Need to run low voltage in same conduit as 240 vac feeders... can someone clarify?

[Jimmyboy]

Installing a 17kw generator / automatic transfer switch for a customer. Unfortunitly, the customer had installed one 2"PVC pipe underground at the same time they had their in-ground pool installed and now due to landscaping/stone work, adding a new pipe is impossible. From Generator location to Transfer switch location is 100 feet.

In the 2" pipe, I obviously need to run the generator feeders, but I need to have 3 other lines (120vac for battery charger) and 3 low voltage lines (maybe #12 thhn also) for start/stop ect.

Can anyone tell me exactly what the code is for this application?

From what I understand, I can put the low voltage in the same conduit, as long as the wire has a 600 volt rating.... but I heard there may be a maximum distance they can run together???

 

[kwired]

Is the low voltage a class 1 control circuit? Otherwise you are likely out of luck, unless you can fit usable cable assemblies in the 2 inch raceway.

Directional boring can be a way to add another raceway that will not require as much tearing up of the landscaping, you will likely need to dig a hole at each end of the run.

 

[masterinbama]

If possible use interposing relays and change the portion of the control circuit in the conduit to 120 volts.

 

[Dennis Alwon]

It is an unusual situation where you can mix different voltages like you describe in the same raceway.

 

[augie47]

Would that not be similar to the situation in this post:
http://forums.mikeholt.com/showthread.php?t=139792

Since the conductors are functionally associated, would using a Class 1 wiring method not solve the problem ?

If not, kwired might have the answer. The conduit might be large enough to accept two install the different wiring methods in individual FNMC or similar means.

 

[Jimmyboy]

Thank you all for your input. It's helping tremendously.

However.. I checked with Generac, and it's not a class 1 control circuit :happysad:

Can someone clarify Augies post:

Since the conductors are functionally associated, would using a Class 1 wiring method not solve the problem ?

Thanks again Guys!

 

[raider1]

Take a look at Exception #2 to 725.130(A).

Chris

 

[augie47]

You may also want to look at the thread I highlighted in Post 5..
It may answer your question

 

[don_resqcapt19]

...
However.. I checked with Generac, and it's not a class 1 control circuit :happysad: ...

What type of circuit is it? If it controls the generator it is an Article 725 circuit and unless they got their internal power supply listed as a Class 2 or 3 power supply it would be a Class 1 circuit.

 

[Volta]

Maybe it's not actually a conduit, but rather just a long sleeve underground that you will pull UF or other cables/raceways through.

 

[Jimmyboy]

Thanks Augie.. I did check your link, and it was very helpful.

Don... When I called Generac Tech Support today, I explained what my issue was, and asked him if they classified that Low Voltage Circuit as Class 1, and he just said "NO". He didn't give me anymore explaination, and actually seemed a little "on edge"...

He did tell me that it's a DC current that pulls the contacts inward, which results in the automatic transfer. It basically is just a low voltage that is sent to the Transfer Switch via the Generator to make it transfer from Utility to Standby Power, and vise-versa.

I apologize for my lack of knowledge with this, but in my 20+ years in the field, it's the first time I'm dealing with this situation. In the past, I've always made provisions for an additional conduit(s) to avoid this problem.

 

[tdaniels]

725.48 also covers this Conductors of Different circuits in the same Cable,Cable tray,Enclosure or raceway

as long as you use the same insulation and voltage rating of the conductor

 

[infinity]

725.48 also covers this Conductors of Different circuits in the same Cable,Cable tray,Enclosure or raceway

as long as you use the same insulation and voltage rating of the conductor

That won't help if the control circuit is class 2 or class 3.

 

[kwired]

725.48 also covers this Conductors of Different circuits in the same Cable,Cable tray,Enclosure or raceway

as long as you use the same insulation and voltage rating of the conductor

That section is for class 1 control circuits only. If the control circuit is class 2 or 3 it can not be in the same cable, raceway, or tray as power conductors.

It could be part of a cable listed for that use, but not a general purpose cable and the installer chooses to use certain conductors as class 2 or 3 controls.

 

[tom baker]

First of all, Low Voltage is a undefined and useless term. There are several articles in the NEC that deal with 'low voltage' and none of them use that term - look at 411, 720 and 725. It would be very simple if generac would tell us this is a NEC Class 1 or 2 circuit (This is in article 725) - but they have us drive ground rods when not required! A class 1 circuit is wired with a chapter 3 wiring method, while class 2 is a limited energy system- 100 VA max. A class 1 circuit can be run with lighing and power, while a class 2 can not.

A simple solution would be to get some 600 V tray cable, say 14 gage, and pull it into your 2" conduit. TC is a chapter 3 wiring method, and provides the seperation from the generator feeder. Plus its DB rated.

 

[augie47]

First of all, Low Voltage is a undefined and useless term. There are several articles in the NEC that deal with 'low voltage' and none of them use that term - look at 411, 720 and 725. It would be very simple if generac would tell us this is a NEC Class 1 or 2 circuit (This is in article 725) - but they have us drive ground rods when not required! A class 1 circuit is wired with a chapter 3 wiring method, while class 2 is a limited energy system- 100 VA max. A class 1 circuit can be run with lighing and power, while a class 2 can not.

A simple solution would be to get some 600 V tray cable, say 14 gage, and pull it into your 2" conduit. TC is a chapter 3 wiring method, and provides the seperation from the generator feeder. Plus its DB rated.

Tom,
I may see a flaw. Isn't TC only permitted in a residential installation if it is in a raceway ?

 

[stickboy1375]

Funny thing is, if you buy a Generac with the pre-installed whip, they run the control circuit and power in the same raceway... go figure.

 

[Dennis Alwon]

Tom,
I may see a flaw. Isn't TC only permitted in a residential installation if it is in a raceway ?

Where does it state that TC cable is allowed in a residence. I understood it cannot be used there.

 

[augie47]

Where does it state that TC cable is allowed in a residence. I understood it cannot be used there.

Perhaps a misunderstanding on my part, but as I read it, Art 336.10 allows:
(1) TC to be used for power circuits
(3) In raceways
(7) Where supported, in industrial establishments

Then 336.12 in the uses not permitted:
(2) Installed outside of a raceway except industrial (336.10)(7)

I see nothing that prohibits it being used in a raceway in residential.

 

[Dennis Alwon]

Perhaps a misunderstanding on my part, but as I read it, Art 336.10 allows:
(1) TC to be used for power circuits
(3) In raceways
(7) Where supported, in industrial establishments

Then 336.12 in the uses not permitted:
(2) Installed outside of a raceway except industrial (336.10)(7)

I see nothing that prohibits it being used in a raceway in residential.

Hmm. you are probably correct I always assumed no go since (7) seems to state Industrial. I took that to mean it could only be used in industrial establishments. Anyway, I would never think to use TC cable in a raceway in a residence, however it may be the answer for a generator situation. I don't think I have ever seen it around here.