Alarm cable parallel to mains cable....

[StealthUK]

Hi,

Could someone clarify a few points for me. I have always installed
alarm cable away from any parallel runs with mains voltage cable
(sockets or lighting) to prevent interference. I am about to do an
install where running the cable to a remote control panel would be
best concealed in some conduit that has mains cable in it already. Can
I get away with this or do anything to prevent problems? What is the
longest parallel run you can get away with anyway?

TIA

 

[Frank Olson]

Hi,

Could someone clarify a few points for me. I have always installed
alarm cable away from any parallel runs with mains voltage cable
(sockets or lighting) to prevent interference. I am about to do an
install where running the cable to a remote control panel would be
best concealed in some conduit that has mains cable in it already. Can
I get away with this or do anything to prevent problems? What is the
longest parallel run you can get away with anyway?

You can't "get away" with any parallel runs. You can use shielded cable if
you're going to run anywhere near AC (ground the control panel end of the
shield only and make darn sure you've got the panel well grounded as well).
I had to do a similar install on an Ademco Vista 50 system some years ago,
only with several relay modules inside a remote graphic annunciator (used
for both fire alarm and security). Haven't had a single problem in close to
six years. Mind you it's running next to 110VAC (not 220 like they have in
the UK). What's the mains cable feeding (lights, fans)? Any way to install
a seperate conduit or run shielded cable in the same wall cavity?

 

[Jackcsg]

You cannot run any low voltage in the same conduit as high voltage. Even if
you did, you will experience allot of problems, and I wouldn't recommend it.
Run another pipe next to it, separate from the high voltage.

Jack

 

[BIG NIGE]

Using screened cable as Frank says should overcome the interference problem,
I dont know how much room you have in this conduit but it would be advisable
to either run a seperate conduit for the low voltage or as a second choice
run another (smaller) conduit within the other for the low voltage.

 

[Bob La Londe]

In most places that would be a code violation. Consider running a seperate
conduit. .



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Yuma, Az
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[Paul Ekins]

In short, DON'T DO IT, although it isn't a code violation in the UK, you
will spend the rest of your life trying to fix problems arising from this.
Use a separate conduit or catenary wire. The idea of another smaller conduit
inside the existing one does work if you have room.

 

[Spike]

In the US unless the insulation on the low voltage cable is rated for the
highest voltage in the conduit, this would be a code no-no. Even if you do
it "to code" you're still risking all kinds of problems with the alarm.
Induced AC in alarm circuits and especially in the keypad databus can cause
all kinds or erratic (calm down, Spike; that's not "erotic") behavior.

weehoo, I 've finally been a thorn enuff in this guy's side, I've made the
snide remark list.
I prefer the exotic, Bob. What with the internet and all, erotic has become,
well, boring.

 

[StealthUK]

Thanks for the advice guys, I'm going to run a separate conduit for it
instead and place it some distance away as well.

I'm installing in a small retail shop for a friend and the wiring is a
complete mess. Above the suspended ceiling there is any number of
lighting and power socket cables connected all over the place and
rather than cut to length loads of excess has been wound up in the
middle. Also the last company to install an alarm in there was ADT and
their engineer ran cable to the bell box along with 5 lighting
cables?? Other cables to sensors have been placed straight over the
top of the suspended light fittings. They certainly didn't send their
best engineer.

The only thing I am confused about is how much screening a separate
plastic conduit can provide? Surely some kind of metal needs to be
present to create any kind of screening?

 

[Paul Ekins]

OK, you got me. I know what catenary means (in short, it's a cable of
uniform density suspended from two points so as to form a perfect hyperbolic
curve) but how is a catenary wire used in an alarm installation? Or was
that a typo? :^)

In the UK we use a catenary cable to suspend the alarm cable between two
buildings. Not the best idea but is within regulations if no other method
posible.

 

[BIG NIGE]

For the screening use SCREENED ALARM CABLE

 

[BIG NIGE]

If you fit any I.D. systems it is always better to use screened cable all
the time

If you cannot get far enough away from other cabling Mains, Telephone, Data
Etc it is also better to use screened cable with all alarm systems (shop
around for your screened cable, prices vary greatly)(but dont mean get cheap
QUALITY cable i mean get quality cable cheaper)

 

[Jackcsg]

That's crazy. If your wondering why your losing bids (jobs) to your
competitors, you might want to look into using (installing) your equipment
correctly. There are capacitance issues with "shielded"/ screened wiring,
not to mention poor installation terminations/grounding (or "draining"
emi/rfi) interferences. Another thing to consider, with equipment using TTL
data, is that you will cut your maximum wiring lengths considerably. Short
runs, such as a residence won't matter much, but in the commercial world?
That could be trouble. Follow the manufacturers specs. A company standard
like that will get you into trouble, not protect your system. Learn to run
pipe, it's good for you, and it builds character...maybe

Jack

 

[Peter]

Sorry, but I disagree, friend. Many alarm systems should NOT have shielded
cable on the keypad runs. It can actually cause more problems than it
solves. Use the cable specified in the manuals. You can use EMT if you
need physical and EMI shielding, but avoid using shielded wire for data
busses unless it is specified.

Regards,
Robert

[Within European Union]
It might depend on the manufacturer but for compliance with revised
CE-directive it could be a must to use shielded cable for remote bus and
external outputs.
Kind rgds
Peter

 

[BIG NIGE]

Shielded cable is recommended by the MANUFACTURER of the id systems we
use.

Shielded cable is recommended by the MANUFACTURER of the non id systems we
use for situations where you have a risk of interference (including not
being far enough away from other cabling.

Sorry, but I disagree, friend. Many alarm systems should NOT have shielded
cable on the keypad runs. It can actually cause more problems than it
solves. Use the cable specified in the manuals. You can use EMT if you
need physical and EMI shielding, but avoid using shielded wire for data
busses unless it is specified.

Regards,
Robert

[Within European Union]
It might depend on the manufacturer but for compliance with revised
CE-directive it could be a must to use shielded cable for remote bus and
external outputs.
Kind rgds
Peter

 

[Jackcsg]

OK, so it's not recommended by mine. What's your point? You said that all
companies should just use it to be standard. Just like here in the US, UL,
CE, ULC (for them clean air guys), NEC, NFPA, BOCA, etc, etc., these are
minimum standards for guidelines. It doesn't mean follow them to a "T", it
means at a minimum. If your Manufacturer states to use it, then use it.
Depending on the type of data your systems communicate on, it would be a
standard, but it's not a standard for every Manufacturer. You can follow a
standard, and still install something incorrectly. I'm quite certain that
their are some European (imported or not) Manufacturers which utilize data
communications that recommend NOT to use shielded wire. The other mistakes
people make is using the "drain" wire, as a ground, and grounding it at both
ends. I'm not saying you do, but a majority of people (companies) do. The
effects of RFI/EMI at that point, are the same as not using a shielded wire
at all. The point is, is that it should be done correctly, either way, and
not just by a company policy. If you are using shielded wire, installing it
correctly, and following a Manufacturers Recommendation and it works, it
means you've installed it correctly, that would be a good standard to
follow. On the other hand, if your competitor is using a different
Manufacturer's method, which costs less to install, you may be at a
disadvantage with an across the board standard using only shielded wire. The
same can be true for Plenum vs. CL2.

Jack

Shielded cable is recommended by the MANUFACTURER of the id systems we
use.

Shielded cable is recommended by the MANUFACTURER of the non id systems we
use for situations where you have a risk of interference (including not
being far enough away from other cabling.

If you fit any I.D. systems it is always better to use screened
cable all the time

If you cannot get far enough away from other cabling Mains,
Telephone, Data Etc it is also better to use screened cable
with all alarm systems (shop around for your screened cable,
prices vary greatly)(but dont mean get cheap QUALITY cable
i mean get quality cable cheaper)

Sorry, but I disagree, friend. Many alarm systems should NOT have shielded
cable on the keypad runs. It can actually cause more problems than it
solves. Use the cable specified in the manuals. You can use EMT if you
need physical and EMI shielding, but avoid using shielded wire for data
busses unless it is specified.

Regards,
Robert

[Within European Union]
It might depend on the manufacturer but for compliance with revised
CE-directive it could be a must to use shielded cable for remote bus and
external outputs.
Kind rgds
Peter