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false alarm conventional smoke in a h.v. room
#11
(11-08-2017, 02:35 PM)alonso Wrote: we have a gent xenex panel with a ziton conventional smoke detector in place in an external h.v. room which has false alarmed about 5 times in a year (nobody told us there was a detector in the h.v. room so we've been looking in the wrong place!) we have changed the ziton smoke for another ziton smoke and it still false alarmed and we have also turned on the 'false alarm rejection' option on the xenex panel. no improvement.

I think it's the environment as the area is unheated and there is groundwater seeping into the h.v. room where the underground cables come in and the mesh on the air vents is so wide open plants can grow through! we have turned up the thermostat to try and dry out the room (and requested finer mesh on the vents to reduce insect ingress and requested a sump pump for the water but nothing gets done)

I was going to suggest an Apollo orbis multi detector to reduce false alarms. anyone got any better suggestions?

one of the site engineers keeps shouting about an ionisation detector but I told him these aren't made anymore for conventional panels. he then said 'well they do domestic ionisation detectors!' and I realised he's right they do. so why have people stopped making ionisation for conventional panels and yet domestic still use ionisation? Not that I'm going off on a tangent or anything...

the sub I'm in today has a discovery and one if these on the same loop


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#12
(12-08-2017, 10:10 AM)bob1 Wrote:
(12-08-2017, 07:34 AM)Alex Milner Wrote:
(12-08-2017, 07:30 AM)alonso Wrote:
(11-08-2017, 07:55 PM)bob1 Wrote: What is the location of the sub, country wise and is it a DNO sub or can the site gain access.

The hv rm is in coventry. We can gain access with one of our own hv engineers. I think maybe i'll go for an ionisation with a deck head mount then. I genuinely thought they were phasing out ionisation detectors. Are they less liable to false alarms for some reason then? Stupid question maybe but if someone could enlighten me why that would be great.

Ps the underside of the mcp was damp so i think that is part of the problem.

They always used the specify Ionisation detectors in HV switch rooms, I think the designer said it was down to the type of smoke emitted from HV Fires was detected earlier by Ion detectors. Also the Deckhead Mounting bases are really good, it them in cellars, basements, sub stations.
To be be honest if it is a disruptive failure the pressure from the arc flash will just blow the detector off the roof. If there is a transformer with an LV board then I would go for optical as they can produce a lot of thick smoke when they overheat.
we have had an old AFA ion that would not trigger even though the room was filled with black smoke.
see the attached pic that blew a sub door open, both the box on the wall

Bob what sub station is in that picture it seems we work on similar sites?
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#13
(12-08-2017, 02:19 PM)Alex Milner Wrote:
(12-08-2017, 10:10 AM)bob1 Wrote:
(12-08-2017, 07:34 AM)Alex Milner Wrote:
(12-08-2017, 07:30 AM)alonso Wrote:
(11-08-2017, 07:55 PM)bob1 Wrote: What is the location of the sub, country wise and is it a DNO sub or can the site gain access.

The hv rm is in coventry. We can gain access with one of our own hv engineers. I think maybe i'll go for an ionisation with a deck head mount then. I genuinely thought they were phasing out ionisation detectors. Are they less liable to false alarms for some reason then? Stupid question maybe but if someone could enlighten me why that would be great.

Ps the underside of the mcp was damp so i think that is part of the problem.

They always used the specify Ionisation detectors in HV switch rooms, I think the designer said it was down to the type of smoke emitted from HV Fires was detected earlier by Ion detectors. Also the Deckhead Mounting bases are really good, it them in cellars, basements, sub stations.
To be be honest if it is a disruptive failure the pressure from the arc flash will just blow the detector off the roof. If there is a transformer with an LV board then I would go for optical as they can produce a lot of thick smoke when they overheat.
we have had an old AFA ion that would not trigger even though the room was filled with black smoke.
see the attached pic that blew a sub door open, both the box on the wall

Bob what sub station is in that picture it seems we work on similar sites?
this one is on upper Thames st, London
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