Air Compressor Branch Circuit Sizing

[Seven-Delta-FortyOne]

Been a minute since Ive done one like this, and I was hoping one of the many minds greater than mine here, would look over what I’ve come up with.

I have delta 3-phase with high leg at the facility.

Air compressor can be wired for 208, 230, or 460, +\- 10%.

Instructions show a minimum circuit ampacity of 53 amps at 230v, and a MOCP of 110A for an inverse time CB, which is what I’ll use.

I’ve come up with #6 phase conductors, good for 65A at 75C, and a CB of 110A.

I don’t have the machine on site, so I don’t have nameplate FLC, but I have the manufacturer’s instructions that 110A is the maximum, so even if 430.52 allowed a larger CB, I would have to stick with 110.

Since the MOCP is 110A, per 250.122, I will need to use a #6 for the EGC as well.

Did I make a mistake on this?

Just hope my supplier can get me orange #6.

 

[LarryFine]

Looks right to me.

Orange is only required where the neutral is also used.

 

[augie47]

A number 8 equipment ground would satisfy 250.122
With no neutral conductr present you don't need to worry about orange + you can use tape if you wish to identify it.

 

[Seven-Delta-FortyOne]

Appreciate the help guys.

Brain fart on the orange. So used to not reidentifying conductors smaller than 4.

How could I use a #8, if the OCPD is 110A?

 

[Little Bill]

Appreciate the help guys.

Brain fart on the orange. So used to not reidentifying conductors smaller than 4.

How could I use a #8, if the OCPD is 110A?

You use the MCA.

 

[augie47]

Appreciate the help guys.

Brain fart on the orange. So used to not reidentifying conductors smaller than 4.

How could I use a #8, if the OCPD is 110A?

Ref: Orange 110.15 "...........Such identification shall be placed at each point on the system where a connection is made if the grounded conductor is also present."

Ref: Equipment ground: 250.122 101-200 amps EG size = #8

 

[Tulsa Electrician]

Ref: Orange 110.15 "...........Such identification shall be placed at each point on the system where a connection is made if the grounded conductor is also present."

Ref: Equipment ground: 250.122 101-200 amps EG size = #8

??

 

[augie47]

??

my bad.... you are correct #6 EGC

That's a better Table than in the Code book... keeps a dumb*** like em from making that mistake

 

[Seven-Delta-FortyOne]

my bad.... you are correct #6 EGC

That's a better Table than in the Code book... keeps a dumb*** like em from making that mistake

I didn’t want to question a Mod here, but I wondering……

 

[augie47]

ALWAYS question this Mod

 

[LarryFine]

We have the greatest Mod Squad around.

 

[Little Bill]

I have the right to remain silent!

 

[Seven-Delta-FortyOne]

 

[letgomywago]

Looks right to me.

Orange is only required where the neutral is also used.

I've only just learned this. It's nice to know I haven't seen it in the field but ya if you don't stock orange 10 or 8 it's nice

 

[drcampbell]

It would be a good idea to confirm that there's an additional 53 amps available, especially on the high leg.

 

[kwired]

I've only just learned this. It's nice to know I haven't seen it in the field but ya if you don't stock orange 10 or 8 it's nice

If it a situation where it must be identified it doesn't have to be orange finish entire length of conductor. Orange tape, paint, or other methods near terminations is sufficient.

 

[Seven-Delta-FortyOne]

It would be a good idea to confirm that there's an additional 53 amps available, especially on the high leg.

53 amps 3 phase, max circuit capacity, running amps is 42, per the manufacturer.

It’s currently an empty building I’m doing the TI on, and it has a 200A 240D/120 service. Theres nothing currently on it besides half dozen lights.

 

[letgomywago]

If it a situation where it must be identified it doesn't have to be orange finish entire length of conductor. Orange tape, paint, or other methods near terminations is sufficient.

I thought that only applied to cables at the smaller sizes. Thhn I thought had to be orange in color. Unless it's a different marking system for the facility

 

[kwired]

I thought that only applied to cables at the smaller sizes. Thhn I thought had to be orange in color. Unless it's a different marking system for the facility

Marking grounded/grounding conductors vs entire finish being white, gray, green is where that conductor size rule applies. Identifying phasing when required (including identifying a high leg) only needs to be identified at/near terminations, and only when the grounded conductor is also present when dealing with high leg identification.

 

[kwired]

53 amps 3 phase, max circuit capacity, running amps is 42, per the manufacturer.

It’s currently an empty building I’m doing the TI on, and it has a 200A 240D/120 service. Theres nothing currently on it besides half dozen lights.

If you have an open delta supply and the high leg pot is only a 10kVA unit it can only supply 41.66 amps before it is contributing more than 10 kVA. That is the sort of thing that I believe drcampbell was mostly getting at, making sure your supply can deliver the load on that one line. Many those systems are built for limited amount of three phase load in mind when they were designed.