? two signal types in same conduit

Hi, I'm running my class 2 wiring and 120V house wiring in separate
conduit like mom always told me to, but now I've run into this worry
about different signals:
I'm using 12VDC for operating latching relays for my lighting system,
and i'm using 24VAC for my HVAC needs (thermostats, zone valves).
Both of these are class 2 and run in the same conduit.
Is there a great risk of running into induced voltage nasties between
the two types of signals? For example, would a 24VAC circuit induce
a relay to trip on the 12VDC circuit it is running aside?
I was going to use the cheaper unshielded cable (of type CL2, CM, CMP
etc) for both types of signal but now I'm not so sure. Maybe I should
shield one or the other.
Any comments appreciated.
--wahzoo
PS. The conduit used will be EMT or IMC, not decided yet. The relay
specs
are:
Magnecraft model 711
coil power: 1.8 watts DC
coil resistance: +/- 10% measured at @ 25C
pulse duration: 50 milliseconds
intermittent duty
contact resistance: 50 milliohms max
contact rating: 12 amps @ 120/240 VAC 50/60 HZ
set/reset time: 35mS max
Reply to
wahzoo
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I maintain the security systems where i work which involve cctv camera systems, electric door strikes and burglar alarms. This equipment that was previously installed before I took this position operates on 12vdc and 24vdc/ac and in some places has been run in conduit with 120/240vac and in the past 2 years I've been there I haven't had any problems with it. I would be more concerned with running data wire in with the setup you described as power shouldn't be a problem. It might be a good idea to shield the cables tho as the ones I mentioned above are shielded (maybe why I haven't seen any probs with it). Just thot I'd share, hope it helps.
wahzoo wrote:
Reply to
Another Anonymous
As long as there is no data combined with the 12 vdc you won't have any problems. Induction would reek havoc on most data signals when combined in the same conduit, especially unshielded.
Jack
Reply to
Jackcsg
That is largely a myth. We did a lot of testing in this area with Token Ring and Ethernet using Shielded Twisted pair T/R and unshielded Cat5 at a big corporation that sold Business Machines Internationally. It took an awful lot of high current noise to cause a very small number of recoverable errors. We were never able to introduce enough noise to significantly impact throughput in spite of tywrapping data cables with power, running them in the same conduit, looping them over flourecent ballasts and all the other "no nos" we could think of. The nature of twisted pair is that it rejects common mode interference. There are safety concerns about low voltage and line voltage in the same raceway but if you don't have a lot of spiky high current switching, your data is pretty safe.
Reply to
Greg
I'll second that on the myth thing. I have been on projects where the electric closet with 480V switchgear shares a corner with the low voltage cabling. The data was UTP CAT 5 running either 16 MB Token Ring or 10 MB Ethernet. The cables, routers, switches, etc. were about 3 ft from the MSB. Perhaps it was the fiber runs to the computer room that saved the day.
I can tell you that Token-Ring was much less stable than Ethernet. At least with Ethernet, you could unplug the cable and the machine did not need rebooted (Windows NT 4.0).
Sincerely,
Donald L. Phillips, Jr., P.E. Worthington Engineering, Inc. 145 Greenglade Avenue Worthington, OH 43085-2264
snipped-for-privacy@worthingtonNSengineering.com (remove NS to use the address) 614.937.0463 voice 208.975.1011 fax
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Reply to
Don Phillips
A lot of that has to do with the type of connectors you use. If they talked someone into RJ45s they were ignoring the fact that this is a "ring". The IBM wiring system connectors maintain the ring with the cable unplugged. There may also be some NT issues. We always ran something more robust.
Reply to
Greg
I was referring to Ethernet being able to repair itself without rebooting when disconnecting the cable. A real PITA when you are trying to troubleshoot a computer since a PC takes more than 2 seconds to boot up.
Sincerely,
Donald L. Phillips, Jr., P.E. Worthington Engineering, Inc. 145 Greenglade Avenue Worthington, OH 43085-2264
snipped-for-privacy@worthingtonNSengineering.com (remove NS to use the address) 614.937.0463 voice 208.975.1011 fax
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Reply to
Don Phillips

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