Which wire type to use?

[Ron1111]

Updating the Kitchen. 60 year old home has FMC (mostly 3/4") and every box is the old and overfilled.

1. Some say use the existing FMC, add bigger 1900 boxes and deep duplex boxes wherever you can and pull new #12
2. Abandon the FMC and go with correct size BX
3. Use Romex and new plastic boxes

My goal is not cost but longevity, safety and last what is easiest. I know this is all a bit vague and each has its merits.

 

[Jadnashua]

Trying to pull 12g wire may be a major pain unless you can access all of the corners and there are pull boxes (may not be the right term!) so you can get it around corners. 12g is required for the new counter receptacles, but the gauge for other bits would depend on the appliance or application. Any of the approved methods should work reliably.

 

[Sponsor]

 

[Ron1111]

True enough on pulling new wire, but the walls and ceiling are now stripped bare for access. Most of the circuits I'll need are home runs (all in the ceiling) to the main (about 20' away) except a couple that pass thru the ceiling boxes (hence the overfilled boxes). I should only need one or two new home runs, if that.
The one I am most concerned about is the counter-top outlets (now all one circuit) and I'll need two. Problem is that is a CMU wall with no access to add a 2nd circuit.
Most new dishwashers, fridges, microwaves require dedicated lines @ 15 or 20A so why just go with #12 and 20A breakers while you can easily.

 

[Jadnashua]

You can always go with larger wire (up to the ability of the device you attach to accept the wire size - it's not unlimited!), but it costs more, is harder to pull, is harder to bend back into the box. Go for it if you wish, it doesn't hurt and gives you the option of changing the breaker later if you wish. Keep in mind, generally, you can use a larger breaker than the device needs (up to the acceptable wire size) - the breaker is to protect the wiring, not the device. IOW, if you use 12g wire, you can wire it for 20A breakers if you wish (or 15A).

 

[Reach4]

You are still allowed to use multwire branch circuits (MWBC). Newer codes require a breaker like 240 volt breaker, where if you flip one side off at the breaker box, the other side goes dead too. This breaker need not open the other side if one side blows due to overload as a 240 volt breaker would. So 3 wires (plus ground if your conduit is not a suitable protective ground) will drive 2 120 VAC circuits.

http://ecmweb.com/code-basics/branch-circuits-part-1

 

[Cacher_Chick]

Just to clarify, you are required to have 2 circuits for the kitchen countertops, separate from any other devices.

 

[Ron1111]

Just to clarify, you are required to have 2 circuits for the kitchen countertops, separate from any other devices.

Yes, exactly, I will require two separate dedicated circuits (GFCI) for counter tops. That's the problem the outlet on one side of the sink supplies the power to those on the other side on the sink. They are embedded in the CMU and have no access other than thru the first outlet.

 

[Reach4]

Just to clarify, you are required to have 2 circuits for the kitchen countertops, separate from any other devices.

Could you clarify that? Are you saying that the two circuits cannot be MWBCs?

 

[Ron1111]

You are still allowed to use multwire branch circuits (MWBC). Newer codes require a breaker like 240 volt breaker, where if you flip one side off at the breaker box, the other side goes dead too. This breaker need not open the other side if one side blows due to overload as a 240 volt breaker would. So 3 wires (plus ground if your conduit is not a suitable protective ground) will drive 2 120 VAC circuits.

http://ecmweb.com/code-basics/branch-circuits-part-1

Thanks. A interesting option but other than saving one wire I don't see a big gain to go that way. I don't plan to use any conduit as a suitable ground

 

[Reach4]

A interesting option but other than saving one wire I don't see a big gain to go that way.

Sounds like you have already rejected option #1.

 

[Ron1111]

You can always go with larger wire (up to the ability of the device you attach to accept the wire size - it's not unlimited!), but it costs more, is harder to pull, is harder to bend back into the box. Go for it if you wish, it doesn't hurt and gives you the option of changing the breaker later if you wish. Keep in mind, generally, you can use a larger breaker than the device needs (up to the acceptable wire size) - the breaker is to protect the wiring, not the device. IOW, if you use 12g wire, you can wire it for 20A breakers if you wish (or 15A).

Thanks for the advice. I will use #14 for lighting but with these new big appliances #12/20A makes more sense. Not worried about cost as much as box capacity and #14 does have the advantage there if it will handle the load and meet code.

 

[Ron1111]

Sounds like you have already rejected option #1.

Why do you say that? Your suggestion of a MWBC could still be used with any of the options.

 

[Reach4]

Why do you say that? Your suggestion of a MWBC could still be used with any of the options.

If you are trying to pull 12 AWG wires yourself through a 1/2 inch Sealtite etc flexible conduit , I would think that 4 wires instead of 5 would be significant.

The new wires would probably have thinner insulation than the existing wire, but it is tough durable insulation. THHN has an outer coating of nylon-- that is what the N stands for.

Are you aware of "pulling compound"? That is a lubricant that is made for the purpose and makes pulling wires through conduit easier.

 

[Cacher_Chick]

Could you clarify that? Are you saying that the two circuits cannot be MWBCs?

No, they can be.

 

[Cacher_Chick]

Yes, exactly, I will require two separate dedicated circuits (GFCI) for counter tops. That's the problem the outlet on one side of the sink supplies the power to those on the other side on the sink. They are embedded in the CMU and have no access other than thru the first outlet.

We cut paths in CMU walls, install conduit and boxes, and then fill the cut back in with mortar.

 

[Ron1111]

If you are trying to pull 12 AWG wires yourself through a 1/2 inch Sealtite etc flexible conduit , I would think that 4 wires instead of 5 would be significant.

The new wires would probably have thinner insulation than the existing wire, but it is tough durable insulation. THHN has an outer coating of nylon-- that is what the N stands for.

Are you aware of "pulling compound"? That is a lubricant that is made for the purpose and makes pulling wires through conduit easier.

Ok, so your suggestion for MWBC is on my problem wall, the one that is CMU. Fortunately, almost all my FMC is 3/4" and I can replace the 1/2" easily. I thought the conduit running into the CMU was some version of Sealtite but on a closer look it is some kind of threaded rigid metal that was bent with sweeping 90s and run to the closest ceiling box. I guess in the mid to late 40s liquid tite flexible was not developed yet. And yes I am aware of pulling compound. I've pulled miles of communication wire and fiber cable in a past life.
Thanks for the ideas and info.

 

[WorthFlorida]

Just to let you know that the two required circuits for the kitchen counter top must be 12 AWG on a 20 amp breaker. In the 2014 NEC book, now reads that the kitchen disposer must be on a GFI circuit. Not sure if electrical inspectors are enforcing this yet.

 

[Ron1111]

That is correct, two independent 20A GFCI circuits. Won't be adding a disposal so good there. My new dilemma is the 2/4 rule. If I follow it strictly I will need to cut into the CMU to add a outlet 5" from the sink. And I hear the inspector always follows that rule. So I'm adding a under cabinet AC strip to meet that. Of course it must be GFCI, rated 20A with TR outlets! The day will come that every outlet has a lockout/tagout plate and a request form for power.

 

[Ron1111]

Update: Wiring is complete. All new 12g stranded was pulled with little effort (mostly). CMU wall was a bit of a problem but got the wire pulled without breaking up the wall. Code required dedicated circuits are in (only had to add 2 new home runs) and all passed inspection.

 

[Speedy Petey]

You have to also remember, if you are under the 2014 NEC pretty much everything in the damn house also needs AFCI protection, so MWBC's are almost out of the question since double-pole AFCI breakers are hard to find, and even harder to troubleshoot when tripping occurs.

And YES, you do need to meet current codes when rewiring.