Increasing Conductors for Voltage Drop

[Little Bill]

Here is my scenario, a customer wants to put an RV hook-up on the property. It is a 30A RV and they want it to have it's own service. There are three mobile homes in line adjacent to the site for the RV.
POCO says they can't run the secondaries any further then they already are because the three mobile homes are all on the same transformer. To run new primaries and set another transformer is cost prohibitive. POCO says they will allow another service at the last mobile home, on/adjacent to the existing pole. This is with stipulations that I won't get into for now.

From the last mobile home it is 108' to where the RV box needs to be. That's not counting the distance from the meter to ground nor ground up to RV box. So lets just say 123'. I know the NEC doesn't require adjusting for voltage drop. But I was talking with the inspector and he suggested running #6 wire due to the fact that the secondaries are already maxed out and adding another 100+ feet might cause problems.

Now normally 30A only needs #10 AWG wire, do you think I would need to go all the way to a #6 for this? I was thinking #8 would do it. AFAIK, the RV would only have one A/C unit, receptacles and lights. Normally the stove would be gas and sometimes the fridge. I'm not sure exactly what the load would be, but it can't be over 30A. In case some don't know, the 30A is single pole, single phase, not 2-pole 30A.
Thoughts?

 

[gar]

190726-0310 EDT

Little Bill:

There are comments in your post that make no sense.

First, for reference #10 copper wire is about 1 ohm for 1000 ft at 20 deg C. Resistance changes by about a factor of 2 for every 3 wire sizes. So #7 would be about 1/2 ohm for 1000 ft.

Thus, a #10 copper loop about 125' long is about 0.25 ohms.

30 A thru a 0.25 ohm resistance is about 7.5 V drop.

If the source voltage at the input to your 125' is a solid 120 V, then 7.5 V is probably not a problem. However, motor starting current might be over 100 A which means a drop of 25 V. Likely a problem especially, if the source voltage is not stiff.

POCO says they can't run the secondaries any further then they already are because the three mobile homes are all on the same transformer. To run new primaries and set another transformer is cost prohibitive. POCO says they will allow another service at the last mobile home, on/adjacent to the existing pole. This is with stipulations that I won't get into for now.

The following is not power company, but interrelates.

But I was talking with the inspector and he suggested running #6 wire due to the fact that the secondaries are already maxed out and adding another 100+ feet might cause problems.

If the power company transformer is already maxed out, then why would they allow more load? If there is much wire and voltage drop from other loads at the point where you connect, then your problem is greater to start because your source voltage would not be stiff.

.

 

[romex jockey]

VD is addressed via 210.19(A) IN No. 4 & 215.2(A)(1) IN No 2 & 310.15(A)(1) IN No. 1 , normally 3%-5% , which most poco's predicate their installs on

~RJ~

 

[Dennis Alwon]

VD is addressed via 210.19(A) IN No. 4 & 215.2(A)(1) IN No 2 & 310.15(A)(1) IN No. 1 , normally 3%-5% , which most poco's predicate their installs on

~RJ~

Yes but they are informational notes not code rules.

 

[Dennis Alwon]

For 123 feet #8 should be fine @ 30 amps- 2.9 volt drop.

 

[Dennis Alwon]

I have to leave here so I am not sure if there is a minimum size conductor for an RV

 

[kwired]

I have to leave here so I am not sure if there is a minimum size conductor for an RV

If he has a 30 amp receptacle on a 30 amp overcurrent device then he needs a minimum of 30 amp conductor just per general rules of 210, 215, 225, 230, 240 and 310.

 

[kwired]

Here is my scenario, a customer wants to put an RV hook-up on the property. It is a 30A RV and they want it to have it's own service. There are three mobile homes in line adjacent to the site for the RV.
POCO says they can't run the secondaries any further then they already are because the three mobile homes are all on the same transformer. To run new primaries and set another transformer is cost prohibitive. POCO says they will allow another service at the last mobile home, on/adjacent to the existing pole. This is with stipulations that I won't get into for now.

From the last mobile home it is 108' to where the RV box needs to be. That's not counting the distance from the meter to ground nor ground up to RV box. So lets just say 123'. I know the NEC doesn't require adjusting for voltage drop. But I was talking with the inspector and he suggested running #6 wire due to the fact that the secondaries are already maxed out and adding another 100+ feet might cause problems.

Now normally 30A only needs #10 AWG wire, do you think I would need to go all the way to a #6 for this? I was thinking #8 would do it. AFAIK, the RV would only have one A/C unit, receptacles and lights. Normally the stove would be gas and sometimes the fridge. I'm not sure exactly what the load would be, but it can't be over 30A. In case some don't know, the 30A is single pole, single phase, not 2-pole 30A.
Thoughts?

Even if you ran 500's it won't lessen any voltage drop you already have up to where you extended things. So it becomes a matter of knowing how much drop you already have and then figuring out how much more you may have on what you extend with.

 

[Little Bill]

I should have mentioned that I don't subscribe to what the inspector is saying about the last mobile home already being maxed. He has no way of knowing that. It's just that the POCO said they aren't allowed to take their secondaries any further. I just presented things like I was told to get opinions. I am only slightly concerned about VD for the 123' to the RV.
I will check the voltage on the mobile home when I go back. Hopefully they will have a load on the service so I can at least get somewhat of an accurate reading of what the voltage is there.

 

[Dennis Alwon]

If he has a 30 amp receptacle on a 30 amp overcurrent device then he needs a minimum of 30 amp conductor just per general rules of 210, 215, 225, 230, 240 and 310.

I was thinking that maybe the nec required a larger conductor run in case of upgrade.... I doubted it but I thought perhaps it was possible. Surely, you didn't think I didn't know what you posted....

 

[Dennis Alwon]

I was thinking of something like this

551.71(C) 50-Ampere. A minimum of 20 percent of existing and
40 percent of all new recreational vehicle sites, with electrical
supply, shall each be equipped with a 50-ampere, 125/250-volt
receptacle conforming to the configuration as identified in
Figure 551.46(C)(1). Every recreational vehicle site equipped
with a 50-ampere receptacle shall also be equipped with a 30-
ampere, 125-volt receptacle conforming to Figure
551.46(C)(1). These electrical supplies shall be permitted to
include additional receptacles that have configurations in
accordance with 551.81.

 

[Dennis Alwon]

Now that I am back I see my error....

 

[kwired]

I was thinking of something like this

According to OP it is a single RV on it's own service, there just happens to be other RV's on other service(s) on the same POCO secondary circuit.