Help calculating

[Matt Mckenzie]

When calculating the loads for a commercial laundry room can we derate commercial dryer loads? For example: 5 - 6kw Commercial dryers in a laundry room.....? 18,000VA.... Derate? Also, to calculate the neutral loads on a 120/240volt single phase service don't we just add up the 120volt loads and divide by 240volt for amps and go to the wire table? What if question specifies use thhn conductors? Can someone please help....

 

[Smart $]

There is no demand factor for commercial dryers.

(5) 6kW dryers amount to 30kW/kVA load... not 18kVA.

For 120V loads, yes... add up VA and divide by 240V if the 120V loads are balanced. If unbalanced, take the larger "side" and divide by 120V (same as multiplying by 2 then dividing by 240V)... and this depends on these being the only loads on the wires.

If THHN is specified, you can use the 90?C table value for derating purposes, but terminal temperature limitations prevent your ampacity/circuit rating from exceeding either the 60 or 75?C value.