New Compressor 50-6P or? Help

[NitroShark]

I’m replacing my 5hp 230V 1Ph compressor with a 7.5 hp model. My home shop already has (5) 240V 50-6R plug connection for other machines. I would like to keep this theme for the compressor but, in an industrial environment they are hard wired to a disconnect. This is a home shop.

Manual says 8-2 wire 35Amp beaker. I’d like to use a 6-2 wire 50Amp Breaker 50-6P plug.

Thoughts from my GJ Sparkys? Please help.


Thanks

 

[sberry]

You have to hard wire it, the 6 is good as is the 50. The plug and recept are only hp rated to 3.

 

[PoorOwner]

6-50 receptacle only rated for 3HP from what I have found. You just need to replace the 6-50 receptacle with a plate and run a whip to the compressor

As far as wire size and breaker if the manufacturer specifies it, it's what I would follow.

 

[mm08822]

35A seems way too small. I wouldn't go smaller than 50A - it is a motor circuit once hard-wired, so you can be up 250% of FLC.

It the compressor is more than 50' from the panel and/or line of sight is blocked, then you need a disconnect local to the comp.
A disco also makes for a good transition to flexible wiring to the comp.

 

[Bert_]

35A seems way too small. I wouldn't go smaller than 50A - it is a motor circuit once hard-wired, so you can be up 250% of FLC.

For sure^

I'm a little curious about that nameplate. It shows a low voltage and high voltage wiring diagram typical of a 115/230v motor, but only lists 208-230 as operating voltage. It does have a slash after the 208-230/ like there was another voltage but they didn't list it. Weird

 

[mm08822]

For sure^

I'm a little curious about that nameplate. It shows a low voltage and high voltage wiring diagram typical of a 115/230v motor, but only lists 208-230 as operating voltage. It does have a slash after the 208-230/ like there was another voltage but they didn't list it. Weird

Maybe Waylead Motor Company saving buck. Only stock 1 n/p in house!
I'm sure UL and CSA didn't see that in the submitted product samples for testing.

 

[Bert_]

The weird thing is I think 230 is the LOW voltage. That would make 460v the high voltage, not real common in a 1 phase motor. Of course this is purely speculation so I might be way off.

 

[mm08822]

The weird thing is I think 230 is the LOW voltage. That would make 460v the high voltage, not real common in a 1 phase motor. Of course this is purely speculation so I might be way off.

I've never seem a 460v single phase motor either and assumed it was just a single voltage motor with an incorrect n/p.
However, Waylead thinks otherwise...........



So I would agree, 230v is using the low voltage connections.

 

[wyliesdiesels]

I’m replacing my 5hp 230V 1Ph compressor with a 7.5 hp model. My home shop already has (5) 240V 50-6R plug connection for other machines. I would like to keep this theme for the compressor but, in an industrial environment they are hard wired to a disconnect. This is a home shop.

Manual says 8-2 wire 35Amp beaker. I’d like to use a 6-2 wire 50Amp Breaker 50-6P plug.

Thoughts from my GJ Sparkys? Please help.


Thanks

As has been said need to ditch the 6-50r because only good for about 3HP. The 5HP comp shouldve been hardwired.

The NEC requires 50a rated wired (FLC = 40a * 1.25 = 50a.)

8/2 NM is limited to 40a so that wont work. The manual is wrong...

Need #8 THWN in pipe or 6/2 NM-b....

Breaker can be max 100a. but a lower rated breaker should be fine.

A bigger issue here is whether your PoCo allows such a large motor and whether their transformer and primary supply can handle the in-rush of that beast. Many PoCos have HP limits....

what is the size of your main service and what loads do you have?

edit: correct nomenclature for nema outlets is 6-50 not 50-6...

 

[sberry]

In my area 10hp is the limit on rural single phase.

 

[NitroShark]

Re: New Compressor 6-50P or? Help

Plan now is to run a 50 amp breaker with 6/2 to disconnect. I have some 6/4 SO cord I could use from the disconnect to the compressor or just get sealtite and 6 THHN I think I got that also.

House is all electric 400AMP (2-200amp sub panels in the home) with separate 125amp service to the home shop.

As for the motor, I’m an engineer with Baldor electric so if I need a motor you can guess what I’ll use if it gives me trouble.


Finally, what would you guy's recommend for a disconnect? I'm don't need a fusible one and the mag starter is able to turn it on/off. Don't really need lock/out tag/out either-got that at the sub panel if needed.

 

[wyliesdiesels]

Re: New Compressor 6-50P or? Help

Plan now is to run a 50 amp breaker with 6/2 to disconnect. I have some 6/4 SO cord I could use from the disconnect to the compressor or just get sealtite and 6 THHN I think I got that also.

House is all electric 400AMP (2-200amp sub panels in the home) with separate 125amp service to the home shop.

As for the motor, I’m an engineer with Baldor electric so if I need a motor you can guess what I’ll use if it gives me trouble.


Finally, what would you guy's recommend for a disconnect? I'm don't need a fusible one and the mag starter is able to turn it on/off. Don't really need lock/out tag/out either-got that at the sub panel if needed.

IIRC Cordage is not to be used for permanent fixed in place equipment.

How far away is the panel from the compressor?

A disconnect is required only if the panel is more than 50' away and not within sight of the equipment.

If you do get a disconnect, make sure its HP rated and the rating is at least the same as the motor HP rating.

AC pullout disconnects are commonly used for this and some models at the big box stores are rated for 10HP...

 

[sberry]

You got to love residential. Been building houses for 100 yrs with electric, 20 extra spaces in a new panel and new build, no way to reach in to route and connect an additional wire to it. All drywalled back in. I saw a 100, brand new in a garage, 20 spaces, 1 installed.

 

[NitroShark]

Re: New Compressor 6-50P or? Help

AC pullout disconnects are commonly used for this and some models at the big box stores are rated for 10HP...

Like ones used for A/C ?

 

[Norcal]

Re: New Compressor 6-50P or? Help

Like ones used for A/C ?

Yes, that is the reason for the discription " A/C pullout disconnect". They are fairly cheap & common.

 

[NitroShark]

Got the compressor today. It appears that the switch for the magnetic starter is not in a very convenient location. Is it OK to leave the mag starter in the on position and switch power on off with either the disconnect(one with a circuit breaker ) or Maybe a disconnect with the lever.

I like to cut the power to my compressor when I leave at night.

You guys are a lot of help and I appreciate it thank you.

 

[Bert_]

I'd either move the current one or add a switch for the magnetic starter. That way all your switching is the coil rather than the full motor current.

 

[NitroShark]

I'd either move the current one or add a switch for the magnetic starter. That way all your switching is the coil rather than the full motor current.

Bert, I don't follow you.

The existing switch for the mag starter is what I was asking about. I would be cutting power on/off to it. (the coil)

Does that make sense?

Switch Picture below: (little red lever in first picture on top left -hard to see )

 

[NitroShark]

Layout Pictures:

.

 

[sberry]

About as good is shutting off a ball valve at the tank, no leaks, no run.

 

[mm08822]

OP,
Bert is talking about interrupting the control circuit while you are talking about shutting off the power using the disconnect or panel cb. I would not want to exercise a disconnect or cb that often.

If you really feel the need to prevent starting, then I would add another switch in series with the existing PS on top of/next to the starter. Leave the PS lever up in the on position and forget about it.

 

[Bert_]

Bert, I don't follow you.

The existing switch for the mag starter is what I was asking about. I would be cutting power on/off to it. (the coil)

Does that make sense?

Switch Picture below: (little red lever in first picture on top left -hard to see )
[/IMG]

It sounded like you wanted to switch the power to the whole compressor, all 30+ amps, with a disconnect or breaker. Either of those will wear out with frequent, multiple times a week use.

I suggested wiring another switch, one that's in a better location, in series with the coil of the starter since it is only fractions of an amp. Let the motor starter handle the high current switching like it is designed for.

If that's what you have been planning all along great, my misunderstanding.

 

[NitroShark]

Thanks Bert. we are on the same page now.


After further looking at the pressure switch/ mag starter setup it appears the relay is manually activated.

Is there an easy way to convert it to an electronic push button type?


.

 

[sberry]

If it is charged up and hasn't lost pressure than the switch or breaker isn't stRting under load. I however have seen them work as switches for decades. I understand if it is going long time without use but if it's pumped it isn't going to start/run.
I have shut some off lately, might have forgot the last day or so bu t havnt done it for 25 years, only off long enough to do repairs.