Exterior Circuits - Underground

[gbeichho]

I'm refinishing the walls in another part of my cottage this spring (Ontario, Canada). I'm re-doing the area around the front door, and I want to mount an external outlet (20A) on the front porch.

I also want to plan ahead for a lamp post that I want to put out at the driveway (if you can call it that). I want the lamp post to have an external sensor flood light (15A circuit), 20A GFCI external recepticle (I already have a dedicated outdoor 20A circuit servicing only outdoor recepticles) and a 30A RV recepticle.

Unfortunately, I want to run the wires down the right side of the outside door, pop them through the wall, go down under the porch, cut across to the other side of the door, then go in a straight line (running paraleel to my septic -- the opposite side of leaching bed) to the driveway and pop up on a post.

I also don't want to dig the wire right now, but I've got the wall open. I'm assuming what one normally does is run regular NMD to an access box on the wall and then run NMWD through conduit underground. I also want to have a recepticle mounted outside on the porch.

The outside of the house is aluminum siding.

Several Questions:

1) Should I wire the three wires to an outside waterproof PVC box now?
1b) I was thinking of wiring a box into the house for the exterior recepticle, then running the three wires to a seperate exterior PVC box so I can eventually run conduit from there down to the ground.
2) It looks like I need to seperate the 30A from the other two to prevent having to derate. (i.e. two conduits?)
3) If I bury the line I have to dig down ~17" and put a plank on top. Is this correct?
4) Would I be better just running PVC conduit underground (or 2 conduits)? Would this let me dig less deep? It's not very far, maybe 20'
5) Can I just use a wood 4x4 as a lamppost and run the wires in PVC up the post?

Thanks

[Homer]

...I'm assuming what one normally does is run regular NMD to an access box on the wall and then run NMWD through conduit underground.You can run the cable in the conduit if you wish but since you are going to use planks, why not just use conduit at the point where the cable goes below grade (a few feet only).

It looks like I need to separate the 30A from the other two to prevent having to derate. (i.e. two conduits?)Don't run all three circuits in the same conduit.

If I bury the line I have to dig down ~17" and put a plank on top. Is this correct?Yes.

Can I just use a wood 4x4 as a lamppost and run the wires in PVC up the post?PVC up the post in a driveway would still be exposed to damage. Rigid metal would be OK.

Homer

[suemarkp]

Why not three circuits in the same conduit? Are canadian derating rules different than US rules? Under the NEC, with THWN-2 type wire you can have 9 wires before you can't use the normal 60C ampacity.

[Mr Fixit eh]

The following is from the ESA website on direct-burial requirements:

Question
What does the Ontario Electrical Safety Code require when burying a non metallic sheathed cable (NMSC) supplying a shed, a detached garage, a post mounted receptacle, a 120 volt light fixture in my yard, or similar things?


Answer
The Code requires non metallic sheathed cable to be buried at least 600 mm (24") below non-vehicular areas and 900 mm (36") below vehicular areas. An example of a vehicular area is a laneway, an example of a non-vehicular area is a lawn.

The Code permits these depths to be reduced by 150 mm (6") where mechanical protection is placed in the trench above the cable.

Direct buried cables shall also be surrounded by at least 75 mm (3") of 6 mm (1/4") nominal screened sand or earth.

A suitable electrical warning marker tape shall be buried along and above the cable route and be located approximately halfway between the cable and finished grade.

Where mechanical protection is used for reduced depth, it shall consist of one of the following and, when in flat form, shall be wide enough to extend at least 50 mm beyond the conductor, cables, or raceways on each side:

(a) Treated planking at least 38 mm thick; or

(b) Poured concrete at least 50 mm thick; or

(c) Concrete slabs at least 50 mm thick; or

(d) Concrete encasement at least 50 mm thick; or

(e) Other suitable material.

Ontario Electrical Safety Code Rule 12-012.

[Homer]

Why not three circuits in the same conduit? Are canadian derating rules different than US rules? Under the NEC, with THWN-2 type wire you can have 9 wires before you can't use the normal 60C ampacity.The CEC is much stricter in the area of ampacity and deration. In this case the small gauge wires (#14, 12, &10) have a starting point for deration of 15A, 20A, & 30A respectively as per Table 2 of the CEC. Rule 4-004 states that the deration factors of Table 5C be used if there are 4 or more current carrying conductors. The factor for 4 to 6 conductors is 0.80 .

Compared to the NEC, the same wires have a starting point for deration of 25A, 30A, & 40A respectively as per table §310.16. For 4 to 6 conductors a deration factor of 0.80 is also prescribed but this still leaves the derated ampacity above the 60°C ampacity.

Homer