Fire Alarm SLC Induction ?

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tatootie

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Hello
I have a question for you experts. I have a chance to run my fire alarm slc loop underground in a large commercial building I am running. I have feeders (480v) running along the foundation as well. I plan on backfilling 2 feet of dirt, and then running my fire alarm on top of that. I am wondering if induction from the feeders could pose a problem in the SLC loop later on - even though it has the 2 feet of dirt seperation.
I could go with shielded wire if you guys think that would help?
What do you think? Any and all advice is welcome.
thx
 
tatootie said:
Hello
I have a question for you experts. I have a chance to run my fire alarm slc loop underground in a large commercial building I am running. I have feeders (480v) running along the foundation as well. I plan on backfilling 2 feet of dirt, and then running my fire alarm on top of that. I am wondering if induction from the feeders could pose a problem in the SLC loop later on - even though it has the 2 feet of dirt seperation.
I could go with shielded wire if you guys think that would help?
What do you think? Any and all advice is welcome.
thx
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I doubt it being a problem. I have installed fire alarm circuits with in two feet of 480 circuits. It was in EMT. Never had a problem. What brand is it?

Do not use shielded cable unless it is required by the manufacturer, it is a waste otherwise, IMHO.
 
Be careful using shielded cable! Only use if the Fire Alarm Panel manufacture says its OK. The shielding reduces the length of the run.

Two feet of separation should be enough to eliminate inductance if you pull good quality cable like WEST PENN. Moisture could be a problem over time. Fire alasrm cable jackets don't always hold up well in moist/wet conduits.

I have done this before in tilt-up buildings by running PVC in the pour back strip below the slab along the exterior walls and stubbing up at the device locations.
 
Only use shielded cable if its required by the manufacturer. in some extreme cases you cannot use shielded data wire ( siemens fire finder)
Also use a underground rated cable not jsut the red jacketed data cable. it wont last long underground and it will start giving you ground faults and opens etc as it deteriorates.
 
Rob454 said:
Only use shielded cable if its required by the manufacturer. in some extreme cases you cannot use shielded data wire ( siemens fire finder)Also use a underground rated cable not jsut the red jacketed data cable. it wont last long underground and it will start giving you ground faults and opens etc as it deteriorates.
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Not true. Siemens FireFinder XLS does not require shielded wire on the SLC, but does permit it. Otherwise the XLS IOM wouldn't tell you to terminate the shields only in the main enclosure.
 
Rob454 said:
Only use shielded cable if its required by the manufacturer. in some extreme cases you cannot use shielded data wire ( siemens fire finder)
Also use a underground rated cable not jsut the red jacketed data cable. it wont last long underground and it will start giving you ground faults and opens etc as it deteriorates.
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You may have difficulty finding underground rated cable that is UL listed FA cable. Even if you find a rated cable you will have signal integrity problems on the long run, unless the installation is in Arizona or somewhere where the ground does not get wet. Any polymer will, over time, get permeated by water and chemicals contained therein that will alter its dielecrtic properties. Consequently if you find such cable with CCA(Continuous Corrugated Armor) sheet you would be OK.

The fire signals transmission protocols do have error correction that takes care of the capacitive, common mode induced errors form adjacent power cables but can not address the above problem of continous 'leakeage' between each signal wire or to ground.

Usual signal separation requirement in industry is 12" parallel run and 6" perpenducilar crossing.
 
weressl said:
You may have difficulty finding underground rated cable that is UL listed FA cable. Even if you find a rated cable you will have signal integrity problems on the long run, unless the installation is in Arizona or somewhere where the ground does not get wet. Any polymer will, over time, get permeated by water and chemicals contained therein that will alter its dielecrtic properties. Consequently if you find such cable with CCA(Continuous Corrugated Armor) sheet you would be OK.

The fire signals transmission protocols do have error correction that takes care of the capacitive, common mode induced errors form adjacent power cables but can not address the above problem of continous 'leakeage' between each signal wire or to ground.

Usual signal separation requirement in industry is 12" parallel run and 6" perpenducilar crossing.
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Yes, I think he must have posted it as a joke, he can.t be serious, fire work is risky business, and over the years I can't remember a system we did that was not engineered.
 
weressl said:
You may have difficulty finding underground rated cable that is UL listed FA cable. Even if you find a rated cable you will have signal integrity problems on the long run, unless the installation is in Arizona or somewhere where the ground does not get wet. Any polymer will, over time, get permeated by water and chemicals contained therein that will alter its dielecrtic properties. Consequently if you find such cable with CCA(Continuous Corrugated Armor) sheet you would be OK.

The fire signals transmission protocols do have error correction that takes care of the capacitive, common mode induced errors form adjacent power cables but can not address the above problem of continous 'leakeage' between each signal wire or to ground.

Usual signal separation requirement in industry is 12" parallel run and 6" perpenducilar crossing.
Click to expand...

We use IMSA 20-1 underground here. Maybe not UL listed for fire, but it is more than capable on a system that does not require twisted/or shielded cable. This is the one situation in which I do not have a problem using a non-fire rated cable.


I have one location in which a class A SLC is 3000'+ all underground on IMSA 20-1. No failures on it.
 
nhfire77 said:
We use IMSA 20-1 underground here. Maybe not UL listed for fire, but it is more than capable on a system that does not require twisted/or shielded cable. This is the one situation in which I do not have a problem using a non-fire rated cable.


I have one location in which a class A SLC is 3000'+ all underground on IMSA 20-1. No failures on it.
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The only problem with that that ALL components of the fire alalrm systems MUST be approved and labeled for that purpose.

I agree that from the technical viewpoint it may not represent a problem, but you just would not know. There are lengths and cable specifications listed with your system that were used to have the approval and whenever you substitute, you no longer know if the test would still be valid.
 
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