Robert Motherselle asks this question, which concerns the fixing intervals of fire rated cables on to cable tray using nylon and stainless steel Ty-Raps. It has been answered by SELECT (Theme – Cables, Wiring and Wiring Accessories):
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Question: We are electrical contractors installing soft skinned fire alarm cables on inverted cable tray. At the moment, we are fixing the cable at 300mm centres with nylon Ty-Raps, which are supplemented at 1000mm centres with stainless steel Ty-Raps.
We have been told by the electrical consultant involved that this does not comply with BS 5839 and that we should be installing stainless steel Ty-Raps at 300mm centres.
We have spoken to a couple of fire alarm companies which say that stainless steel Ty-Raps only need to be installed at between 1000 - 1500mm centres and that supplementing these with nylon Ty-Raps at 300mm centres is perfectly acceptable.
Who is correct?
Answer: BS 5839-1 does not consider the cable support in the detailed way in which you describe. The standard does, however, require that the system installation conforms with the general requirements of BS 7671.
It goes on to state that cables fixed to the surface should be neatly run and secured at regular intervals in accordance with the cable manufacturer's instructions (therefore some consultation may be required).
In addition, there is reference to the use of fixings that can withstand high temperatures.
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