Keeping small (but busy) shop cool

Liberty_Machine · Mar 27, 2018

Hello,

1,000 sq/ft or so, two CNC mills (Mori DuraVertical and Kitamura 3XD) (2x) digital phase converters, (1x) Quincy 7.5hp Recip Air Compressor.

Looking for advice on keeping the place cool(er) in the hot summer months. Last year wasn't too bad, but I wasn't running both machine 12 hours a day every day. Tended to be maybe one always on and another 50% of the time. I've added an employee, so both machines are running at all times.

I have an "in-the-wall" AC (20k btu's), but it didn't do very well last year when it was really hot. I called a local HVAC company and they ballparked me a cost between 10-15k. Well outside of my price range.

The work I do is very tight tolerance, so I'd rather not deal with huge temperature swings. Furthermore, I work 60-80 hours a week, I'd rather not tack on the added misery of sweat pouring down my face and everything getting sticky. (the shop is attached to the house)

I recently added a wall vent up high on my end wall to help draw out some of the hotter air (Mori is housed in a cathedral ceiling addition)

Any thoughts/comments?

Liberty_Machine · Mar 27, 2018

Oh, and just as an example: This past winter we had several brutal weeks of sub zero temps (F). Once the machines were up and running and the heat was pumping out, around 10-11 am or so, my furnace stopped coming on. So, sub zero outside, 2x4 walls with insulation, and the furnace sat idle because the machines and converters were generating enough heat to keep the place warm. Towards the end of the day, Id actually crack open the garage door to draw in some cold air.

Guest · Mar 27, 2018

How about portable AC units, one stationed at each machine that just blows on the operator? They exhaust through a flex hose like comes out of a dryer and you can run longer than the original if you use a duct fan. Just a thought. I did that when I was in So Cal. At the time they were like $500 a piece, that was a dozen years ago or so.

adama · Mar 27, 2018

IMHO you need to vent the heat from the machines straight outside before you try the air-con route. Things like the phase converters and compressor, box them in and extract the heat straight outside. Should be easy to drop a lot of the thermal gains with some smart ventilation before you contemplate any actual AC.

macgyver · Mar 27, 2018

I agree, get the compressor and converters outside of the conditioned space so you aren't paying to make that heat and then paying to cool it back off. I don't know enough about HVAC to offer any advice there but I'd spend some time and money making it so you don't have to spend as much on AC to begin with. If you own the building I'd consider more insulation etc.

Antarctica · Mar 27, 2018

I found an old 5 ton unit from a house on craigs (they replaced it with a new unit prior to selling the house), sat the indoor unit on the floor, plumbed to the outdoor unit and fired it up. $300 and the thing will draw down about 800 square feet from 100 to 68 in about an hour.I have no duct work - it just draw from the bottom and blows from the top.

Mud · Mar 27, 2018

More or bigger AC units. I have 2 24K BTU window shakers and a 33K unit in a 33 x 100 X 12 ft area with 3 VMCs, 2 turning centers and a bunch of other stuff (mills, welding, lathes etc, and 5 garage doors). and they do fine when it's under 95°. Previously had 2 15K units and a 30K and they weren't nearly enough.

Bill D · Mar 27, 2018

Move the ac outside for less noise and heat inside. Not sure what a digital phase converter is but, if they make heat, duct the cooling air outside. For the biggest motors can the warm exhaust air be ducted outside using insulated flex ac air ducts.
Split ac units is my suggestion for cooling. How hot does it get in summer? I assume swamp coolers would not work in your climate.
If it is cooler then roof vents will draw in cooler outside air.
Bill D.

norb · Mar 27, 2018

My Shop has AC but I use "max-fan" can fans with flexable ducting to vent the hot air from my wire EDM chillers. Works great. I have to leave the door slightly ajar so I don't have negative air pressure.

Pete Deal · Mar 27, 2018

How about open a furnace return in your shop to move some of the heat from the machines to the house and dump some of the furnace discharge into the shop. Leave the fan running. Winter only of course.

DanielG · Mar 27, 2018

Last summer was pretty hot. My building's AC isn't great either, so I felt your pain.

One option would be to move the air compressor outside. That would take some load off your AC. The downside of moving it outside is that you waste the heat in the winter. A company I used to work at had the air compressor in a small shed-like building on the side of the shop.

Instead of looking at AC, have you looked at putting in a heat pump. It's less expensive than oil for heat, will cool in the summer, and Efficiency Maine has some incentives, even for commercial installations.

Most of the time, it's cooler outside than inside, so you might consider something like a whole house fan. Another option, since our ground stays cold, that I've read about, but not seen/used, is to have in intake fan that pulls air through a buried pipe. The ground cools the incoming air.

Hobby Shop · Mar 27, 2018

Save the money and do it yourself. I have the same size building, 25’x40’ and putting on a 500sq.Ft. addition this summer. I bought a 95%-75k btu furnace and 3.5ton AC NIB (with line set) off CL for $1200. I installed the furnace myself and did the ductwork with the help of my brother and buddy in 2hrs. It was only $750 for the ductwork and Ac coil. Here’s a few pictures. I still have a lot of loose ends to clean up but I’m getting there. Hopefully, the lighting and electric is happening this weekend.

garyhlucas · Mar 27, 2018

Simple thing here. ALL the electric you use turns into heat at a rate of 3450 BTUs per KW. Look at your summer AC bill. The KW number is the heat load from your machines that needs to be removed to simply stop the temperature from rising. Then you add on the heat load of the empty building and that total is how much AC you need. Nothing is cheaper than window units simply because they are manufactured by the millions and all you guys already know that volume is everything on cost. So I'd calculate how many BTUs of capacity are needed and punch a few more holes. Note that if all you want is comfort then you need a lot less because they will reduce the humidity and you will feel cooler.

cnctoolcat · Mar 27, 2018

You should consider a 4- or 5-ton package unit, the kind normally seen on roofs. They can also be mounted on a slab outside your wall.

Set the unit, cut two holes in your wall (one for supply air, one for return), add some basic ductwork, hook up the power, and you're in business.

The heat pump types heat as well as cool.

Surplus city liquidators in Lebanon, Indiana specialize in these units, offering new units at significant discounts over list price.

They have 5-ton package unit heat pumps for around $3-4k.

I am hoping to install a 15-ton unit soon for my 4,000 sq. ft. shop.

ToolCat

JP Machining · Mar 27, 2018

I would look at something like this, way more efficient than the window units and the hole thru the wall is like 3" diameter thats it. Plus a heat pump version can run backwards and supply heat as well if you needed it. Can also get a version that has one outside unit and 2 inside units, put one in the house and keep the wifey happy too. Also would look at some of the larger heat sources and see if there was any reasonable way to exhaust that heat directly but I dont think I would go so far as to box in the phase converters etc.
Midea MCHS-36PSH2 MEHS-36PSH2 Premier 36, BTU 18 SEER Ductless Mini Split Heat Pump 23V

munruh · Mar 27, 2018

JP Machining said:
I would look at something like this, way more efficient than the window units and the hole thru the wall is like 3" diameter thats it. Plus a heat pump version can run backwards and supply heat as well if you needed it. Can also get a version that has one outside unit and 2 inside units, put one in the house and keep the wifey happy too. Also would look at some of the larger heat sources and see if there was any reasonable way to exhaust that heat directly but I dont think I would go so far as to box in the phase converters etc.
Midea MCHS-36PSH2 MEHS-36PSH2 Premier 36, BTU 18 SEER Ductless Mini Split Heat Pump 23V

this looks interesting. Anyone have one?

Bill D · Mar 27, 2018

munruh said:
this looks interesting. Anyone have one?

I have installed two 3/4 ton split ac units in my house. Just two copper tubes with flares at each end and a 3? conducter romex cable connecting the units. Fredrich is the quietest unit by 50% or more over some name brand versions. I already owned a ac manifold gauge set and vacuum pump so install by myelf was easyOne unit is about 10 years old the other in my bedroom is about 3 years. So far so good. Max temp they have seen so far is 120. I oversized the units so I can run them at low speeds for less indoor noise.
Bil lD

Bill D · Mar 27, 2018

DanielG said:
Last summer was pretty hot. My building's AC isn't great either, so I felt your pain.

How hot is hot to you? I know after a week of 100 degree days I get tired and cranky. Anyone have experience with chilled water vests to cool the torso.
As a school teacher I see a lot of athletes who drink over one gallon of water a day. This is a regular school day not even a hot day or game day. Coaches now measure hydration levels and push athletes to keep drinking all the time. My sister in law from China claims that drinking ice water is bad and water should be at least room temp or even body temp.
Bil l D.

SIM · Mar 28, 2018

Roof vents, light colored roof and consider early in early out.

Start early in the am when suns down, the ground, building and air are as cool as it will be. Then you knock off early afternoon as the sun starts to take hold, as the building loses its coolness and that mercury starts really rising inside.

Seems by 2-3 is when the heat really takes hold and becomes uncomfortable...that's when the guys are punching out.

In my area I have another issue aside from the afternoon heat...its the kids, moms and dads coming home cranking the A/C's around then...our power company meets this demand by dialing back the voltage a bit, Rolling Brown Outs. Took me awhile to figure it out...but seemed every afternoon the older CNC became a bit quirky, started tossing odd alarms...then down the road it was a new board, servo motor...something. After a couple years of this we picked up on it and as we started seeing those quirks...I just shut down the machines. That stopped alot of service calls and helped make the decision towards early in, early out.

gustafson · Mar 28, 2018

I have run a 2 ton wall/window unit in larger though perhaps less busy shops successfully, on all but the hottest days

Late i the year when all the concrete heats up it gets harder to maintain

AC is a lifestyle, turn it on when it threatens to get hot, leave it on. Resist the temptation to open the door on days when it is nice in the morning but is going to get hot. Do not turn it off at night, put it on energy saver. You need to dehumidify, or it will never get cool. If you keep opening the door all that humidity must be gotten rid of before you can get cool.
Act like you are in the Arctic and your life depends on keeping the 'heat' in
Chase air leaks, be a nazi about doors being open and especially the overhead. Don't stand and chat with the UPS guy with the door open.

Cold air will puddle, don't try to AC the ceiling, it doesn't matter.

Cheapest in the short term is another 2 ton wall unit

A bigger minisplit can be done for a bit more. If it is your building, buy a brand name.

Find one or two of those big floor fans, makes the days when the AC falls behind more tolerable

Keeping small (but busy) shop cool

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