Best cable choice for suspended ceiling

Coppersmith

Senior Member
Location
Tampa, FL, USA
I need to run some class 2 low voltage wiring above a suspended ceiling in a large hall.

Am I allowed to run thermostat cable which is rated class 2 without conduit?

Is there a heavier class 2 cable I can run without conduit? The thermostat cable is 18 AWG. I'm worried about voltage drop.
 

lordofthisworld

Senior Member
Location
Massachusetts
I need to run some class 2 low voltage wiring above a suspended ceiling in a large hall.

Am I allowed to run thermostat cable which is rated class 2 without conduit?

Is there a heavier class 2 cable I can run without conduit? The thermostat cable is 18 AWG. I'm worried about voltage drop.
What are they serving? You can run low voltage wire above suspended ceilings, the wire has to be plenum rated though.
 

Coppersmith

Senior Member
Location
Tampa, FL, USA
It's being used to control 24 volt relays that are switching 240 volt power. I haven't identified the relay product yet so I don't know how many (milli)amps they will be drawing. Additionally, the wall switch will have an LED pilot light on a separate conductor.
 

Coppersmith

Senior Member
Location
Tampa, FL, USA
I actually would prefer to run 14/3 NM for this application, but NEC says NM can't be run in suspended ceilings non-residential. There is no voltage exemption given that I know of.
 

Cow

Senior Member
Location
Eastern Oregon
I need to run some class 2 low voltage wiring above a suspended ceiling in a large hall.

Am I allowed to run thermostat cable which is rated class 2 without conduit?

Is there a heavier class 2 cable I can run without conduit? The thermostat cable is 18 AWG. I'm worried about voltage drop.
18 gauge sprinkler wire gets ran for pretty long distances for 24v irrigation valves without issue....

If you want to be safe, look up the coil data for the relays you're using and do a calc.

I've personally seen phone cable, 24 gauge?, running 24v air solenoids at more than 1000' for some dairy barn flush valves, just for reference.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
As long as it's not an air handling space you can certainly use thermostat (thermostat is CL2) but check it out first. I always assumed 18ga but lately I've been seeing 20. If that doesn't work for you there are plenty of CL2 cables out there from 18ga up way past 12 in both riser and plenum if you need it. Check out ADI.

No, you can't use NM and don't use CAT5!:rant:

-Hal
 
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