H.V.A.C CONTROL WIRE
- Thread starter frank
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bphgravity
Senior Member
- Location
- Florida
Re: H.V.A.C CONTROL WIRE
300.3(C)(1) allows mixing of voltage ratings within the same raceay as long as all conductors have the same insulation rating equal to at least the maximum circuit voltage applied to any of the conductors. However, you must determine the class of the power supply to the H.V.A.C. controls. 725.26(B) allows class 1 circuits to be installed with power circuits. 725.55 states class 2 and 3 circuits can not be installed in the same raceay. The classification of the H.V.A.C. control power supply should be labeled on the transformer itself, it can be looked up in the UL directory, or the manufacturer should be able to tell you.
300.3(C)(1) allows mixing of voltage ratings within the same raceay as long as all conductors have the same insulation rating equal to at least the maximum circuit voltage applied to any of the conductors. However, you must determine the class of the power supply to the H.V.A.C. controls. 725.26(B) allows class 1 circuits to be installed with power circuits. 725.55 states class 2 and 3 circuits can not be installed in the same raceay. The classification of the H.V.A.C. control power supply should be labeled on the transformer itself, it can be looked up in the UL directory, or the manufacturer should be able to tell you.
- Location
- Bremerton, Washington
Re: H.V.A.C CONTROL WIRE
Generally no. Although 300.3(C)(1) would seem to allow it, the rules in 725 modify the rules in chapters 1-4 see section 90.3
bph is correct it depends on the class of the circuit. However you can reclassify a class 2 or 3 circuit to class 1, see section 725.52(A) ex 2, which is new for the 2002 NEC
Generally no. Although 300.3(C)(1) would seem to allow it, the rules in 725 modify the rules in chapters 1-4 see section 90.3
bph is correct it depends on the class of the circuit. However you can reclassify a class 2 or 3 circuit to class 1, see section 725.52(A) ex 2, which is new for the 2002 NEC
- Location
- Bremerton, Washington
Re: H.V.A.C CONTROL WIRE
GWZ if anyone is required to be authorized it would be by the AHJ. Otherwise it can be done per Article 725. This was added to the 2002 NEC as a similar allowance exists in Art 640 Fire Alarms
GWZ if anyone is required to be authorized it would be by the AHJ. Otherwise it can be done per Article 725. This was added to the 2002 NEC as a similar allowance exists in Art 640 Fire Alarms
mikeackley
Senior Member
- Location
- Washington
Re: H.V.A.C CONTROL WIRE
Tom B.
FYI good guy -- you might have temporarly dropped a neutral while typing post above.
Tom B.
FYI good guy -- you might have temporarly dropped a neutral while typing post above.
- Location
- Bremerton, Washington
Re: H.V.A.C CONTROL WIRE
This execption in 725 came up once or twice on the forum in the last year. I never paid much attention to it until I reviewed Mike Holts Part 2 of Understanding the NEC. No code chage books mention it. It would be interesting to see how the AHJ would react to this field modification.
This execption in 725 came up once or twice on the forum in the last year. I never paid much attention to it until I reviewed Mike Holts Part 2 of Understanding the NEC. No code chage books mention it. It would be interesting to see how the AHJ would react to this field modification.
Re: H.V.A.C CONTROL WIRE
For those that can, go to www.ul.com then to ' regulators ' then to ' Field Modification ' .
For those that can, go to www.ul.com then to ' regulators ' then to ' Field Modification ' .
- Location
- Bremerton, Washington
Re: H.V.A.C CONTROL WIRE
The post above and the modification allowed in 725.52(A) are not the same thing. Here is the literal text of 725.52(A)
725.52 Wiring Methods and Materials on Load Side of the Class 2 or Class 3 Power Source.
(A) Class 1 Wiring Methods and Materials. Installation shall be in accordance with 725.25.
Exception No. 2: Class 2 and Class 3 circuits shall be permitted to be reclassified and installed as Class 1 circuits if the Class 2 and Class 3 markings required in 725.42 are eliminated and the entire circuit is installed using the wiring methods and materials in accordance with Part II, Class 1 circuits.
FPN: Class 2 and Class 3 circuits reclassified and installed as Class 1 circuits are no longer Class 2 or Class 3 circuits, regardless of the continued connection to a Class 2 or Class 3 power source.
So we are not modifing, we are reclassifying according to the NEC.
The post above and the modification allowed in 725.52(A) are not the same thing. Here is the literal text of 725.52(A)
725.52 Wiring Methods and Materials on Load Side of the Class 2 or Class 3 Power Source.
(A) Class 1 Wiring Methods and Materials. Installation shall be in accordance with 725.25.
Exception No. 2: Class 2 and Class 3 circuits shall be permitted to be reclassified and installed as Class 1 circuits if the Class 2 and Class 3 markings required in 725.42 are eliminated and the entire circuit is installed using the wiring methods and materials in accordance with Part II, Class 1 circuits.
FPN: Class 2 and Class 3 circuits reclassified and installed as Class 1 circuits are no longer Class 2 or Class 3 circuits, regardless of the continued connection to a Class 2 or Class 3 power source.
So we are not modifing, we are reclassifying according to the NEC.
Re: H.V.A.C CONTROL WIRE
We had this discussion this morning and the matter is still unresolved. "Is it allowable to run the HVAC control circuit in the same raceway as the 120/240v power circuit?" I said it was OK based on 300.3(c)(1). One of the other electricians said NO because of 725.55(a). But the rebuttal is the class 2 & 3 can be reclassified to Class 1 by 725.52(a).
So--What is the real answer? Did we miss soomething somewhere?
We had this discussion this morning and the matter is still unresolved. "Is it allowable to run the HVAC control circuit in the same raceway as the 120/240v power circuit?" I said it was OK based on 300.3(c)(1). One of the other electricians said NO because of 725.55(a). But the rebuttal is the class 2 & 3 can be reclassified to Class 1 by 725.52(a).
So--What is the real answer? Did we miss soomething somewhere?
- Location
- Bremerton, Washington
Re: H.V.A.C CONTROL WIRE
90.3 is the most important section of the NEC and is often overlooked. It states the rules in chapter 1-4 apply generally unless modifed by chapter 5-7. In this case 725.54 modifies 300.3(C)(1) and does not allow limited energy and power wiring in the same enclosure, raceway or cable, and of course 300.3(C)(1) does have a FFN that is often overlooked.
You can reclassify the circuit, this is a new provision added to the 2002 NEC that is not well known. Most installers are not familar with Art 725 and it would be better to keep the circuits seperate.
90.3 is the most important section of the NEC and is often overlooked. It states the rules in chapter 1-4 apply generally unless modifed by chapter 5-7. In this case 725.54 modifies 300.3(C)(1) and does not allow limited energy and power wiring in the same enclosure, raceway or cable, and of course 300.3(C)(1) does have a FFN that is often overlooked.
You can reclassify the circuit, this is a new provision added to the 2002 NEC that is not well known. Most installers are not familar with Art 725 and it would be better to keep the circuits seperate.
Re: H.V.A.C CONTROL WIRE
i wouldn't recommend running any wiring other than same type of wiring in the same conduit. years ago, worked for j-man who had me run wiring for doctors ofc telelphone system in same pipe as receptacles for receptionist. telephone system was fried. telephone repairman came out, replaced receptionist's main phone, fried system again. i know sec 800 applies to communication systems but i still would not run control wiring in same pipe with power/lighting. its not worth the risk.
i wouldn't recommend running any wiring other than same type of wiring in the same conduit. years ago, worked for j-man who had me run wiring for doctors ofc telelphone system in same pipe as receptacles for receptionist. telephone system was fried. telephone repairman came out, replaced receptionist's main phone, fried system again. i know sec 800 applies to communication systems but i still would not run control wiring in same pipe with power/lighting. its not worth the risk.
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