Conductor sizing 375 foot run

[hotblueelectric]

Ok let me see if I have this right. I'm running (2) 120 volt circuits 375 feet for two gate openers that use 12 amps starting and 8.5 amps running. I will be installing (2) # 4's on 20 amp circuit breakers, and (1) #10 neutral and one #10 ground. All in pvc. This should keep my voltage drop to 2%. Do these calculations look correct. Any comments are appreciated.

 

[petersonra]

I think your EGC is undersized.

Is this a MWBC?

 

[Smart $]

I think your EGC is undersized.

It is. It must be upsized proportional to the upsizing of the ungrounded conductors [250.122(B)].

 

[augie47]

Since your neutral will be part of the circuit, it would need to be sized the same as your phase conductors.

 

[hotblueelectric]

Yes mwb circuit, why run 2 neutrals for only the unbalance. According to 250.122 ECG for 20 amp circuit is actually a # 12

 

[Smart $]

Since your neutral will be part of the circuit, it would need to be sized the same as your phase conductors.

I'm not aware of any such requirement. Code???

 

[Smart $]

... According to 250.122 ECG for 20 amp circuit is actually a # 12

Read 250.122(B)

 

[GoldDigger]

I'm not aware of any such requirement. Code???

I agree. As long as the upsizing is done for voltage drop you can choose to upsize just the hot, or just the neutral or both depending on what VD you need and how you want to get it.
In the OP's case if the two openers are normally used at the same time, configuring it as an MWBC for the purpose of voltage drop makes it reasonable to use a smaller neutral.
But you cannot do the same thing for the EGC.
(If you choose to upsize only the grounded conductor to reduce VD, you would not trigger the upsized EGC???)

 

[Smart $]

Yes mwb circuit, why run 2 neutrals for only the unbalance. ...

Agree, not necessary. However, if the loads operate at different times, you have to figure voltage drop differently, that is if you want to maintain a certain level of voltage drop.

 

[hotblueelectric]

Ok I see increase in size proportionately according to the cir mil of the ungrounded cond. How do I arrive at that size?

 

[Smart $]

...
(If you choose to upsize only the grounded conductor to reduce VD, you would not trigger the upsized EGC???)

Correct. But the voltage drop on a balanced MWBC with loads operating concurrently would not see any benefit.

 

[ptonsparky]

Yes mwb circuit, why run 2 neutrals for only the unbalance. According to 250.122 ECG for 20 amp circuit is actually a # 12

So both circuits will be operational, under load, at the same time. Always. In that case the neutral will carry the imbalance. There will never be a time when you have only a L-N . Right?

 

[weressl]

Ok let me see if I have this right. I'm running (2) 120 volt circuits 375 feet for two gate openers that use 12 amps starting and 8.5 amps running. I will be installing (2) # 4's on 20 amp circuit breakers, and (1) #10 neutral and one #10 ground. All in pvc. This should keep my voltage drop to 2%. Do these calculations look correct. Any comments are appreciated.

Run the calculations to installing a single 40A ckt with 2-20 CB at the user end to see if it is more cost effective. (Unless the two breakers are on the opposite legs you would need a separate neutral and EGC for each.)

 

[Smart $]

Ok I see increase in size proportionately according to the cir mil of the ungrounded cond. How do I arrive at that size?

With 20A circuits, just make it the same size as the ungrounded conductors.

 

[weressl]

I agree. As long as the upsizing is done for voltage drop you can choose to upsize just the hot, or just the neutral or both depending on what VD you need and how you want to get it.
In the OP's case if the two openers are normally used at the same time, configuring it as an MWBC for the purpose of voltage drop makes it reasonable to use a smaller neutral.
But you cannot do the same thing for the EGC.
(If you choose to upsize only the grounded conductor to reduce VD, you would not trigger the upsized EGC???)

The argument should be the same as for any other NEC issues: you can not predict the future use of these circuits, so you shouldn't be sizing it for special, non-simultaneous use.

 

[hotblueelectric]

So #4's for each hot, (1) #4 for the neutral and (1) #4 for the ECG. Correct.

 

[Smart $]

Run the calculations to installing a single 40A ckt with 2-20 CB at the user end to see if it is more cost effective. (Unless the two breakers are on the opposite legs you would need a separate neutral and EGC for each.)

I'm not getting your comment in parentheses. Seems appropriate only if breakers are on the same legs at supply end.

 

[Smart $]

So #4's for each hot, (1) #4 for the neutral and (1) #4 for the ECG. Correct.

Need the answer regarding the loads operating at the same time or not...

There may be other options to explore, but will wait for your reply.

 

[hotblueelectric]

So #4's for each hot, a #4 for the neutral and a #4 for the ECG. Correct. Cb on separate phases. I'm not sure but I think both gate openers will operate together. I sized the #4 for starting amps for each motor. Now that I digest this I should size the conductors for running amps at 8.5 each reducing my wire size to #6's.

 

[Smart $]

So #4's for each hot, a #4 for the neutral and a #4 for the ECG. Correct. Cb on separate phases. I'm not sure but I think both gate openers will operate together. I sized the #4 for starting amps for each motor. Now that I digest this I should size the conductors for running amps at 8.5 each reducing my wire size to #6's.

If it's two gate openers for opposing gates, most likely will operate at same time.

You are correct, size for running amps typically, you have to make sure the motors will not stall upon start (most likely will not).

Another option...

2P15A circuit breaker
(2) 10AWG, (1) 10AWG GRD
8.5A load at 240V
2.8% Vd
3kVA XFMR 240PRI/120SEC at load end
25A rated secondary current
10AWG secondary conductors to loads, considered protected by primary OCPD.

Ohhh... you'll also have to drive two ground rods at least 6' apart and run # 6 to one leg of the transformer secondary.

Price it and make cost comparison including labor.

Breaker size corrected above.