Intercom cable choice

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MAK

MAK

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Massachusetts-Boston
I have a scenario where we are to change out 3 intercom stations in a steam tunnel that is about 700' long. This tunnel is very warm maybe between 120-135 degrees when the ventilation fan is running. :rolleyes:
The existing intercom cabling had melted to the inside of the conduit and rendered it useless. The plant electricians had removed the old damaged cable from the conduit by breaking open the conduit @ each coupling and pulling out the old stuff 10' at a time.

The equipment requires a 18-2 OAS that is to home run from each intercom substation to the master station.

So today I was sent out with some 18-2OAS (CMR) cable to pull into a 1/2" EMT conduit in the tunnel. I did not choose this stuff it seems that was what was available at the time.
When we pulled the cable in the jacket had virtually melted exposing the shield. Every time the cable would exit a box or elbow the jacket would stretch and break. I had thought about using cable lubricant to facilitate an easier pull (and less damage to the cable) but was worried if it would just screw things up once it sat in the conduit and baked for a day.:confused:

Could anyone recommend a cable that might hold up to the extreme heat that is present in this tunnel?
I have not had to work in this kind of environment before so if anyone had some suggestions I would appreciate your input.
Thanks:smile:
 
I think it will be too hot for THHN and besides, there is no shield. What you need is a high temp teflon cable. For starters I would look at Belden and you might want to give Clifford a call to see what they can make up for you.

-Hal
 
hbiss said:
I think it will be too hot for THHN and besides, there is no shield. What you need is a high temp teflon cable. For starters I would look at Belden and you might want to give Clifford a call to see what they can make up for you.

-Hal
Click to expand...

Thanks I'll have to check out some high temp teflon cable. Is the jacket on that type of cable thicker or is it more resistant to high temperatures? My concern is that I have to use a existing 1/2" EMT conduit system that has already had some cable melt inside it and I am wondering if I will be able to pull something in with a thicker jacket.
 
Watch the twist / lay pattern

Watch the twist / lay pattern

Doesn't intercom cable have specific twist and lay properties for the purposes of crosstalk mitigation? The intercom systems I've installed simply would not work correctly without the manufacturer specified Belden cable. I would be very wary about running building wire such as THHN.
 
richwaskowitz said:
Doesn't intercom cable have specific twist and lay properties for the purposes of crosstalk mitigation? The intercom systems I've installed simply would not work correctly without the manufacturer specified Belden cable. I would be very wary about running building wire such as THHN.
Click to expand...

NO! A lot of systems can be used on any old wire, they do however suggest, but do not require, their own brand of cable. Of course in a new install CATA5e is best for the higher end systems

http://www.aiphone.com/data/pdf/products/instructions/GH%20Product%20Showcase.pdf
 
One of the industrial intercoms that I have worked on use a tray type cable with no shielding and the 120 volt power conductors in with the audio conductors. There is no twist or shielding. This system works fine with standard building wire in conduit. The only thing that is special about their cable is the color coding of the conductors, the mix of conductor sizes and the price.
 
It looks like the people "in charge" are going to use plenum rated 18-2 OAS. I do not know which cable manufacturer they have selected so I am having trouble finding the specs on the insulation temp integrity. I want to do the job once and be over with it. I am not sure if plenum will be suitable for the long term operation of this intercom system.
They also have added 3 more stations to the job now.
 
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