New AC unit - Wiring, Code?

grandmumAugust 7, 2013

Thinking of getting new AC compressor unit. Currently the old has been supplied by 10/2 I think on a 30 amp breaker.

I live in Chicagoland, everything is in conduit. In my house that is the case.....except for this line and my dryer line.

Both have flexible black cable that houses the conductors (kind of like the flexible yellow romex). Is this against code?

Do you think its acceptable to use the new AC with the old flexible cable or will I be forced or would want to change it to rigid conduit?

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Ron Natalie

I'm not an expert on the Chicago Municipal code, but certain cables are permitted (MC, MI) in some circumstances. What does the writing say on the outside of the cable jacket?

    Bookmark   August 7, 2013 at 5:40PM
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The AC line reads
"Columbia 10/3 ground type UF sunlight resitant"

its a flater cable than the dryer line that reads:

"Type NM 8-8-3 with ground 600 volts"

Both of which run in ceiling joists about 40 feet between panel and appliance. AC been in service 30 years and the dryer for 15.

Its not municipal Chicago either, which may or may not have different codes than the surrounding area.

    Bookmark   August 7, 2013 at 6:10PM
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What size A/C unit do you have? 10/3 and 30A is rather small. My 4-ton A/C unit is 6/3 and 50A. If you are upgrading the A/C unit, that might force your hand to increase the wiring.

    Bookmark   August 7, 2013 at 8:27PM
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Generally speaking the closer you live to Chicago the more likely it is that non-metallic cable is prohibited. Of course, you can buy the stuff anywhere, so plenty of people use it. There are also some municipalities at allowed it, then disallowed it.

    Bookmark   August 7, 2013 at 8:49PM
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Ron Natalie

Well, I won't argue the vagaries of Chicago's code but the internal use of NM would be valid elsewhere.

I however, have concerns about using UF to connect between a disconnect and an external (freestanding?) AC compressor. This may not meet the requirements for support in exposed work and further may be subject to physical damage. Usually we use small pieces of flexible conduit ("appliance whips").

    Bookmark   August 8, 2013 at 7:21AM
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I have plenty of BX in the house, I wonder if indeed the UF needed replacement, can I just run BX for that kind of distance (40 feet)... that is something I would be comfortable in doing myself...... or should I prepare to have to have an electrician bend conduit for that type of run or do I even have to anything?

As far as beefing up the wiring, I dont have any idea on what size AC I will be getting and if that is needed. I assume it will be the same size as the old one has been satisfactory for its lifespan.

I am assuming if new wiring needs to be run that will be a significant increase in cost. And also beyond the scope of the HVAC installer, meaning I i will have to hire an electrician as well.

    Bookmark   August 8, 2013 at 8:11AM
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Ron Natalie

You can't run "BX" for anything. True BX hasn't been made in years. AC cable, often called BX these days, is NOT approved for outside. MC cable can be used for this when it's jacketed (and otherwise approved for wet locations).

This should *NOT* be a big deal. You haven't fully described your situation, but most places I've sen you have a disconnect (may or may not have fuses with it) mounted to the outside of the house and then something running between that disconnect and the compressor. It appears you have UF for that, which I would be leary of if it is just dangling there. Putting in a short piece of flexible conduit between the disconnect and the unit would neither be expensive nor difficult.

    Bookmark   August 8, 2013 at 9:20AM
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As it stands now the UF exits the basement and connects to the disconnect outside. From the disconnect to the unit it is already flex conduit.

Or are you suggesting that it should it be flex conduit for the portion exposed to the elements as well?

ANother thing I am curious about, where the UF cable should enter the panel there is a junction box set up next to the panel where the connections are wirenuted... a seperate pipe goes from panel to this junction box.

Is that a strange setup? Should the UF have gone directly into the panel?

    Bookmark   August 8, 2013 at 11:23AM
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Ron Natalie

OK, I misunderstood. UF should be fine for this as far as the NEC is concerned. The only proviso is that any UF that's exposed to the outside sun needs to be marked for such (UV resistant). Much of it is these days.

It's junction box to switch from the interior wiring to UF to get through to the outside isn't particularly strange.

    Bookmark   August 8, 2013 at 12:45PM
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thanks, maybe just to clarify about the junction box. Its not at the point it goes thru to the outside.

The junction box is directly next to the circuit panel instead of connecting the UF directly inside of the panel. Some 40+ feet away from where it exits the house.

Could be completely normal or another "unique" wiring issue I have discovered so far.

    Bookmark   August 8, 2013 at 1:33PM
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Ron Natalie

It's still little more than a curiosity as to why they did it that way. Perhaps the compressor got moved over time or some other construction occured on the house. There's nothing code-wise wrong with it and I'd not be concerned.

    Bookmark   August 8, 2013 at 2:17PM
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