ATS/Generator Control wires

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sfav8r

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I have always seen the control wires from an ATS to a GENSET run in a separate conduit. We were wiring a generator earlier today and one of the guys asked me why the control wires had to be in a separate conduit instead of running them with the feed wires since they both terminate at the same place. After thinking for a minute (I try to limit my thinking to a minute to prevent overload) it does seem that if the control wires have 600v insulation they should be able to share the conduit. I've just never seen it that way. Does anyone have a code section that addresses this? 702.9 just mentions that the standby power can share conduit with other systems. It doesn't mention the control wires. This is a non-mandatory system, but I didn't see anything in 701 either.
 
Even if insulated to the same voltage, the control wiring has to be functionally related to the power wiring to be in the same raceway.
One AHJ was reported to not even consider the remote start and voltage monitoring wires for a generator to be functionally related to the generator output. :(

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GoldDigger said:
Even if insulated to the same voltage, the control wiring has to be functionally related to the power wiring to be in the same raceway.
One AHJ was reported to not even consider the remote start and voltage monitoring wires for a generator to be functionally related to the generator output. :(

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Click to expand...

How can wires to control a generator not be related to the generator? Seems like an odd call to me. Still not sure if the control conductors can share the raceway, but I haven't seen a code section that prohibits it.
 
700.9 Wiring, Emergency System.
(B) Wiring.
(D) Fire Protection. Emergency systems shall meet the additional requirements in 700.9(D)(1) and (D)(2) in assembly occupancies for not less than 1000 persons or in buildings above 23 m (75 ft) in height with any of the following occupancy classes: assembly, educational, residential, detention and correctional, business, and mercantile.
(3) Generator Control Wiring. Control conductors installed between the transfer equipment and the emergency generator shall be kept entirely independent of all other wiring and shall meet the conditions of 700.9(D)(1).
 
I can't speak about larger commercial gen sets but on a smaller residential scale Generac ships their "Essential Circuits" systems with the control wiring and generator power wiring inside a 30' greenfield whip. With that in mind, it would seem ridiculous to install a whole house transfer system and install the control wiring in a separate conduit. IMHO, unless the manufacturer states specifically that they have to be run separately I would include them in the same conduit. BTW, I've been told by some generator technicians that there exists a possibility that induced (or eddy) currents could affect the functions of the transfer switch during a power fail condition. Not sure if there's any truth to that. Bear in mind that there's 12 VDC as well as line voltage in that control wiring whip.
 
david said:
700.9 Wiring, Emergency System.
(B) Wiring.
(D) Fire Protection. Emergency systems shall meet the additional requirements in 700.9(D)(1) and (D)(2) in assembly occupancies for not less than 1000 persons or in buildings above 23 m (75 ft) in height with any of the following occupancy classes: assembly, educational, residential, detention and correctional, business, and mercantile.
(3) Generator Control Wiring. Control conductors installed between the transfer equipment and the emergency generator shall be kept entirely independent of all other wiring and shall meet the conditions of 700.9(D)(1).
Click to expand...

The OP is referring to a 702 install. Optional stand by system.

goldstar said:
I can't speak about larger commercial gen sets but on a smaller residential scale Generac ships their "Essential Circuits" systems with the control wiring and generator power wiring inside a 30' greenfield whip. With that in mind, it would seem ridiculous to install a whole house transfer system and install the control wiring in a separate conduit. IMHO, unless the manufacturer states specifically that they have to be run separately I would include them in the same conduit. BTW, I've been told by some generator technicians that there exists a possibility that induced (or eddy) currents could affect the functions of the transfer switch during a power fail condition. Not sure if there's any truth to that. Bear in mind that there's 12 VDC as well as line voltage in that control wiring whip.
Click to expand...

On the larger industrial units I have the mfg. instructions are to run control wires separately. Some of my units the control panel on the generator is the "brains" that "talks" to the ATS.
On the small residential units the control wires, N1 N2, are carrying 240v as utility sensing wire. So I see no problem as has been said running them in the same conduit as long as the wire is rated the same.
 
I suggest you gentlemen read article 725, it covers the different classifications of control circuits and the code associated with them.

PJHolguin :cool:


ceb58 said:
The OP is referring to a 702 install. Optional stand by system.



On the larger industrial units I have the mfg. instructions are to run control wires separately. Some of my units the control panel on the generator is the "brains" that "talks" to the ATS.
On the small residential units the control wires, N1 N2, are carrying 240v as utility sensing wire. So I see no problem as has been said running them in the same conduit as long as the wire is rated the same.
Click to expand...
 
sfav8r said:
. Does anyone have a code section that addresses this? 702.9 just mentions that the standby power can share conduit with other systems. It doesn't mention the control wires. This is a non-mandatory system, but I didn't see anything in 701 either.
Click to expand...

ceb58 said:
The OP is referring to a 702 install. Optional stand by system.
Click to expand...

True he did say that the current transformer install would be a 702 install,

but he also asked a broader question to include other installs such as a 701 install.

I simply posted to the broader question as to when control conductors were required to be separated from other conductors
 
infinity said:
Look at 725.136.
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May be way off but I don't see 136 coming into the picture. Where are the class 2 and 3 conductors?

725.48 Conductors of Different Circuits in the Same
Cable, Cable Tray, Enclosure, or Raceway.
Class 1 circuits
shall be permitted to be installed with other circuits as
specified in 725.48(A) and (B).
(A) Two or More Class 1 Circuits.
Class 1 circuits shall be
permitted to occupy the same cable, cable tray, enclosure, or
raceway without regard to whether the individual circuits are
alternating current or direct current, provided all conductors
are insulated for the maximum voltage of any conductor in the
cable, cable tray, enclosure, or raceway.
(B) Class 1 Circuits with Power-Supply Circuits.
Class 1
circuits shall be permitted to be installed with power-supply
conductors as specified in 725.48(B)(1) through (B)(4).
(1) In a Cable, Enclosure, or Raceway.



Class 1 circuits and
power-supply circuits shall be permitted to occupy the same
cable, enclosure, or raceway only where the equipment powered
is functionally associated.
Click to expand...
 
EC&M had an article about class 1,2&3 circuits. Below is a relevent section. The entire article is viewable at http://ecmweb.com/code-basics/classifying-and-using-class-1-2-and-3-circuits

Conductors of different circuits. Class 1 circuits can occupy the same cable, enclosure, or raceway without regard to whether the individual Class 1 circuits are AC or DC, provided all the Class 1 conductors are insulated for the maximum voltage of any conductor in the cable, enclosure, or raceway. The NEC allows Class 1 circuits and power supply circuits to occupy the same cable, enclosure, or raceway in situations where the equipment power system is functionally associated.

After reading that article, I have to admit I am not 100% sure what all of the circuit types are. I suspect it varies from ATS and GENSET. The L1 & L2 sensors should be class 1 because they sense line voltage at the GENSET. However, the remote start generally activates a 12 or 24v relay. This would mean that the circuit is fed from a power limited transformer and most likely a class 2 circuit. While the NEC does allow Class 1 circuits to share a raceway with power supply circuits when the systems are functionally related, it does not seem to allow it for class 2 and 3. This may be the answer to my original question.
 
But as long as the class 2 or 3 circuits are reclassified as class 1 and insulated accordingly, they can be run according to class 1 rules.
This does require that the entire circuit and the components connected to it be handled as class 1, not just the portion in question.

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GoldDigger said:
But as long as the class 2 or 3 circuits are reclassified as class 1 and insulated accordingly, they can be run according to class 1 rules.
This does require that the entire circuit and the components connected to it be handled as class 1, not just the portion in question.

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Click to expand...

What do you mean "reclassified as Class 1?"
 
sfav8r said:
EC&M had an article about class 1,2&3 circuits. Below is a relevent section. The entire article is viewable at http://ecmweb.com/code-basics/classifying-and-using-class-1-2-and-3-circuits

Conductors of different circuits. Class 1 circuits can occupy the same cable, enclosure, or raceway without regard to whether the individual Class 1 circuits are AC or DC, provided all the Class 1 conductors are insulated for the maximum voltage of any conductor in the cable, enclosure, or raceway. The NEC allows Class 1 circuits and power supply circuits to occupy the same cable, enclosure, or raceway in situations where the equipment power system is functionally associated.

After reading that article, I have to admit I am not 100% sure what all of the circuit types are. I suspect it varies from ATS and GENSET. The L1 & L2 sensors should be class 1 because they sense line voltage at the GENSET. However, the remote start generally activates a 12 or 24v relay. This would mean that the circuit is fed from a power limited transformer and most likely a class 2 circuit. While the NEC does allow Class 1 circuits to share a raceway with power supply circuits when the systems are functionally related, it does not seem to allow it for class 2 and 3. This may be the answer to my original question.
Click to expand...

Let me ask the OP this. What type, brand generator are you talking about? If you are speaking of something like the residential Generac units then you would only have class I control wiring. When utility power is lost on N1 N2 it drops a relay out in the and the generator cranks. It is the voltage from the generator that energizes a relay in the ATS to do the switching. There is no back and forth "talk" between the gen. and the ATS.
 
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