I was hoping to get some clarification on a wiring issue. I have a 120' run from my 200 amp main panel to a pool house that will house a pool pump for an indoor pool. I was planning on putting in a 50 amp sub panel there with 6 circuits to power the pump and eventual outdoor lighting, outlets and perhaps a heat pump for the pool. I was going to run Uf-B Underground Feeder cable 6/2 in a 1 1/2 conduit underground to the pool house sub panel. My research has told me I cannot do this and that I must use #6 thhn/thwn wire (4 pulls - 2 hot, 1 neutral, 1 #8 ground). As you know, the cost of #6 thhn is through the roof. Is there a specific reason why the 6/2 Uf-b is disallowed for this application?

The easy part of your quest is the why you cannot use a 2 wire w/ ground cable.

The NEC requires that feeders for remote panelboards be four wire cables or pulls.

2 Hots, 1 Neutral and 1 Ground.

Secondly, I suggest that you use a 2" trade size conduit. The extra space makes it easier to pull the cable or wires and allows an easy replacement means if the cable should fail or you need to increase the size of the feeder to you remote panel.

At the remote panelboard, the Neutral and Ground conductors need to be isolated from each other.

Neutral will be the return path to the main service panelboard.

A grounding system must be used at the remote panelboard and you cannot mix neutral conductors and ground conductors on the same bus.

Also, a light has to be installed at the entrance to the structure.

Do I need to run the thhn wire all the way to the main panel or can I junction it at a junction box once it enters the house and carry via standard NM?

The feeder for this pool equipment panel must be in conduit all the way back to the main panel.

2" conduit is way overkill. 1-1/4" is plenty big enough for this.

You mentioned 6/2UF. That would not have been right in any case. You would have needed 6/3. Thing is, a feeder like this (pool equipment) and most circuits associated with a pool must be in conduit and utilize a green insulated ground.

I must say, although all copper wiring is quite high right, you are installing an indoor pool with a pool house. If the (relative) minimal cost of this wire is a concern how are you affording the rest of it?

Stan,

The OP is running a feeder to a remote building panelboard, not to the pool.

The issues surround the feeder and the panelboard. From the panelboard to the pool would be different issues.

As I stated, I'd prefer to use the 2"conduit" with a eye toward future expansion and or repair issues.

Don, I am aware that this is a feeder, but it is a feeder to a remote panel board for pool equipment.



680.25 Feeders.
These provisions shall apply to any feeder on the supply side of panelboards supplying branch circuits for pool equipment covered in Part II of this article and on the load side of the service equipment or the source of a separately derived system.

(A) Wiring Methods.

(1) Feeders. Feeders shall be installed in rigid metal conduit or intermediate metal conduit. The following wiring methods shall be permitted if not subject to physical damage: See related UL
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(1) Liquidtight flexible nonmetallic conduit

(2) Rigid polyvinyl chloride conduit

(3) Reinforced thermosetting resin conduit

(4) Electrical metallic tubing where installed on or within a building

(5) Electrical nonmetallic tubing where installed within a building

(6) Type MC cable where installed within a building and if not subject to corrosive environment

Stan,

"I was planning on putting in a 50 amp sub panel there with 6 circuits to power the pump and eventual outdoor lighting, outlets and perhaps a heat pump for the pool."

I'm sorry but I understood that the feeder to the remote panelboard was to supply the pool house primarily.

There were to be secondary feeds from the panelboard to supply pool equipment. My error.