Shower Design Document not compliant

[doni]

Proposal - 6mm T&E clipped direct, 9m from CU protected by 40A MCB supplying an 8.5kW shower.

BC has informed me that table 4D5 shows cable not compliant, but I cannot see how this is the case.

I have it that the design current would be 37A and the CCC of the clipped cable would be 47A from Table 4D5 and 46A from Table 4D2A and my voltage drops are fine.

I cannot see what is wrong with this design?

Still at design stage, so things are flexible at the moment - As a secondary question, the cable will be clipped to joists, by itself, and when it comes down from the above joists, I have created a non-insulated stud wall (the thickness of CLS) away from a concrete wall, and plan to clip the cable to the CLS.

1. Can I still assume that this will still suffice as clipped direct.

Further, I am providing some design documentation to BC for radials - this cable will be clipped to joists from above, but in this instance some of the cable will come down from the ceiling into an insulated stud wall. I plan to also clip this cable to the CLS.

2. As the cable is in an insulated stud wall for some of its run, but clipped for all of it, how would this normally be classified - "In wall, in thermal insulation" or "clipped direct", and if it's a grey area, what method might I adpot to keep the CCC higher, e.g. keeping the thermal insulation away from the cable by nails, ... using more CLS to prevent contact ... as when I get the BC visit, I want to be sure of my position.

Any help would be appreciated.

 

[PrenticeBoyofDerry]

Please tell me what you are referring to by using the letters CLS?

2. As the cable is in an insulated stud wall for some of its run, but clipped for all of it, how would this normally be classified - "In wall, in thermal insulation" or "clipped direct", and if it's a grey area,

worst case scenario

what method might I adpot to keep the CCC higher, e.g. keeping the thermal insulation away from the cable by nails, ... using more CLS to prevent contact ... as when I get the BC visit, I want to be sure of my position.

Keeping the insulation away from cable will have the desired effect, regarding CCC. But does the wall need insulating to be BC compliant?
Other options are to run in conduit but will still be a de-rating, if the circuit is a radial (Type A3) you can protect it via a 20A device and you can still use 2.5mm cable, this will also allow you to use ref method 102 with de-rating being almost the same.

 

[sparkticus]

Please tell me what you are referring to by using the letters CLS?

CLS=Canadian Lumber Stock -

 

[sparkticus]

From a purely practical point of view, I would run 10mm CSA. There is every chance that that the shower could/would be upgraded to 9.5KW or higher in the next few years.

 

[PrenticeBoyofDerry]

Please tell me what you are referring to by using the letters CLS?

CLS=Canadian Lumber Stock -

so we are talking about the stud timber then, not The Community Legal Service.

 

[PrenticeBoyofDerry]

1. Can I still assume that this will still suffice as clipped direct.

if it's not insulated yes

 

[sparkticus]

BC has informed me that table 4D5 shows cable not compliant, but I cannot see how this is the case.

BC need to tell you exactly why it is not compliant.

 

[doni]

Keeping the insulation away from cable will have the desired effect, regarding CCC. But does the wall need insulating to be BC compliant?
Other options are to run in conduit but will still be a de-rating, if the circuit is a radial (Type A3) you can protect it via a 20A device and you can still use 2.5mm cable, this will also allow you to use ref method 102 with de-rating being almost the same.

Yes - for the studwork I will have to insulate for BC compliant, which will affect the radials - so do you think BC will take the "worst case scenario", or if I clip the 2.5 to the CLS and the insulation is kept away from the cable by nailing, that would suffice.

 

[PrenticeBoyofDerry]

Proposal - 6mm T&E clipped direct, 9m from CU protected by 40A MCB supplying an 8.5kW shower.

BC has informed me that table 4D5 shows cable not compliant, but I cannot see how this is the case.

I have it that the design current would be 37A and the CCC of the clipped cable would be 47A from Table 4D5 and 46A from Table 4D2A and my voltage drops are fine.

I cannot see what is wrong with this design?

Is this circuit clipped direct or run in a different method?

 

[doni]

From a purely practical point of view, I would run 10mm CSA. There is every chance that that the shower could/would be upgraded to 9.5KW or higher in the next few years.

Yes - I got that, but based upon my design, as I quoted above they say non compliant, which I don;t really get.

 

[PrenticeBoyofDerry]

Yes - for the studwork I will have to insulate for BC compliant, which will affect the radials - so do you think BC will take the "worst case scenario", or if I clip the 2.5 to the CLS and the insulation is kept away from the cable by nailing, that would suffice.

I don't know what your BC will accept, but as an electrician, I use the reference method for the circuit as to where it is is at it's most vulnerable. So if I run a circuit that is 50m in length and if at only one area of it's route does it pass through 50mm of insulation, I refer to that point.

 

[doni]

Proposal - 6mm T&E clipped direct, 9m from CU protected by 40A MCB supplying an 8.5kW shower.

BC has informed me that table 4D5 shows cable not compliant, but I cannot see how this is the case.

I have it that the design current would be 37A and the CCC of the clipped cable would be 47A from Table 4D5 and 46A from Table 4D2A and my voltage drops are fine.

I cannot see what is wrong with this design?

Is this circuit clipped direct or run in a different method?

I have placed some CLS timber on the back wall, and created a flush wall against this timber using some board to create a void the width of the CLS . This void will be uninsulated (it doesn't need to be insulated, unliked the partition wall for the radials). The void is 50mm, and the 6mm T&E will be clipped to the CLS. I think this should be classes as clipped direct all the way from the CU, and the cable size is fine - incidentally, BC are saying it doesn't suffice without a visit.

 

[PrenticeBoyofDerry]

What type of board?
Sounds like BC are talking bollux!

 

[doni]

I don't know what your BC will accept, but as an electrician, I use the reference method for the circuit as to where it is is at it's most vulnerable. So if I run a circuit that is 50m in length and if at only one area of it's route does it pass through 50mm of insulation, I refer to that point.

And I suppose that is the crux of my question - is a cable "passing through" the min specified 50mm insulation if the insulation is "covering" the cable, or can it be classed clipped if I ensure the insulation is not touching the cable. I appreciate that the ambient temperature might be higher, as the cable will be within a stud wall containing insulation, but could I use the "ambient temperature" correction factors rather than the "in wall in thermal insulation" correction factors as it seems that these would imply the cable cannot emit heat due to the insulation? I know this is a question directly for my BC, and I guess that different BC's may approach it differently, but I wondered what experience would suggest?

 

[sparkticus]

2. As the cable is in an insulated stud wall for some of its run, but clipped for all of it, how would this normally be classified - "In wall, in thermal insulation" or "clipped direct", and if it's a grey area, what method might I adpot to keep the CCC higher, e.g. keeping the thermal insulation away from the cable by nails, ... using more CLS to prevent contact ... as when I get the BC visit, I want to be sure of my position.

This is most likely the problem. Did BC see the cable clipped to the CLS in an insulated wall? If so then I assume they will decide it is REF METHOD 2 which limits your CCC to 35 amps. But again you need to get them to specifically tell you what they perceive as the problem.

EDIT: meant ref method 102