Compressor/Disconnect/breaker

[SportBikePC]

Morning everyone, I’m new here have been reading what I could find on my situation..
first off here’s what I have:
10Hp duplex air compressor ( 2-5 hp electric motors)
I need to connect each to its own disconnect which I think should be 60 amps each ? But not sure if it should be fused or not?
Once that’s done I’m getting confused on the actual breaker size needed in the panel for each motor do they have to be the size of the disconnect or can I use 40 amp breakers?
The compressor is inside a separate building from my pole barn.. so I should be ok to use the nema type 1 enclosure for the disconnects right? Or should it be 3R?

Total run of wire is maybe 30 ft (60ft for both motors) 5 ft underground and the rest is inside building ..
I’d be using 8 guage ..

If anybody could help me out here I would appreciate it .. if you need more info I can supply that also..

Picture of my lead motor plate, the lag motor is identical..
And the compressor itself..

 

[nadogail]

I would use 30 amp disconnects, fused if the are both being fed from the same breaker, Time Delay fuses are IMHO the optimum choice.

 

[SportBikePC]

I would use 30 amp disconnects, fused if the are both being fed from the same breaker, Time Delay fuses are IMHO the optimum choice.

They will have separate breakers

 

[wyliesdiesels]

Do both pumps run at the same time?

 

[Norcal]

Are you planning to run the circuits from the pole barn to the compressors? Only one feed is permitted to a outbuilding so it will need to be sized for both compressors and whatever other loads planned.

 

[SportBikePC]

Do both pumps run at the same time?

Yes and No..

If the one pump can’t keep
Up with demand the other will automatically kick in to help .. otherwise it’s only one running

 

[SportBikePC]

Here’s the compressor panel..

 

[wyliesdiesels]

The disconnect needs to be HP rated. If both pumps run at same time then you may need a 10HP disconnect as it looks like both motors may be controlled by the box mounted on the compressor.

Wire needs to be 35a rated wire if each motor wired independently 28a FLC x 1.25 = 35a.

If one circuit is ran to compressor, then you need 53a rated wire. 50a FLC x 1.25 = 62.5a.

 

[SportBikePC]

Are you planning to run the circuits from the pole barn to the compressors? Only one feed is permitted to a outbuilding so it will need to be sized for both compressors and whatever other loads planned.

Yes my 200amp panel is in my pole barn and the compressor is in a separate building..

 

[wyliesdiesels]

Yes and No..

If the one pump can’t keep
Up with demand the other will automatically kick in to help .. otherwise it’s only one running

Here’s the compressor panel..

So where is the circuit connection point?

 

[SportBikePC]

So where is the circuit connection point?

Like this..

 

[wyliesdiesels]

Ok so each starter’s input is connected independently?

 

[SportBikePC]

Ok so each starter’s input is connected independently?

Yes either one can run on its own, or how it’s currently setup in which both will run if demand calls for it .. (this is controlled by the orange box in the compressor panel pictured previously)

So each motor needs it own disconnect and breaker

 

[SportBikePC]

 

[Bert_]

It does not need individual disconnects and breakers. One circuit with #6thhn and a 70-100 amp breaker could run both. A 60 amp disconnect would work for both motors I believe. A 30 cannot be used at all since most are only rated for 3 hp.

Alternatively you could put a sub panel in the compressor shed and run individual circuits from there. That would also serve as a disconnect.

 

[wyliesdiesels]

I would use 30 amp disconnects, fused if the are both being fed from the same breaker, Time Delay fuses are IMHO the optimum choice.

doubt a 30a D/C would be rated for 5HP and no need for fuses...

It does not need individual disconnects and breakers. One circuit with #6thhn and a 70-100 amp breaker could run both. A 60 amp disconnect would work for both motors I believe. A 30 cannot be used at all since most are only rated for 3 hp.

Alternatively you could put a sub panel in the compressor shed and run individual circuits from there. That would also serve as a disconnect.

Agreed.

that was gonna be next reply. I couldnt quite tell if these had one feed that supplied both are they needed individual circuits.

If it were mine, I would run a feeder to the shed, then install a subpanel so I had the ability to run other circuits if needed.

 

[SportBikePC]

It does not need individual disconnects and breakers. One circuit with #6thhn and a 70-100 amp breaker could run both. A 60 amp disconnect would work for both motors I believe. A 30 cannot be used at all since most are only rated for 3 hp.

Alternatively you could put a sub panel in the compressor shed and run individual circuits from there. That would also serve as a disconnect.

doubt a 30a D/C would be rated for 5HP and no need for fuses...



Agreed.

that was gonna be next reply. I couldnt quite tell if these had one feed that supplied both are they needed individual circuits.

If it were mine, I would run a feeder to the shed, then install a subpanel so I had the ability to run other circuits if needed.

Ok cool didn’t think it could use 1 line in to compressor.. just assumed each motor needed it’s own circuit..

I think I’ll just run a sub panel inside then and get an outlet and light in there.. while I’m at it, seems easier that way..

 

[Stuart in MN]

Yes either one can run on its own, or how it’s currently setup in which both will run if demand calls for it .. (this is controlled by the orange box in the compressor panel pictured previously)

I'd double check that...those alternating relays are most often configured so that depending on the position of the little toggle switch they will only run motor 1, only run motor 2, or will alternate between motor 1 and motor 2 each time air is required.


I'm guessing this compressor came from a place where it was used to provide instrumentation air for operation of pneumatic valves, or maybe to keep air pressure in a fire sprinkler system. For those applications, the compressor is typically sized so that one pump is adequate to provide the necessary air, the second one is there only for redundancy.


If in fact it can only run one motor at a time, your branch circuit only needs to be sized to accommodate one motor.

 

[TRWham]

Does this equipment have a nameplate with ratings, or only on the individual motors?

 

[TRWham]

The disconnect needs to be HP rated. If both pumps run at same time then you may need a 10HP disconnect as it looks like both motors may be controlled by the box mounted on the compressor.

Wire needs to be 35a rated wire if each motor wired independently 28a FLC x 1.25 = 35a.

If one circuit is ran to compressor, then you need 53a rated wire. 50a FLC x 1.25 = 62.5a.

That's not how you calculate ampacity for multiple motors. You take 125% of the FLC of the largest motor plus 100% of the FLC of all other motors. You would also add any non-motor loads, but there are none in this case. The difference is small for this particular unit (63 vs 62.5 A), but can be larger for equipment with more motors.

If it's factory wired, it really should have a nameplate. I calculated hundreds of these when I was designing refrigeration units.

 

[SportBikePC]

I'd double check that...those alternating relays are most often configured so that depending on the position of the little toggle switch they will only run motor 1, only run motor 2, or will alternate between motor 1 and motor 2 each time air is required.


I'm guessing this compressor came from a place where it was used to provide instrumentation air for operation of pneumatic valves, or maybe to keep air pressure in a fire sprinkler system. For those applications, the compressor is typically sized so that one pump is adequate to provide the necessary air, the second one is there only for redundancy.


If in fact it can only run one motor at a time, your branch circuit only needs to be sized to accommodate one motor.

Well here’s the info I have.. and it’s a regular compressor to produce air for a shop you can easily visit saylor beall dot com and it’s brand new it came from factory ..

Page 3 you can read the description ..

https://www.saylor-beall.com/wp-content/uploads/SaylorBeall-Duplex-Compressors.pdf

 

[SportBikePC]

Does this equipment have a nameplate with ratings, or only on the individual motors?

Only on motors I have found

 

[TRWham]

Only on motors I have found

SB says it's UL listed, so I imagine there is a nameplate somewhere. What are those labels inside the control panel?

 

[wyliesdiesels]

That's not how you calculate ampacity for multiple motors. You take 125% of the FLC of the largest motor plus 100% of the FLC of all other motors. You would also add any non-motor loads, but there are none in this case. The difference is small for this particular unit (63 vs 62.5 A), but can be larger for equipment with more motors.

If it's factory wired, it really should have a nameplate. I calculated hundreds of these when I was designing refrigeration units.

Yeah youre right. Dont know what I was smoking when i wrote that.

I will edit it!

 

[SportBikePC]

SB says it's UL listed, so I imagine there is a nameplate somewhere. What are those labels inside the control panel?

Inside the panel there’s this..
white paper inside of door
Only thing ..
besides the mag . Starter

And fuse info

 

[Stuart in MN]

Well here’s the info I have.. and it’s a regular compressor to produce air for a shop you can easily visit saylor beall dot com and it’s brand new it came from factory ..

Page 3 you can read the description ..

https://www.saylor-beall.com/wp-content/uploads/SaylorBeall-Duplex-Compressors.pdf

OK, no worries. You're correct, this compressor can run both motors if necessary.

 

[TRWham]

That white label seems to be a poor attempt at a nameplate that does not appear to me to provide all of the required information. It does show minimum wire size, but the reference to minimum ampacity (MCA) is unclear and there is no information on maximum over-current protection (MOPD). I would say contact SB for better guidance.

Overall, I am underwhelmed by that control panel. Wire is available in many colors- there is really no good reason to use only 2. Woe be to anyone tracing that monochromatic red control wiring once the labels fall off. The wiring shows some effort to be neat, but not consistently and those adhesive wire tie bases will be popping loose once the glue has failed (which it will). I imagine it will work, but does not reach a standard I would expect of Saylor-Beall. Make them earn their pay with some tech support.

 

[wyliesdiesels]

Yeah when i first saw that, I cringed. All wires one or 2 colors makes troubleshooting a pain. Why not multiple colors.

Ick

 

[SportBikePC]

Well appreciate the help guys..
I figured all was needed to hook this up was the info on the motors..

I’ll try and call SB today.. what specific info. Would I need besides what TRWham mentioned ( MCA & MOPD)?

I’m going with a 100amp sub panel, so can I eliminate the need for safety disconnect since there will be a Breaker in site?
Also have a friend coming by today to check out what I have going on..

Apologize for all the questions..

 

[Norcal]

Well appreciate the help guys..
I figured all was needed to hook this up was the info on the motors..

I’ll try and call SB today.. what specific info. Would I need besides what TRWham mentioned ( MCA & MOPD)?

I’m going with a 100amp sub panel, so can I eliminate the need for safety disconnect since there will be a Breaker in site?
Also have a friend coming by today to check out what I have going on..

Apologize for all the questions..

No need to apologize, that is what this forum is for.

 

[TRWham]

Well appreciate the help guys..
I figured all was needed to hook this up was the info on the motors..

I’ll try and call SB today.. what specific info. Would I need besides what TRWham mentioned ( MCA & MOPD)?

I’m going with a 100amp sub panel, so can I eliminate the need for safety disconnect since there will be a Breaker in site?
Also have a friend coming by today to check out what I have going on..

Apologize for all the questions..

I think the main thing you need to ask SB is the circuit breaker size. Both motors can run briefly, so you want to be sure the breaker can hold that. It also seems like you could have them starting together in the event of a power interruption. I don't see any time delay in there.

As for the disconnect, yes, as long as the circuit breaker is in sight (meaning visible and within 50') it can serve as the disconnect.

 

[mike93lx]

Well appreciate the help guys..
I figured all was needed to hook this up was the info on the motors..

I’ll try and call SB today.. what specific info. Would I need besides what TRWham mentioned ( MCA & MOPD)?

I’m going with a 100amp sub panel, so can I eliminate the need for safety disconnect since there will be a Breaker in site?
Also have a friend coming by today to check out what I have going on..

Apologize for all the questions..

I would target a 90a panel, which would mean #2 aluminum. Xhhw if in conduit, MHF if you want direct burial. 100a would require larger wire and wouldn't really provide a benefit here.

A light and outlet makes a ton of sense to have. Makes service a whole lot easier.

Don't forget two ground rods at the destination.

 

[mm08822]

That white label seems to be a poor attempt at a nameplate that does not appear to me to provide all of the required information. It does show minimum wire size, but the reference to minimum ampacity (MCA) is unclear and there is no information on maximum over-current protection (MOPD). I would say contact SB for better guidance.

Overall, I am underwhelmed by that control panel. Wire is available in many colors- there is really no good reason to use only 2. Woe be to anyone tracing that monochromatic red control wiring once the labels fall off. The wiring shows some effort to be neat, but not consistently and those adhesive wire tie bases will be popping loose once the glue has failed (which it will). I imagine it will work, but does not reach a standard I would expect of Saylor-Beall. Make them earn their pay with some tech support.

The is no reference to the MOPD b/c they didn’t provide one. Since the equipment can have 1 or 2 feeds they could have provided both scenarios but not required.
The max ocpd rating has to simply follow standard NEC requirements for motor ckts.

The reference to minimum wire size is very odd when there are two supply methods possible and there is no distinction make for which wiring scenario it applies to. Min ampacity specified would be best for both scenarios.

It is a long running industry standard to use red for ac control circuits and blk for power circuits. For such a small panel/equipment this is hardly a challenge. Wire markers work just fine. Don’t by **** and they last a long time.

The info on the label should be on the exterior of the enclosure.

It’s a low frills panel no doubt.