How to wire a 240 air compressor?

Question

I have a 60 gal. 7hp. 2 stage air compressor that needs15amp 240 volt. I ran the 240 line but a 240 line has 4 wires and the compressor only has 3 wires on it. how do i hook it up

Answer 1

Sounds like you indeed have a 3 phase compressor. If you are installing this at your house/garage chances are you only have single phase power and this won't work. You have a few choices:

Change the motor to a single phase unit. When buying the motor make sure http://www.control.com/thread/1026160827... get the right voltage and you will also need the same frame style, you can find this on the motor nameplate. This will ensure proper shaft dimensions. However, you may have to change your starter and overload block.

You can find a single to 3 phase converter and use that.

Your last option may be that you might want to sell it and find yourself a single phase compressor if you find that the other two options are too expensive.

But to be sure you have a 3 phase motor, again check the nameplate, it will show a number next to PH usually.

I should also add that the rotation of the motor is important to compressors so be sure to check this, you can find the direction on the fly wheel of the compressor or a sticker on the belt guard. On three phase systems if you need to switch rotation switch any two of the three power feeds.

Answer 2

use a 15amp 2core+earth(3core +earth will be to big for the plug)

get a sparkie to check out power supply from fuse box to the outlet

then get him to hook it up,it's safer

Answer 3

This is a 3 phase unit, so you should have a black, red, blue wires from the panel. Black to one connection, red to the next, blue to the last. Connect the ground to the ground terminal in the compressor controller. Maybe you could clarify the about the power panel.

Answer 4

I assuming this is a 3 phase circuit if your saying you have 4 wires, 1 wire should be a green ground wire.

Jerry L

http://www.furnacepartsonline4u.com

Your control panel electrical drawing should indicate earth ground lug to land the ground conductor on. Be careful not to wire one of the hot leads to ground>>>  the 3 hot leads will probably  land on the contactor or overloads.

Jerry L