Air Compressor Wiring

[yardlongdraft]

Hello all... If this is the wrong forum I apologize in advance.

I have lurked around here for ages but have been reluctant to post.. in over my head and am seeking advice on wiring a Baldor 240 V 1.5 hp motor to an Emglo air pump I inherited. It is 1725 rpm and 18/9 amps.

I am not a total novice with electricity...probably just knowledgeable enough to be dangerous. I have run a 30 amp disconnect to energize the compressor and I know you need 2 hots and a ground and you have 240 volts. The compressor actually runs fine with the way it is now wired. I am concerned that I don't have a proper ground.Using the 3 wires from the motor I have connected a white wire to load and a green (I'm aware green is usually ground) to the pressure switch load terminals and the black (black is generally hot) wire to ground. When I connected the way things are usually wired... black to hot, green to ground, one of the 30 amp time delay fuses kept blowing. I took a cover off of a toggle switch (which appears to be inoperable) and I can see that the green wire is apparently attached to the motor frame, which leads me to believe it should be the ground. I just want to be safe. Any input would be welcome. I can add pics, etc if it would help. Also, sorry for the length of this post.

 

[bobby g]

The green wire is never a hot wire. The wiring is typically black to black, white (or red) to white and green to green. What size time delay fuse keeps blowing?

bobby g

 

[Gotcha6]

bobby g Re: Air Compressor Wiring
The green wire is never a hot wire. The wiring is typically black to black, white (or red) to white and green to green.

+1

You should also reduce the size of the fuses to 15 amp. The motor you are using says 240v 18/9 implying it is a dual voltage motor capable of running on 120v if configured correctly. In its 240v configuration, it only pulls 9 amps. Circuits should be sized to 120% of the intended load. Oversizing may result in inadequate circuit protection. In this case, you aren't protecting the wiring to the motor if it is <10 gauge. Unless it is a long distance from the panel, 14 gauge wire & a dedicated 15 amp circuit is all that is needed. Be sure to look at the motor wiring connection cover to confirm you have the leads on the right terminals.

 

[yardlongdraft]

Hey Bobby, Thanks for answering...I thought green was always ground too. The fuses are 30 amp time delay. This unit was pretty strange (as far as the wiring is concerned) when I got it. There is a toggle switch in a housing (which appears to be inoperable) and connected to the toggle are 2 black and 1 white which in turn go into the motor. Then there is the green connected to the motor frame which seems to obviously be the ground. Coming out of the toggle switch housing and going to the pressure switch are 3 wires...white green and black. I initially tried the white and black to pressure switch load side and green to ground which was the condition that blew the fuse. Thanks again, Randy

 

[Bill Clemmons]

Without seeing a close up pic, it's hard to say, but the toggle switch arrangement seems strange. Is the toggle switch connected to the motor? Was this motor used for something else previously?

Here's why I'm asking: on some machines I install a dpdt toggle switch to easily switch the motor into reverse. If someone tried that and didn't get it exactly right, it could be causing a problem. Just a thought.

Bill

 

[yardlongdraft]

Thanks Gotcha and Bill for answering. Gotcha, my plan was to just get it running if possible and then change out the disconnect, etc. I was just using things as is to see if I could get it working. I appreciate your input as to what size breaker, etc. I should use. That will be helpful if and when I get this running.

Bill, the motor was definitely used in some other application. My father-in-law acquired the motor and pump from various places and had it up and running for years in his shop before he passed. It was always quiet and could deliver an impressive volume of air. He was pretty crafty and obviously did some modding/rigging on it to make it work. The black wire coming from the motor was spliced together with a green end and there was a squeeze on lug on the end of it, so I'm assuming it must have been connected in the pressure switch. That is why i thought maybe it was actually a ground. But knowing him it might have been the only wire he had on hand. There was a second black wire in the same length that was pulled back and taped so it couldn't be used. I'll try to take some good quality photos and post them...maybe they will help.

From what I have researched on the Emglo pump it is certainly a fine so that is why I am working hard to get it to work. I am looking forward to using it in place of my noisy oil free cheapo unit. Thanks again for everyone's help. Randy

 

[Bill Clemmons]

Randy, I'm going to suggest you remove all the current wiring and start fresh. Your Father-In-Law wired it to fit his needs, but may not have followed any standard convention. Get yourself an appropriate length of 10/3 (black, white, & green wires in one sheath) and wire it according to the diagram on the motor. It may sound like an unnecessary step, but I think you'll be better off (and safer) in the long run. From what you've said, both the motor and pump are worth saving, it's just the wiring that needs work.

Bill

 

[bobby g]

+1 to Bill's last post. Start fresh.

bobby g

 

[yardlongdraft]

Bobby and Bill, That was my original intent if I got it working. I'm certain the FIL didn't follow any convention except his own, LOL. I'm confused by the 2 blacks and 1 white on the toggle switch. I took a couple of photos if it would be of value to anyone. Thanks for all the good advice so far, and if anyone can make out anything of this i would really be grateful.

View image in gallery

View image in gallery​

 

[bobby g]

Hard to tell from the photos. You can load it up and come on down if you like. Looks like we're about 1 hour and 15 minutes apart. I'll be around most days this week. I'm sure we can get it squared away.

And Bill... you are invited to join us.

bobby g

 

[FredP]

not sure if this is relevant but years ago my BIL had a wheelbarrow style compressor with a toggle switch just like yours does. the cord had a 240V plug and there was an adapter to change the plug end to a 120V plug. by flipping the toggle switch and using or not using the adapter it could be used according to whatever was available on the job-site. 240 was preferred but not always available.:dontknow: that may be what you have? [or not!]

 

[Bill Clemmons]

Hard to tell from the photos. You can load it up and come on down if you like. Looks like we're about 1 hour and 15 minutes apart. I'll be around most days this week. I'm sure we can get it squared away.

And Bill... you are invited to join us.

bobby g

Thanks Bob. Let me know if you two get together and I might try to join you, if for no other reason than to see your shop again.:eusa_danc As for the wiring issue, I suspect once you take a look, it will be pretty straight forward to run a new cord and eliminate any confusion / safety hazard.

Bill

 

[yardlongdraft]

Thanks to all for your suggestions...I've just about got the monster back in the cage now. There was a chart with various hook-up configurations low opp, low std, high,opp, high std., It as wired as high opp...not really sure what that means, but replaced all old stuff with new as recommended by Bill. I worked back from there and replaced the wire as suggested. My only issue is now belt slippage and I'm hoping that a new belt and devising a way to exert tension (I'm thinking blocks and wedges) will fix that. Thanks again, Randy.