I have just laid a #10 underground cable for 250'. At the end is a pump house with a pump and an overhead light. These are 110 volts. About halfway there is a receptacle at an arbor. My questiom is: What amp breaker should I use? As I understand it, the cable is rated for 30 amp. What difference does the length of the run of 250' make?
I await your expert responses.
Thanks, Tom
| I have just laid a #10 underground cable for 250'. At the end is a pump | house with a pump and an overhead light. These are 110 volts. About | halfway there is a receptacle at an arbor. My questiom is: What amp | breaker should I use? As I understand it, the cable is rated for 30 amp. | What difference does the length of the run of 250' make?
How much power will the combined pump and light load use?
With #10 wire, you cannot go any higher than 30 amps. But you might want to use less, as appropriate, based on details you have not provided. The light itself may require not more than 20 amps, or separate additional protection just for the light. The receptacle may also limit your amperage depending on what its rating and/or configuration is.
The receptaclal limits him to 20a
It could be a 30a receptacle. :o)
Louis--
********************************************* Remove the two fish in address to respond
What about putting in a GFCI 'breaker'?? Seems like, outside, receptacle and 'pump' kind of need a GFCI to be code.
daestrom
If the receptacle is 30a it doesn't need GFCI unless this is a spa ... but we are getting pretty far away from what he asked I doubt there is a dryer in his arbor. The GFCI is a good question. The arbor receptacle should be GFCI protected one way or another.
Is there not a 20A limit to breaker size for circuits with outlets such as the overhead light?
jThe length of the run could make a lot of difference, depending on the current draw of the pump and the light. You need to multiply the total maximum load current by the resistance of 500' (to get the voltage drop in both conductors) of 10 awg wire, which is around 1.2ohms/mft. The voltage drop should not exceed 3% under full-load conditions, or 3.6v. This means that the maximum load should not exceed 6 amps (3.6v/0.6ohms). The main reason for running "oversized" wire in a case like this is to limit voltage drop.
The outlet at the arbor must be protected by a GFCI since it's outside, and GFCI outlets generally come in 15A and 20A sizes. Given the limitations already imposed by the length and wire size, I'd probably use a 15A breaker, but certainly no larger than 20A.
Al
Thomas M> I have just laid a #10 underground cable for 250'. At the end is a pump
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