50A selector switch? Two 50A devices on single 50A circuit

[bochnak]

I want to run a single 50A circuit to the garage to power the following:

1. 7.5hp compressor
2. 50A outlet for welder

Both will never be used at the same time. It would always be one or the other. Can I build a box with a 3 position cam switch? Off, compressor, welder outlet.

Link to switch for reference only:

https://www.automationdirect.com/adc/shopping/catalog/circuit_protection_-z-_fuses_-z-_disconnects/disconnects_-a-_switches/rotary_cam_switches/z656-3.h09b?gclid=Cj0KCQjwy5maBhDdARIsAMxrkw0YBx7GGBgXMJTCc0eNrezIZZ-xOVfbiNDssjZeAoM7TGJPrtyUHV4aAkKIEALw_wcB

 

[larry4406]

I think I would just run a subpanel to the garage. From the sub, then independently feed the two outlets.

 

[bochnak]

I think I would just run a subpanel to the garage. From the sub, then independently feed the two outlets.

Yes, however the conduit pipe would be larger, and run the run is a little more complicated through the basement > crawl > garage. Also, wire is not cheap right now.

I had a sub in my other garage, just moved and planning what I should do here.

 

[BillK]

Not sure why you need a selector switch ? Just put two boxes on the circuit with the correct outlets for each piece of equipment. No different than any other circuit with a number of outlets. You are over complicating it.

 

[bochnak]

Not sure why you need a selector switch ? Just put two boxes on the circuit with the correct outlets for each piece of equipment. No different than any other circuit with a number of outlets. You are over complicating it.

True. I was just worried about breaker tripping if both are in use (which would be rare).

 

[PCustoms]

If that compressor is a true 7.5hp it needs to be hardwired.

 

[mike93lx]

Yes, however the conduit pipe would be larger, and run the run is a little more complicated through the basement > crawl > garage. Also, wire is not cheap right now.

I had a sub in my other garage, just moved and planning what I should do here.

Why would it be larger? Just feed it with the same wire, if they really will never run at the same time

 

[wyliesdiesels]

Not sure why you need a selector switch ? Just put two boxes on the circuit with the correct outlets for each piece of equipment. No different than any other circuit with a number of outlets. You are over complicating it.

You cannot put a 7.5HP compressor on a nema receptacle. Needs to be hardwired

 

[wyliesdiesels]

Attached or detached garage?

 

[beemerphile]

You cannot put a 7.5HP compressor on a nema receptacle. Needs to be hardwired

$$$

Not everything that can be done should be done, but would this NEMA FB11 not pass code?

 

[sparky 1971]

Besides the fact that a 7.5 hp compressor shouldn't be plugged in iis another potential problem. 50 amps may not be enough. Code allows for up to an 80 amp breaker on #8 wire for the compressor.

 

[rlitman]

Besides the fact that a 7.5 hp compressor shouldn't be plugged in iis another potential problem. 50 amps may not be enough. Code allows for I believe up to an 80 amp breaker on #8 wire for the compressor.

Sounds about right. I've got #6 wire supplying my 7.5 HP compressor via a 15 HP disconnect switch, because it's what I had. It's been on a 30A breaker (also what I had) for a lot of years and hasn't nuisance tripped yet, even with some serious continuous hours running (keeping a chipping hammer going), so YMMV.

 

[sparky 1971]

Sounds about right. I've got #6 wire supplying my 7.5 HP compressor via a 15 HP disconnect switch, because it's what I had. It's been on a 30A breaker (also what I had) for a lot of years and hasn't nuisance tripped yet, even with some serious continuous hours running (keeping a chipping hammer going), so YMMV.

That's why I said 50 may not be enough. It may also be plenty but I wouldn't want to go to all that work to find out the compressor won't start because the breaker trips. I always use the largest breaker allowed just to cut down on the chance of callbacks.

 

[engineer2]

Mt. Prospect: A permit and final inspection are required. The electrical work must be done by a Village of Mount Prospect Licensed Electrician. If the homeowner can provide verification of adequate knowledge and experience, they may perform the electrical installation. A friend used to live in MP and got caught remodeling his bathroom. He figured an A-hole neighbor saw him with materials and called it in. Lots of old people there with time on their hands.

 

[wyliesdiesels]

Sounds about right. I've got #6 wire supplying my 7.5 HP compressor via a 15 HP disconnect switch, because it's what I had. It's been on a 30A breaker (also what I had) for a lot of years and hasn't nuisance tripped yet, even with some serious continuous hours running (keeping a chipping hammer going), so YMMV.

may have a bad breaker. the FLA on a 7.5HP motor is quite a bit higher than 30a. What is the FLA listed on the nameplate on your motor?

 

[mogandave]

If you have to be inspected:
1. Hardwire the compressor
2. Hide the welder
3. Get inspected
4. Add a receptacle to the box the compressor is wired to
5. Plug the welder in

 

[bochnak]

If that compressor is a true 7.5hp it needs to be hardwired.

You cannot put a 7.5HP compressor on a nema receptacle. Needs to be hardwired

Attached or detached garage?

True 7.5hp in attached garage.

 

[bochnak]

The FLA on the 7.5hp is 36A. This should be on #6 and 50A breaker. It also runs fine on 40A breaker.

Here is the video of the compressor build:

 

[bochnak]

Mt. Prospect: A permit and final inspection are required. The electrical work must be done by a Village of Mount Prospect Licensed Electrician. If the homeowner can provide verification of adequate knowledge and experience, they may perform the electrical installation. A friend used to live in MP and got caught remodeling his bathroom. He figured an A-hole neighbor saw him with materials and called it in. Lots of old people there with time on their hands.

This is my second home in Mt P and haven't had a problem.

 

[rlitman]

may have a bad breaker. the FLA on a 7.5HP motor is quite a bit higher than 30a. What is the FLA listed on the nameplate on your motor?

I'd have to check the FLA, but it's going to be at the low end of the thermal region for a 30A breaker's trip curve, which is why I expected to get away with it. That's the area where you'd expect a SquareD QO to trip after 3 hours of continuous use, but even longer for a cheaper brand (CH is what I have there IIRC). Regardless, it's safely far away from the magnetic trip region.

Keep in mind that FLA is not what a motor actually draws, just what it's rated to draw (not accounting for SF). In the real world, current depends on power output, which depends on load. I'd have to clamp meter a full refill cycle to get a better idea of what that is, but in general, aside from a short peak of starting current, I'd expect the highest sustained current to be at the end of the cycle, with the highest pressure where it might actually be attaining 7.5HP (and that's all assuming I have the correct ratio of sheaves installed, and my belt is in good condition).

 

[rlitman]

The FLA on the 7.5hp is 36A. This should be on #6 and 50A breaker. It also runs fine on 40A breaker...

Looks right to me, and nice build. That's a screaming great deal you got even though the new motor is expensive.

I have a similar two stage, though my pump is splash lubricated. Speaking of current, I can see some lights in my house flicker when the compressor is cycling. 7.5HP does draw a lot, and it feels like the flickering is in tune with the pistons.

 

[wyliesdiesels]

I'd have to check the FLA, but it's going to be at the low end of the thermal region for a 30A breaker's trip curve, which is why I expected to get away with it. That's the area where you'd expect a SquareD QO to trip after 3 hours of continuous use, but even longer for a cheaper brand (CH is what I have there IIRC). Regardless, it's safely far away from the magnetic trip region.

Keep in mind that FLA is not what a motor actually draws, just what it's rated to draw (not accounting for SF). In the real world, current depends on power output, which depends on load. I'd have to clamp meter a full refill cycle to get a better idea of what that is, but in general, aside from a short peak of starting current, I'd expect the highest sustained current to be at the end of the cycle, with the highest pressure where it might actually be attaining 7.5HP (and that's all assuming I have the correct ratio of sheaves installed, and my belt is in good condition).

ive metered a lot of motors in my life and they all end up being pretty close to the FLA on the nameplate. I metered a clients brand new 7.5HP 3phase 208v compressor couple months ago. nameplate was 18a and it was pulling 18a through the entire cycle. in-rush current on startup was over 100a for 100ms... (yes i have a meter that can read startup current- Fluke 381)

 

[bochnak]

Looks right to me, and nice build. That's a screaming great deal you got even though the new motor is expensive.

I have a similar two stage, though my pump is splash lubricated. Speaking of current, I can see some lights in my house flicker when the compressor is cycling. 7.5HP does draw a lot, and it feels like the flickering is in tune with the pistons.

Thanks. Yes it was a good deal considering new are crazy expensive right now. This unit is also splash lubricated. And yes, lights dim a bit during start up.