Electrical question.

Looking at wiring in a small fan for an air cooler to my compressor so the fan runs when the compressor does. Compressor is 240, fan is 120. Do I wire in on one of the motor legs from the coil and just use a dirty neutral?
Thanks, Rich
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Rich, are you sure you HAVE a neutral in the wiring to your 240V equipment?
dave
Rich wrote:

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Dave,
I did not run an extra wire with the 240V line but there are other 120v outlets in the "doghouse" with the compressor that I could use.
Rich

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gotcha. and I didn't read your OP carefully enough to realize what you are really asking about is how to run the fan ONLY when there is a current draw on the motor. Do you have a Grainger's catalog?
dave
Rich wrote:

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Yes I do. I'm on my way to Grainger today to get the compliment of regulators and filters.
Rich

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I don't think it's strictly to code, but the small current for a fan isn't going to hurt anything being in the neutral. I'd do it, otherwise, you need a relay for it...or a transformer (240 to 120), then you could connect the fan housing to neutral. Wilson

wire
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Is that necessary, normally the large pulley on the compressor pump is plenty. These things run hot and last for years running hot. A company that I worked for had a compressor room with 8, 200 gallon compressors running virtually non-stop all day long and the room was HOT.

wire
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Depending on the make and model of your compressor you may get away with this mod I did on one some years back. I was able to change one of the pulleys to a double pulley that I then used to drive a small fan rig device thingy that I concocted. Use your imagination and you'll probably get what I mean. Anyway the fan ran whenever the compressor did and helped to cool it.
Jim

the
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But hot is not good. Shortens the life of the unit so even one that runs for years can run even longer in a better environment Industrial compressors are cooled with fans or outside cooling towers to keep temperatures down. Air intakes are often outside to keep the temperature down. Discharge air temperatures can easily reach 250+ degrees. Ed
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Just buy a 240v fan. They are dirt cheap from computer junk recyclers.
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"Rich" writes:

wire
Don't go there, it's not worth it.
I could tell you a legal way to do it, but the cost of the equipment far outweigh the benefits.
Find a 120V outlet and plug fan into it.
Forget to unplug it some night, so what?
By your own description, it is small, so power consumption is not an issue.
KISS definitely applies here.
--
Lew

S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
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What you are contemplating can be done correctly if the supply wiring contains 4 wires including a separate ground conductor, You can connect to any neutral along the path of the wiring that supplies a load that is connected only to the opposite side of the 240 v. connection you use to connect the fan. A word of caution. Usually the pressure switch for a 240 v. compressor contains 2 switch connections, They are not always both used on some units. Meaning that the motor is not completely disconnected only the current path is broken, if this is so connecting a fan to the single switch will result in the fan continuing to draw current through the compressor windings from the opposite leg after the compressor has shut off. A small fan would continue to run, possibly a bit slower. You could utilize the second switch set to disconnect the fan and remedy this.
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Chipper Wood

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