2nd electrical panel off main panel

[Bardessono]

Am having a well installed in back yard. well pump requires 30 amp 220/240 volt breaker. Would like to provide electrical to well and a future garage near the well.
I've an existing 3/4" PVC sch 40 conduit near the well (for pool pump). Would like to use the 3/4" PVC for pool, well and future garage. What is the largest amp subpanel that I can install of the main house 200 amp panel? I would replace the existing wires in the conduit. wire run in about 130 feet.

Thanks!
John Bardessono

 

[Norcal]

3-6 AWG THWN + 1 ECG, 6 THWN is rated at 65A, if a 60A breaker is used, then a 10 AWG grounding conductor can be used, if the load is under 65A, then the next higher up rule can be used which is a 70A breaker, but a 8 AWG equipment grounding conductor would be required, the neutral has to have white insulation on it's entire length, and the grounding conductor will have to have green colored insulation, because both are smaller then 4 AWG, taping black insulated conductors is not permitted by the NEC.

The reason for the upsizing of the grounding conductor if a 70A breaker is used, is the 10 AWG EGC is only good up to 60A.

 

[u2slow]

Most panels have a label inside saying the maximum allowable branch circuit breaker. On a 200A Square D QO 40 space, its 125A max.

Your 3/4" conduit is going to be the limiting factor.... likely capping you at 40-60A depending on the wire, and if you can reduce the neutral. Check your NEC for conductor ampacities and conduit fill.

EDIT: You can put in a larger subpanel (100A) and feed it with less until you replace (upsize) the conduit and wire.

 

[sky jumper]

it is unfortunate they only put in 3/4" pipe. I have been criticized for saying if you're going to dig the trench (which is most of the work) then you should put in bigger pipe. this is a perfect example of why.

 

[AntonLargiader]

You can put 60A 4-wire service through that. But unless you put the new garage on top of the conduit stub, you're going to be modifying stuff anyway. I would not let yourself be limited by an existing conduit run. It's peanuts in the grand scheme of things.

 

[Innovate1]

3/4 can hold 3 - #6 + ground. But it's a hard pull. I did a 50' run with two regular 90s years ago and got it done but it would have been a lot easier with larger pipe and/or large radius bends. For the length of run you have it is going to be worse. Consider putting in a larger pipe for power and using the 3/4 for low voltage - network/phone/alarm/etc.

 

[Bardessono]

Thanks to all of you for your help and suggestions. seems best to plan on a larger conduit when I build the outbuilding/garage. For now the "rest of the story".

The existing 3/4" conduit services a swimming pool with 2 each 20 amp 220 volt (two #12) and 1 each 15 amp 110 volt (2 #14) and 1 "green" #14.

Any thought on adding a 30 amp 220 volt for the well (temporary) in the same conduit?

John Bardessono

 

[sky jumper]

https://www.southwire.com/calculator-conduit

 

[wyliesdiesels]

Thanks to all of you for your help and suggestions. seems best to plan on a larger conduit when I build the outbuilding/garage. For now the "rest of the story".

The existing 3/4" conduit services a swimming pool with 2 each 20 amp 220 volt (two #12) and 1 each 15 amp 110 volt (2 #14) and 1 "green" #14.

Any thought on adding a 30 amp 220 volt for the well (temporary) in the same conduit?

John Bardessono

couple issues.

the #14 is too small for the EGC for the 240v pool circuit and it would be too small for a 30a circuit. so you would need to either abandoned or remove the #14 EGC and pull in 3 #10s

It will fit but it will be fun if its a long run with bends