Disconnect for Compressor Question

[CalgaryJoe]

Looking to wire in a disconnect for my compressor - adding a new circuit from main panel in home to an attached garage but would like to have a disconnect in sight for the compressor (which I believe is also code a requirement). Previously I had a sub panel in my detached garage and used that as the physical disconnect for the compressor. Compressor is wired with a 30 amp plug, 30 amp breaker in main panel, 8/3 from panel - not hardwired.

I'm looking at this (Siemens 60 amp, 2 pole) non fusible disconnect however i have a question about the neutral wire. Am i able to simply connect the neutral line from the panel to the neutral line heading to the plug receptacle for the compressor and use the disconnect for the two hots? Quick sketch attached.

 

[Norcal]

A neutral is not required for a compressor.

 

[CalgaryJoe]

Thanks for the quick response - so I'm able to terminate the neutral inside the disconnect and I'm good to go as outlined in the sketch? Would there be any harm in continuing the neutral for the receptacle?

 

[mm08822]

The plug and recept can serve as your disconnect. If you install a 4-wire receptacle you must bring the neutral to the receptacle.

What is the NEMA config # of the recept?
What is the hp, full load amps and voltage from the motor nameplate?

 

[CalgaryJoe]

Nema 1430-R
FLA - 20
Volt - 230

Pic from name plate attached.

 

[wyliesdiesels]

Nema 1430-R
FLA - 20
Volt - 230

Pic from name plate attached.

you need to backup.

The NEMA plug you are using is not rated for 5HP

If you want to use a plug on this motor you will need to either a) use pin and sleeve plugs or b) hardwire it

Its good you used 8/** NM-b because a 5HP motor needs 35a rated wire.

you will need a disconnect if it is not within sight of and further than 50' from the breaker panel.

 

[CalgaryJoe]

I think the hardware route is in my best interest - the main panel is out of sight and more than 50' away. Interestingly this nema plug/receptacle setup passed a previous inspection, my initial intent was to simply replicate this previous setup.

Appreciate the quick responses and assistance.

 

[mm08822]

You need to get a larger disconnect switch. Without fuses in the circuit, the one you picked is only rated for 3 hp.

 

[wyliesdiesels]

I think the hardware route is in my best interest - the main panel is out of sight and more than 50' away. Interestingly this nema plug/receptacle setup passed a previous inspection, my initial intent was to simply replicate this previous setup.

Appreciate the quick responses and assistance.

Inspection by whom?

A building inspector? They miss stuff all the time

 

[CalgaryJoe]

Yeah a building inspector... who knew...

I was under the impression the disconnect I linked to was rated for 3-10hp - am I reading the spec sheet wrong? Page 59, 3-8 (LNFC222R). If in fact this one doesn't work, can you recommend one that will?

 

[DieselNut88]

Look at page 67 (GFC222N) this is what you need.

 

[Richard_F]

You do not need "pin & sleeve." Hubbell HBL8431C=Heavy Duty, Industrial/Commercial Grade, Straight, 3-Pole 4-Wire Grounding,30A 3 Phase 250V AC, 15-30P
-or- HBL9331=Heavy Duty, Industrial/Commercial Grade, Angled, 2-Pole 3-Wire Grounding, 30A 250V, 6-30P

Or, search Amazon for 250v 30a twist lock.

 

[wyliesdiesels]

Yeah a building inspector... who knew...

I was under the impression the disconnect I linked to was rated for 3-10hp - am I reading the spec sheet wrong? Page 59, 3-8 (LNFC222R). If in fact this one doesn't work, can you recommend one that will?

Apples and oranges. Im talking about the 6-30 plug you have the compressor.

Youre talking about disconnects. 2 completely different things.

You do not need "pin & sleeve." Hubbell HBL8431C=Heavy Duty, Industrial/Commercial Grade, Straight, 3-Pole 4-Wire Grounding,30A 3 Phase 250V AC, 15-30P
-or- HBL9331=Heavy Duty, Industrial/Commercial Grade, Angled, 2-Pole 3-Wire Grounding, 30A 250V, 6-30P

Or, search Amazon for 250v 30a twist lock.

Epic fail. Did you even read the specs on either of those? Obviously not.

The first plug you listed is incorrect as it is 3 phase and max 3HP. NEMA 15-30. OP's motor is single phase and 5HP. How would the OP use that with a nema 6-30 outlet?

The second one you listed is 2HP max.

https://www.hubbell.com/wiringdevic...de-Devices/High-Amp-Devices/HBL9331/p/1634141

Have any others you'd like to try?

BTW a plug for a motor needs to be HP rated for the same HP as the motor especially when used as a disconnect. Telling the OP to search for a 30a plug is incorrect. The outlet needs to have the HP rating as well. Good luck finding one. They dont exist past about 3.5HP.

 

[CalgaryJoe]

@wyliesdiesels: I'm aware the plugs and disconnects are different, my apologies I thought I was was clear when I indicated I would hard wire from the disconnect to the compressor - eliminating the plug all together.

@DieselNut88: the disconnect you indicated looks to bridge the neutral and is a fused disconnect. Dont need the neutral for the compressor and I was under the impression I dont want a fused link - the circuit is protected by the breaker and if one leg of the hots blows a fuse it would/could cause damage to the motor?

Thanks again - appreciate the responses.

 

[mm08822]

You do not need "pin & sleeve." Hubbell HBL8431C=Heavy Duty, Industrial/Commercial Grade, Straight, 3-Pole 4-Wire Grounding,30A 3 Phase 250V AC, 15-30P
-or- HBL9331=Heavy Duty, Industrial/Commercial Grade, Angled, 2-Pole 3-Wire Grounding, 30A 250V, 6-30P

Or, search Amazon for 250v 30a twist lock.

This is so wrong for reasons already explained …..twice.

Would you please delete this.

 

[mm08822]

You need to get a larger disconnect switch. Without fuses in the circuit, the one you picked is only rated for 3 hp.

Yeah a building inspector... who knew...

I was under the impression the disconnect I linked to was rated for 3-10hp - am I reading the spec sheet wrong? Page 59, 3-8 (LNFC222R). If in fact this one doesn't work, can you recommend one that will?

Look at page 67 (GFC222N) this is what you need.

@wyliesdiesels: I'm aware the plugs and disconnects are different, my apologies I thought I was was clear when I indicated I would hard wire from the disconnect to the compressor - eliminating the plug all together.

@DieselNut88: the disconnect you indicated looks to bridge the neutral and is a fused disconnect. Dont need the neutral for the compressor and I was under the impression I dont want a fused link - the circuit is protected by the breaker and if one leg of the hots blows a fuse it would/could cause damage to the motor?

Thanks again - appreciate the responses.

The disconnect you picked has 2 max hp ratings. The std hp rating (3 hp) is without fuses in the circuit. The 10 hp rating is obtained with time-delay fuses installed somewhere in the circuit. If you were to do so, a fused disconnect makes the most sense.

Yes, you did interpret the rating wrong by ignoring the footnotes in the product specification.

You don't need the neutral for the compressor. You can either tape it off, wire nut it in the disconnect or more preferred, terminate it in a neutral block within the disconnect.

Fuses provide more precise protection. But you need spare fuses on hand if you blow one. Many people forego that protection and just use cb's. You will be fine with just a cb.

If one leg of the 240vac circuit were to blow a fuse, the motor would simply stop. Unless the fuse blew because of damage within the motor, there is no extra damage within the motor.

This is probably the cheapest 10 hp rated disconnect you will find w/o fuses:
https://www.homedepot.com/p/Halex-6...-Fuse-Metallic-AC-Disconnect-HNF60R/205785642