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Topic Title: plenum ceiling requirements
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Created On: 08 February 2013 05:38 PM
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 08 February 2013 05:38 PM
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hi all.
anyone aware of any particular criteria to meet regarding installing wiring and lighting[ via marshalling boxes] within a plenum ceiling?

thanks in advance
 08 February 2013 05:50 PM
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OMS

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depends on what that plenum is doing

If it's a horribly aggresive space above a pressure rated ceiling capturing all sorts of pathological or other contaminant nasties then your systems will need to be suitable for that environment (or ideally not in there at all)

If it's more a slightly positive or negative air plenum in a conventional environment then depending on the ceiling type you would have no specific requirements other than the ambient temperature of the plenum. They can get pretty hot if designed as a dirty, vitiated air return path even in an office. Limits on the length of flexes would be one to look out for.

Luminaires will be designe either to allow air through them, for heat recovery off the lamps, or will generally deny air movement so as not to disturb the mechanical engineers return air grille design

What particular criteria are you thinking of ?

Regards

OMS

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Failure is always an option
 08 February 2013 05:55 PM
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dg66

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Ensure all equipment is accessible for future maintenance,inspection & testing. If the plenum is to be used for heating/ventilation use suitably IP rated equipment , ensure fire barriers are in place where containment passes between fire compartments and ensure cables, containment are suitable for the enviroment(possible moisture ingress)

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Dave(not Cockburn)
 08 February 2013 06:28 PM
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its a strip out projct,returning the office area back into an open office area.
ceiling replaced,with new kighting to suit current requirements.

there were original lighting troughs x 6 [300mm wide] which ran front to back of building [45mts]
these were kept in situ by previous tenants ,with lamps etc removed and ceiling tiles inserted to replace the discarded diffusers[not sure what type]
there are two air gaps also running the length of building on each side,which i assume[i know i shouldnt] are the flow outlets.
i there4 assume the lighting troughs acted as return paths to the ceiling.
client has asked for air handling fittings or transfer grills as existing 600 x600 fittings compromise the set up.

ive been quoted approx £80 per fitting for a air handling fitting[120 for em type.considering approx 140 fittings this makes a big difference to anticipated costs.
question is am i thinking along correct lines?

lighting supplies installed in galv trunking from sub mains,fp200 and flexes from marshall boxes to be low smoke
 08 February 2013 06:37 PM
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OMS

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Sounds as if you have perimeter slot supply air diffusers with return air back through the luminaires to recover heat. they were often wired with permanent supply and pull cords at each luminaire.

You could abandon the troughs and use return air honeycomb grilles instead of luminaires and go for a 600 x 600 solution.

Be very careful though, dilapidations often require the tenant to return the space exactly as it was found. I've lost count of the hoops I've gone through to achieve this (often at great cost) only to see the whole lot ripped back out when the tenant moves in.

Landlords (or thier agents) can be totally bloody minded about these sorts of things becaue it forms part of the dilapidation claim.

Regards

OMS

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 08 February 2013 06:46 PM
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i think youve hit the nail on the head.

the last tenants thought a coat of paint would suffice.
they are faced with a bill for removing all internal partitions they built,a new ceiling due to the damage and alterations,a new complete lighting system,repairs to raised floor where floor boxes were installed and carpet tiles etc.

i have no doubt the new tenants will alter things to suit and it will start again !
 08 February 2013 07:14 PM
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should mention that the work is for the landlords,not tenants .
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