PVC Conduit versus Underground wire

[paulhiggs]

Hi

I am wiring up an outside 50amp GFCI for my hot tub installation with a wire run of about 30' to the sub-panel in the basement. There will also be a 15amp branch circuit for an outside GFCI outlet near the spa GFCI.

A couple of questions come to mind.

1. Is it better to use PVC conduit for the parts of the wire-run that are underground instead of "ungerground" wire?

2. If running PVC conduit, can I run the conductors for the 15amp (14ga) in the same conduit as those for the 50amp (6ga)?

Thanks
Paul

[pushkins]

Hi

1. Is it better to use PVC conduit for the parts of the wire-run that are underground instead of "ungerground" wire?

2. If running PVC conduit, can I run the conductors for the 15amp (14ga) in the same conduit as those for the 50amp (6ga)?

Thanks
Paul

1. Direct bury cable is going to need to be buried at least 18" underground and as well your going to have to use schedule 40 pipe to bring the cable above ground at your sub panel.

If you use conduit it needs to be buried only 12". It will need to be schedule 40, to fit the 2 wires you want in I think your going to need 1 1/4 , this will make it easy to pull the cables.

[HayZee518]

Direct burial cable needs to be buried 24 inches down and encased in rock free beach sand. This type of cable is called UF - moisture and sunlight resistant.
Rigid metal or PVC conduit is supposed to be buried 18 inches down also encased in rock free beach sand. Any wires can be installed in the conduit as long as they are rated equivelant to the highest voltage within. Most thhn ot thwn is rated 600 volts. Another thing to consider is that if the number of conductors in a conduit system are 4 to 6 - total current is reduced by 80% - 7 to 9 - 70%, 10 to 20 - 50% and so on [see table]
Number of Current-Carrying Conductors Percent of Values in Tables 310.16 through 310.19 as Adjusted for Ambient Temperature if Necessary
4-6 80
7-9 70
10-20 50
21-30 45
31-40 40
40 and above 35

[paulhiggs]

So if I run multiple conduits, what type of spacing do they need to be at to avoid the loss?

[HayZee518]

seperate conduits in the same trench does not apply to the derating figure.

[normel]

Type UF wire is NOT allowed for wiring associated with a hot tub or pool.... the ground wire must be insulated. That means this must be in conduit and type THWN wire must be used.

[paulhiggs]

Thanks, so for the 50amp GFCI panel I'll pull three 6ga (two hots and one neutral) and one 8ga (ground) through a conduit.