Re: Wiring 220V Compressor

[jeff-register]

Chris,
I have had my electrical contractors license here in Arizona. Just because it’s 240 volts (check with a meter) you still need to find your rla amperes. That is your running load amperes. Multiply that times 125% to come up with your required amperes. Now your dryer outlet @ 30 amperes you should use 80% of that max which is 24 amperes. Now compair your 24 usable amperes to your motor RLA is to see if it is a match. Remember to use 125% times your RLA, If your numbers are good buy a S.O. type cable with a 4 wire rating. It should have two for 240 volts, one for a grounded conductor usually for the control circuit voltage 120 VAC & the grounding circuit for bonding the compressor to the building ground system. Most compressors only use three wires but if it is newer it will have 120 for the control voltage. Let me ask this. Is your dryer plug have a 3 or 4 pin rectepical. Match the cord cap to the one installed. To make that easy look on the recteptical for the N.E.M.A. number & tell the sales guy is that is what you have to get the correct match. N.E.M.A. = National Electrical Manufacturing Association. If this confuses you send me an E mail @ jeff.50@cox.net… & I’ll help you do it correctly. One more thing, The dryer recept should be rated at 30 amperes. If that is not enough #10 wire, You should install a 50 ampere two pole common trip circuit breaker, Number #8 stranded wire THHN type insulation & then at the compressor site fuse it down to the required amperes. Don’t forget to get your amperes from the motor name plate & find the R.L,A. running load amperes times 125% to come up with your requirements.
Be careful & DO NOT build a fire hazzard!!
Jeff