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Code Question: Residential Elec Equipment Mfg Suggests Running 120v Conductors In Conduit Without Neutral

etbrown4

Mechanical
Apr 16, 2012
28
A similar thread was posted last week but this identifies the issue more clearly.

Reliance Controls makes manual residential generator transfer switches and sells them by the thousands.

On a 6 circuit 30a transfer switch and panel, Instructions tell the installer to route 6) 120v hot wires from 6) breakers in a panelboard out on 6) #12g red conductors to the transfer switch, and back to the panel on 6) #12g black. No circut neutrals to be run.

It is simply a 14' loop on the hot side of these 6 circuits with no neutral present.

The 2 conduits for the 6 circuits are 3/4 pvc, however those conductors do pass through ferrous metal when entering the transfer switch cabinet and the main panel. There are 6 conductors per conduit.

Nec 300.3(b) requires all conductors of the same circuit to be in the same wireway.

Even though when connected we observe no heating at this point, doesn't the setup as described, appear to violate the Nec?
 
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Solution
I'm confused. Where are the circuit conductors connected to the load? At the panelboard, at the transfer switch, or both? Can you provide a one-line showing the circuits? Your other post said that the panelboard provided o/c protection when connected to the utility and the transfer switch provided o/c protection when connected to the generator.
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Personally, I'd be more concerned about the lack of grounds in your description.
 
Ferrous Encirclement is an effect of unbalanced currents.
If the conductors of each circuit are in the same conduit, the currents will cancel and thee rule is complied with.
If you use on conduit for outgoing and on conduit for return, you are in violation.
Of more concern is the lack of a neutral.
Each conduit should have a neutral sized to carry the most possible unbalanced current.
For three 15 Amp circuits in a conduit that may be a neutral ampacity of 30 or 45 Amps.
Be aware that there is a lot of stuff on the market that is not approved nor code compliant.
 
Personally, I'd be more concerned about the lack of grounds in your description.
From the information in another thread, they are calling for an external Equipment Grounding Conductor and calling it a neutral.
 
I'm confused. Where are the circuit conductors connected to the load? At the panelboard, at the transfer switch, or both? Can you provide a one-line showing the circuits? Your other post said that the panelboard provided o/c protection when connected to the utility and the transfer switch provided o/c protection when connected to the generator.
 
Solution
From the Reliance website:
(A) Arrangement to Prevent Objectionable Current. The grounding of electrical systems, circuit conductors, surge arresters, surge-protective devices, and conductive normally non–current-carrying metal parts of equipment shall be installed and arranged in a manner that will prevent objectionable current.

(B) Alterations to Stop Objectionable Current. If the use of multiple grounding connections results in objectionable

current and the requirements of 250.4(A)(5) or (B)(4) are met, one or more of the following alterations shall be permitted:

(1) Discontinue one or more but not all of such grounding connections.

(2) Change the locations of the grounding connections.

(3) Interrupt the continuity of the conductor or conductive path causing the objectionable current.

(4) Take other suitable remedial and approved action.



Basically, the Code says, if something doesn’t work properly because of multiple neutral-to-ground bonds, then fix it. But if your generator is wired such that the twist-lock is not GFCI protected (only the 5-15’s are), then when you plug that generator into your Pro/Tran, everything works fine. And if it doesn’t you can un-bond it.
Th twist lock should be 4 pole;
Line 1, line 2, Neutral and Ground.
For many tears, the NC allowed some equipment such as electric ranges to be grounded by the neutral conductor.
1. If you have a four pole twist-lock and cable, then lift the neutral-ground jumper at the generator. Run a proper neutral and an equipment grounding conductor.
2. If you have a three twist-lock and cable, change it out for four pole equipment.
3. If you are stuck with three pole equipment, Then leave the neutral-ground jumper at the generator, run a properly sized neutral in each conduit and let the neutral ground the generator and the transfer switch..
While this is not code compliant it once was (or close to it).
 
Jgrist, you have the overcurrent protection stated correctly.

Think of it this way. The 6 circuits with loads were originally connected to 6) sp 15a breakers in the main panelboard. This particular brand of transfer switch requires that those 6 conductors become detached from their original respective breakers.

6) new 12g red conductors run from the original 6 breakers out to the transfer switch, and those circuits then extend back to the main panelboard on 6) black 12g conductors and are connected to the original circuit wires which had been attached to the 6 panelboard breakers.

So as mentioned the 6 hot wires out and back just form a loop. The switch mfg calls for no neutral to run with them. By running these circuits thru this transfer switch, the switch can manually select them to be powered by gen or utility.

They are run in pvc, and no heating has been detected, though it seems this setup must violate Nec 300.3b.

Both the main panel and tsf switch are grounded. The neutral conductors for the original 6 circuits are left as found in the original panelboard. The neutral ground bond occurs in the main panelboard.
 
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Where are the circuit conductors connected to the load?
This will be a multi-pole transfer switch.
The load conductor will be removed from the breaker and spliced to a conductor running to the transfer switch.
The conductor will be connected to the load side of a transfer switch pole.
A conductor connected to the normal-power side of the transfer-switch-pole will return to the existing panel and connect to the original breaker.
The standby side of the transfer switch pole will be connected to the local breaker which will be fed from the generator bus.
This is basically a single circuit transfer repeated six times on a Six-Pole-Double-Throw switch.

Not: this is a violation of the Canadian code.
The load conductor will be removed from the breaker and spliced to a conductor running to the transfer switch.
 
At least some of those come with all the inter-panel wires and a piece of flex to connect to the main panel and the whole thing is UL listed, so it seems like it's been proven as OK.
 
At least some of those come with all the inter-panel wires and a piece of flex to connect to the main panel and the whole thing is UL listed, so it seems like it's been proven as OK.
That is a different system.
Most of those that I have seen, and I have had to correct one installation, have a sub panel connected to the generator by a flex and cables (That we hope are long enough).
A sub feed breaker is installed in the existing panel and the new panel is wired as a sub panel.
Each circuit is removed from the existing panel and reconnected in the new sub panel.
The panel under discussion is switching each individual circuit.
The panel under discussion has the following possible code violations:
1. Magnetic encirclement, (When running on the generator).
2. Using the main panel as a junction box. (Not allowed in Canada).
3. Apparently using one conductor as a combined equipment grounding conductor and a neutral.
For what it's worth, Lionel, these systems seem to be aimed at the DIY market.
I am not a fan of the pre wired sub-panel systems for residential standby and less a fan of the individual circuit switching systems.
That said, there are niches such as standby only for emergency lighting and critical loads where I may use one of these systems, but field installed, not pre-wired.
 
It seems clear that Waross and other posters have a clear understanding of the wiring of the Reliance switch under discussion.

As per the Reliance diagram, in our installation, we have run a seperate #10 ground and #10 neutral from the main panel, seperately to the ground terminal and seperately to the neutral terminal on the incoming gen receptacle on the transfer switch. There is no neutral buss or bar in the transfer switch.

Waross mentions possible magnetic encirclement during generator operation. Please note that there is a continuous neutral and separate ground from the gen, through the receptacle in the transfer switch back into the main panelboard. Based on this do you still see an encirclement possibility there?

Originally we followed the mfg diagram and did not run neutrals in 2) 3/4 pvc conduits carrying 6) 15a hot circuit wires each, 3 out to the transfer switch and 3 back to the panelboard .

Subsequently a #10 neutral was added to each conduit with one end each connected to the main panelboard neutral bar, and the other ends connected to the neutral terminal on the incoming gen power receptacle on the transfer switch.

What's notable is as mentioned, the 6 circuit hot wires are essentially a loop in the hot leg of each of those original panelboard circuits, and the neutral for each of those 6 circuits does not run with them as extended. Even though we ran two extra neutrals as noted, they are actually not in the specific electrical circuits of those 6 extended hot wires, and are not functioning neutrals for those 6 circuits.

Even though wired per the mfg instructions or exceeding them, does the previous paragraph cause a concern for magnetic encirclement on those conductors?
 
Actually, not at those current levels. Magnetic encirclement becomes a real issue at 200 Amps and above.

If Reliance has an approval on their method, then I'll step away and stop preaching "Best Practice" methods.
 
Waross made the statement that there also might be magnetic encirclement with the generator connected.

I explained the continuous neutral from the gen, to the receptacle on the transfer switch and back to the panelboard. Clarifying that, do you still have a concern there when the gen is providing backup power?
 
Subsequently a #10 neutral was added to each conduit with one end each connected to the main panelboard neutral bar, and the other ends connected to the neutral terminal on the incoming gen power receptacle on the transfer switch.
That sounds good. Remember to try to lift the neutral to ground connection at the generator if possible.
If it is not possible to lift the neutral to ground connection at the generator, live with it. At these current levels an negative effect will be negligible.
 
Waross and other comments are most appreciated.

Many posters seemed unaware that this type of transfer switch is available. I see it as somewhat like a large 6 pole, 3way switch.

I gather that Waross's initial concern over likely magnetic heating "when the gen is connected," is now less a factor, after i shared that neutral and grount are continuous through the gen cord, the switch enclosure, and back to the panel, and they are isolated from each other. Has op surmised correctly?

Op does understand that it is preferred that ground and neutral are isolated in the gen as well, if possible.
 
That is a different system.

No, the "some of them" is this one, basically the same thing but also including the inter panel connection wiring parts.

I don't get the "instructions" saying no neutral or ground, those connections are required to complete the circuits. I can't see any magnetic fields being a problem at these current levels.

1740489999448.png
 
Lionel, you basically have the correct transfer switch.

What did you mean by, "No, the "some of them" is this one, the same thing. "
If you meant the above pic you posted is right, then we agree.

So I'm pretty sure Waross agrees and is on the same page.

What I have asked about from the onset is about the lack of 6 individual circuit neutrals, as those are not in the Reliance drawing. That drawing just shows the hot only circuit conductors being looped over to the transfer switch in red and back on black.

There is a single neutral shown and it is to be connected to the neutral buss in the main panel on one end and to the neutral screw on the input receptacle for the generator cord. Nowhere else.

Waross seems to believe that because these are 15a circuits and we have only 6, that apparently the risk of magnetic heating is low.

So Lionel or others, what is your view?
 

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No, the "some of them" is this one, basically the same thing but also including the inter panel connection wiring parts.

Thanks for the picture, Lionel.
This is the first that I have encountered this system.
Thank you for adding to my knowledge.
I have seen quite a few pre-wired sets on display. All of the pre-wired display sets I have seen have been the sub-panel type with automatic transfer switch.
Some comments;
Your posted information shows all conductors in the same flexible conduit. No problem.
Magnetic encirclement is an issue with unbalanced currents. The wiring layout shown will be balanced currents whether on normal or standby power. No problem.
The picture shows both a green grounding conductor and a white neutral conductor. No problem.
The neutral conductor is not needed when running on normal power. The wiring is basically switch legs which do not need a neutral. The neutral is needed when running on generator power.
A couple of issues;
The diagram (etbrown4) shows a two-pole, 240 Volt breaker. The generator connection in the picture (Lionel) is suitable for only 120 Volts.
The diagram posted by etbrown4 shows a 240 Volt circuit. While the transfer switches are linked, there should also be a link on the two breakers in the transfer switch.
In Canada, the splices in the breaker panel would not be allowed. The circuits would be taken out to a junction box and the splices made there.
Both Lionel's picture and etbrown4's diagram show the wiring properly run in one flexible conduit.
For two conduits, I would run both the outgoing and return conductor of each individual circuit in the same conduit. That is don't split a circuit between both conduits.
Include a ground and a neutral in each conduit and I will be satisfied. Why? I'm fussy.
 
Waross seems to believe that because these are 15a circuits and we have only 6, that apparently the risk of magnetic heating is low.
Six 15 Amp circuits running at 12 Amps each on a 120 Volt supply may have an unbalanced current of 72 Amps if the out-going conductors are in one conduit and the return conductors are in a second conduit. Hence my advice to keep both hot conductors and a neutral in the same conduit.
With a neutral conductor in each conduit, the neutral currents will tend to split in such a way as to minimize unbalanced current.
 
Gentlemen, One pic shows a 4 circuit, all 120v transfer switch. The other shows a 6 circuit switch with 1 240v circuit and 4 120v circuits. They are basically the same. We're doing all 120v.

As I've often said, we ran 2 pvc conduits between tsf sw and main panel at a 14' distance. We ran 3 red 12g hot wires, and 3 black 12g return wires in each conduit. Though the neutral pictured, is NOT part of those 6 circuits, we ran one in each conduit anyway. It is not connected to the transfer switch, except to the neutral terminal on the incoming receptacle on the front of the transfer switch, receiving power from the gen.

Waross mentioned that those 6 circuits are like switch legs and require no neutral. I described them as a loop out of the main panel and back. Same thing. That's what Reliance pictures, however we have the Nec and 300.3b.

I'm a rules guy and if the Nec says, in a conduit you must run the neutrals that are part of the circuit with the hot wires. The Reliance instructions and pic seems to violate the Nec.

On the other hand we observe no heating in 5 days of operation, but all so far has been in "utility" mode. Nonetheless, isn't it true that even in "utility" mode the 6 hot wires are run out and back in conduits to the transfer switch without the actual neutrals for those 6 circuits? The actual neutrals for those exact circuits begin at the main panel neutral buss and are instead routed all over the residence in romex, basically returning to the breakers in the main panel, because it is "ac", it is alternating current with the black wire in the romex.

Waross seems to be saying it's low current so it should be ok. What say others?
 

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