SWA & Alarm/ cable

[zuki79]

Morning all

im running SWA cable to my shed from the CU in my house

im also going to run alarm cable to the shed, Im told i cant run the SWA with the alarm cable together as the alarm may pick up interference from the mains cable

how far away from each do the cables need to be kept?

thanks

 

[edpgc]

I'd seriously doubt you'd have a problem, alarm signals are just contacts - there's no data transmission. Also the steel wire presumably works quite well as a shield anyway. Buy a screened multi-core cable for the alarm if you're really concerned.

 

[zuki79]

fantastico!

i was going to run the armoured stuff in a plastic trunk with the alarm cable, but was told i couldn't

i will stick it in an see what happens

cheers

 

[edpgc]

However standard alarm cable probably won't survive long sitting in water, so I suggest you make sure your ducting is going to stay dry or use an alternative outdoor rated cable.

 

[riveralt]

Morning all
im running SWA cable to my shed from the CU in my house
im also going to run alarm cable to the shed, Im told i cant run the SWA with the alarm cable together as the alarm may pick up interference from the mains cable
how far away from each do the cables need to be kept?
thanks

You will need to speak to your Local Authority Building Control before you start the SWA work - pay their fee and explain how you intend to design, install and test the new circuit and complete the appropriate certification.
You cannot complete the installation and then get a registered electrician in to test the installation at the end - he has to be involved in each stage of the process.
For example in terms of design, what do you intend to use the circuit for since this will be one of the factors that determine what size cable you need?
What about circuit protection?
What about voltage drop?
Do you have the necessary test equipment to complete both dead and live testing?

 

[bernardgreen]

I'd seriously doubt you'd have a problem, alarm signals are just contacts - there's no data transmission.

If the alarm sensor is just a contact and the contact debounce in the alarm panel can cope with transients then you probably will not have a problem.

A large change in current in the SWA will create a large magnetic pulse around the live and neutral, these are opposite to each other and generally cancel each other out if the live and neutral are close together. a few inches from the cable and the effect is insignificant. But if the alarm cable is run closer to one of the wires ( either live or neutral ) than to the other the effect is not insignificant on the alarm cable. This could result in the panel seeing what appears to be a very short duration change in the state of the contact in the sensor even though the sensor contact remains closed.

Contact debounce makes allowances for the contact not being a clean ON OFF operation but a series on rapid ON-OFF-ON-OFF-ON as the contacts operate and briefly bounce against each other.

Some alarm systems have a resistor in series with the contact so the current in that circuit varies between no current for alarm state, some current for no alarm but tamper and more current for no alarm and no tamper. So there is "data" of a sort.

Also the steel wire presumably works quite well as a shield anyway. Buy a screened multi-core cable for the alarm if you're really concerned.

Earth current in the SWA ( if it is used as the protective earth ) does not have any counter currents so the steel wire can create disturbances to the adjacent alarm cable.

 

[RF Lighting]

I've got an alarm network cable running along side the SWA to my garage and it's been fine for years. I'm sure ther will be no problem at all.

 

[zuki79]

thanks for all the info guys

the alarm in question is a Texecom Veritas

where i have drilled the wall for the SWA an alarm cable its in the electricity cupboard at the front of the house (easiest place to pull the cable) by the CU for the main house

because im planning on putting the alarm cable in the electricity cupboard is it recommended to use screened cable?

i wont be connecting anything up, im just doing the donkey work for the spark who arrives on the weekend, i just wanted to give him a hand an have all the cables ready to be connected up