Class 2 wire and 208 volt

Merry Christmas

Paramonga

New User
Location
1267Pipi
Occupation
Electrician
Can I install class 2 (control wire) with 208 volt in the same conduit for a condenser unit


Sent from my iPad using Tapatalk
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
Simple answer is no. However, if you take a sharpie and remove the words "class 2" from the power supply you can install the wiring as class 1 which means in conduit 300v rate wire the entire length.
 

kwired

Electron manager
Location
NE Nebraska
Simple answer is no. However, if you take a sharpie and remove the words "class 2" from the power supply you can install the wiring as class 1 which means in conduit 300v rate wire the entire length.
But in doing so you must treat the entire control circuit as class 1 and not just which portions of it becomes convenient for you. That means you must also use class 1 wiring methods and not CL2 cable, your indoor thermostat that is likely only rated for class 2 circuits must also be replaced with something rated class 1, which is likely not that easy to find much that is for typical HVAC thermostats with same functions in class 1 rated unit. Simple SPST or DPDT temperature operated switches is what will be easiest to find.
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
But in doing so you must treat the entire control circuit as class 1 and not just which portions of it becomes convenient for you. That means you must also use class 1 wiring methods and not CL2 cable, your indoor thermostat that is likely only rated for class 2 circuits must also be replaced with something rated class 1, which is likely not that easy to find much that is for typical HVAC thermostats with same functions in class 1 rated unit. Simple SPST or DPDT temperature operated switches is what will be easiest to find.
I would be interested in others take on this. Without putting a lot of research in to this, I don't agree with you about the thermostat, only the wire going to it. The code requires you to reidentify the power supply, not to replace class two components, and I also believe the thermostat is "acceptable to wire class 2" not "class 2 rated". Thoughts?
 

kwired

Electron manager
Location
NE Nebraska
I would be interested in others take on this. Without putting a lot of research in to this, I don't agree with you about the thermostat, only the wire going to it. The code requires you to reidentify the power supply, not to replace class two components, and I also believe the thermostat is "acceptable to wire class 2" not "class 2 rated". Thoughts?
I would have to look to confirm, but pretty certain you must reclassify the entire control circuit and not just whatever is convenient for you. You can convert signal types with relays and such and have different classifications in isolated segments.

If your control circuit got crossed up with the power circuit within the outdoor unit, can your class 2 thermostat safely handle voltage that might be imposed on it? If it were class 1 rated it likely can.
 

tom baker

First Chief Moderator
Staff member
Simple answer is no. However, if you take a sharpie and remove the words "class 2" from the power supply you can install the wiring as class 1 which means in conduit 300v rate wire the entire length.
Also the wiring compartments are separate for the t-stat and power wiring on the condenser unit.
For changing a class II to class 1, the entire circuit has to use wiring method and materials for a class I circuit, which I take to mean a non class II t-stat
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
Also the wiring compartments are separate for the t-stat and power wiring on the condenser unit.
For changing a class II to class 1, the entire circuit has to use wiring method and materials for a class I circuit, which I take to mean a non class II t-stat
But show me where the device is listed as class 2. I don't believe they are. They are suitable for use meaning that any wiring separation requirements of UL are followed. Technically a device is not part of the branch circuit.
 

Strathead

Senior Member
Location
Ocala, Florida, USA
Occupation
Electrician/Estimator/Project Manager/Superintendent
Don't many Class 2 power supplies say something like "Class 2 Only"?
Regardless, the NEC says all you have to do is cross that out with a Sharpie and run the wiring and class 1. (paraphrased) It doesn't say anything that would even lead you to believe you have to be concerned whether the power supply could handle it. I feel the main reason for the whole requirement/allowance is to protect personnel from inadvertently coming in contact with non power limited voltage from a shorted wire. Worrying about the components would be similar to worrying about components when 277 and 120 are run in the same conduit. Just my thoughts. I have no scientific foundation for this.
 
Top