Bridgeport input power question

[Glenn Brooks]

I am trying to plan future 220 1P power requirements for my shop, and would like to add a Bridgeport mill in the future. Can anyone advise what amperage circuit I should install for a typical BPort Mill?

I am thinking a typical 240v 2-3 HP two stage motor used on light to medium duty machines...

BTW I have an existing 10hp three phase RPC for my lathe, that could be used, but really dont want to add anymore three phase equipment.

Thanks!

[Harold_V]

The breaker is intended to protect wiring, not the motor, so the wire size you select will dictate the breaker, at least the maximum size. Perfectly acceptable to use one rated under the wire size, but not one rated over wire size.

If you already have a rotary phase converter, why not consider using it to power the mill, too? Three phase motors are far more common, less expensive and provide far better performance than single phase motors do. You'll benefit by having plug reverse, a feature I couldn't live without.

I'm not current on electrical code, but it may be required that you use 10 gauge wire, even though, with three phase, overall demand will be less than ten amps. Could be wrong, although I wired all of my motor circuits for small machinery accordingly, from my BP up to my five horse Quincy compressor.

Harold

[hammermill]

A ten gauge wire will address a nominal thirty amp circuit

[Glenn Brooks]

Thanks, I need to read my RPC manual through, as am just initial stages of implementing the RPC to drive My newly acquired 3P lathe. e.g., It isn't installed yet. I would like to pick up a Bport at some point. But do not have one on hand, so dont have an way to readily address power needs.

Harold, it sounds like most bridgeports draw 10 amps or less with three phase; I assume 20 amps if set up with a 220v 1P motor? So would it be correct to say either a 3P 20amp circuit, or 30amp 1P circuit?

Thanks
Glenn

[hammermill]

3phase 20 amp circuit but probably a 15 amp circuit.

[Patio]

The size of the motor and the voltage, will determine how much current will be drawn.
If it is a 3hp/3P at 230V, it will have a, Full Load Current, of 9.6A as per charts.
A 3hp/1P at 230V, will have FLC of 17A as per charts.
Sizing of wires, for motors, need to be 125% of the FLC draw.
So. 9.6AX1.25=12A and could be run on a #14 wire and protected by a 15A breaker.
So 17AX1.25=21.25A and could be run on a #10 wire, protected by a 30A breaker.

You could disconnect your lathe from the RPC output and install a small panel box on the output. Then connect your different machines to the panel. Depending on the size of the machines you may be able to run more than one at a time. It will make it easy to add more 3p machines later.

Phase converter of 10hp at 230V/ 1P, will have a full load draw of 50A and could be run on a #6 wire size, protected by a 50A breaker. Then run the #6 wire into a sub panel, run the lathe and the mill from the sub panel on their own circuits.

Breakers are sized to protect the smallest wire, that is down stream of them. The wire is sized according to the load that is put upon it.

If you are trying to decide how much power you want to run into the shop for the future, that is a different matter.

Disclaimer:
This is a simple version of calculations, there are other factors that may apply that would change the outcome. If you do not FULLY understand this, then you should seek a professional electrician.



I hope that helps

[Kevin45]

If you have a 10 horse RPC, you should be able to tie into it and run the mill off of that also. That is what I would do, but if you don't want to do that, then you may want to go with a VFD. THat way you will have variable speed plus not have to listen the RPC run. I have an RPC for my Lagun mill, but I put a plug on the mill and an outlet on the wall, I later on bought a Bridgeport Series 1 CNC and added a plug to it, so whatever I want to run, I plug into the outlet.

I am getting ready to add on to the garage though and rewire and move some machines, so I may go with a VFD for the Lagun mill, and then run the CNC off of the RPC. Luckily my lathe is single phase 220, so that was no big deal with that.

[w6br]

Hi, I may be a day late and a dollar short with this but here goes; I would wire in a 30 Amp 220 V single phase circuit. That way you can split it off to two 15 Amp circuits yet still retain the 30 amp 220 V!!

Do a main run in 10 gauge wire to the junction box and to the 220V, then split it off with two 12 gauge circuits to the rest of the shack. That way you have 220 V and two 115 V 20 Amp circuits!!

Just my two cents

Ron, w6br

[TomB]

....
Do a main run in 10 gauge wire to the junction box and to the 220V, then split it off with two 12 gauge circuits to the rest of the shack. That way you have 220 V and two 115 V 20 Amp circuits!! ...
Ron, w6br

I would check with an electrician before using this approach. If you brought a 30 amp feed to a sub-panel then put in the two 115v circuits with 20 amp breakers and 12 gauge wiring it would meet code. However if you mean a 'junction box' as just a point where you can wirenut 10 and 12 gauge wires together it will not meet code. The 30 amp CB would be protecting 12 gauge wiring and that is a no-no.

Tom