under ground wire help

[jack707]

I'm hooking up my outside boiler and the trenches are dug, but my question is what gauge of wire do I need? the OWB has 2 I want a cable with 3 so I can ground it to the frame.

 

[Rustyferrious]

That will depend on the draw of whatever you are powering. What does the rating plate say on the boiler?

 

[CobyRupert]

My guesses:
Does it have a: Blower? (60-250 watts)
Solenoid for air? (10 watts)
A convenience light? (13-150 watts)
A receptacle (widely variably, call it 180 watts) That's a worst case of say 600 watts, which is 5 amps at 120 volts.
How far is boiler from panel?
For 5 amps a #12 gauge should be able to run a few hundred feet (others with can confirm) with under a 3% (3.6V) voltage drop.

You need to run a 3/c cable so that if your circuit ever shorts to the boiler, there's a low resistance path on the green wire back to the utility's transformer so that lots of current can short into the boiler and the breaker will trip.

 

[Mendonsy]

THis might help.
wire size calculator

 

[Rustyferrious]

THis might help.
wire size calculator

That's handy little calculator. Thanks!

 

[CobyRupert]

THis might help. wire size calculator

That says #12 is good for 5 amps out to 205 feet and still keeps above 3% voltage drop.

 

[jack707]

That says #12 is good for 5 amps out to 205 feet and still keeps above 3% voltage drop.

Well then I'm good at 95'

 

[LD1]

Well then I'm good at 95'

Depends on the amp draw.

Wire size is based on 2 things. Length, and amps. You have only provided 1 part.

 

[jack707]

I'll go with #12 that should be good enough to run the pumps and the light.

 

[Ed of all trades]

THis might help.
wire size calculator

Thanks just what I needed. Ed