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  1. #21
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    I have been using the same 2 ton wall unit for AC for 25 years with a rag of foam over the intake

    Does what it does

    A friend had a little shop that ran hardinge HCNC with oil, had a similar unit caked with goo


    All depends on what you are doing

  2. #22
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    Default Heating & Cooling New Shop

    When it does come time to source your heating/cooling system, check out Surplus City Liquidators in Indiana. They are the largest seller of new and surplus HVAC equipment in the U.S.

    No affiliation, just a satisfied customer.

    Most local HVAC companies will charge 2 to 3 times the cost for the unit(s) than could be sourced new from SCL.

    For a machine shop, in my opinion the best solution is a packaged unit(s), often placed on the roof. (All Wal-Marts, Home Depot’s, etc. are heated and cooled using these units.)

    But, for the easiest installation and maintenance, placing the unit on the ground is better.
    Just cut a couple holes through the wall for the return and supply air ducts, and you are in business.

    Of course the unit has to connect to properly designed and installed ductwork, with the air-return using several layers of filters, which are easy to access at ground level inside the shop. Good filtering is a must to help keep those evaporator coils clean.

    The packaged units come pre-charged with refrigerant, and this makes them a do-able self install.

    Proper unit sizing, placement, and ductwork are critical though...
    Last edited by cnctoolcat; 04-20-2019 at 06:42 PM.

  3. #23
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    ZK,
    My company is in final finishing of a building improvement project on 18,000 SF of concrete-floor metal-roof building with stucco-finished metal-stud walls, reasonably well-insulated. Building is located in southern AZ. We added HVAC to about 8.000 SF, split into two approximately equal spaces, and the mechanical calcs indicated that we were right on the borderline of 10 tons per 4000 SF being enough/not enough. Essentially no reserve for heavy load or HVAC equipment failure. Of course, that's the way we went, rather than adding an additional 5-ton unit for each space...Out here, ~400 SF/ton is the rule of thumb, especially in residential AC design. 600 SF/ton may be perfectly valid for northern US, though.

    One thing to keep in mind for adding rooftop units on existing construction is the roof structure load. That was a question that consumed a few weeks at the beginning of the project, whether the existing manufactured roof setup could sustain additional load of both AC units and sprinkler system

  4. #24
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    Given a choice I would not punch holes in a roof.

  5. #25
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    Didn't read if you have gas available but-In your area heating I believe may be the most used.For a shop I would go with gas heating units(space heaters,not the little cheapo's) that are suspended from your joist say couple down both sides of the shop.During those cold months if one heater goes down you have others.Cooling go with a package unit that sets on pad on the ground where the returns is right at floor level then the ductwork running overhead ever how high it needs to be.The duct work could be what is called a sock type duct work which would be lot cheaper than sheet metal,but sheetmetal will last a lot longer

  6. #26
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    Read this post again. You are in a northern state so your first concern is probably heat in the winter. Whatever electricity that you consume will help there so your HVAC contractors will probably get that right.

    BUT summer heat is another thing and is a greater concern. In the summer all that power that is consumed inside the buildings and, as metlmunchr has pointed out, will become heat and will add to the heat that must be removed. I had an electronic facility in Iowa and we ran about 14 KW of electric energy while operating in the day and often in the evening. 14 KW = 47.770 BTUs which roughly translates to 4 tons of air conditioning. We were in the middle of a building and there was interior, heated space above our ceiling so that is what we based our cooling on (5 tons). In your case you will need to add the wall and ceiling load.

    If I were you, I would estimate the amount of electric power that you will be using at peak times. Try to make this estimate good for 5 or 10 years. Then call in your local HVAC companies. Tell them it is a working machine shop and give them the wall and roof data. Ask for their estimate. If they don't ask about the electrical load, DON"T USE THAT COMPANY! If they don't ask about the electric load, they don't know what they are doing. And if they do know their business, they will do a much better job than you can. Get two or three good estimates: they should agree on the tonnage that you need.

    PS: In that Iowa facility the boss wanted to update the heating system for the building and was going to install a new, high efficiency, hot water system in that area. I told him that no matter how efficient it was, he would not get his money back in 100 years because we didn't heat the area in the middle of an Iowa winter, we ran air conditioning; much to the misery of my HVAC guy who had to make it work in -20 F and below. That heating was never installed.



    Quote Originally Posted by metlmunchr View Post
    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.

  7. #27
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    Quote Originally Posted by specfab View Post
    .....................Out here, ~400 SF/ton is the rule of thumb, especially in residential AC design. 600 SF/ton may be perfectly valid for northern US, though.

    ..............
    Which is why you find a contractor who correctly does the project by doing Manual J calculations to figure the actual amount of heating and cooling loads instead of using "rules of thumb".

    My 1600 sq ft shop is heavily insulated and is cooled by a 10K BTU (12K is a ton) window air conditioner and heated in the winter with 3 - 1500 watt baseboard heaters (winter heating cost is about $150 per winter).

    Steve


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