Test question

[blueheels2]

A combination load consisting of 15KVA of resistance heat and a motor rated 1.2KVA is served by a 240v branch circuit. What is the minimum required rating for this branch circuit?


I get 84 amps. Test booklet says the answer is 90. What say you guys?

 

[Little Bill]

A combination load consisting of 15KVA of resistance heat and a motor rated 1.2KVA is served by a 240v branch circuit. What is the minimum required rating for this branch circuit?


I get 84 amps. Test booklet says the answer is 90. What say you guys?

You have to size it according to breaker sizes. Look at 240.6

 

[blueheels2]

You have to size it according to breaker sizes. Look at 240.6

Thanks I was thinking it was asking for load to be considered when sizing the ocpd.

 

[charlie b]

I get 84 amps.

Perhaps I need more coffee this morning. But I don't see how you came up with 84.

Taking the motor at 125% of 1.2 KVA gives you 1.5 KVA. Add 15 KVA for the heaters and you are up to 16.5 KVA. If this is single phase, then 16.5 KVA / 240 V = 68.8 amps. If this is three phase, then divide again by 1.732 and you get 39.7 amps.

Please explain your math, while I go pour myself another cup of wake up juice.

 

[blueheels2]

15000 + 1200= 16,200 ÷ 240= 67.5 x 1.25 because it's a continuous load gives you 84.375A.

Edited to add you calculated the motor as continuous but the heaters are considered continuous as well based off of 424.4 (b) I think.

 

[JFletcher]

15000 + 1200= 16,200 ÷ 240= 67.5 x 1.25 because it's a continuous load gives you 84.375A.

Edited to add you calculated the motor as continuous but the heaters are considered continuous as well based off of 424.4 (b) I think.

Yes, fixed space heating is considered a continuous load. That said, there is no 85 amp breaker, so you must go to the next size up which is a 90 AMP.

That also said I do not see how you could put both of those loads on the same circuit, unless they were a package deal like an HVAC unit.

Edited to add... When posting test questions, it is incredibly important to post them completely as written... Not saying you didn't, just that even a missing, in the wrong place could change the answer

 

[blueheels2]

Yes, fixed space heating is considered a continuous load. That said, there is no 85 amp breaker, so you must go to the next size up which is a 90 AMP.

That also said I do not see how you could put both of those loads on the same circuit, unless they were a package deal like an HVAC unit.

I would agree. This is just the questions you have to answer to get a license in NC.