Is the interconnecting cable between outdoor and indoor AC units classed as a control cable or power cable?
Is the interconnecting cable between outdoor and indoor AC units classed as a control cable or power cable?
They don't have to be exact - that can specify a large-ish cable (say 1.5mm2 - as that's often the min for many countries wiring regs anyway) which will likely be fine for several amps for anything that's not run in a perfect vacuum, say don't group it (it's usually run alongside the pipes anyway so they'll have an idea of temperature it'll be in when operating), a suitable maximum length (the refrigerant pipework will limit how far apart the units can be anyway) and probably specify a 30mA RCD so they don't have to worry about Zs.
- Andy.
OK, so are the two portions of the heat pump supplied separately, or does one supply the other?
HVAC isn't my area of expertise, but AFAIK, you have a motor which drives a compressor, and a fan to draw air over both the compressor and the evaporator.
The control unit is presumably located within one or other box, but it could be separate. So let's assume that it is in the box containing the evaporator. The thermostat clicks in and closes the contactor, which energises the compressor, the temperature falls and the thermostat opens. And so on.
Granted the contactor could be situated in either box, but what do the manufacturer's instructions say?
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?
Depending on the environment e.g external and LSZH the cable tyoe specified in some manufacturers manuals do not comply, so i believe the designer/ installer needs to understand this and use s cable suitable type and size to enable certification
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.
This circles back round to another discussion I have opened up on the IET eng X forum called
cable tyoe specified in some manufacturers manuals do not comply,
Comply with what though?
- Andy.
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.
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