Alarm Wire In Conduit To Shed?

ContractorSteve

Hello everyone,

I have a customer that wants me to wire 120V AC and a 24V DC alarm wire to his shed. I was planning on using just one PVC conduit with #10 THWN wires for the electrical, but am unsure as to whether I can (or rather, should) run his 4-wire 24 gauge alarm wire in the same conduit. The concept is to setup alarm pins on the windows and a door pin as well, so the alarm wire is really just an open or closed low voltage circuit.

What's the consensus on this? I would like to avoid having to run two conduits out there, if possible. It is about a 100' run from house to shed.

Thanks!
-Steve (Newtown, CT)

MALCO.New.York

It is my experience that Alarms can be sensitive to RFI/EMI and running the wires in the same conduit certainly MAY increase the chances of the RFI/EMI the 120v line creates interfering with the Alarm.

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GregS

Based on previous discussions here, low-voltage needs to be contained separately.

http://www.contractortalk.com/showth...hlight=conduit

mdshunk

Steve, the only way you can really have the two conductors in the same "conduit" would be if you had one fat "conduit", open at both ends, and just used it as a sleeve for two cables otherwise rated for direct burial. I put the word conduit in quotes in the first sentence because it is really not a conduit if both ends are open. It is just a tunnel between two buildings. No different than if both cables were laying on top of each other in a filled in dirt trench or went through the same set of bored holes in framing members.

In your case, you could run a 1-1/4 pipe between the two structures, stubbed and open at both ends, and pull maybe a 12-2 UF and a whatever OSP cable you need for your alarm.

Hope that helps.

Kgmz

Spend the $20 it would cost you to run a extra 3/4" PVC conduit run with fittings, etc. for the alarm wire. Because the direct bury wire for the alarm usually will cost you more than the other wire in conduit unless you buy the direct bury wire in bulk, 1000 ft. spools.

Teetorbilt

I'm with Kgmz. Your major expense is the ditch, why try to cheap out on the details?

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mdshunk

Oh, I agree fully. My post wasn't a recommendation, but merely a method to make it legal if you insisted on doing it this way. We sometimes have to do things like this if there's only one existing pipe, etc.

Kgmz

I don't have a problem with your recommendation, as I have done something like that before for my Dad.

He built a shop next to his house 10 years ago and he put in 50 ft of 2" PVC conduit running from the just outside the house to next to the shop for just in case he needed to add something in the future since this area would be paved. Last year he put in a alarm and heat detectors in the shop and put in a electric gate in the driveway. So I ran the power for the gate and the alarm wire through the 2" conduit both direct bury wire, and at the ends of the conduit ran the wire in ditch to the house and then split them into individual pvc counduits to the house and just one into the shop with the wire from the gate running on down to the gate.

But if I have a open ditch, its nothing to throw in another run of conduit. and if it was me I would throw in another empty run for just in case.

Cajun Carpenter

If it is a long run to the shed, what we always did was run 14/2 underground to keep the voltage drop to a minimum on the alarm circuit.This way you can tie wrap it to the "conduit". Otherwise you will find yourself creating what will act like a "swinger" if you run 24 gauge any distance. And you can not run it in the conduit from a tech standpoint . . . some of the newer panels monitor the integrity of the no/nc circuit . . . .he doesn't need 4 wires, just two . . .it will all be one loop.

mdshunk

Anyone who runs any underground wire and doesn't put it in conduit ought to have their ears lopped off. I says ears, because they've already lost their brain. If you're digging a ditch anyhow, why wouldn't you put it in conduit? All underground wire goes bad at some point, and the conduit is your insurance policy against having to ever dig again. If the area above the ditch is to be paved or highly landscaped, extra empty spares are well advised also.

Magnettica

I agree with MD here. Do it right the first time.

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Cajun Carpenter

I agree with the conduit . . . but here in Louisiana at least . . . phone service is direct burial, cable is direct burial . . . . and they don't dig a ditch . . . They use a Vibra-Tencher that pushes it below the surface about 6". . . . If he has a ditch big enough I would agree with at least a small seperate conduit. But most alarms are installed with zero profit margin to get the monitoring biz . . . we don't have a frost line here . . .he could also run a shielded cable through the conduit with the 120vac.

mdshunk

He could, but that is a pretty big code violation.

Cajun Carpenter

DIVISION 16 - ELECTRICAL
Section 16120 - Wire and Cable
Introduction

All wire to be in conduit UNLESS APPROVED BY UA Electrical Inspector or Electrical Engineer.
Design is to make conduit system available for use in future.
Maximum of three circuits in each conduit for all new installations. Remodels may have six.
Where more than one 20 amp circuit is installed in a conduit with a common neutral, size neutral conductor to
#10.

Part 1 – General

• Wiring of different system voltages shall be in separate raceways separated gutter compartments required.

mdshunk

Sure, but I was talking about using the conduit is a bore casing, open at both ends. You can run two cables through that same casing, since it is not a conduit or racway using it that way.

Cajun Carpenter

For whatever it's worth, I think the "RIGHT" way to do it is use two seperate PVC conduits in the same ditch and that would cover everything . . ..

mdshunk

Right on. Sometimes, though, you're stuck with an existing situation, so it's good to know what your legal options are.

Cajun Carpenter

Is your avatar actually you? I just returned from the area . . .my son lives in Harrisburg . . . Beautiful country there . . . .

mdshunk

No, no. I just thought a picture of an Amish man for an electrician's avatar would be funny. I live about 20 miles south of Harrisburg.

mdshunk

Case in point:

I had a commercial customer with parking lot lights that were out. The wire from the building to the first fixture in the row was burned up underground, and not in conduit. The parking lot was paved. Right next to this first fixture that I had to feed was the telephone pedestal box. That box had a fat 4" conduit running from it (underground) to the side of the building. It was open at both ends (ended underground just short of the phone pedestal, and was stubbed up at the side of the building about 3 feet). That 4" conduit only had one 25 pair phone cable installed in it. That conduit was customer owned, and all that extra space in it was just begging to be used, and it saved the day. I pulled a 3/4" flexible nonmetallic conduit in that 4" next to the phone cable. This basically gave me a conduit inside of that 4" "tunnel". This is how I was able to refeed the parking lot lights without having to dig up the parking lot. That 4" pipe I pulled inside of was technically not a raceway since it was not terminated at either end. It was just originally installed to make it easy to replace the phone cable if the need ever arose.