jack707
Veteran Member
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.
under ground wire help
- Thread starter jack707
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Rustyferrious
Silver Member
That will depend on the draw of whatever you are powering. What does the rating plate say on the boiler?
CobyRupert
Super Member
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.
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
Veteran Member
THis might help.
wire size calculator
wire size calculator
Rustyferrious
Silver Member
That's handy little calculator. Thanks!
CobyRupert
Super Member
That says #12 is good for 5 amps out to 205 feet and still keeps above 3% voltage drop.
OP
jack707
Veteran Member
Well then I'm good at 95'
LD1
Epic Contributor
Depends on the amp draw.
Wire size is based on 2 things. Length, and amps. You have only provided 1 part.
OP
jack707
Veteran Member
I'll go with #12 that should be good enough to run the pumps and the light.
Ed of all trades
Elite Member
Thanks just what I needed. Ed
LD1
Epic Contributor
3% voltage drop and 95' of 12AWG should be good to 11.04A
If your pumps and lamp are under that, then you are good. If they are over that, 10AWG would be good for 17.5A
CobyRupert
Super Member
Whoa, whoa, whoa. Pumps? As in more than one? The pump is not in your house?
Is there a blower too?
You need to calculate what the load (current) will be.
davesl708
Elite Member
You need to consider this;
The number of amperes drawn by the load is to be obtained from the manufacturer of the equipment. For motors, the current must be obtained from tables 430-148 (single-phase) and 430-150 (3-phase) of the NEC. Care must be taken to follow the guidelines of the NEC with regard to the number plugged into the calculator.
The NEC requires that for single motor installation, the current used in the calculation be 1.25 times the load current from the above mentioned tables. When more than one motor is used, the current of the largest load must be multiplied by 1.25, plus the sum of the rest.
aczlan
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I would run conduit and put your wire in that. Less chance of having to dig it back up after a rock nicks the wire that way.
Aaron Z
Aaron Z
Birdhunter1
Veteran Member
When I used to put them in most of them required we run #12-2 w/ ground.
What we did was ran a 10-2 with ground, put an outlet at the woodburner and installed a ground rod at the unit for an equipment ground. The reason we put an outlet on the outside of the unit with a disconnect (light switch inside the control cabinet) was so that we could hook up a light or other tool if we needed to and be able to kill power to the unit as a whole if we needed to. We figured we may be working on them at night and almost always it would be in the winter when it would be cold and probably with the ground being muddy or snow covered and we wouldn't have to go in the house to kill or energize the circuit.
And since we were an HVAC company we didn't do any underground electric other than these wood boilers and we'd buy a large spool of 10-2 underground wire that would cover anything we ever needed to do, and we usually put them in for farmers notorious for adding on to an existing circuit where a circuit was already ran. Often time the owner would build some sort of structure nearby to house wood under which had lights for working in the dark.
What we did was ran a 10-2 with ground, put an outlet at the woodburner and installed a ground rod at the unit for an equipment ground. The reason we put an outlet on the outside of the unit with a disconnect (light switch inside the control cabinet) was so that we could hook up a light or other tool if we needed to and be able to kill power to the unit as a whole if we needed to. We figured we may be working on them at night and almost always it would be in the winter when it would be cold and probably with the ground being muddy or snow covered and we wouldn't have to go in the house to kill or energize the circuit.
And since we were an HVAC company we didn't do any underground electric other than these wood boilers and we'd buy a large spool of 10-2 underground wire that would cover anything we ever needed to do, and we usually put them in for farmers notorious for adding on to an existing circuit where a circuit was already ran. Often time the owner would build some sort of structure nearby to house wood under which had lights for working in the dark.
Birdhunter1
Veteran Member
Or run the UF wire and your insulated piping all in the same 4" corrugated drain.
OP
jack707
Veteran Member
The 5 " drain tile is filled with foam no room to put it in.I looked at the boiler plate is rated for 120 volts so I picked up a 100 ' of 12/3 with ground.
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