Hi,

I'm asking for a friend who is to replace smoke heads and bases on a fire alarm wired in micc. he wont be disconnecting the micc from the besa boxes, just reterminating the individual conductors.

Simple enough?

But, someone has planted a seed of doubt saying that even just doing this, 3/4 of them will short and need making off again, obviously time consuming to say the least!

So, what do you think?

Unlikely.

I think that seed info, should be planted elsewhere.

Unless your bending the pyro all over the place, twisting conductors etc. It should be fine

thought so, thanks for your help i have told him to look at getting some tools for pyro anyway just in case

Agreed, but if you have not potted before, I would suggest you make up a few on the bench and insulation test your efforts - especially if you find you have to make one up standing on a ladder.

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Chris Matheson MInstMC

it wont be me doing it, but if he does get the tools, we will no doubt have a few goes at it on the bench

I had to repair some 1.00mm pyro a few months ago, (don't ask, just think sds drill!) having not done any for nearly forty years, there's very little spacing between the conductors and conductors and copper sheath but it all worked ok,

Dave.

while on the topic of micc, has anyone heard of using single core pyro on ELV emergency lighting central battery systems?

I've seen it before - although not that often as at a final circuit level, it's a bloody nuisance to be glanding two cables where one would do. I've used bigger single core cables to feed emergency lighting dist boards from big battery sets in the past (usually 16mm2 or above as at ELV voltage drop is the killer, so you need lots of copper)

What do these single core cables do ?

Regards

OMS

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Failure is always an option

Yes, seen it on 24V and 48V DC systems with slave luminaires, with the outer negative. It was something like a 4mm imperial equiv. single core, and an absolute pig to get pots for. Eventually used metric pots, reamed out the entry and soldered to the pyro.

its not something i have seen, but something i have read, i took it to mean that the single would be +50v or whatever, and the copper sheath would be 0v

OK - then yes, it was used with the sheath as negative (usually up to about 50V systems) on DC.

Regards

OMS

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Failure is always an option

ok, thanks, just me being geeky that

dont be tempted to blow in to the pot to clean it out

put the biscuit in place then remove before you put the compound in so you can check visually there are no burs touching the sheath.

which reminds me,, years back we used to carry out a lot of fire alarm installs using Gents equipment, i was quite friendly with the local rep.
we met up up one day and he had just been to a job at a local hospital because the electrician could not clear a fault on the system..

Long story short he found the sparky had used builders mastic in stead of the compound for sealing the pots... doh!!

Have to say that sounds quite painful.

Did the local rep hold it for you?



Sorry...

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S George
http://www.state-it.com

I used to know one of the old directors at Gent, he had some good stories

terrible joke stateit

Biscuit? I assume you mean seal?

i knew what he meant

I do

So called because in the old days, the termination seal was a flat disc with just holes rather than the moulded "stub caps" we have today.

Regards

OMS

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Failure is always an option