subswitch box isolation

[Chris Bernhardt]

Do subswitch boxes and subswitches with overcurrent protection downline of the main panel have to have four conductor feeders and isolated ground and neutral busses?

For example those 220V subswitch boxes containing breakers or fuses that are usually added clustered around old panels to feed water heaters and clothes dryers etc.

Chris, Oregon

[Brian G]

If they're only 220v the fourth wire is unnecessary. There is no neutral on 220v.

Brian G.

In Neutral Today [:-sleep]

[Chris Bernhardt]

If they're only 220v the fourth wire is unnecessary. There is no neutral on 220v.

So only subswitches having grounded conductors would need a four conductor feed or only those that also have EGCs?

Chris, Oregon

[Brian G]

Originally posted by Chris Bernhardt

So only subswitches having grounded conductors would need a four conductor feed or only those that also have EGCs?

Only those with neutrals/grounded conductors need four wires. The 220v circuits will have the equipment grounds, but the third wire takes care of that on 220v.

What gets tricky is when someone uses a small 4 or 6 circuit panel as a 220v disconnect switch, leaving spaces open that some other knothead may hook-up for 110v later. Gotta warn 'em about those.

Brian G.

Fun Things to Explain to Average Joe [:-headach

[ghentjr]

"Do subswitch boxes and subswitches with overcurrent protection downline of the main panel have to have four conductor feeders and isolated ground and neutral busses?"

Yes.

"For example those 220V subswitch boxes containing breakers or fuses that are usually added clustered around old panels to feed water heaters and clothes dryers etc. "

A 240v switch box for one appliance only needs 3 wires.

[Brian G]

Originally posted by Chris Bernhardt

Do subswitch boxes and subswitches with overcurrent protection downline of the main panel have to have four conductor feeders and isolated ground and neutral busses?

For example those 220V subswitch boxes containing breakers or fuses that are usually added clustered around old panels to feed water heaters and clothes dryers etc.

I guess we need clarification here Chris. Are we talking about various fused 220v disconnect switches or sub panels with more than 2 circuits?

Brian G.

Should've Asked Before [:-indiffe

[Chris Bernhardt]

How about this. What number of conductors are needed to feed the following subswitches having overcurrent protection for:

Case 1: An old ungrounded water heater

Case 2: Newer grounded water heater

My guess for case 1 is just the two phases and for case 2 the two phases and an EGC.

I am thinking now that the only time an extra conductor is needed in the feed is when both a grounded conductor and an EGC is needed on the supply side of the subswitch. Is that correct?

Chris, Oregon

[Brian G]

Originally posted by Chris Bernhardt

How about this. What number of conductors are needed to feed the following subswitches having overcurrent protection for:

Case 1: An old ungrounded water heater

Case 2: Newer grounded water heater

My guess for case 1 is just the two phases and for case 2 the two phases and an EGC.

I suppose, but I would probably recommend adding an EGC to the first one anyway.

I am thinking now that the only time an extra conductor is needed in the feed is when both a grounded conductor and an EGC is needed on the supply side of the subswitch. Is that correct?

Not necessarily. Say you found a large 110v appliance with a disconnect switch. It needs both a grounded conductor and an equipment ground, but 3 wires will still cover that. No 4th is needed because there are no 220's there to use a second hot wire. Offhand I can't think of anywhere other than a sub panel where all four would be needed, but we see some weird stuff.

If it's a small panel, something like I described above, the extra spaces are problematic. Do you tell them to have it rewired as a sub panel even though it's only being used to disconnect one or two 220v appliances, or do you explain that it's okay as is, but no 110's can be added without rewiring the panel? I've done the second one a few times.

Feel free to jump in here Jim.

Brian G.

Technically Correct vs. Conservatively Practical [:-fight]

[Kyle Kubs]

Originally posted by Chris Bernhardt

How about this. What number of conductors are needed to feed the following subswitches having overcurrent protection for:

Case 1: An old ungrounded water heater

Case 2: Newer grounded water heater

My guess for case 1 is just the two phases and for case 2 the two phases and an EGC.

I am thinking now that the only time an extra conductor is needed in the feed is when both a grounded conductor and an EGC is needed on the supply side of the subswitch. Is that correct?

Chris, Oregon

If your talking strictly about electrical disconnects then it needs only the wires that are necessary to properly wire the appliance. Think about the disconnect for an A/C comressor...it is essentially a switch and requires no additional wiring then the appliance would without the disconnect. If your talking about a sub panel that will serve other circuits, then that, obviously is a different case, but if it serves only a single, dedicated appliance, ie. A/C compressor, water heater... then it is ony a disconnect, fused or not.

Also, Chris... it is not 2 phase. 220v appliances are still single phase. Unless of course your doing inspections in 100 year old industrial complexes. If you need more on this, ask, otherwise I will spare my carpel tunnel some punishment.

[Jim Katen]

Originally posted by Brian G.

. . . Feel free to jump in here Jim. . . Brian G.

Technically Correct vs. Conservatively Practical[/navy] [:-fight]

You & Kyle have it covered.

The only thing I'll add is that it's incredibly shortsighted to wire a sub-panel without a neutral. Someday, someone will want to add a single-pole circuit and they'll curse the cheap SOB who didn't run a neutral.

- Jim Katen, Oregon

[Kyle Kubs]

I'm just re-reading my own post and I think I could have been a little more clear... I think what I said about the disconnect is clear. But if I find a distribution box (could serve more then one circuit) and it is not wired with a four wire feed, even if right now it is only serving a single appliance (water heater...), if it has room to snap in another breaker and serve another circuit elsewhere at some time in the future, it is a sub panel and I would write it up as improperly wired.

[Brian G]

Originally posted by Kyle Kubs

But if I find a distribution box (could serve more then one circuit) and it is not wired with a four wire feed, even if right now it is only serving a single appliance (water heater...), if it has room to snap in another breaker and serve another circuit elsewhere at some time in the future, it is a sub panel and I would write it up as improperly wired.

I can understand that, I just don't think all cases are exactly the same. The few times I've left it at a warning about not adding 110's have all been alike. A 6 circuit raintite panel at the rarely-visited end of the house, being used to disconnect two condensers for two different HVAC systems. The HVAC guys did the wiring, they know squat about sub panels, and the supplier didn't have a 4 circuit panel the day they needed one. The expense of rewiring the panel correctly is significant. The danger of not doing so isn't (unless 110v circuits are added later).

In those circumstances I choose to explain things to the client and let it go, but I wouldn't fault any other inspector for seeing it differently.

Brian G.

Speaking Only For Myself [:-cyclops