inspect and was shite. CBS blocks had shifted in numerous places ( I stopped counting at 30 ), leaving gaps in the walls up to 1-1/2" wide. Big crack in the floor concrete. There was more wrong with it, too.

Onward... the search continues...

Wall insulation will be the key to calculating. We built a cinder block house a few years ago. Around the corners, doors, and windows the blocks were filled with concrete. The rest with a foam insulation. On the exterior 1 1/2 inches of Styrofoam with another 3/4 inside under the sheet rock. This house is a lot easier to heat and cool than an earlier house we lived in with just paint on the inside and outside of the cinder blocks. Also it is way more comfortable.
Heating and cooling is impossible to guess till you know how it is insulated.

I see you have dismissed the building, but for future reference, the heat load calculation is wicked simple

BTU = square footage of surface x delta T /R value for that surface

You should calc in air leakage, but on large buildings with few doors and windows, it is probably not as big a deal as a house with more openings per sq foot

If you air condition, that will drive system size, since everything creates heat, nothing creates cold....

Zahnrad Kopf said:

Either way, it's a non starter at this point. Got out there to inspect and was shite. CBS blocks had shifted in numerous places ( I stopped counting at 30 ), leaving gaps in the walls up to 1-1/2" wide. Big crack in the floor concrete. There was more wrong with it, too.

Onward... the search continues...

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Ugh...
You building, renting or buying.
I think the optimal is probably SIP construction if you have a choice.
Maybe radiant floor if you don’t need to bolt things down.

Miguels244 said:

Ugh...
You building, renting or buying.
I think the optimal is probably SIP construction if you have a choice.
Maybe radiant floor if you don’t need to bolt things down.

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Yes. ( but no renting )

Not being evasive. Honestly could go either way. We are looking for property large enough and zoned correctly to have both home and business buildings upon it. ( easier than expected, actually ) We can work with either condition. If it has both already, and is suitable, good to go. If it only has the one, but the price, land enough, and zoning for the other, then we build it.

The biggest issue we've run into is owners flat out lying about the property, or flat out misrepresenting it with old pictures and descriptions. We looked at one yesterday that the pictures had a large, Penn Dutch style flower painted on the out-building. It was newer, and vibrantly colored. Building appeared to be perfect. 5K square feet, concrete floor, electric available, water, etc... When we arrived there, the flower was half gone from weather wear, and so faded as to be at least 4 - 5 years old. And the property followed suit physically, as well. SOME concrete floor, one 20 amp circuit for light bulb, building literally ready to fall down. Chunk of door came off when I went to open it...

We have been looking for almost a year now. Very actively for 6 months. Visiting about 6 properties per week at times. Normally about 3 per week. I am SO over that. What a complete time suck.

I looked at commercial property for a long time. One thing I figured out is all commercial property owners are insane

I have a bunch of cousins in and around Oconomwok...
All wound up buying a house and building their shop.
Most homes came with a pole building for the equipment.

I’d suggest just figuring on building the shop, it’s not something you are going to find...but if you do be ready to pull the trigger that morning.

Rules of thumb for sizing cooling loads as used for residential or retail/office type commercial buildings are useless for sizing equipment to cool a machine shop.

Every watt that passes thru your meter is ultimately converted to heat. Doesn't matter whether that watt is powering a light bulb, a spindle motor, a coolant pump, a hydraulic pump, or a personal computer, its all converted to heat.

If you had an average load equal to 20hp all day long, that's 15kW neglecting inefficiencies. 15kW X 3413 BTU/kW = 51,200 BTU/hr, or 4 1/4 tons of cooling just to offset that load. Add in the various inefficiencies, all of which are also converted to heat, and you're likely pushing 5 tons.

A competent contractor can run a heating and cooling load on any building you may buy or build, but to have accurate numbers on the internal loads, you'd need to collect some information on your own. The last thing you want is someone to walk thru and add up the horsepower of every machine in the shop and base the equipment selection on that number as it would result in a grossly oversized system. That said, if the contractor has nothing else to go on, he'd tend to oversize to cover himself rather than take a chance on undersizing and risking a civil action later for installing a system that won't cool.

You can get your load information now, as it would normally be independent of the location of the business. Its as simple as using a clamp on amp meter to check and record your incoming amperage once per hour during work time for a couple weeks. Also, keep a daily record of how much total coolant mix you have to add during that same 2 weeks. The coolant amounts will give whoever's doing the load calcs a good idea of the latent (humidity) load, as that can be a far greater percentage than one will normally encounter in most other commercial buildings.

When you give the load numbers to anyone who's doing the overall load calcs, make sure they understand that your numbers are for internal loads alone and do not include the normal building load calculations.

I'd stay away from even thinking about using mini-splits (the precharged units you mentioned) due to the fact that coolant mist will gunk up the evaporator coil on those units in no time and make a maintenance nightmare that will cost you more than you'd save via their high efficiency. Mini-splits are fine for use in a garage or similar setting, and would be okay in a machine shop if all the cutting was done dry, but that's not the normal shop situation.

Personally, I wouldn't consider any bare concrete block building in your area unless you're willing to spend a bunch of money on insulation. We rented a 4000 sq ft building with 16" thick poured concrete walls for a few years prior to building our shop in the late 80's. Those walls have roughly the same R value as 8" block walls. In the coldest months, we would burn thru a thousand bucks worth of natural gas per month and the place was still about like working in a tomb. In comparison, our current building is a 9000 sq ft pre engineered metal building with a gas furnace for the office area and vacuum tube radiant heat for the shop, and in the coldest part of winter the gas bill never runs more than $400 while the working conditions are very comfortable. And FWIW, the winter design temperature here is 20 degrees higher than in your area.

"I've never seen a mandate that insulation be attached to the walls. Have I led a sheltered life?"

In word, yes. At least in some jurisdictions (quite possibly including WI from post above) you won't be allowed to add real heat, let alone A/C, without a certain level of insulation. In some jurisdictions near me in WA state commercial buildings have to have elaborate lighting controls to avoid wasting power lighting areas where people aren't. In effect government forcing people to spend capex now to (maybe) save energy latter.

On the other hand, if you are going to build, you'll want decent insulation and HVAC anyway.

metlmunchr said:

I'd stay away from even thinking about using mini-splits (the precharged units you mentioned) due to the fact that coolant mist will gunk up the evaporator coil on those units in no time and make a maintenance nightmare that will cost you more than you'd save via their high efficiency. Mini-splits are fine for use in a garage or similar setting, and would be okay in a machine shop if all the cutting was done dry, but that's not the normal shop situation.

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shit! i made a big mistake. it's been 4 years now i wonder when they will fail? you got me nervous however i got flood coolant is that sorta like mist?

metlmunchr said:

Personally, I wouldn't consider any bare concrete block building in your area unless you're willing to spend a bunch of money on insulation. ..............

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Pretty much is the only answer.


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OP - If you want to rough out the heating load for this building:

The formula for heat transfer is:

HT = SF times U-value times Delta T

SF is square footage of surface
U-value is the inverse of R-value
Delta T is the difference in temperature between the outside and the inside.

You will need to do this for each building surface and openings.

The Pikes Peak building department requires an energy calc spreadsheet on new construction. Fill in the square footages and R-values of the various surfaces and it gives a total BTU heating load. The T values in columnn G should be adjusted to your local climate but it can be used as is.

Residential Handouts - Pikes Peak Regional Building Department

You want the Heat load spreadsheet in about the middle.

Steve

cg285 said:

shit! i made a big mistake. it's been 4 years now i wonder when they will fail? you got me nervous however i got flood coolant is that sorta like mist?

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I didn't say the units will fail. I said they will become a maintenance nightmare if you do what's necessary to keep them operating at the efficiency level you paid for. They just become less and less efficient over time as coolant is deposited on the fins of the evaporator coil. The mist I spoke of comes from running flood coolant on an endmill spinning at several thousand rpm's, or the same thing from a turning center spinning a part at a thousand fpm or so. Both common situations in a cnc shop with lathes and mills.

The solution is regular cleaning of the indoor section of the unit, but when you're using this type unit in a business where the only thing you have to sell is time, that cleaning costs money both in wages and in lost opportunity to spend those same wages on productive work.

The OP would obviously buy heat pump units rather than cooling only if he used mini-splits. In the heating season, where the indoor coil temperature can be running 130 degrees or higher, the coil will immediately cook the water out of any mist and deposit what amounts to super concentrated coolant on the coil. Obviously, this goo will impede heat transfer, but it also makes the coil act as a sticky filter to catch anything that passes thru the normal unit filter (which typically isn't a highly effective filter). At this point, cleaning the unit to restore its ability to transfer heat becomes a much more difficult job, much like the difference in cleaning dried coolant off a machine as opposed to rinsing down coolant that's still wet.

IMO, any heat pump is a poor choice for a machine shop, for the maintenance issues listed above. Coolant in the air isn't nearly the problem when running air conditioning as the evaporator coil stays wet and will tend to carry the coolant off with the condensate. And, for any type shop. I'd use radiant tube heaters for the heat due to a combination of comfort and low operating cost. And, in the case of a machine shop, the fact that their efficiency isn't affected by the presence of some coolant in the air.