Sizing a HVAC

[goodoboy]

:? Sorry, I am still learning. Are you stating that the voltage drop from my MCC bucket to where I plug in the unit should not exceed 5% per NEC code?

Help me understand please

Whats confusing me is this statement:
1. Branch Circuits ? This FPN recommends that branch circuit conductors be sized to prevent a maximum voltage drop of 3%. The maximum total voltage drop for a combination of both branch circuit and feeder should not exceed 5%. [210-19(a) FPN No. 4], Figure 2.

2. Feeders ? This FPN recommends that feeder conductors be sized to prevent a maximum voltage drop of 3%. The maximum total voltage drop for a combination of both branch circuit and feeder should not exceed 5%. [215-2(d) FPN No. 2], Figure 2.

Ok, let me explain a bit better.

I am running wire from the my MCC bucket to the a vendor explosion proof panel. So according to code the voltage drop must not exceed 3% for the feeder circuit. This is why I was using 3% as my voltage drop to size my wire to #4

From the panel to the unit is about 5-10 ft away and this is considered the branch circuit, and the vendor will size appripate size wire for that distance, which will be much smaller than my wire from the mcc bucket to maintain 3% voltage drop.

However, adding another 10ft, to the 1500ft, I can use a #6 and within 5% of voltage drop according to code. For total distance of 1510 ft, a #6 gives me about 4.16% voltage drop.

Correct me if I am wrong.

Question:

1. From panel to unit, does the vendor have to use the same size wire as me?

Thanks for the help.

 

[david luchini]

So according to code the voltage drop must not exceed 3% for the feeder circuit.

As others have pointed out, the code does not say that. The code only recommends staying within voltage drop limits, but does not require it (with the exception of fire pumps and sensitive electronic equipment.)

From panel to unit, does the vendor have to use the same size wire as me?

No.

 

[goodoboy]

The code only recommends staying within voltage drop limits, but does not require it (with the exception of fire pumps and sensitive electronic equipment.)

Yes, you are correct. Thanks

 

[kwired]

:? Sorry, I am still learning. Are you stating that the voltage drop from my MCC bucket to where I plug in the unit should not exceed 5% per NEC code?

Help me understand please

Whats confusing me is this statement:
1. Branch Circuits ? This FPN recommends that branch circuit conductors be sized to prevent a maximum voltage drop of 3%. The maximum total voltage drop for a combination of both branch circuit and feeder should not exceed 5%. [210-19(a) FPN No. 4], Figure 2.

2. Feeders ? This FPN recommends that feeder conductors be sized to prevent a maximum voltage drop of 3%. The maximum total voltage drop for a combination of both branch circuit and feeder should not exceed 5%. [215-2(d) FPN No. 2], Figure 2.

Yes, you are correct. Thanks

I think you maybe figured it out, but I will mention that FPN's, which were changed to be called "informational notes" in 2011 are not requirements of the code, they are just information inserted in key places that some may find useful.

 

[goodoboy]

I think you maybe figured it out, but I will mention that FPN's, which were changed to be called "informational notes" in 2011 are not requirements of the code, they are just information inserted in key places that some may find useful.

LOL, yes. I am finally figuring it out. Only with the help of you good people.

I have come to this forum 3 times and each time I received good help. Thank you. And soon I can contribute!