Mechanical Equipment Grounding

[faresos]

We are installing two new chillers (60 Tons each) outside the building and I was asked if we need to provide a ground ring & rods around the pad to ground the frame. With all honestly, I have done it before but not really sure if this is required, I thought this pertains maybe for the lightning protection system.

1. Do we need to provide a ground ring around the chillers pad and bond the frame to it? if yes, what is the purpose of it?
2. Is this an NEC requirement? if so, what section we need to comply with.
3. Is there any rule that will force us to ground any mechanical equipment outside the building?

This is building is still under construction and at the final stages, the building has a ground ring so not sure if I just need to bond the chiller frame to the existing building ground ring. Thanks all in advance!


Thanks,

 

[infinity]

The only thing required by the NEC is an EGC run with the chiller circuit.

 

[faresos]

The only thing required by the NEC is an EGC run with the chiller circuit.

so why many engineers bond it to the building grounding ring? Just would like to know the purpose of it, is it for lightning protection?

 

[ptonsparky]

Separate structures do require a GES. Maybe that is what your chiller pad(s) is being considered. Sometimes it's quicker to ask the engineer and/or the AHJ the why.

 

[infinity]

Separate structures do require a GES

That would not apply when the separate structure is fed by a single circuit. If the structure is likely to be become energized then it gets connected to the branch circuit feeding the equipment.

 

[wwhitney]

That would not apply when the separate structure is fed by a single circuit.

Yes if it's a branch circuit, no if it's a feeder. Is a 60 Ton chiller a large enough unit that it would have its own distribution panelboard, making the circuit supplying it a feeder rather than a branch circuit?

Cheers, Wayne

 

[infinity]

A chiller is equipment not a structure so the argument is moot as to whether or not the NEC requires a GES for a chiller.

 

[ptonsparky]

Read second sentence of my post, then the third.

 

[electrofelon]

so why many engineers bond it to the building grounding ring?

I think it's a combination of the cult of the green wire and it being easy to spend someone else's money.

 

[don_resqcapt19]

A chiller is equipment not a structure so the argument is moot as to whether or not the NEC requires a GES for a chiller.

The issue is that some say the concrete pad, or other types of support for equipment are structures. I submitted a PI for the structure definition to try and clarify this. If the support does nothing other than support the equipment, I don't see a reason to consider the support system a structure.