[kramberry]

I am placing my pump and water softner inside a garage and also want to supply the garage with power. I want to put in a 125 amp breaker box. I have to run it about 150' from the power pole to the garage. What size pipe and wire should I run to make sure there is no voltage drop.

[Handyman2007]

If you are running overhead, 2/0 aluminum feeder is adequate. If you are running underground, you will have to use 4/0 because of heat considerations.
Conduit size underground would be 2" PVC. You don't mention your location and there are certain considerations that your power provider may deem necessary. Check with them to be absolutely sure what you need to do.

[stanfortyman]

If you are running overhead, 2/0 aluminum feeder is adequate. If you are running underground, you will have to use 4/0 because of heat considerations.
Conduit size underground would be 2" PVC.

What?? Where are you getting these numbers from? You must have a really different code book from me.

[stanfortyman]

I have to run it about 150' from the power pole to the garage. What size pipe and wire should I run to make sure there is no voltage drop.

What is at the power pole now as far as equipment? If it's just the meter you cannot come from that.

[donf]

Why do you want to come off the top of the power pole?

If that pole belongs to the utility company and that utility company is supplying a meter to your home, you have to supply the shed from your home's service side, not the utility's pole.

You can still choose whether you want to go overhead or below ground.

However you get there, you must supply an outside light. You must bring a 4 wire feed. And you must install a grounding system at the garage because Neutral and Ground cannot be bonded together at this feeder panelboard.

You will need to know what the Ambient temperature is for your area, prior to making any adjustments because of conduit heat. If the Ambient temperature is greater or less than 86(F) you would use NEC Table 310.15(B)(2)(a) to find the factor needed.

You also have to select the proper type insulation for your feeder cable. If you are using overhead cable, it must be capable of withstanding both the temperature and UV rays from the sun and weather conditions.

If you choose underground then you must make sure that the conductors are listed for a wet location even though they are in conduit.

Voltage drop is only a recommendation by the NEC. It is not a requirement. Typically, the NEC recommends a total drop of not more than 5%. It is further broken down to 3% on the feeder and 2% on the branch circuit.

For example, A 125 Amp panelboard would typically be loaded to 80% (100 Amps).

To get a working 100 amps, underground for a distance of 150', you will need # 1 AWG conductors for copper or #1/0 aluminum.

If you go overhead, then for copper you will need #3 AWG or # 1/0 for aluminum.