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

David Alcock

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

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  • 0

    Could be either ... or both.

    It's certainly part of 'machinery' as defined in the Supply of Machinery (Safety) Regulations, and therefore not completely in the scope of BS 7671 ...

  • 0 in reply to gkenyon
    • I believe it should be in scope of BS7671, as someone needs to certify it on install as compliant, and any cables used for Power should comply with BS or harmonised standards
  • 0 in reply to David Alcock

    Not sure about that - there is no reason a competent person cannot install to the relevant machinery standard by following well written maker's instructions, which may need you to do things that are not be as simple as BS7671.
    Actually we already see this with things like heating controller wiring and alarms and so on, where '7671 does not really cover the situation. As a very noddy example how would you test a Honeywell Y plan boiler installation to BS7671 ? Concepts like Zs go out of the window with 3 way valves stalled in mid position with diodes across micro-switches.Usually, as the boiler is considered an appliance, so you don't test the installation components, just the whole thing.

  • 0 in reply to David Alcock
    David Alcock said:
    I believe it should be in scope of BS7671, as someone needs to certify it on install as compliant

    Compliant with what? I agree with Graham, there seems little doubt that the cable is connecting two parts of a machine.

    Let's suppose that your friendly local sparks installs a new circuit which terminates in an isolator. He (or she) notifies the new circuit to building control. That is BS 7671 sorted.

    Householder then pops down to Screwfix and wires in the ACU. There may be a requirement to notify under another part of the building regulations, but that is not what we are talking about here.

  • 0 in reply to mapj1

    Without some kind of entry in BS7671 it leave the engineering judgement open to the Designed and/or the Installer.  Now let me put this question forward.

    In the UK have you seen an AC unit with wiring outside using SY or CY cable?  If so how will that cable deal with UV from the sun?  Does the MI specifically forbid SY/CY cable outside and recommend/demand a HO5 or 7 variant?

  • 0 in reply to Sergio Fernandez

    wiring outside using SY or CY cable? 

    Plenty, and we use a lot of SY at work for voltages well above mains because of the RF shielding properties. Over a decade or so, if fully exposed to sun, and most is not, I'd expect SY failures at the clear jacket, and one can see the steel wires begin to rust where the outer has opened, and after perhaps another decade the shielding efficiency is lost. At that point it is pretty much as good as permanently installed  arctic flex.

    There is a lot of '7671compliant surface mounted and catenary slung twin and earth and arctic style PVC cable as well, that slowly embrittles, cracks and fails on a similar timescale. 

    As SY actually reveals it is failing, by the discoloration as the inner cores rust I personally like that inspectable quality. What I do not like is that almost no-one seems to have bothered to learn  what to do with the braid in termination. 

    I think it is a bit silly and unfortunate that there is no BS recognised standard for SY and CY cables, but they have their place (out of the sun, ideally).

    Mike.

  • 0 in reply to Sergio Fernandez
    Sergio Fernandez said:
    recommend/demand a HO5 or 7 variant?

    Be careful with those cable specs - H only means it's a harmonized type, 05 or 07 the voltage range - so nothing there specifies UV resistance at all.

      - Andy.

  • 0 in reply to AJJewsbury

    AJJewsbury said:
    recommend/demand a HO5 or 7 variant?

    EG    H07RN-F

    H07RN-F cable is UV resistant and suitable for long-term outdoor use, including direct sunlight exposure. Its robust PCP (polychloroprene) sheath protects against environmental, chemical, and mechanical stresses, making it ideal for industrial, agricultural, and construction applications

    Key features regarding durability include: 
     - Weather Resistance: Designed to withstand exposure to sunlight, moisture, and extreme temperatures (-30 - +60 degrees celcius).
     - Structural Integrity: The UV-resistant outer sheath prevents the material from drying out, cracking, or bursting when exposed to sunlight.Versatility: 
     - It is oil-resistant and flexible, commonly used for connecting machinery, heavy-duty tools, and temporary power supplies in open air

  • 0 in reply to Sergio Fernandez

    Exactly my question, this specified by the manfacturer, which distribute the same equipment around the world, ive never seen  this cable used in the UK for AC interconnections, but, this cable is not LSF so not suitable in some locations

    To another point on the design of the machine, it's also a requirement to design the installation and certify it, along with conplying with the UK regulations

  • 0 in reply to David Alcock

    Might be wroth speaking with Doncaster Cables Technical team?

    Tel 01302 821700

    email sales@doncastercables.com

    website.   https://doncastercables.com

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