The Stovebolt Site Forums The Shop Area The Electrical Bay compressor motor wiring help

I bought an older compressor to use for blasting and hvlp. I'm not sure how to wire this critter to my 220v line. The wiring diagram on the dayton motor for 230v shows:
T1 - line
T3,T8,T2 - tape
T4,T5 - line

This is for cw rotation. It states to swap T5 + T8 for ccw.

I'm guessing "line" refers to incoming hot. What about "tape"? Is this your neutral? How do you ground?

Hoping not to fry the motor or myself.

Thanks,
Dave

There is no ground. Connect the wires marked as "tape" together and insulate. Connect the lines to the 220 wires from your power. Connect the chassis to ground if you like.

There are two live feeds, to give you the 220V. Never, never use equipment that isn't grounded. This is the most important connection.

davem, does the compressor motor have an overload contactor built into it? If not, you should really use a motor starter / contactor with overloads. You can use a 3-phase unit like this one. and run one of the power leads in series through all 3 legs (Line in top of one leg, jump bottom of first leg to bottom of second leg, top of second leg to top of third leg and bottom of third leg to motor). That way the overload sensors see single phase full motor current.

I have a setup like this on my compressor and it works well. Use 1 size bigger wire than is recommended by NEC along with anti-oxidizing lube on the compression terminals. You will have a setup that will still be working when you are long gone and no worries about fires / lack of starting current, etc.

Thanks for the quick replies. Ken: Yes it does have a capacitor on it.

For 220v don't you usually have two hots, one neutral and a ground? I understand where to hook the hots and the ground. How about the neutral?

I'm much happier working on things you can hit with a hammer (my '54).

Your house is fed from a transformer that has a winding with a centre tap. You have three wires comming in, the two poles and the neutral. Between the neutral and one pole the voltage is 110 V and between the other pole and the neutral is 110 V. The voltage between the two poles is 220 V.

The ground is a separate safety conductor that is connected to earth ground at your main panel.

Davem, you sound a little confused A 240 volt motor uses no neutral, just the two hot phase conductors like the guys above state.What is the amp draw on the motor?There should be a plate with data on it . The motor running amps should be list as that or FLA. It no data, do you know the motor HP? tape together means using a wire nut or other pressure wire connector.Its important to size the wire correctly for the amp draw. By the way, in most areas of the USA, the voltage is 120/240 volt for residential services.

Tony - the motor is 3hp, 18 amps, 230v. Yes I have 240v coming in. Was planning on using 10/3+grnd. Sounds like I can use 10/2+grnd. The outlet is around 30' from the box. I understand the 2 lines + grnd now (late night homework).

I'm sorry ken, but I have to disagree with the way you have yours wired. The mag-starter should open both legs of the 220. You have one leg opened three times and the other leg is always hot. The two line wires should connect on top and the two load(motor) wires on bottom. The third leg or side is not used at all and only two Melting Alloy Relay Blocks are used.
The pressure switch on the tank controls the starter. You need one other item. A manual fusible disconnect switch to feed the mag-starter. Wired the same as the starter. Two in, two out, and one fuse on each leg.
10/3+grnd?? Are you thinking of using UF or NM plastic sheathed? If you're pulling a permit, the inspecter will be happier with two Black THW or THWN + a green inside some conduit.

Richard,
out of curiosity, does your code specify that the disconnect be visible from the equipment location. I think ours has a requirement like that for isolation.

Fred

Richard,

My mistake - both Hots should be disconnected from the load.

As for use of a 3 phase motor starter on single phase motors - I rechecked my facts (based on recommended wiring documentation for A/B motor starters) first leg should be routed through first two contacts as described and second leg through the third contact.

I missed the melting thermal overloads on the ebay auction - for that particular starter your method would be fine, but that starter's overloads are not resettable and I would avoid it. Most conventional starters use bi-metallic thermal overloads that should each see the same current - thus the series wiring of the hot leg through the first two contacts and second leg through the third contact.

Your point about controlling the coil on the motor starter with the pressure switch is also good.

Fuseable disconnect? If a circuit breaker / disconnect is within line sight of the compressor, a disconnect is not required. Not sure what value a fuseable disconnect would have if the CB feeding the line is sized appropriately for the wires you are using in your starter box.

One additional note on wiring to the starter - after razzing from Tony about a year ago . . . I fed my starter box with 4 wire single phase (H1, H2, N and G). I used H1 and N (120V) for the control ciruit (motor starter coil in series with the pressure switch) You should put a 1Amp slow blow fuse in this circuit right at the motor starter location to protect the control circuit wiring.

Davem, if your motor is not internally protected against overload, most newer single phase motors are, then you need a motor controller with thermal overloads or fuses.And the fuses or overloads must be sized properly.If your panel with the breaker suppling the feeder to the conroller is within sight and generally this is considered to be no more than 50 feet.Your panel breaker is fine if it meets the above.You 18 amp motor on #10 wire should use a 30 amp HCAR rated breaker to avoid nuisance tripping on start up . This stuff goes on and on to meet the requirements of the national electrial Code.
So anyway,lets say the motor is internally proteced against overload. The compressor has a pressure switch? is the swith amp rating more than the motor? If so, install a disconect if the panel is not in sight. The disconnect switch can be a general duty 30 amp 240 volt unfused 2 pole.Run one wire from there , through the switch in series, then to the motor. The other wire does not have to be broken by the switch. This is fine and legal in accordance with the National Electrial code article 430. The controller is not required to break all circuit conductors if not used as a disconnecting means. If by chance, the switch is two pole, great, run both wires through it. Using "Romex or NM type wiring is legal in a residential setting according to the NEC, there might be a few places that its use in this case might raise an eyebrow. The wiring that goes to the actual motor or compressor must be stranded wire, either a cord or wire in flexable conduit, to allow for vibration.My 16 amp 240 volt compressor has been wired this way, a simple pressure switch, for 8 years.I suspect that you may not want to get all involved here, it won't get inspected and you need the thing running. Remember , don't butcher anything, use a proper ground, proper wiring methods. If something happens, like a fire or you buddy gets zapped by your compressor ,your insurance co may have a fit and hold you responsible.