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Mixed Wiring

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Mixed Wiring

Posted by stevechrry on Jul 18, 2019 3:12 pm

We have been invited to tender for the rewire of lighting and power to a government building.
The single compartment trunkings carry recently installed ELV cabling consisting of fire alarm and general alarm cabling. We have been asked to replace the existing LV singles.
Existing services to the ceilings means there is no capacity left to install new containment and would almost be impossible to install.
To install the LV wiring would depart from BS7671 528.1 / 515.2 / 528.3 along with BS5839 and BS8519
7671 states ‘Any intended departure from these Parts requires special consideration by the designer of the installation and shall be recorded on the appropriate electrical certification specified in Part 6. The resulting degree of safety of the installation shall be not less than that obtained by compliance with the Regulations.’
Since there is no design or intervention by any electrical consultants I would assume we become the designers simply by installing the cables into the trunkings and terminating into the various items of equipment.
As a result I wouldn’t say that the resulting degree of safety of the installation shall be not less than that obtained by compliance with the Regulations is met, as stated above.
Is just merely noting the departure on the EIC sufficient or should I be looking for some form of written agreement that the installation will not comply with current standards.
 

Re: Mixed Wiring

Posted by Alcomax on Jul 18, 2019 4:04 pm

I know it does not help but

recently installed ELV cabling consisting of fire alarm and general alarm cabling

has caused the problem in the first instance. Sounds like standards were compromised for a bit of cost saving and the client is hoping the electrician takes on the risk or comes up with a solution.
Did they specifically ask

We have been asked to replace the existing LV singles

Maybe lost in translation, but on its own an unusual request. Is there something wrong these existing LV singles?

Re: Mixed Wiring

Posted by stevechrry on Jul 18, 2019 4:21 pm

Hi Alcomax.
There is a very 'loose' specification which states using existing trunkings but that is all it states, nothing about compliance with reguations etc. The existing wiring needs replacing due to fire damage and the building has been left vacant for 3 years or so. As mentioned the alarm cabling has been installed by others recently. I have yet to see their certification and if any variations have been noted, though I doubt this will be the case. There is also the problem of removing and installing LV cabling without causing any damage.......

Re: Mixed Wiring

Posted by Alcomax on Jul 18, 2019 6:19 pm

Ah... then it is likely that existing light and power [ in the containment ] was disconnected at source after fire damage, then minimal electrical supplies maintained at the origin of the building and fire cabling put in after the light/power made safe for the void period. The cheeky thing is the ELV is probably all fine compliance wise as all the LV stuff it shares compartments with is dead and now just spare copper.  I would ask if there was fire and security cabling before the fire, if so what happened to it and where was it routed? May be simplistic,as only you have seen the install, but can the ELV stuff be lifted out of containment and something else be done with it. You then have the containment back for its original use.

Re: Mixed Wiring

Posted by OMS on Jul 18, 2019 6:24 pm

stevechrry:
 There is also the problem of removing and installing LV cabling without causing any damage.......

 
Which is principally why BS 5839 requires segregation/separation - to stop people fiddling with non life safety systems from damaging life safety systems.

Don't know what your appetite for risk is like, but I wouldn't touch it with a bargepole without an upfront recorded exchange during the tender period to clarify the issue.

If you've been invited to tender, then send in a tender clarification letter raising this issue (be as blunt as you like) , and if necessary ask for a tender extension period

Or just bang in a really big price with a further load of caveats attached and close the file - at least you'll have returned a compliant tender and kept yourself on the "list"

Regards

OMS




 
The trap we've fallen into is to believe that a thousand incompetents properly organized can do the job of a few dozen outstanding people

Re: Mixed Wiring

Posted by Timeserved on Jul 19, 2019 12:16 am

Is there anyway of putting in a separation panel within the trunking?

Regards TS

Re: Mixed Wiring

Posted by MHRestorations on Jul 19, 2019 4:43 am

Is the ELV fire or intruder alarm? If intruder (which I suspect) then I have no ideas over and above what's already suggested, but if Fire alarm, it will likely be FP200 or equivalent and thus already insulated to the required standards to share the trunking?

Re: Mixed Wiring

Posted by Alan Capon on Jul 19, 2019 7:45 am

MHRestorations:
. . . if Fire alarm, it will likely be FP200 or equivalent and thus already insulated to the required standards to share the trunking?

I agree that FP200 will be rated sufficiently, but it will still be a breach of BS5839. Aside from the technical breach, it may also be a breach of the Contract Conditions (which we have not seen), and the company ordering the works may be entitled to withhold payment until it is rectified. 

Regards,

Alan. 

Re: Mixed Wiring

Posted by Alan Capon on Jul 19, 2019 7:53 am

stevechrry:
. . . Is just merely noting the departure on the EIC sufficient or should I be looking for some form of written agreement that the installation will not comply with current standards.
 

You have a number of problems here. If you don’t install to the standards and something goes awry later, you (or hopefully your insurers) may be liable for the cost of repairs etc. The other problem that I can see, is that if you are not complying with the technical and commercial conditions in the Invitation to Tender document, the client may be entitled to withhold some or all of the money until the defects are rectified. It all depends on how skilled the client’s technical and commercial authors are. 

Regards,

Alan. 

Re: Mixed Wiring

Posted by stevechrry on Jul 19, 2019 8:58 am

Good morning all and thank you for your responses.
In answer to you reply’s:
Yes there was mixed wiring contained with the trunkings before the fire and as Alcomax states the circuits were isolated and disconnected. In theory the fire alarm and alarm companies have not made any variations by installing their cabling into trunkings filled with unused ‘dead’ cables.
Installing additional containment is pretty much out of the question with the existing services installed.
Yes agreed the FP200, although mains rated, is still a problem with 5839. There has been a case where mains and fire alarm cables have been installed in the same containment and when testing commences the fire panel lights up like a Christmas tree…. Just one example. As Alan mentions these issues may well appear after later after completion.
As QS I’d be a lot more comfortable with a piece of paper with someone’s signature confirming it’s fine to proceed.  
 

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