Disconnect for Air Compressor

[faresos]

We have specified a 300HP, 480V/3-Phase air compressor with a manufacturer mounted controller with integral disconnect switch. I was told the controller showed up on site with E-Stop button on the controller but no disconnect. My question, can the E-Stop considered to be a disconnecting means? My intuition tells me no because for example you cannot lock it in open position if it needs to be serviced. Adding a disconnect is not convenient due to it's size. Other option will use the upstream breaker (located in different room) as a disconnecting means if we can be locked in open position. I don't have a wiring diagram yet on how the E-Stop is wired but I thought if someone came across this before.

Thank you!

 

[infinity]

No book with me but I seem to remember a prohibition of using the control circuit for a disconnecting means. If it has an integral disconnect why do you need anything else?

 

[hillbilly1]

No book with me but I seem to remember a prohibition of using the control circuit for a disconnecting means. If it has an integral disconnect why do you need anything else?

The op said he ordered it that way, but it didn’t come with it like it was supposed to, and I think you are correct, the e-stop would not qualify as a service disconnect, just as an emergency stop.

 

[retirede]

Where will the motor control (starter, or ?) be located. That’s where the disconnect will be.
The compressor control panel would not normally include motor control on a unit this big.

 

[hillbilly1]

Where will the motor control (starter, or ?) be located. That’s where the disconnect will be.
The compressor control panel would not normally include motor control on a unit this big.

The op said it was to be factory mounted, and I would assume this is an air screw, so probably the entire thing is huge cabinet.

 

[retirede]

The op said it was to be factory mounted, and I would assume this is an air screw, so probably the entire thing is huge cabinet.

He stated the controller was factory mounted. That’s likely the compressor control system less motor control (starter). When I was in the business, a NEMA size 4 (or equivalent) was the largest we would mount on the unit.

 

[infinity]

So it did not come with a disconnecting means built in. Got it. I would install one next to the unit and back charge the company that sent it out with the integral disconnect that you ordered.

 

[rambojoe]

You will quickly learn that you really really need a disconnect.

 

[hillbilly1]

He stated the controller was factory mounted. That’s likely the compressor control system less motor control (starter). When I was in the business, a NEMA size 4 (or equivalent) was the largest we would mount on the unit.

Should look something like this. Starter is a freq drive for this size, and would be inside this enclosure

 

[retirede]

Should look something like this. Starter is a freq drive for this size, and would be inside this enclosure

Yeah….no disconnect included.

 

[faresos]

Thank you all of the reply. The challenge is, the manufacturer came back and offered a Non fused disconnect at no cost, however, we have specified the control assembly to have a minimum of 65K SCCR, which they did supply (without integral disconnect), the calculated fault current at the controller is approx. over 40KA, so I told them, the disconnect needs to be fused with class R to get the 100AIC. As we all know, the none fused disconnect has 10KA SCCR rating (by default). I do understand the SCCR rating might increase depending on the upstream breaker but that's my last reserve because I will need to contact the manufacturer so they can check the series rating for the disconnect and the upstream breaker (hopefully they have this documentation).