HVAC Short Circuit Withstand Rating

[powerpete69]

I think you might be misinterpreting...

He is not saying that the Available Fault Current at his site is only 5kA, he is saying that the HVAC EQUIPMENT is only rated 5kA SCCR; it's HIGHLY likely that his AFC is much much higher.

I understand this, no misinterpretation. It could very easily be fed by a 1000 KVA or 1500 KVA transformer or even bigger.

In my business, I typically specify the short circuit rating on the new piece of electrical gear or electrical equipment. The vendor typically meets the request in their submittal. If there was a case that the vendor didn't meet the request, the submittal would be rejected and another vendor with the correct short circuit rating would be selected.

Again, if you inherit a used piece of equipment like this, you inherit a problem. Perhaps you are the installing electrician and the engineer approved the 5kA rating. Then you have a problem with both the engineer and the piece of equipment.

 

[ron]

Maybe this should be a new thread, but now you have me wondering if it is a violation to use residential equipment in a commercial project.

I've not seen HVAC equipment identified as specifically deemed residential. The code section I was referring to was 440.4(B) Ex 3, which says (not exactly) equipment used in a dwelling application, so if you put a giant chiller and cooling tower in a dwelling application, you can use that exception.

 

[kwired]

I believe you and all, but that is strange considering an average home panel breaker is rated at 10kA.
When you consider the 500 amps, 5kA is ridiculous!!

That home panel won't ordinarily have 10kA available, but even if it does, that 14 to 6 AWG conductor going out to most typical loads in the home will have enough impedance to lower the available current at the load end of the conductor.

That said a chiller that is supplied with 500 amp circuit will have less available current at the unit then what is at the service equipment, but might be many cases where it still would be above 5kA.