Is the interconnecting cable between outdoor and indoor AC units classed as a control cable or power cable?

AJJewsbury said:

I suppose there is rather a precedent for the HVAC industry using SY

HVAC is, in general, 'machinery' as defined, so I see no issues, as it's not in the scope of BS 7671 and therefore not all the provisions of BS 7671 need apply.

David Alcock said:

how is the cable size calculated where these type of control cables have very little data to enable calcs? in industrial/ commercial applications some indoor units fed from the Outdoor are large and require considerable amps to run multiple fans/ pumps?

BS EN 60204-1 points to IEC 60364 series for this as an option. This is published in BS 7671 in the UK ... one thing to note, is that only specific parts or Clauses of IEC 60364 are referred to, not the whole series, so that doesn't mean all of BS 7671 applies, just bits.

broadgage said:

I would say that in most circumstances it is a power cable. Since it carries mains voltage to operate the compressor or condensing unit fan.

Agreed if it powers the fan motor ... but I would note that there's nothing to prevent mains voltage for being used for controls (e.g. on/off signals for contactors or digital inputs) ... BS 7671 would term these 'auxiliary circuits' even if operating at Band II voltages.

Which applies depends upon what you are doing, but why are the cables troubling you so much?

Home many machines are being installed, one or two please?

EG    H07RN-F

Indeed- but not say H05VV-F (which is ordinary 3183Y PVC flex) - that was my point.

   - Andy.

I dont believe there is one standard alone that you need to consider, its in some degree in my opinion that if you use just one i.e. manfacturers recommendation then it may fall fiul of other uk regulations or locations where you are installing the cable, so its engineering judgement, My judgement is it should be a power rated cable and type to suit the environment

For example, recently a contractor submitted data sheets for a cable that was not LSF in an environment that required it, and after its rejection another cable chosen was the same standard of cable but LSF whilst also being of the same standard to the manufacturers recommendations

H07RN-F not LSF to H07ZZ-F so for AC interconnector its power rated as supplies the indoor unit snd suutable for externsl use and LSF

David Alcock said:

I dont believe there is one standard alone that you need to consider, its in some degree in my opinion that if you use just one i.e. manfacturers recommendation then it may fall fiul of other uk regulations or locations where you are installing the cable, so its engineering judgement, My judgement is it should be a power rated cable and type to suit the environment

This is also true ... the installation of the cable is Construction Work as defined in CDM Regulations, and therefore, particularly for places of work, there are safety factors to consider.

However, some of the environmental and safety factors might include EMC ... so if the manufacturer recommends a cable like CY or SY for EMC purposes, then a suitable alternative arrangement of a wiring system is needed ... it could include, for example, cables in metallic conduit or trunking that provide an equivalent EMC performance. See also Section 444 of BS 7671, and BS IEC 61000-5-2.

Agree