Gate Opener Voltage Drop

Location
Mississippi
Occupation
Electrician
First post here I'm sure this has been covered before. I have a gate opener and two LED coach lights a customer wants power to. The opener is 1100' away from an outbuilding with it's own poco transformer and meter. Voltage at panel is 123.5 at mdp. Thanks for any advice.

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texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Off the top of my head I think I would be inclined to run a straight 240 circuit out (no neutral) since this is likely a pretty small load. At the load end put a 240 X 120 transformer with the 120 secondary bonded and grounded. #4 CU @ 240 volt would give you about 20 amps @ 120 at the transformer secondary with less that a 3% drop. I would not try to run 120 all the way out there as the wire size will get pretty big.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
And it might, might, be even better to step up to 480 and send that. You'll have to do the numbers of transformer cost vs copper cost (a lot of the installation cost will be that 1100'- trenched/buried or overhead?).
I was just thinking that given the small load it may not be worth the expense and hassle of using a transformer at the supply end. But your right, a little cost analysis is in order.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Welcome to the forum.

If the gate opener has batteries, the power only supplies a charger.

Between that and two LED lights, there wouldn't be much voltage drop.
 
Location
Mississippi
Occupation
Electrician
Welcome to the forum.

If the gate opener has batteries, the power only supplies a charger.

Between that and two LED lights, there wouldn't be much voltage drop.
That's kind of what I was thinking I did the numbers at 7 amps I came up with 8awg. I installed an outlet for a comparable gate opener today it pulled less than 1 amp.

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texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
If the current draw is really low do to batteries that's great. But I would be careful that you don't end end up with a circuit where with, say, a 15 amp OCPD that you end up with a situation that will not trip in the event of a short circuit.
 
Location
Mississippi
Occupation
Electrician
If the current draw is really low do to batteries that's great. But I would be careful that you don't end end up with a circuit where with, say, a 15 amp OCPD that you end up with a situation that will not trip in the event of a short circuit.
Can you explain why it wouldn't?

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Since I'm doing wild ideas at the moment- A small solar setup. Inverter to make AC for the gate, batteries to store, panels to charge, loooonnngggg run of AC for backup and a small charge current.

Nah, way too complicated :ROFLMAO: .

A lot depends on the gate motor voltage & starting current. Add a side note that the moment someone sees 120v power out there, they're going to want to connect something else (small fountain, de-icer, more lights, security camera, etc).
 
Location
Mississippi
Occupation
Electrician
Since I'm doing wild ideas at the moment- A small solar setup. Inverter to make AC for the gate, batteries to store, panels to charge, loooonnngggg run of AC for backup and a small charge current.

Nah, way too complicated .

A lot depends on the gate motor voltage & starting current. Add a side note that the moment someone sees 120v power out there, they're going to want to connect something else (small fountain, de-icer, more lights, security camera, etc).
To shaded for solar. I know what you mean I'll have to deal the the electric leaf blower being plugged in every year.

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Dsg319

Senior Member
Location
West Virginia
Occupation
Journeyman Electrician
Could you show me an example
Use Ohm's Law to figure out how low a resistance must be to make sure, say, 20 amps will flow on 120v.

Then calculate what size wire is needed to get that resistance (or lower) through 2,200 feet of it.
Could you show me an example of how to do this properly?
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
Could you show me an example

Could you show me an example of how to do this properly?
I don't think its quite that simple. using E/I=R 120/20 = 6 ohms. Dividing 6 by the resistance of #12 awg will give you the total feet one way. That is the worst case and while 20 amp will flow, its not enough to trip a 20 amp CB. You would need to look at time current curves of the CB or fuse to determine when you are happy with the time it takes to opening the circuit. Reducing the length of the wire or increasing the size will give the results you want.
 

Dsg319

Senior Member
Location
West Virginia
Occupation
Journeyman Electrician
I don't think its quite that simple. using E/I=R 120/20 = 6 ohms. Dividing 6 by the resistance of #12 awg will give you the total feet one way. That is the worst case and while 20 amp will flow, its not enough to trip a 20 amp CB. You would need to look at time current curves of the CB or fuse to determine when you are happy with the time it takes to opening the circuit. Reducing the length of the wire or increasing the size will give the results you want.
Seems like a lot. Just a thought out of curiosity if you kept the circuits voltage drop within the 3 percent recommended range should it typically have low enough impedance to properly open the OCPD in a fault.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
Question. For available fault current should I put infinite bus....... or if I had a series rated panel with a main breaker with a 22kiac rating would that be my available fault current?
I’m cheating on this. I’m not Looking to see if the breakers can handle the maximum fault. I want to know if the the fault current is enough to operate the fuse or breaker. I would use what you think is actually available. Use the results of your first calc for The start of the second, etc. Work all the way from the poco transformer down through the feeders to the end of the branch circuit. I worked this for some pivots last year and found it was going to take 15 or more seconds to blow 30 amp fuses for the wires I used. Not good in my opinion.

You know by now I’m not an engineer, so I’m sure there are better methods.
 
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