AC/DC wires in same conduit for Generac generator

[Twebber1812]

I have been installing generators for close to 8 years. I figure somewhere in the neighborhood of 1,500 generators. The company has existed for 20 years prior to me. I have always run a single conduit from the ATS to the generator, and pulled the feeder and control wires all in the same conduit. This is how Generac always did it when purchasing an ATS with a prewired whip. This is the same way that the tray cable sold by cablemaster does it as well. I had an inspector the other day tell me that wires 194 and 23 that carry dc voltage are not allowed to be in the conduit with the control wires that carry ac voltage. I'm fairly confident he is wrong; i'm just not sure how to prove it. any thoughts?

 

[Mr. Serious]

Are these control wires considered a Class 2 or Class 3 circuit? If so, I believe 725.136 (D) applies. It allows them to be routed within the same conduit under certain conditions. They must be associated with the same equipment as the power conductors and they must have certain insulation types or be installed using Class 1 wiring methods.

Or if they're considered a Class 1 circuit, 725.48 still permits them within the same conduit if they're functionally associated.

 

[LarryFine]

Many years go, Generac specified separate conduits for the feeder and for the control wires, even though they were combined in their whip, but the AC and DC control wires were still run together.

I run them all in one conduit unless there is a good reason not to.

 

[David Castor]

As long as the dc wiring is insulated at the level of the maximum ac voltage, the NEC allows it (up to 600 V). It could be a requirement or recommendation of the supplier if there are concerns about electrical interference. Just because the NEC allows it doesn't mean it will always work.

 

[retirede]

Ask the inspector to cite the code section that is violated.

 

[electrofelon]

There is no general requirement to separate AC and DC. Show him 300.3(C)(1).

 

[don_resqcapt19]

As long as the dc wiring is insulated at the level of the maximum ac voltage, the NEC allows it (up to 600 V). It could be a requirement or recommendation of the supplier if there are concerns about electrical interference. Just because the NEC allows it doesn't mean it will always work.

It really depends on how the control circuit is classified and not not the insulation rating of the conductors.

 

[tortuga]

This is the same way that the tray cable sold by cablemaster does it as well.

As others have said if your using 600V tray cable or TFFN/THWN that is compliant,
If not read on.

It really depends on how the control circuit is classified and not not the insulation rating of the conductors.

In the manufacturers instructions for the Generacs I installed it says:
"NOTE: This wiring can be run in the same conduit if the appropriate insulation rated wire is used."
Unfortunately some installers take that to mean 18AWG 'door bell' cable along with the 600V rated conductors can be used.
IMO it would be a violation to use anything other than 600V rated conductors, and not an uncommon violation at that.
I have even seen a few 'professional' installs where the installer pulled cat5 for the control circuit.
look at the installation instructions under electrical:

 

[solarken]

According to Generac transfer switch manual, the dry contact 2-wire start is a class 1 signaling circuit, which would fall under 725.41(B). The conductor requirements in 725.49 permits 18AWG or 16AWG and larger, with insulation voltages rated for the system voltage and not less than 600V. 725.48(B)(1) permits class 1 circuits to be installed in the same conduit or cable with power-supply circuits. I believe the inspector is incorrect.

 

[hillbilly1]

As others have said if your using 600V tray cable or TFFN/THWN that is compliant,
If not read on.

In the manufacturers instructions for the Generacs I installed it says:
"NOTE: This wiring can be run in the same conduit if the appropriate insulation rated wire is used."
Unfortunately some installers take that to mean 18AWG 'door bell' cable along with the 600V rated conductors can be used.
IMO it would be a violation to use anything other than 600V rated conductors, and not an uncommon violation at that.
I have even seen a few 'professional' installs where the installer pulled cat5 for the control circuit.
look at the installation instructions under electrical:
View attachment 2569926

I’ve come behind some where they used thermostat wire for ALL of the control wires! I don’t think they realized four of the six are line voltage. (On the older models) Sense wires were 240, charger was 240, and they only had two dc wires which powered the transfer relay. Then newer ones are as the above chart.

 

[tortuga]

I’ve come behind some where they used thermostat wire for ALL of the control wires! I don’t think they realized four of the six are line voltage. (On the older models) Sense wires were 240, charger was 240, and they only had two dc wires which powered the transfer relay. Then newer ones are as the above chart.

Well at least they did not use cat5 like the 'professionals' around here used.

According to Generac transfer switch manual, the dry contact 2-wire start is a class 1 signaling circuit

Thats interesting do you have a source for that?
If they classified it as class 1 from the getgo then a chapter 3 wiring method would be required.

 

[solarken]

Well at least they did not use cat5 like the 'professionals' around here used.

Thats interesting do you have a source for that?
If they classified it as class 1 from the getgo then a chapter 3 wiring method would be required.

I just looked at a typical Generac transfer switch manual, like this one. It's on page 7.

https://www.generac.com/generaccorporate/media/library/content/all-products/transfer-switches/automatic%20transfer%20switches/a0000023930.pdf?ext=.pdf

 

[David Castor]

It really depends on how the control circuit is classified and not not the insulation rating of the conductors.

I've never seen one that wasn't Class 1, which can be in the same raceway as the power circuit as long as insulated at the appropriate level. But I'm not involved in residential work (other than my own residence), so maybe these are different.

 

[farmantenna]

It really depends on how the control circuit is classified and not not the insulation rating of the conductors.

bingo! this is the correct anwser. What class? not voltage insulation. Generac specifically states in their instructions that the control wires are a class1circuit and can all be in the same cable assembly(which they sell) or conduit.

 

[tortuga]

Then one should never see a class 2 cable like this:

 

[electrofelon]

On this topic, and out of curiosity: I watched a YouTube video on a Generator installation in Canada. They said that if the control wires were in the same conduit as the power they needed to be shielded. Is that a CEC thing, hogwash, or a manufacturer thing?

 

[solarken]

bingo! this is the correct anwser. What class? not voltage insulation. Generac specifically states in their instructions that the control wires are a class1circuit and can all be in the same cable assembly(which they sell) or conduit.

The voltage rating of the insulation is still relevant, and needs to be at least rated for the system voltage contained in the same cable or raceway, and not less than 600V. See 725.49(B).

 

[solarken]

On this topic, and out of curiosity: I watched a YouTube video on a Generator installation in Canada. They said that if the control wires were in the same conduit as the power they needed to be shielded. Is that a CEC thing, hogwash, or a manufacturer thing?

I am not aware of a code requirement for shielding, but when putting control wiring in with power conductors, the type of control signal is important when considering shielding. For a two-wire start/dry contact control like discussed here, there is not reason for shielding, as it would not be likely that any noise from the power conductors could affect the open or closed contact signal. For analog control signals, like low voltage current transformer signals, especially for low voltage signals that travel from/to high impedance sources and inputs, it is more likely. At least that is my view.