Help with wire gauge and breaker size for condensor

vivitron21June 6, 2010

I am trying to wire up a lennox ac condensor hs21-060-1p and am trying to find the correct wire size and breaker.

my wire run length is 50 ft

it says on the condensor my voltage is 208/230 v

its 1 ph 60 hz

its says min ckt ampacity amperage min 40.2

max fuse or ckt bkr 60

now i worked out id need a 60 amp breaker and #6/3 cable would this be correct as im doubting myself that

1. i should go with a smaller breaker to be on the safe side since i think its telling me 60 is max

2. i could use #8/3 cable but knowing #6 is safer

3. i tought for 208230 volt id need /3 wire as in 2 hots i neutral and 1 ground but when i checked the condensor wiring it looks like there are 2 big thick red wires for the 2 hots nothing that i can see for a neutral and only a screw to the chassis for the ground.

im afraid im a Brit in the USA lol and i get a lil confused at times with how you guys wire things lol so im thankfull for any help lol

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Use the #6. A 50 amp breaker might, or might not, hold while the unit starts. Momentary amperage draw while starting is quite high. That is a big unit. Seems out of the category of do-it-yourself project size.

    Bookmark   June 6, 2010 at 6:39PM
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yes its a 5 ton unit i have someone comiing to do the refridge lines on monday and i gotta get it wired before hand im gunna go with the #6/2 and a 60 amp breaker since i found out the old breaker where the unit was installed was an 80amp but im gunna double check my clacs with an electrician first was just hoping to find one here lol and thanks for your input

    Bookmark   June 6, 2010 at 6:57PM
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I would use 6/2 on a 60A breaker. Using conduit and conductors you could just as safely use #8's. With NM cable you must use #6.

208/230v simply means that it can be used on a 208V system as well as a 230/240v system.

    Bookmark   June 6, 2010 at 9:30PM
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thank you. i got a 60 amp breaker and #6/2 plus conduit so im hoping everything should all be fine i also managed to get a hold of the guy that had the system in his house and its was about the same length run and his was on 60 amp breaker and #6/2

    Bookmark   June 6, 2010 at 9:42PM
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Conduit? For what?

    Bookmark   June 7, 2010 at 6:30AM
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The conductor size is set by 120% of the 40.2 running current.

The circuit breaker can be any size up to 60 amps to ensure reliable starting.

Hermetic compressors use a similar n method to induction motors for selecting wire size and breaker size.

The two are NOT tightly coupled like on general use circuits.

Conductor size is based on the running current, while breaker size can be increased to allow for starting current surges.

The compressor has its own internal thermal protection to prevent it from overloading the conductors, and all the breaker is doing is providing short circuit protection to eh feeder.

The device label should also list LRA (locked Rotor Amps).

This current can be used to determine what the voltage drop in the feeder is and make sure it is not excessive.

If no LRA is available, compute the voltage drop using the 60 amp maximum size to make sure the voltage at the unit will remain adequate when it tries to start up.

    Bookmark   June 7, 2010 at 12:32PM
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To answer your third question, the condensor doesn't use a Neutral. Our 220v appliances over here (dryer, ovens) use a neutral because the electronics inside is 120v, not 220v.

    Bookmark   June 7, 2010 at 4:20PM
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