Starting 5HP Electric Motor

Corley5 · February 27, 2014, 07:52:25 PM

What's needed for a switch to start a 5hp compressor duty electric motor? It has overload protection with manual reset built in and is capacitor start/capacitor run, whatever that means ;D I've got it wired up with a 220v switch but it doesn't work. It blows the breaker when it's turned on. I'm not doing something right

The motor is wired correctly. It just won't start :-\ Do I need a magnetic switch ??? The motor is Surplus Center Item # 10-2530

yukon cornelius · February 27, 2014, 09:07:34 PM

check the wiring again. can you post a pic of the wiring as in where it is hooked to the motor. do you have a voltage meter? what is the amperage of the motor and what amp breaker do you have. I will do my best to walk you through checking it out.

Corley5 · February 27, 2014, 10:51:34 PM

15 amp motor. 30 amp breaker. #10 wiring. Double pole switch rated for 30 amps for pumps, motors, etc. Wired according to diagram. Line one to 1. Line two to 4. Black to 2 and red to 4 for CW rotation.

yukon cornelius · February 27, 2014, 11:32:12 PM

ok first without a test meter you can star by isolating a short. pull off the 2 power wires from the motor, wrap them with electrical tape very well and turn on the power to see if it still trips. if it does. pull the double pole switch and disconnect from the switch, tape the incoming wires (from the breaker) turn on breaker and see if it trips. if it does its somewhere between the breaker and switch. does it trip when breaker is turned on or when you turn the switch?

this is how I would proceed if I had no access to multi meter.

please be careful when wrapping wires to insure they cannot touch anything or most important anyone.

I zoomed in on your pic and it looks very professional. If I had to guess I would say a wire touching another most likely the ground in the switch box. just a guess. it happens a lot.

BE CAREFUL AND HAVE SOMEONE ELSE AROUND IF POSSIBLE!

Gary_C · February 27, 2014, 11:36:37 PM

If it immediately blows the breaker, it could be a faulty breaker or a short somewhere. If it growls and then trips, it could be bad capacitors. Yes, even new motors have bad or shorted capacitors right out of the box.

Try it without the belts and see if it starts with no load.

Corley5 · February 28, 2014, 12:34:44 AM

I tried my extension cord on the dust collector on both circuits and both are fine. I've got two 30 amp 220V circuits. I pulled the switch box apart and checked the connections and for shorts. All looked fine. I also pulled the plug apart just to be sure. Nothing wrong there. I do have another switch and almost changed it but it's late. I checked the connections in the motor and don't see anything touching anything that it shouldn't. No bare wires etc. I switched circuits and it popped the breaker almost as soon as I flipped the switch. The motor makes just a slight momentary noise before the juice cuts off. Capacitor ??? There's nothing hooked to the motor. It's a no load situation

I wanted to make sure it worked before I put the belts on ;D The breakers that pop are in the house box not the overload on the motor.
I've got a new multimeter around here but it's missing tonight.
"I zoomed in on your pic and it looks very professional." Thank You. I was trying to do it the right way and it still isn't working :

underdog · February 28, 2014, 12:35:47 AM

The book says 5hp will draw 28amps on 240V and around 13 amps running
They also claim 40A breaker and 8 gauge wire should be used

Corley5 · February 28, 2014, 01:02:36 AM

I ran these circuits with 3HP in mind.

36 coupe · February 28, 2014, 05:58:44 AM

I have used 5 hp motor on my planer for over 30 years now with a plain 2 fuse switch and 30 amp time delay fuses.Number 8 wire and 242 volts.I have had a fuse blow in hot weather at times.I think current increases when a motor gets hot.I stop running the planer when a fuse blows.5hp motors cost too much to take chances.Have the motor checked in a motor shop.

yukon cornelius · February 28, 2014, 08:51:52 AM

did you say you tried those wires on your dust collector? if you did and it was fine it has to be at the motor. you have to isolate where the problem is. I always start at the furthest part of a circuit and work back.

Corley5 · February 28, 2014, 08:54:23 AM

The issue appears to be at the motor. It's brand new from Surplus Center. I guess it needs to be returned :(

yukon cornelius · February 28, 2014, 08:58:06 AM

I think a 30 amp breaker would start it without any belts hooked to it. I would change it out before putting it to work. the undersized breaker is not nearly as important as undersized wire.

Corley5 · February 28, 2014, 09:01:33 AM

I should say it appears to be at the motor unless the breakers aren't heavy enough to start the motor.

yukon cornelius · February 28, 2014, 09:01:56 AM

can you post a pic of the wiring diagram? I could at least look at it to see if anything was overlooked before you return it.

Corley5 · February 28, 2014, 09:03:37 AM

Anyway the DanG thing doesn't work. That's my luck to get something brand new and it's not right. Thanks everyone 8) 8)

Corley5 · February 28, 2014, 09:07:15 AM

Yup 8)

Corley5 · February 28, 2014, 09:13:03 AM

That's all it came with

Raider Bill · February 28, 2014, 09:25:49 AM

Quote from: Corley5 on February 28, 2014, 09:03:37 AM
Anyway the DanG thing doesn't work. That's my luck to get something brand new and it's not right. Thanks everyone 8) 8)

You are not the only one this happens too my friend...

yukon cornelius · February 28, 2014, 09:34:29 AM

well it looks to me that you did it all right. I guess you got a bad motor. it does happen. I was hoping I could help ya get it goin. there is only 1 check left and that would be putting a 40 amp on it but I don't think it will help your situation.

Corley5 · February 28, 2014, 09:40:33 AM

I think I'll give a 40 amp breaker a try just because I can ;D :D I'll be going by HD later today. It's real PITA to re-box this thing, haul it to UPS etc >:( I was hoping to plane some lumber this weekend with it :-\ Thanks again everyone 8)

pineywoods · February 28, 2014, 10:06:53 AM

Critical question..When you throw the switch, does the motor grunt or hum a bit before it trips the breaker, or does the breaker trip immediately ? Motor may be bad, but even at best , you have a very marginal situation with a 5 hp motor on a 30 amp circuit. The amp spec on the data plate is for current draw while running with no load. Starting current is another matter entirely, and is usually between 2 and 3 times the running. If the 15 amp figure is accurate, you are looking probably 40-50 amp draw to get the motor started. The 30 amp breaker is doing what it was designed to do, protect the wiring from overheating.

Corley5 · February 28, 2014, 10:21:19 AM

It will make a slight noise, maybe move a tiny bit before the breaker pops. After some further cogitation I'm thinking I'll pack it over to the shop and plug it into the welder circuit. That will tell the tale

If it works there I'll get some #8 wire and wire in another circuit for it. If it was warmer or was going to warm up I'd do the planing at the shop but with no heat and single digit temps I'd rather do it in the house ;D

sprucebunny · February 28, 2014, 10:26:02 AM

Quote from: Raider Bill on February 28, 2014, 09:25:49 AM
Quote from: Corley5 on February 28, 2014, 09:03:37 AM
Anyway the DanG thing doesn't work. That's my luck to get something brand new and it's not right. Thanks everyone 8) 8)

You are not the only one this happens too my friend...

Yup. Put me in that group. I swear the auto parts store has a special shelf of broken stuff they save to sell me :

:D

terrifictimbersllc · February 28, 2014, 11:50:38 AM

Quote from: Corley5 on February 27, 2014, 10:51:34 PM
15 amp motor. 30 amp breaker. #10 wiring. Double pole switch rated for 30 amps for pumps, motors, etc. Wired according to diagram. Line one to 1. Line two to 4. Black to 2 and red to 4 for CW rotation.

I had 50 ft of #10 on a 5HP motor on an IR compressor. Motor went bad within 6 months even though this wire should have been enough. IR person told me this, but was also generous and sent me a new motor free, which I put on #6 wire same length. Haven't had a problem in over 10 yrs now.

DeepCreek · February 28, 2014, 01:03:29 PM

The purpose of the circuit breaker is to protect the wiring, not the load. General rule is to size the wiring and breaker at 125% of the rated continuous load, not the starting current. Chances are the math will work out so that it doesn't fall directly on any specific wiring ampacity or breaker rating. In that case you go up to nearest standard rating. However motors are done a little differently resulting in a slightly larger breaker.

My own compressor has a 5 HP motor rated at 22 amps. It is on a 30 amp breaker with #10 conductors, which was installed by an (allegedly) licensed electrician. Even though the breaker has never tripped, it is technically undersized. He should have installed a 40 amp breaker instead of the 30. And yes, he knew it was a dedicated compressor circuit.