Commercial compressor 90 amps

[Stevenfyeager]

The tire store we do work for is replacing a compressor with a 90 amp one At least that’s what the salesman says. Store has a 100 amp 208 Delta high leg panel. It’s pretty full, of course we will delete one 3,phase breaker. He says it needs a 90 amp breaker. The specs he sent says min copper wire size #6, FLA 48 amps. But Circuit Breaker size does say 90 amp industrial breaker. Also requires heavy a heavy duty 60 amp switch with dual element time delay fuse.
My concern is the 100 amp panel. I did put a amp meter on it and none of the 3 leads went over 30 amps , car lifts, balancing machines etc, ( of course I couldn’t get the two compressors to kick on )
Looking for advice, as I have not wired for a heavy duty compressor. Thank you.

 

[don_resqcapt19]

Depending on what size utility transformer is feeding the existing service, there may be excessive voltage drop when the compressor motor starts. That could cause other issues.

 

[Stevenfyeager]

Depending on what size utility transformer is feeding the existing service, there may be excessive voltage drop when the compressor motor starts. That could cause other issues.

Thank you. This store has one 225 single phase panel and one 3 phase high leg 100 amp panel. I was surprised that the 3 phase panel is only 100 amps. I do mostly residential so I appreciate your help. I’m thinking on telling the salesman to just replace the two existing compressors, instead of selling this larger one.

 

[Jraef]

Some of this will depend on how the compressors operate. Do they cycle on and off only as needed (likely in a tire shop) or run continuously and cycle an unloaded valve depending on demand? Given that you mentioned the other two not being on, I would imaging a cycling system. That may help with your power demand calcs.

 

[retirede]

I’d also verify that the compressor is specifically a 200V unit, not 230!

 

[suemarkp]

I wouldn't call this a 90 amp compressor because its breaker is 90A. Motor breakers can typically be 250% of the amp draw. With a 48A FLA, I'd call it a 48A compressor which will have a conductor size requirement of 60A. That being said, its LRA will be pretty high (could be around 200A). Do you know how large the transformer(s) are feeding this panel? Is it combined with that other single phase panel, or does each panel have its own transformer? How large was the old compressor that had been there?

 

[suemarkp]

I’d also verify that the compressor is specifically a 200V unit, not 230!

He said a 208 high leg delta service which to me implies 240V delta with a 120/240V tap on one leg making it 208V from one leg to neutral. Shouldn't the nameplate be 230V 3 phase for this? If what he really meant was 208V 3 phase wye (no high leg), then a 200V motor nameplate would be what he wants.

 

[hbiss]

You didn't mention how many HP the new one is. 15HP maybe? This isn't HVAC, you have to use the table in Art 430 to determine the current draw, not the nameplate or the salesman.

What about a starter? Does it come with one?

Also, it's replacing two existing units? How big are those which will free up capacity.

-Hal

 

[retirede]

He said a 208 high leg delta service which to me implies 240V delta with a 120/240V tap on one leg making it 208V from one leg to neutral. Shouldn't the nameplate be 230V 3 phase for this? If what he really meant was 208V 3 phase wye (no high leg), then a 200V motor nameplate would be what he wants.

I missed that. As soon as I saw 208, I immediately thought wye. I’ve never heard of a delta system before referred to by the high-leg voltage.

 

[retirede]

You didn't mention how many HP the new one is. 15HP maybe? This isn't HVAC, you have to use the table in Art 430 to determine the current draw, not the nameplate or the salesman.

What about a starter? Does it come with one?

Also, it's replacing two existing units? How big are those which will free up capacity.

-Hal

48A at 230V sounds like 20HP.

 

[zbang]

Depend on factors not mentioned, the PoCo might be interested in the additional load.

 

[texie]

OMG. there is no such thing as a "90 amp compressor". With all the highly skilled NEC minds here why would we not simply tell the OP we need motor and starter specs and simply apply the NEC requirements. All this other talk is pure speculation.

 

[Stevenfyeager]

Now he is down sizing from a 15 hp to a 10 hp after my hesitation to install a 90 amp breaker in a 100 amp panel. It’s specs he sent are #8 wire, fla 32, 60 amp breaker, 50 amp fusible switch. It lists 208 v with these specs. It’s a chart, not a nameplate like I keep asking for. But 208v doesn’t tell me enough. Please, forgive me of my ignorance. There are two 208 3 phases, correct? I’ve installed a 208 Y panel for a customer before and circuits to machines. But this store panel is definitely 208 high leg delta. Every third space is 208 to ground.
How do I know which 208 this compressor needs? Or do they come with option to change on site?

 

[LarryFine]

Please, forgive me of my ignorance.

Not asking would be ignorance.

There are two 208 3 phases, correct? I’ve installed a 208 Y panel for a customer before and circuits to machines. But this store panel is definitely 208 high leg delta. Every third space is 208 to ground.

No, there is only 208v wye and 240v delta. (There are other configurations not relevant here.)

A high-leg delta IS a 240v delta source superimposed on a 120/240 1ph source.

They both have 208v in them because of math.

Your service is 240v delta as far as 3ph loads are concerned, not 208v.

Most 208v motors are actually rated for 208v through 230v.

 

[Stevenfyeager]

Not asking would be ignorance.


No, there is only 208v wye and 240v delta. (There are other configurations not relevant here.)

A high-leg delta IS a 240v delta source superimposed on a 120/240 1ph source.

They both have 208v in them because of math.

Your service is 240v delta as far as 3ph loads are concerned, not 208v.

Most 208v motors are actually rated for 208v through 230v.

Thank you.

 

[kwired]

48A at 230V sounds like 20HP.

I'm thinking possibly 15 HP with additional loads on the unit? 48 is kind of between 15 and 20 HP in NEC table.

 

[kwired]

Now he is down sizing from a 15 hp to a 10 hp after my hesitation to install a 90 amp breaker in a 100 amp panel. It’s specs he sent are #8 wire, fla 32, 60 amp breaker, 50 amp fusible switch. It lists 208 v with these specs. It’s a chart, not a nameplate like I keep asking for. But 208v doesn’t tell me enough. Please, forgive me of my ignorance. There are two 208 3 phases, correct? I’ve installed a 208 Y panel for a customer before and circuits to machines. But this store panel is definitely 208 high leg delta. Every third space is 208 to ground.
How do I know which 208 this compressor needs? Or do they come with option to change on site?

Is this a single phase machine or a three phase machine?

10 HP and 32 amps suggests 208 volts rating.

Ask to see what nameplate data is. Many motors this size would typically be rated to run on 208 or 240.

The fact you have the high leg is 99.99% indication you have 240 volt nominal between each phase conductor.

 

[Stevenfyeager]

The chart he sent says 3 phase

 

[jim dungar]

The chart he sent says 3 phase

That is not sufficient to meet the NEC.
You need motor sizes or total machine amps. You need your nominal supply voltage system.

He has simply sent you a picture of a OCPD manufacturers selection chart.
You need to see the compressor manufacturer's data, either a nameplate or catalog page.

You definitely do not have a 208V delta. You may be using a local slang term for a standard high leg 240/120V 3phase 4 wire system.

 

[Stevenfyeager]

That is not sufficient to meet the NEC.
You need motor sizes or total machine amps. You need your nominal supply voltage system.

He has simply sent you a picture of a OCPD manufacturers selection chart.
You need to see the compressor manufacturer's data, either a nameplate or catalog page.

You definitely do not have a 208V delta. You may be using a local slang term for a standard high leg 240/120V 3phase 4 wire system.

Thank you, I asked him again for a nameplate, and he responded “it is not built yet “
How do I know that my 240 v Delta (with the 208 v high leg) is the right 3 phase for this compressor? Can I assume it is the correct power source since there are two existing compressors powered from 3 phase breakers in this panel? Other machines on a another job required me to install a 3 phase 208 Y panel. Thank you so much.