Wire gauge & conduit sizes

[Unregistered]

I'm making the assumption that the CEC specifies which type and gauge of wire should go into a particular size of conduit. For example, I know I can fit 12/3 in a 3/8 PVC conduit, but is it permitted? Is there a table somewhere?

Thanks!

[Homer]

I'm making the assumption that the CEC specifies which type and gauge of wire should go into a particular size of conduit. For example, I know I can fit 12/3 in a 3/8 PVC conduit, but is it permitted? Is there a table somewhere?

Thanks!Try this link to a PDF Handbook (http://www.nexans.ca/egy/tecdoc/ElectriciansHandbook/elec-hbk.pdf).

Remember that 1 cable can only fill a conduit to a maximum of 53% area under Canadian and US rules. Also, you need to use the largest dimension as the diameter when calculating the cross sectional area of the cable.

Homer

[fletch49]

I am roughing in the wire for my new spa arriving soon!

I have a question regarding table 6 of the Electricians Handbook...conductor sizes/conduit sizes. I want to run a 3/4" liquid-tight conduit with #6/3 wiring for a SPA.

Table 6 says one conductor per 3/4" conduit. Is a conductor one wire or the whole bundle (2 hot, 1 neutral, 1 ground)?

Basically, can I run NMD90 6/3 wire through 3/4 liquid-tight rubber conduit in a 30' run?

[Homer]

Basically, can I run NMD90 6/3 wire through 3/4 liquid-tight rubber conduit in a 30' run?No!

First of all you can only use liquid-tight for the length that you need the flex, up to a rule of thumb of 5 feet.

Second, Table 6 that you are refering to states that four #6 T90 conductors can fit in a 3/4" conduit. A 6/3 +ground cable will be much bigger and isn't covered by the table.

Table 9 gives the approx. cross-sectional area of 3/4" conduit as 0.53 sq. inches.

The cross sectional area of NM 6/3 is 0.3318 sq. inches (Southwire info) and you are only allowed to use 53% of the conduit area if you have 1 cable. This is over at about 63% fill ratio. You need 1" not 3/4".

The wiring of a spa is not something to guess at. You need to be very careful with this.

You need a GFCI and a disconnect switch for the spa. Why don't you just use the flex from the disconnect onward.

Make sure that you have this inspected to make sure that you have done everything safely.

Homer

[fletch49]

Thanks!

I was going to rough-in the wiring but, perhaps, I'll let the electrician handle it.

I wonder why Cutler-Hammer makes the maximium openings 3/4" on the knock out tabs at the bottom of the 50amp GCFI enclosure. I need to run the wire from the bottom of the GCFI enclosure. I suppose the electrician will run 1" to the unit then reduce it to 3/4".

Thanks for your help.

[Homer]

I suspect that the electrician will not use a single 6/3 cable but will use three #6 and one #10, T90 conductors in a 3/4" conduit.

As I mentioned, the table showed you that four #6 T90 conductors can be placed in 3/4" conduit.

BTW, Cable should only be run in conduit in short lengths to protect against damage. Individual conductors are intended to be run in conduit.

Homer

[fletch49]

What if I pull the sheith off of the NMD90 nylon wiring and run that in 3/4" conduit? Or should I just purchase T90. What about RW90 would that be better?

[Homer]

What if I pull the sheath off of the NMD90 nylon wiring and run that in 3/4" conduit?Technically, that would be a violation but some do get away with it.

It will be easier to use the T90/TWN75 dual rated conductors that are stranded.

Where are you placing everything?

Homer

[fletch49]

It's being run from the panel in the basement, through a bulk head to the back of the house, up 5 feet to the attached walk out deck. The GFCI will be placed on the deck approx 15' away from the tub, and the wiring will be routed back under the deck and run along the joists, then back up to the tub on the other end of the deck.

Should I run a #6 bond wire in addition to the 2Hot, 1Neutral and ground?

No worries if these are dumb questions...I AM NOT wiring the tub. My kids will be using this tub. I just don't want my brother, the electrican to show up from FLorida next week and have me remove everything that I have done.

Thank for all your help

[Homer]

Should I run a #6 bond wire in addition to the 2Hot, 1Neutral and ground?If you are running #6 for the two HOT(blk&red) and Neutral(wht), you can run a #10 for the ground(grn) to the spa. In addition, any conductors forming the bonding grid of any metal parts will be in and around the spa, and will incidentally interconnect to the grounding conductor.

The spa instructions should list any bonding points.

BTW, are you sure this spa needs a neutral (wht) conductor? Are there any 120V loads within the unit in addition to the 240V loads?

Homer

[fletch49]

The manual does call for a neutral hook up. I did read through the manual and it does indicate two bonding lugs are to be hooked up to the local common bonding grid.

My guess is the 'local common bonding grid' is the existing bonding grid established in the home panel. Is this right?

[Homer]

Any hardwired appliance has a grounding conductor along with the circuit conductors. This conductor is typically bonded to a motor frame or appliance chassis.

In the case of an appliance like a spa with various metal components that are isolated from each other, those metal components are bonded together to guarantee that no voltage potential can develop between them.

It just so happens that these bonding points will also end up being joined to the motor frame which is already connected to the grounding conductor which goes back to the panel.

Homer

[Wgoodrich]

The second bonding system being the bonding grid [not bonding ground] is an entirely seperate bonding system than the equipment grounding of your electrical system.

The bonding grid is a number 8 copper wire interconnecting any piece of metal 4" square or larger associated with that hot tub. This bonding grid only connects noncurrent carrying metal parts of the hot tub within that hot tub area not leaving that hot tub area. It is not intended for the bonding grid system to be connected to the electrical systems equipment grounding or be connected to a ground rod. It only interconnects all pieces of noncurrent carrying metal parts associated with that hot tub not leaving that hot tub.

As stated before the bonding grid may incidentally interconnect with the equipment grounding system by noncurrent carrying metal parts within your motor for example where the bonding grid system connects to a lug mounted on the exterior of the motor unless double insulated while the equipment grounding conductor connects to the green screw in the junction box where the hot wires connect. This is what is called incidental connection. Not required but happens by nature of design within a component such as a motor.

The intent of a bonding grid system is to create equal potential between all noncurrent carrying metal parts 4" square or larger so current will not flow allowing shock risk. If current is equal to all pieces of metal all potential is the same thus current is nonexistant and can not happen.

Hope this helps

Wg