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Old 02-05-2012, 07:47 AM   #1
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Can I mix conduit and romex


Hello all.

I am working on a septic Alarm project (I currently don't have an alarm).

I have become convinced that PVC conduit from the house to the septic pump tank is the best way to go. In that conduit, as I understand it, I want to run #12 stranded THHN. So for power to the pump the wires will be one black, one white, and one green. (The pump is 110/20 amp half horsepower)

Because I am thinking about keeping the alarm inside the basement, I will need to also run wires through the same conduit for the alarm float switch. What color and size wire should these be?

Finally, here is the hard question. From the main service panel to the point of penetration for the conduit is ~20 feet. What I would like to do is run #12/2 with ground romex. In the junction box at the point where the conduit penetrates the wall I would like to put a plug for the alarm.

So here is what would be in the junction box.

1-plug
splices going from romex to stranded THHN
2 wires passing through for the alarm float switch

Is any of this legal (VA, USA)?

Otherwise I will buy an external alarm and pump control panel. Run romex from main service panel to a junction box. Switch to stranded THHN for the run inside the pvc conduit which goes to the septic control panel at the septic pump chamber.

Thank you,
Fred

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Old 02-05-2012, 07:58 AM   #2
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Can I mix conduit and romex


What's the voltage of the float switch?

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Old 02-05-2012, 08:22 AM   #3
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I see no problem doing it that way.
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Old 02-05-2012, 08:33 AM   #4
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Can I mix conduit and romex


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What's the voltage of the float switch?
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I see no problem doing it that way.
I agree, but if the float switch is low voltage make sure the wiring going to it is rated as high or higher than 120 volts.
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Old 02-05-2012, 08:39 AM   #5
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Can I mix conduit and romex


As long as you use the same thwn rated wire you are using for the pump no problem running them in the same conduit, not matter what the voltage. It's the insulation rating of the wire that is important. Use any colour you wish except for green for the alarm.
No problem with the junction box either.
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Old 02-05-2012, 08:49 AM   #6
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As long as you use the same thwn rated wire you are using for the pump no problem running them in the same conduit, not matter what the voltage. It's the insulation rating of the wire that is important. Use any colour you wish except for green for the alarm.
No problem with the junction box either.

joed, let me make sure I get this one right. You can run mixed voltage in the same conduit as long as the wire has the same rating, to match the highest voltage/amps?

Writer’s information is for discussion purpose only and should be confirmed by an independent source.
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Old 02-05-2012, 08:55 AM   #7
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joed, let me make sure I get this one right. You can run mixed voltage in the same conduit as long as the wire has the same rating, to match the highest voltage/amps?

Writer’s information is for discussion purpose only and should be confirmed by an independent source.
That is correct.
The lowest voltage wire has to have the same rating as the highest voltage wire.
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Old 02-05-2012, 08:58 AM   #8
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That is correct.
The lowest voltage wire has to have the same rating as the highest voltage wire.

I know these things, just can't remember why anymore.
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Old 02-05-2012, 09:00 AM   #9
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joed, let me make sure I get this one right. You can run mixed voltage in the same conduit as long as the wire has the same rating, to match the highest voltage/amps?

Writer’s information is for discussion purpose only and should be confirmed by an independent source.
That is correct. Also note that wire being underground must be THWN rated. It was stated as THHN in the original post. However most THHN is also rated THWN. Just make sure it is dual rated.
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Old 02-05-2012, 09:01 AM   #10
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I know these things, just can't remember why anymore.
I usetacould do things I can't do now
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Old 02-05-2012, 09:17 AM   #11
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That is correct. Also note that wire being underground must be THWN rated. It was stated as THHN in the original post. However most THHN is also rated THWN. Just make sure it is dual rated.
yes I know this thanks.
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Old 02-05-2012, 09:21 AM   #12
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I usetacould do things I can't do now
Yeah I know this feeling too. I used to be able to jump fences fast, I still can. Just slower, because now if I fall I lay there for awhile before I get up.
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Old 02-05-2012, 09:52 AM   #13
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I agree, but if the float switch is low voltage make sure the wiring going to it is rated as high or higher than 120 volts.
True, just using all 600 volt wiring is the easiest way but there seems to be some misunderstanding with the voltage ratings in the same conduit. First, bare wire has no voltage rating, it is the insulation that gives it a "voltage rating".

300.2 Limitations.
(C) Conductors of Different Systems.
(1) 600 Volts, Nominal, or Less. Conductors of ac and dc circuits, rated 600 volts, nominal, or less, shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.

So I stand by my original post in saying that the OP is code compliant by using wire of different voltage ratings as long as ALL wires are listed above the maximum voltage.
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Old 02-05-2012, 10:24 AM   #14
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Quote:
Originally Posted by joed

That is correct. Also note that wire being underground must be THWN rated. It was stated as THHN in the original post. However most THHN is also rated THWN. Just make sure it is dual rated.
It still must be THWN even in conduit?
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Old 02-05-2012, 10:37 AM   #15
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It still must be THWN even in conduit?
Yes absolutely...conduit is considered a wet location. Most THHN is also listed as THWN. I'm not sure you could still find THHN only.

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