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  • Air Compressor freezing?

    I'm trying to eek out an bit more space in the shop (got a deal on a horizontal mill) and I'm wondering about moving my air compressor into an unheated part of the building, Be advised I'm in Minnesota !!!!!! Any advice or ideas welcome, Thanks
    Rick

  • #2
    Freezing can be a problem with the unloader system, not often but it does happen. The unloader system is that momentary "Hiss" you hear when the compressor reaches pressure and shuts off, it's purpose is to bleed off the head pressure so the pump will not be under load at restart. What kind of compressor do you have? If the unloader is the very common type that is operated by the pressure switch that also controls the motor it will be more prone to freezing than the centrifugal type. What happens if it freezes is the pressure will not bleed off between the pump and the tank (there is a back-flow valve in the tank to prevent reverse flow) and the pump will still be under pressure when the tank pressure drops to the restart setting and this will cause the motor to overload due to the excessive torque required to start the pump spinning while under pressure. The usual result is simply a tripped breaker but a much worse possibility would be a burned out motor. This does not happen often but that bleeder line and the valve located in the switch are very small and it only takes a drop of moisture to cause this problem, like I said it don't happen often but when it does it can range from being just an annoyance to being a serious problem!

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    • #3
      If your tank drain valve or line has water in it, that can burst. At least your air is pretty dry in the winter!

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      • #4
        Originally posted by gitmkr
        I'm trying to eek out an bit more space in the shop (got a deal on a horizontal mill) and I'm wondering about moving my air compressor into an unheated part of the building, Be advised I'm in Minnesota !!!!!! Any advice or ideas welcome, Thanks
        Rick
        Rick, I live in N/W Pa. and have had my air compressor outside in a shed for about 27 years, and it has not had any problems. I upgraded from a 50's era freon pump to an Eaton tri-Y three cylinder compressor about six years ago, and the new pump has lived in the shed from when it was new. I does pull hard when temperatures drop into the single digits and -0F ranges. If you can manage it build a well insulated room and add an electric space heater for when the temperature get real low.
        Dan.

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        • #5
          The only problem I can think of is the increased load on the motor that will occur because of the oil thickening up (I'm assuming you have a pump with an oil sump). That could be mitigated by using synthetic compressor oil, if you can find any. I think AMS/OIL may sell it.
          ----------
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          • #6
            im in n.w. wisconsin and mine is in a unheated garage and have not had any problems. real 5 hp, old system. i'd think you'd be fine.

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            • #7
              Originally posted by SGW
              The only problem I can think of is the increased load on the motor that will occur because of the oil thickening up (I'm assuming you have a pump with an oil sump). That could be mitigated by using synthetic compressor oil, if you can find any. I think AMS/OIL may sell it.
              SGW, synthetic compressor oil does not help all that much, I am running a high grade synthetic since last winter and the starting load does not seem to be any different from the Mobil oil I was running before. I have not checked amperage draw to be scientific about it.
              I am currently adding a permanent room for the compressor onto my shop, just starting the ground work, that will be insulated and have a piece of fin tube in it to heat it.
              I am also thinking of adding a platen under the compressor pump to circulate fluid from my radiant floor heat exchanger through to warm the crankcase instead of heating the whole room. I am still debating whether or not this would be worth the time and effort to design and build the platen.
              Dan.

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              • #8
                The peoplewho make heat pumps make a crankcase heater thingy just for cold weather starts. Look in Johnstone supply or Grainger.

                Or something like this:

                http://motors.shop.ebay.com/i.html?_...e+block+heater
                Last edited by Forrest Addy; 10-11-2011, 10:56 AM.

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                • #9
                  Fellows don't just brush off the fact that the unloader can freeze, I have seen this occur on two different occasions. Again it does not happen often but when it does it can be a real (and sometimes expensive!) problem.

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                  • #10
                    Originally posted by radkins
                    Fellows don't just brush off the fact that the unloader can freeze, I have seen this occur on two different occasions. Again it does not happen often but when it does it can be a real (and sometimes expensive!) problem.
                    Wonder if a piece of electric heat tape for pipes would help here?

                    David
                    David Kaiser
                    “You can have peace. Or you can have freedom. Don't ever count on having both at once.”
                    ― Robert A. Heinlein

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                    • #11
                      I have a 7 1/2 Hp 80 gallon compressor in my unheated garage. I run Velocite 6 in the crankcase. I also have installed a timed solenoid drain valve to the tank drain, and wrapped about three ft of self regulating heat trace around the crankcase (6 watts per ft). Never had an issue with it in 15 years (West Virginia gets some pretty cool weather).

                      Mark

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                      • #12
                        Since your still keeping your compressor inside your shop, I would think about a simple rigid styrofoam box that's taped or glued together around your compressor with a low wattage heater (or even a poultry lamp) placed closed to floor to keep things warm when they're not in use. That should be enough to keep any water you might have in the unloader and volume tank from freezing. Just leave vent holes top and bottom for air flow.
                        Perhaps the biggest problem you might face, will be airlines that are in the unheated area that get cold enough to allow any moisture in them to freeze.
                        Small pieces of ice that might form in the lines would be enough to block misters, schrader valves, regulators, air tools with small ports, etc., until enough warm air can flow from the compressor can thaw things out. Just slighly cracking a valve open so that you have a small hiss will sometimes do it, opening the valve a lot can cause the thawed moisture to re-freeze and block the valve.
                        Of course, all of this depends on how cold things get, how good your water separator is, humidity, moisture collected in the volume tank, etc.
                        Breathing compressed air with ice crystals in it is like breathing razor blades.
                        I cut it twice, and it's still too short!
                        Scott

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                        • #13
                          Originally posted by 38_Cal
                          Wonder if a piece of electric heat tape for pipes would help here?David


                          After it happened to me a few years ago I just placed a heat light near the regulator and line to the pump. All the "I've left mine out in the cold for years with no problems" stories won't help much if that unloader freezes and overloads the motor which is a real possibility.

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                          • #14
                            Thanks everyone. I think I'll box it in and use a light bulb when it gets real cold.

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                            • #15
                              Using a light bulb that you can't see and / or know it has burned out will leave you unprotected. High quality heat tape or the block heater is the most reliable protection.
                              Byron Boucher
                              Burnet, TX

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