XXXL Branch Circuit

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Natfuelbilll

Senior Member
A 2100' branch circuit is to be installed from a 120/240V panelboard to a contol panel.
The voltage is to be 240V. The circuit will be installed underground in either PVC or rigid.

The load is a radio tower.

What can I do to electrically harden the installation?

My concern is the long line may be suceptable to lightning and voltage disturbances.

Thanks
 
Dennis Alwon

Dennis Alwon

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Is the poco power close by? If so set a small service. If that is out of the question just size the wire for the drop and don't forget to upsize the egc if used. 250.122(B)
 
kwired

kwired

Electron manager
Location
NE Nebraska
Step voltage up at source and step back down at load. Advantages: you do not need a neutral so less conductor expense, higher voltage = less voltage drop, higher voltage = smaller conductors for same VA of load.

You will need to figure out if cost of 2 transformers plus extra switch(es) and other possible equipment is more or less than cost of larger conductors sized for voltage drop. Sometimes it doesn't make any sense to use this set up from an installation cost perspective, sometimes it does.
 
iwire

iwire

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I did a little checking and if his load is just 5 amps 1 AWG AL would be sufficient. But of course he has not said the actual load.
 
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natfuelbill

Senior Member
The POCO is a long ways away.

The load at the tower is 240Vac at one (1) amp.

The conductor size selected is #12.

The OCP size is being discussed to be 15A.
 
kwired

kwired

Electron manager
Location
NE Nebraska
bluesmoke...oops said:
Would that be cost effective?
Click to expand...

I don't know, that is why I said it is a good place to consider it.

It apparently does not require much load so it would not need to be a very big unit. Whole different ballgame if one were wanting to power a 50 hp motor that far away from the utility.
 
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jaggedben

Senior Member
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Northern California
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Solar and Energy Storage Installer
Some rough numbers:

If the radio tower transmits at 240 watts constantly, 24/7/365, then you will need something like a 4kw solar system, plus batteries, to get through the winter, depending on location. Probably that isn't cost effective, since it would cost upwards of $20,000.

However, we really need to know the actual usage of the radio tower, in kWh. If it doesn't transmit at full power 24/7/365, then the system can be much smaller. My guess is that at roughly a fifth of a constant 240 watts, solar comes into a cost competitive range compared to the project you're describing, which I would gather requires a budget of roughly $5,000 minimum.

Also we would need a rough location to estimate the solar resource.
 
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Natfuelbilll

Senior Member
Thank you for your ideas on constructing this branch circuit.

If I may ask please discuss the topic of the OP.

I am mostly interested in identifying methods to electrically harden using surge and lightning protection of the source panelboard and of the load.

Would a pair of isolation 240 to 240 help?
 
don_resqcapt19

don_resqcapt19

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Location
Illinois
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retired electrician
Natfuelbilll said:
Thank you for your ideas on constructing this branch circuit.

If I may ask please discuss the topic of the OP.

I am mostly interested in identifying methods to electrically harden using surge and lightning protection of the source panelboard and of the load.

Would a pair of isolation 240 to 240 help?
Click to expand...
Rigid steel conduit buried as deep as possible and good surge protection equipment at each end.
 
tom baker

tom baker

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Control circuits to contactors and relays don't work well over long distances. The coil will pull in but not drop out due to capacitance. DC is a good way to go for this, if its for contactors or relays.
 
kwired

kwired

Electron manager
Location
NE Nebraska
tom baker said:
Control circuits to contactors and relays don't work well over long distances. The coil will pull in but not drop out due to capacitance. DC is a good way to go for this, if its for contactors or relays.
Click to expand...

I run into these kinds of distances with irrigation equipment all the time and have never had that kind of problem with controls.

Not too uncommon to have a contactor coil that is about 4000 feet from the switch that is powering it. (120 volt ac normally)
 
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