What's new
What's new

SHOP Cooling and Heating - Need education from people in the trade or knowledgeable

Zahnrad Kopf

Diamond
Joined
Apr 5, 2010
Location
Tropic of Milwaukee
Looking at upgrading the shop's air conditioning. I have read more posts than I care to have and still have no real answer, so I am hoping that someone here is knowledgeable and/or in the trade.

I am looking at wall and window units, and it is surprising how much of a price difference there is between them, for otherwise seemingly equal specifications. Why the price disparity? If a window unit can be installed in a wall, then why do wall units exist?

Is there a difference that matters in this specific situation? I don't care which we purchase. I simply want it to be the correct choice for our needs.

We don't need much for this instance. There is a 1 Ton unit in there already. ( 12,500 BTUs ) It is an old Kenmore unit that the manual says can be used in wall or window configuration. With more machinery in there than when the unit was installed, it is struggling lately. I can only imagine this will get worse as the summer approaches, as well as the unit ages. Not to mention that we are busier than ever and seemingly getting busier.

With the machining center, the WEDM, surface grinder, and a gear hob running at the same time, it can get warm in there. And I haven't even been running the turning center the last week or so. I am thinking to go right toward doubling the capacity. ( 24,000 - 25,000 BTUs ) But which one? Wall or window? Why don't we find many wall units that large? Why do wall units of equal size cost almost double that of a window unit?

Are wall units that much more efficient that one does not require as many BTUs? Are they simply whacking you for having a wall unit? What's the deal?

I am also considering getting one with heating as well, and getting rid of the large Reznor hanging in there, too. Bad idea? Fine idea? I know that it puts both eggs in one basket, but maybe it is worth it. Yes? No?

Thanks.
 
In my experience, nothing is going to help more than insulation. The more the better.

I think you'll be sorry going to a heat pump. They're cheap and easy, but on a cold morning you'll wish you had the Reznor back
 
Looking at upgrading the shop's air conditioning. I have read more posts than I care to have and still have no real answer, so I am hoping that someone here is knowledgeable and/or in the trade.

I am looking at wall and window units, and it is surprising how much of a price difference there is between them, for otherwise seemingly equal specifications. Why the price disparity? If a window unit can be installed in a wall, then why do wall units exist?

Is there a difference that matters in this specific situation? I don't care which we purchase. I simply want it to be the correct choice for our needs.

We don't need much for this instance. There is a 1 Ton unit in there already. ( 12,500 BTUs ) It is an old Kenmore unit that the manual says can be used in wall or window configuration. With more machinery in there than when the unit was installed, it is struggling lately. I can only imagine this will get worse as the summer approaches, as well as the unit ages. Not to mention that we are busier than ever and seemingly getting busier.

With the machining center, the WEDM, surface grinder, and a gear hob running at the same time, it can get warm in there. And I haven't even been running the turning center the last week or so. I am thinking to go right toward doubling the capacity. ( 24,000 - 25,000 BTUs ) But which one? Wall or window? Why don't we find many wall units that large? Why do wall units of equal size cost almost double that of a window unit?

Are wall units that much more efficient that one does not require as many BTUs? Are they simply whacking you for having a wall unit? What's the deal?

I am also considering getting one with heating as well, and getting rid of the large Reznor hanging in there, too. Bad idea? Fine idea? I know that it puts both eggs in one basket, but maybe it is worth it. Yes? No?

Thanks.

I'm actually 'school trained' at all this s**t, and at US Gov expense at that.

However.. time has passed, and Chinese and Mexican factories dominate what is back of the labels we can readily afford.

Pragmatic approach is to treat 'hole' mounted units as basically interchangeable 'expendables'.

Buy maybe only one or two steps up from the very lowest cost, if even that, goal to do so at season's END when they been put on markdown/closeout, and replace when they fail.

Heat-pump only if it is a freebie or nearly-so, price-wise. Do NOT remove the other heater even if you get a good one. You are too far North for a heat-pump to be of much use in wintertime.

Use two mediums rather than one heavy. You'll have better balance of comfort zones, hottest days, save more by running but one harder, longer on-time cycle than by running a higher-SEER rated single on low-load, less demanding days.

That also provides redundancy when, not if, one fails and lower size and mass to manhandle to swap 'em in and out.

'Wall' units, used by the brazilions in hotels and motels, are usually quieter than 'window', may or may not have any other significant difference from a window unit using much the same technology. "Split" units have refrigerant plumbing, two, not one electrical terminations, are not as friendly to DIY. I am not up for paying a premium price there.

The "residence" side of the walls here has a well-engineered central air system. Durable, cheap to operate, efficient and quiet R22. Well worth the extra work I put into that and the need to rathole a lifetime supply of R22.

Shop gets wotever is cheapest, any given year.

If nothing else, the doors are opened and LEFT open too often to get anal about 'efficiency'.

A large global market already sees to it that they all work well-enough.

As to "Global?" Our 1024 Sq Ft five-million USD flat in Quarry Bay, HKG has FIVE through-holers. Actually "split" units in our case, as we had the money to upgrade to that, but they are back-to-back right up against the same hole even so, just as the unitary ones were.

The other 35,000-40,000 folks in our one small development of 20 and 30 story towers have much the same A/C ration, 3, 4, or 5, per each flat.

China utilizes more thru-hole and split A/C units than we have unemployed rats, and they actually DO know how to make both types rather well, so there isn't a huge risk in going 'cheapest' for shop use.
 
Good points on the heat, both of you. Larry brings up a good point that I failed to mention in the original post - Building _IS_ insulated. It's pretty good, actually. We did it when we were putting it up. There are some places it needs better sealing. But what building doesn't have those? Point is - this is not an insulation issue. This is a machinery converting electric and motion into heat problem. That is what I need to control. If anyone has ever run a WEDM in a small space, they understand just how much heat they pump into a room. It can get brutal. And they NEED to be kept cool ( rather the DI water does ) to perform well and accurately.
 
Yes, bingo. I was just about to reply to the "insulation" post with a "that is not at ALL the issue in this case" but ZK has already been there done that. As there is quite a lot of heat-producing machinery in there, I'm guessing the only recourse would be to increase the cooling capacity. Whether window or wall unit would be better I can't help with. Do the machines have chiller units for oil cooling? That would probably help somewhat for keeping temps down as well. I installed one of those on a horizontal boring mill once and it brought temps down in the whole machine quite a lot. Running at high RPM with that machine before the chiller was a nightmare - the spindle would grow out in the Z axis by .015" or more as the machine heated up at the top end of the RPM range. (Long spindle, significant heat and the spindle clamp was in the rear).
 
With AC there may be one thing that is more important than insulation or at least as important as. That is anything that will keep water vapor out. A big percentage of your AC BTU's goes into condensing water out of the air so anything you can do to keep it out will make your AC more effective. I see Larry is in CA so maybe not as much an issue.
 
Good points on the heat, both of you. Larry brings up a good point that I failed to mention in the original post - Building _IS_ insulated. It's pretty good, actually. We did it when we were putting it up. There are some places it needs better sealing. But what building doesn't have those? Point is - this is not an insulation issue. This is a machinery converting electric and motion into heat problem. That is what I need to control. If anyone has ever run a WEDM in a small space, they understand just how much heat they pump into a room. It can get brutal. And they NEED to be kept cool ( rather the DI water does ) to perform well and accurately.

Mine is so well insulated it heats even on sub-zero days with but a pair of 'Delonghi' electric oil-filled rad types, rest of the time on 6 to 9 100-150 W incandescent ceiling lights. I swap those out for LED summertimes.

The machinery? Add-up the current it is hauling. 100% of that, and not one erg less, ends its journey as HEAT, whether has helpfully lighted the room, made or eaten chips, cooled or evacuated them along the way or not.

Entropy law or some such egghead s**t.

:)

And then there are those big doors..

I love my uber-insulation. But it is after all no more than a passive 'delay line'.
The only thing it 'creates' is better comfort and a lower power bill, winter or summer.

I'm good with that part, but it isn't enough by itself.
 
Given your location insulation may be part of the problem. You have a large heat load in the building. Insulation in most weather in your climate will keep heat in the building, increasing your air conditioning load. The hot water from your lathe and edm increase the humidity as well, increasing the perceived temperature.

I agree with two smaller units. That way one can be on nearly constantly to help dehumidify the workspace. Do you have a hygrometer to measure relative humidity?

With your heat load an exhaust fan may be useful. How much of the time is the outside air cooler than the shop? With forced ventilation, the size and location of the incoming air is very important. ISTR the incoming air velocity should be around 1000 fpm. To slow and you get lazy air that just falls to the floor, to fast and it makes drafts, doesn't mix well, and is noisy.
 
I am looking at wall and window units, and it is surprising how much of a price difference there is between them, for otherwise seemingly equal specifications. Why the price disparity? If a window unit can be installed in a wall, then why do wall units exist?

Is there a difference that matters in this specific situation? I don't care which we purchase. I simply want it to be the correct choice for our needs.

I've got six scattered around 2000 sq ft. Poked through the bottom fixed pane in awning windows, or in sleeves in the wall. I think the difference is window units are built in their case; wall units usually slide out of their "sleeve" which can stay in the wall while you pull the guts for service or replacement. The other possible difference is the window units, depending on size and capacity, may have louvers on the condenser side (outside) of the unit that extend too far back along the sides, so would be blocked by the thickness of the wall.

Dennis
 
Given your location insulation may be part of the problem. You have a large heat load in the building. Insulation in most weather in your climate will keep heat in the building, increasing your air conditioning load. The hot water from your lathe and edm increase the humidity as well, increasing the perceived temperature.
+1

Forget to mention I also have two fair-sized power vent fans, each 2-speed.

Much of the year, those do all I need w/o A/C, as my uber-insulation will indeed trap heat when I don't need it to do.

And.. there is also a roll-about de-humidify-only unit with a garden-hose drain fitting.

I don't have a rust problem, nor want one...

:)
 
Given your location insulation may be part of the problem. You have a large heat load in the building. Insulation in most weather in your climate will keep heat in the building, increasing your air conditioning load. The hot water from your lathe and edm increase the humidity as well, increasing the perceived temperature.

I agree with two smaller units. That way one can be on nearly constantly to help dehumidify the workspace. Do you have a hygrometer to measure relative humidity?

With your heat load an exhaust fan may be useful. How much of the time is the outside air cooler than the shop? With forced ventilation, the size and location of the incoming air is very important. ISTR the incoming air velocity should be around 1000 fpm. To slow and you get lazy air that just falls to the floor, to fast and it makes drafts, doesn't mix well, and is noisy.

I am COMPLETELY willing to be wrong about this, but I do not imagine that most shop owners are very concerned about humidity to the point of actually obtaining a hygrometer in effort to monitor it.

It's a machine shop. EVERYTHING CNC has a coolant sump. It sounds like chasing one's tail to avoid humidity. I would imagine that most others are like me - They're keeping the sumps properly filled and throwing a cooling unit at the problem.

Like I wrote, though - I am willing to be wrong about that. Am I?
 
You're right that little moisture generators are everywhere and there is only so much you can do. I have a little psychometric calculator on my phone (I am an engineer at a pharma company and this stuff is what I do by day) and did a quick calculation of energy required to cool air from 80 deg F, 70%rh down to 70 deg F, 58%rh. 2/3 of the cooling energy goes into condensing moisture and 1/3 into cooling the air. If you can put lids on tanks, covers on machines, etc I would think that would help. Also, sealing up cracks in the building. The point is if you ignore moisture then you are ignoring 1/2 to 2/3 of the problem- particularly in areas where it is humid.
 
I am COMPLETELY willing to be wrong about this, but I do not imagine that most shop owners are very concerned about humidity to the point of actually obtaining a hygrometer in effort to monitor it.

It's a machine shop. EVERYTHING CNC has a coolant sump. It sounds like chasing one's tail to avoid humidity. I would imagine that most others are like me - They're keeping the sumps properly filled and throwing a cooling unit at the problem.

Like I wrote, though - I am willing to be wrong about that. Am I?

It is so cheap to have the answer it is borderline 'free'.

I have a few sets of these four-to-the-package 'Wireless' thermometers with remote central display. Humidity percentage is included. About nine or ten bucks the set for throw-away cheap, under $40 for the better ones, IIRC.

Environment here:

79 F heading for 81 F outdoors, nearby KIAD (Dulles Airport), 52% humidity

Shop temp & humidity readings showing on the kitchen wall master unit as I type are:

68 F, 61%
70 F, 51%
69 F, 50%

and at the shop-attic head of pull-down stairs, presently open/down 80 F, 62%

Nothing in use just now, but no heat, fans, nor AC running either.

That cheap. That easy. Pack of AAA batteries once or twice a year.

I have OTHER stuff to measure motor temps, temps inside of electrical cabinets where WiFi might struggle, even Sound Pressure Level meter, and a great deal more.

Such toys have gone plentiful and right cheap, these days.

Most have paid-back right away, too, some at several times their cost in a single use or a single month.
 
I'm not in the trade, but I have had to "engineer" more than one HVAC system. The first thing I learned was that the average AC guy would estimate the size needed from the square footage and he would usually look at absolutely nothing else. Only the very good ones, the exceptional ones would look at what was in that space. The systems I had to engineer were usually designed around the power panel that fed the area. I would take a clamp on amp meter and see just how much current we were using and then translate that to BTUs or tons of AC. This is because every single Watt of electricity that you consume in that area WILL be turned into heat with 100% efficiency. ALL of it. The only exception would be any light that would escape from the shop through a window or door AT NIGHT. In the day time, more will come in than out so the windows and doors will be a net gain in heat during the day, even on a rainy day.

The formulae/tables for translating electrical usage to BTUs or tons of AC are on the web, just search. You can add the square footage estimate for your climate on top of that, but in many situations that will be a small fraction of the total. It always was for my situations.

Efficiency? Efficiency is not a measure of how much cooling you will get. That's what BTUs or tons of AC are for. Efficiency is how much you will pay for that amount of cooling on your electric bill. So two 5 ton AC units that have greatly different efficiency ratings will cool the exact same area by the exact same amount. But the less efficient one will cost more to operate. That's all there is to efficiency. You figure out the size that you need as described above and then consider the efficiency on an initial cost vs. down the road electric bills basis.

Window vs wall mount? First, all window mount units can be installed in a wall. Just cut a hole. But not all wall mount units can be easily be installed in a window. That's about the only physical difference I have ever seen. Cost? well, they probably sell ten times as many window units as wall units so there is an economy of scale.

Personally, I have a shop in a two car size garage. I it has a window so I bought a window unit. I started with a small, inexpensive one. It lasted one summer and did not cool very well. I had not added insulation at that point. I bought a second one that was about twice the size of the first. It was only marginally better at cooling and it lasted two summers. So, I ripped the paneling off the exterior walls and added insulation. And I bought a good quality, hopefully US made Frederich unit. It was about the largest window unit available, around 22,000 BTUs. It also has heat which I use in the winter, but winters in south Texas are not very severe. So far, it has lasted for about four or five years and is still going strong. From what you are saying, I suspect that about two of these may be good for your shop.
 
What EPAIII said.. and those El Cheapo remote t'stat?

Log the readings every 30 minutes or an hour over a week's time along with the outside ones, and you'll have some useful info on the cheap as to how your insulation is balancing against those Ammeter readings, real-world. Weather service publishes historical temps and even 'degree days' for each major station.

I also use the power company-furnished usage history to see if I have been gaining enough to pay for the materials over the long haul. So far, more than enough, plus waaay less stress if either overall power, or just heat or AC go out.
 
I'm not in the trade, but I have had to "engineer" more than one HVAC system. The first thing I learned was that the average AC guy would estimate the size needed from the square footage and he would usually look at absolutely nothing else. Only the very good ones, the exceptional ones would look at what was in that space. The systems I had to engineer were usually designed around the power panel that fed the area. I would take a clamp on amp meter and see just how much current we were using and then translate that to BTUs or tons of AC. This is because every single Watt of electricity that you consume in that area WILL be turned into heat with 100% efficiency. ALL of it. The only exception would be any light that would escape from the shop through a window or door AT NIGHT. In the day time, more will come in than out so the windows and doors will be a net gain in heat during the day, even on a rainy day.

The formulae/tables for translating electrical usage to BTUs or tons of AC are on the web, just search. You can add the square footage estimate for your climate on top of that, but in many situations that will be a small fraction of the total. It always was for my situations.

Efficiency? Efficiency is not a measure of how much cooling you will get. That's what BTUs or tons of AC are for. Efficiency is how much you will pay for that amount of cooling on your electric bill. So two 5 ton AC units that have greatly different efficiency ratings will cool the exact same area by the exact same amount. But the less efficient one will cost more to operate. That's all there is to efficiency. You figure out the size that you need as described above and then consider the efficiency on an initial cost vs. down the road electric bills basis.

Window vs wall mount? First, all window mount units can be installed in a wall. Just cut a hole. But not all wall mount units can be easily be installed in a window. That's about the only physical difference I have ever seen. Cost? well, they probably sell ten times as many window units as wall units so there is an economy of scale.

Personally, I have a shop in a two car size garage. I it has a window so I bought a window unit. I started with a small, inexpensive one. It lasted one summer and did not cool very well. I had not added insulation at that point. I bought a second one that was about twice the size of the first. It was only marginally better at cooling and it lasted two summers. So, I ripped the paneling off the exterior walls and added insulation. And I bought a good quality, hopefully US made Frederich unit. It was about the largest window unit available, around 22,000 BTUs. It also has heat which I use in the winter, but winters in south Texas are not very severe. So far, it has lasted for about four or five years and is still going strong. From what you are saying, I suspect that about two of these may be good for your shop.

THIS. This appeals to my sense of logic and reason. Thank you for posting that, EPAIII.

Still... I am left with the questions in the original post...

I think at this point, I am going to leave the Reznor up if only to keep my bets hedged and not lose two systems if one goes down, so to speak.

eKretz - The WEDM has a chiller and a largish ( 55 gal? ) DI tank. The other machines would not really benefit from one. I'm largely a one man band, doing everything. However, that is changing lately and I have had to bring in some part time help to keep. Still, the machines are not really ran hard enough to benefit from a chiller, vs. having better air conditioning.

Monarchist - Your point is well taken and as you and EPAIII point out, I need to check into just what we are expending. I'll find out and convert to BTUs.

Modelman - Your point about the difference in wall and window units is what I have come to learn as well. But it seems confusing to me that louver placement causes this 100% price difference in some models. I have seen prices literally DOUBLED for otherwise similar units, save the difference of being labelled a wall or a window unit. Something is amiss, here. It just does not reconcile in my pea brain.

Can it really be a matter of measuring for exhaust clearance, and having ensured that, one can then save 50% of the price by purchasing a window unit and sticking it in the wall??? I am happy to do it, but not before I can make SOME manner of sense out of it...

Pete Deal - The machining center's sump is pretty much covered, save some entry/exit gaps. The WEDM tank IS covered. ( it still manages to evaporate :rolleyes5: ) The turning center sump is not really covered easily, as coolant has to get back in somehow and it is largely a "fall back in" affair. I have modified it to be partially covered in the area that is not directly under the work area. The area that is in the work zone is covered by perforated sheet metal.

All things considered, there is approximately 100 Gallons of sump in here. Half is coolant mixture, half is DI water. How does one calculate the needed BTU capacity of that? ( that being the stated 1/3 - 2/3 of total capacity needed )

Otherwise, the square footage is pretty small by most's standards, and insulated well. ( I make very good use of the space and try hard to avoid clutter ) The loft is largely sealed off from the ground area. Windows are gas filled double glass.

What is the down side to going right to 2 Ton? I can get a 24,000 BTU window unit for ~ $600 - $700. However, if I have to get a wall unit, that price doubles. Then again, maybe I don't need 2 Ton in a wall unit... This is where things get confusing for me....

As for two smaller units, I don't know that this place is large enough to take advantage of that. I am willing to be wrong on that, too though. It is only 20 x 30... And yes, I have to go outside to change my mind... We are going to have to buy a building in the next year I think. But I want to be comfortable and avoid machinery repairs ( electronic ) due to heat while we are still here.
 
I was going to stay out this, but everyone has neglected the most valuable guide, The ASHRE Guide. It's published by the American Society of Heating and Refrigeration Engineers. This explains all the facets of calculating the heat load. A big part is infiltration though openings, probably more than through the walls. Check your local library, they may have a copy. Also, a big HVAC company may have copy. I have a copy if you want to borrow it.

Tom
 
Just for grins, price-out a split unit in the attic, center-ceiling air-handler if a place to put it is problematic.

As to wall vs window?

If you need to got thru-wall, just make and properly frame a larger opening to suit the biggest unit in your long-range plan.

Not rocket science to then fill the area around a smaller first-experiment one with proper insulation, packaged, and with foam seals, rather than just the plastic airplane-window-blind crap they arrive with.

As to 'calculations"? Don't go overboard. The math always works. The s**t you left out or guessed wrong at is where the variances enter. "Instrument" the space with cheap Temp & humidity gadgets. Log what they find, variances will already make themselves felt.

AC unit doesn't really care WHICH contributor was the greatest villain, as long as the shop air supply hasn't been corralled in sections independently stored in salvaged weather-balloons or such..

:)
 
Want to fly on a plane that was seat of the pants engineered?

Tom

I'd class the AA5B I've clocked a few hours in pretty much that way, liked most of it above the level of the silly 'self-castering' (sometimes!) nosewheel.

Also add that I could wish quite a few oddities of Cesspool 172's were even as good as to show evidence of any 'Engineering' of any kind!

:)
 








 
Back
Top