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  1. #1
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    Fan Cycle Control

    Had a headmaster fail today, can't get the new valve for a few days so i just put in a fan cycle control for the meantime. It's a 208v single phase motor. It's wired straight with the compressor contactor to always run fan when comp's running. I wired it to break 1 leg of the power at the fan cycle control. Now i'm thinking about it, that means 1 leg of power is always going to be fed to the motor whenever the comp contactor is pulled in. Is that an issue? Or is that how you're suppose to do it. Having a brain fart and electricity was never my strong point...
    Last edited by Apprenticanic; 01-27-2014 at 11:20 PM.

  2. #2
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    Sep 2011
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    sounds good to me

    Quote Originally Posted by Apprenticanic View Post
    Had a headmaster fail today, can't get the new valve for a few days so i just put in a fan cycle control for the mean time. It's a 208v single phase motor. It's wired straight with the compressor contactor to always run fan when comp's running. I wired it to break 1 leg of the power at the fan cycle control. Now i'm thinking about it, that means 1 leg of power is always going to be fed to the motor whenever the comp contactor is pulled in. Is that an issue? Or is that how you're suppose to do it. Having a brain fart and electricity was never my strong point...

  3. #3
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    manufactures do that all the time to save money on components - it is electrically correct and in the short term it is fine. However, In my opinion (which when combined with anywhere from 3 to 9 dollars will get you a cup of coffee) I think it is bad form. It makes a system harder to trouble shoot and more unsafe for a technician. You can use a 2 pole contacter on a 3 phase compressor and motors - and a single pole contacter on 208/240 single phase motors and compressors.
    For the Government to Give Something to you - THEY HAVE TO TAKE IT WAY FROM SOMEONE ELSE FIRST...

  4. #4
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    Thread Starter
    Quote Originally Posted by genman View Post
    manufactures do that all the time to save money on components - it is electrically correct and in the short term it is fine. However, In my opinion (which when combined with anywhere from 3 to 9 dollars will get you a cup of coffee) I think it is bad form. It makes a system harder to trouble shoot and more unsafe for a technician. You can use a 2 pole contacter on a 3 phase compressor and motors - and a single pole contacter on 208/240 single phase motors and compressors.
    Ah that's right, i have seen that done before with single pole contactors and comp's. Thanks for the clearing that up in my head. And I think I would tend to agree with you on your arguement on it being in bad form though.

  5. #5
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    Quote Originally Posted by genman View Post
    manufactures do that all the time to save money on components - it is electrically correct and in the short term it is fine. However, In my opinion (which when combined with anywhere from 3 to 9 dollars will get you a cup of coffee) I think it is bad form. It makes a system harder to trouble shoot and more unsafe for a technician. You can use a 2 pole contacter on a 3 phase compressor and motors - and a single pole contacter on 208/240 single phase motors and compressors.
    What is more difficult about a single pole contactor to diagnose? I'm having trouble thinking of ways that it's less safe, too.

    Unless you want the luxury of checking a capacitor or something without having to turn the disconnect off. However, I think that would be even worse form than using a single pole contactor.

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  6. #6
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    Quote Originally Posted by genman View Post
    manufactures do that all the time to save money on components - it is electrically correct and in the short term it is fine. However, In my opinion (which when combined with anywhere from 3 to 9 dollars will get you a cup of coffee) I think it is bad form. It makes a system harder to trouble shoot and more unsafe for a technician. You can use a 2 pole contacter on a 3 phase compressor and motors - and a single pole contacter on 208/240 single phase motors and compressors.
    $1.29 at McDonalds.
    It's electrically correct and will work until it stops working. It's done all the time on single phase motors. The only time a contactor is necessary is if the motor amp draw exceeds the rating on the switch. IMO the only reason it would make it unsafe for the technician is if the technician didn't have knowledge on how the equipment works. If that's the case, he shouldn't be touching it. Fact is, cycling the fan, IS NOT GOOD FOR THE MOTOR and it's not ideal for the refrigeration circuit.
    Officially, Down for the count

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  7. #7
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    Quote Originally Posted by 2sac View Post
    $1.29 at McDonalds.
    It's electrically correct and will work until it stops working. It's done all the time on single phase motors. The only time a contactor is necessary is if the motor amp draw exceeds the rating on the switch. IMO the only reason it would make it unsafe for the technician is if the technician didn't have knowledge on how the equipment works. If that's the case, he shouldn't be touching it. Fact is, cycling the fan, IS NOT GOOD FOR THE MOTOR and it's not ideal for the refrigeration circuit.
    X2

  8. #8
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    "I'm having trouble thinking of ways that it's less safe, too. "

    I have had the crap knocked out of me when the motor was replaced by a previous contractor without hooking up the ground wire.... the motor is mounted on rubber isolators and I reach to the fan blade and give it a little spin to check the bearing.... It happened once on a condenser unit and once on a window unit.... It hurt both times... I always try and learn from these kinds of things... so now I always teach new guys to approach everything like it is energized.... always touch it with the back of your hand first. That way if it is energized your hand will be rejected instead of hooked up... I know its legal - I know it works - I know how to trouble shoot the system if it has one leg of power energizing all the motors all the time.... but In my opinion its bad form to not break all legs of power to a unit that is not required to run. There is just less chance of an accident or hurt service person...
    For the Government to Give Something to you - THEY HAVE TO TAKE IT WAY FROM SOMEONE ELSE FIRST...

  9. #9
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    Anything installed incorrectly is going to be less safe.

    I feel where you're coming from, but the single pole contactor didn't cause your shocking experience and a double pole contactor only would have masked the problem slightly better. Your motor had a short to ground and on top of it all was installed improperly.

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  10. #10
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    I always like when they break the contactor coil voltage with a toggle switch. NO DISCONNECT just a toggle switch.

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