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CMS
Former Community Member
Hi everyone, this is my first post , after spending 8 hours on line and no success ,being an M&E Manager electrically biased, I check for conformity on twelve domestic construction sites, one in particular has a design and build electrical contractor, my issue is in the electrical intake room in the basement of a new build 5 storey apartments, the tray and trunking is installed to a good standard however all the conduit from a stop end box on the trunking is in white plastic, at least 60 lengths serving both high level lights, sockets and life safety systems, can someone please tell me is their is a BS or regulation which opposes this install, also where do the fire regulations sit with this.
Welcome to the forum - we probably need a bit more info about your concern.
however some general points for starters.
If the question was is it OK to go from cable tray to plastic conduit?, then yes, generally it is. (or from metal to plastic enclosures and back in any sequence really.)
If however if the question is more are there regs to keep in mind for plastic conduits?, Oh yes.
For example, in a fire cable supports must not fail in a way that could entrap someone escaping - so there should be some if not all metal clips/straps or similar if this could happen. Clearly a cable sagging down a wall beside a corridor is ugly but not an immediate safety issue, but a similar level of drooping over a doorway or stairwell might be very serious. Detailed info about the situations is needed to judge (or just specify metal clips anywhere there is a long unsupported span seems to be some folks preferred approach.)
There should be questions about fire zones, and how these conduits (and cables more generally) get from one zone to the next - intumescent seals that rise like bread when heated and then block off flames and smoke while folk escape need to be fitted in the right places - what the right places are we do not know of course, but any hole in a wall you can feel a draught through is bad, and missing bricks etc. should raise a query.
There may be more, and I may not have fully understood what you were asking, looking forward your reply.
What sort of 'life safety systems' do yo have in mind - alarms have their own rules and may require different cable types.
Thank you for the quick response, much appreciated, the main concern I have as well as a few Electrical Contract Managers and Designers is that galv metal conduit has always been used in Electrical intake rooms, Plantrooms and external this has been to norm, however, I cannot find anything that says you should, the electrical sub-contractor in my mind are cutting cost , the questions with answers I require to bring to the table are:
1: does the plastic meet the requirement of IP protection for this area which includes all joints and boxes that are glued on.
2: does the fact that due to the glue the conduit or boxes are not interchangeable.
3: is there a specific fire rating for conduit in these areas.
4: the conduit will also carry circuits for fire alarms within the framework.
In a nut shell I am not content with install all the trunking is IP4 rated and fitting a plastic conduit via a 20mm bush and lock ring would this also compromise the IP rating of the trunking.
Generally conduit and trunking does not have to be IP rated indoors - it may just be providing some mechanical protection and marshalling for cables inside that have their own water proof insulation. IP4x is not watertight, just rather better than finger proof - the test is a wire probe.
From BS7671 perspective trunking and conduits can be quite a bit more open than that and comply - IPXXD and or IP30 are common alternatives. previous discussions on this
I agree steel is normally used, as it looks the part and then there is then no question about robustness, or earthing arrangements, but it may be more a case of house style rather than strictly required in all cases.
Fire load (the 'free fuel' built into the fabric of the building by choice of materials) is a holistic question, and conduit may well be OK if other things around it do not burn, and you do see some funnies. That said I cannot imagine anyone rushing to fit plastic cladding in the near future.
Who is the fire risk authority for the design - is that you ? A site visit from a specialist may be needed.
Fire alarms are interesting - does the system have its own central battery back up - if it has a 'control panel' then it probably does, so the mains supply failing in a fire may not matter. I'd still expect the fire rated cable to be used however, inside a plastic pipe or on the surface.
I really appreciate and understand your reply, as you quite rightly say, nothing is in black and white and all our regulations are open to interpretation, I am trying to standardise my companies electrical installation of 12 sites, however things like this totally blow me out of the water, I will take your advice and get the Site team to arrange for a visit by both a Fire Consultant and Building Control.
one in particular has a design and build electrical contractor, my issue is in the electrical intake room in the basement of a new build 5 storey apartments, the tray and trunking is installed to a good standard however all the conduit from a stop end box on the trunking is in white plastic, at least 60 lengths serving both high level lights, sockets and life safety systems, can someone please tell me is their is a BS or regulation which opposes this install, also where do the fire regulations sit with this.
It would appear that by only specifying BS without specifying your "house rules" of what you'd like to see to be included over and above what is required, seeking competitive quotes has led to this situation/issue that you're now "opposed to".
I respect your reply and quite honestly say you are correct, however standard practice and good install have been over taken by cost, eg trunking cut and not filed or sprayed, my question about the plastic conduit is all about cost and not standard practise, we have BS, BSEN, Manufactures recommendations, Building regulations etc etc, these are all interpreted in different ways nothing is cut in stone making our industry to diverse, yes contractors have to make money but not at the cost of the electrical installation.
Why would plastic conduit be an issue? Its a plantroom, not somewhere where its going to get constantly clouted by forklifts. As long as its adequately supported for fires to prevent the cables from falling excessively what is the problem. It sounds like the contractors thought there was no reason to waste alot more time and cost on metal and went plastic for ease of install. Can't really see what's wrong here?
Hi Bod. I respect your reply and quite honestly say you are correct, however standard practice and good install have been over taken by cost, eg trunking cut and not filed or sprayed, my question about the plastic conduit is all about cost and not standard practise, we have BS, BSEN, Manufactures recommendations, Building regulations etc etc, these are all interpreted in different ways nothing is cut in stone making our industry to diverse, yes contractors have to make money but not at the cost of the electrical installation.
Thank you Martin. Unfortunately someone in your organisation made the decision not to pay for a design that presumably you would have been able to contribute any particular "extras" being specified, so that all those who quoted for your work would have had the same, level playing field.
I'm not convinced that inviting D&B to possibly 3 or more contractors works out cheaper as ultimately the 2 non-winning contractors factor in the cost of design that is ultimately added to all quotes so the client "savings" on design cost is spent by 3 or more contractors with only one winning. It is a race to the bottom without a comprehensive design being provided as you've now experienced....................
As to the actual workmanship issues, these need to be inspected and require remedial work being handover (and final payment no doubt).
