dual voltage from ocpd,referencing an old post.

[milwaukeesteve]

Re: dual voltage from ocpd,referencing an old post.

Again, I am still waiting for a reason that this is correct.
The exception #2 is not valid because that is for multiwire branch circuits.

The NEC allows branch circuits and multiwire branch circuits.
What we are talking about is neither.
The NEC doesn't say anynthing MULTI CIRCUIT BRANCH WIRES. That's what you guys are talking about with multiple circuits sharing a phase conductor.

I have asked for this several times, but nobody has explained anything beyond exception#2, 'the NEC doesn't say not' and 'steve you are getting rediculous'.

Thanks alot

 

[don_resqcapt19]

Re: dual voltage from ocpd,referencing an old post.

I still don't understand where this circuit is a hazard.

 

[hurk27]

Re: dual voltage from ocpd,referencing an old post.

By Steve: The NEC allows branch circuits and multiwire branch circuits.
What we are talking about is neither.
The NEC doesn't say anynthing MULTI CIRCUIT BRANCH WIRES. That's what you guys are talking about with multiple circuits sharing a phase conductor

Now Steve for the purpose of the NEC A multiwire branch circuit has been given a definition:

Branch Circuit, Multiwire. A branch circuit that consists of two or more ungrounded conductors that have a voltage between them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system.

This clearly states that a multi wire circuit is simply a circuit consisting of two hots and a neutral. The two hots have voltage between them, and the neutral has equal voltage between it and each hot.

So any branch circuit that has two hots and a neutral is a multiwire branch circuit!

It does not say anything about any loads it serves or what the voltage of the load is.

A dual voltage receptacle that has two hots on different legs in the panel (voltage between them) and a neutral (equal voltage to each hot) is being fed by a multiwire branch circuit period!

Now 210.4(C) states:

(C) Line-to-Neutral Loads. Multiwire branch circuits shall supply only line-to-neutral loads.

so if each circuit of a multiwire circuit is fed from a single pole breaker then we can only supply line to neutral loads.
But:

Exception No. 1: A multiwire branch circuit that supplies only one utilization equipment.

This allows us to use the multiwire circuit with line to line loads to feed one piece of equipment

Exception No. 2: Where all ungrounded conductors of the multiwire branch circuit are opened simultaneously by the branch-circuit overcurrent device .

Now if we feed both circuits from a two-pole breaker we can also feed line to line loads at the same time.

An exception to a rule is a permission to a rule to allow something that was not allowed. But requirement's within an exception is a requirement that safely allows us to deviate from a requirement.

Allowing line to line loads would be dangerous as you have stated because of voltage feedback through the 240 volt load, A good case of this is when a single fuse blows on leg "B" feeding a trailer home and the electric water heater passes voltage from leg "A" through the element to loads on leg "B" But the requirement in the exception to 210.4(C) only allows this installation if both legs (A&B) are both disconnected in the event of a overload or short. With both legs being disconnected there is no danger anymore. This is why it is allowed as long as you do what the exception Say's in this case "protect both legs with a two-pole breaker rated for the load.

I hope this will open your mind up as we are all here to learn. I have learned many things that I would have made large bets that I was right. I have also learned that the more I stay open minded the more I can learn.
Threads like this has been my biggest learning tool as it makes me dig deeper to find the truth and I have been wrong many times I'm just human.

 

[milwaukeesteve]

Re: dual voltage from ocpd,referencing an old post.

Hey Wayne, thank you for the lengthy response. In that you did state things that are correct. There are two exceptions. (1) allows L-L loads if going to feed One piece of equipment. (2) when all phase conductors are disconnected.

Neither of these exceptions fit this argument that we are discussing. We are not using this for One piece of equipment. We were originally talking about a well pump and a sump pump. The second exception states ONLY that if all phase conductors are handle tied. It says nothing about sharing on of those poles for two different types of loads.

Again nobody is telling me why or how you can justify this. I don't want to hear 'the NEC doesn't tell me no'.
Anything else is welcome. I am open to hearing arguments, but not hearing that I am being rediculous.

 

[don_resqcapt19]

Re: dual voltage from ocpd,referencing an old post.

Steve,

The second exception states ONLY that if all phase conductors are handle tied. It says nothing about sharing on of those poles for two different types of loads.

First it doesn't permit the use of "handle ties", it requires a common trip device. Second the exception is silent about the type of load(s) served. There are no restrictions on what loads I can serve from this circuit. Again, there is not a code or safety hazard here. It is a design issue, not a code issue.
Don

 

[milwaukeesteve]

Re: dual voltage from ocpd,referencing an old post.

I stand corrected, Don. It does say common trip, and not 'handletied togther'.

I cannot argue my point anymore.

If I don't want to wire it this way, I won't.
Would I suggest anyone else wire it this way? No.
Can I prove it to them why not? I don't know.

 

[iwire]

Re: dual voltage from ocpd,referencing an old post.

After thinking on this thread for a while it came to me I should be installing this outlet...



I find that most office copy machine require either a 20 amp 120 volt or 20 amp 208 volt outlets.

[ July 09, 2005, 03:50 PM: Message edited by: iwire ]

 

[peter d]

Re: dual voltage from ocpd,referencing an old post.

But Bob, you can't, that would be poor wiring practice!

 

[physis]

Re: dual voltage from ocpd,referencing an old post.

Well I can't stay out of this thread forever.

Like a week ago, I was looking through the book (because of this thread) and it looked to me like a 240 v. circuit with a neutral is a multiwire branch circuit even when it supplies a single 240 v. load. I've never thought of 240 v. that way. Would you guys agree with that?

 

[peter d]

Re: dual voltage from ocpd,referencing an old post.

Sam, I don't quite understand what you are saying.

 

[LarryFine]

Re: dual voltage from ocpd,referencing an old post.

Originally posted by physis:
Well I can't stay out of this thread forever.

Like a week ago, I was looking through the book (because of this thread) and it looked to me like a 240 v. circuit with a neutral is a multiwire branch circuit even when it supplies a single 240 v. load. I've never thought of 240 v. that way. Would you guys agree with that?

Yes, I would agree: you've never thought of it that way.

That suggests that, say, a water heater, being a line-to-line load, is not a multi-wire circuit, while, say, a clothes dryer, with both line-to-line (heating element) and line-to-neutral (motors, etc.) loads is a multi-wire circuit.

The debate appears to be whether the line-to-line and line-to-neutral loads must be within a single piece of equipment. In my opinion, the answer is "no", they need not be.

 

[peter d]

Re: dual voltage from ocpd,referencing an old post.

Doh! Ok, I get it now. We could consider all services multiwire circuits too. Also strange, but electrically it is no different.

 

[iwire]

Re: dual voltage from ocpd,referencing an old post.

Originally posted by LarryFine:
That suggests that, say, a water heater, being a line-to-line load, is not a multi-wire circuit, while, say, a clothes dryer, with both line-to-line (heating element) and line-to-neutral (motors, etc.) loads is a multi-wire circuit.

If we go by the definitions the utilization equipment is not the deciding factor.

If you ran a neutral to a 240 volt water heater and left it capped and unused at the water heater it would still be a multiwire branch circuit.

 

[physis]

Re: dual voltage from ocpd,referencing an old post.

Thanks for agreeing Larry, I think.

 

[physis]

Re: dual voltage from ocpd,referencing an old post.

By Peter:

Sam, I don't quite understand what you are saying.

 

[iwire]

Re: dual voltage from ocpd,referencing an old post.

Originally posted by peter d:
We could consider all services multiwire circuits too. Also strange, but electrically it is no different.

Yes electrically the same thing.

But keep in mind that we where talking about 210.4 which is multiwire branch circuits.

That puts feeders and service conductors out of the discussion.

There is no 'Serve only line to neutral loads' for services or feeders......thankfully.

 

[peter d]

Re: dual voltage from ocpd,referencing an old post.

Originally posted by iwire:
But keep in mind that we where talking about 210.4 which is multiwire branch circuits.

Don't worry Bob, I can assure you that I wasn't confused about that.

 

[roger]

Re: dual voltage from ocpd,referencing an old post.

I like using 4 of the duplex receptacles Bob has posted around the perimeter of an office area, each on its own 20 amp MWBC, with a #4 neutral common to all 4 circuits, This way you only have one neutral to land in the panel.


Roger

[ July 09, 2005, 05:28 PM: Message edited by: roger ]

 

[iwire]

Re: dual voltage from ocpd,referencing an old post.

Originally posted by roger:
each on its own 20 amp MWBC, with a #4 neutral common to all 4 circuits,

Now Roger you can not twist the code so it fits your point of view.

That is not workmanlike.

The NEC does not tell you to keep your fingers out of the mower blades but you would not do that either.

[ July 09, 2005, 05:38 PM: Message edited by: iwire ]

 

[peter d]

Re: dual voltage from ocpd,referencing an old post.

Originally posted by roger:
I like using 4 of the duplex receptacles Bob has posted around the perimeter of an office area, each on its own 20 amp MWBC, with a #4 neutral common to all 4 circuits, This way you only have one neutral to land in the panel.


Roger

Roger, how dare you suggest that! You would fry an awful lot of equipment if that neutral ever opened!!