HVAC SCCR

R

Rock86

Senior Member
Location
new york
Occupation
Electrical Engineer / Electrician
Situation: Mechanical engineer sent a cut sheet for a temporary chiller. Voltage, load calc, and OCP all checked to be compatible. The cut sheet says the SCCR is 5kA. I ran an available fault current calculation and the result was over 12kA. I went to my mechanical engineer to discuss this with him and he said that no electrical engineer in his 25 years has ever mentioned a concern for SCCR.

Do I have a valid point telling him the SCCR is underrated for the electrical condition, or am I misunderstanding SCCR vs AFC?

Note: I am not talking about the AIC rating.
 
You are correct. Most manufacturers use the default 5kA and do not provide the components needed for a higher SCCR unless specified at the time of the order.
 
It's a very common issue. I've encountered it with elevator system components as well. To be frank, I don't recall ever encountering a reasonable, all-encompassing solution. I do recall that current-limiting fuses are not a viable option, nor is the placement of series resistance to limit fault current. Getting the manufacturers to only use components that can collectively provide a higher SCCR is not cost-effective for them. If you are in need of a way out of the conundrum, I fear that I have none to offer.
 
Did you calculate the AFC including the branch citcuit conductors to the unit? If so, can you make them much longer to limit the current? Waste of wire, but may be an easy solution.
 
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