Correct Cable Types

[gwilliamson]

We always use SWA cable for our installs, both domestic and commercial. I keep coming across other peoples installs that have used other cable such as SY or even just multicore and not armoured at all. What is the official line on this connecting indoor to outdoor units?. Does it differ from Commercial to domestic?. Any help on this would be greatly appreciated. Many Thanks

Come on guys, there must be some advice out there? We all use use 4 core everyday...Just want to know what type everyone uses?.

[monkey spanners]

We use swa or conduit on commecial/farm work (have seen rats chew the outer covering off swa allowing the steel wires to move and the rats get at the inner wires, BANG )
For AC installs we use that hightuff double insulated cable or the stainless braided stuff (pipework usually run in trunking)

Cheers Jon

[Andy AC]

I agree with gwilliamson - there must be an official line on cable types but wish somebody would spell it out for us. We use a black 1.5mm 5core multicore type for most of our installs, it looks good, pretty heavy duty insulation but who knows whether it follows regulations or not?
While I'm on the subject of regulations, what is the official line on isolators on indoor units? - when power fed to outdoor first like cassette units

[Jase]

Andy,
There should always be a point of isolation say within 1.5 metres of electrical appliance.
I always use switched spurs @ indoor units,even if the power supply is fed to the outdoor unit.

Regards
Jase

[LRAC]

Hi Guys
Try www.contractortalk.com

Regards
Lrac

[frank]

There is a regulation within BS7671 regarding isolation but I can't quote it at the mo because the book is in the office. From memory, local isolation with a separation of at least 3mm must be within 2 m of the equipment.

Even if the power is fed from the outdoor, the indoor is live when you are working on it.

Say you were getting an electric shock while working on the indoor, fell off the steps etc, passed out and still being electrocuted - would you want someone to have to run around to the outdoor to switch the power off?

Local isolation is there for a reason - not just because you want to change a pump.

The interconnect cable can be any type of cable so long as it is sized correctly for the current draw and provides mechanical protection. SWA has inherant mechanical protection, as does SY, and the metal sheaths must be earthed at one end. If you are using singles then the cable must be in mechanical containment (trunking, conduit etc)

Would you like to stand on a 3 core flex carrying 415v?

[Andy AC]

Thanks Guys, just one more thing, can the isolators be hidden above a false ceiling ? or do they have to be visable. I've worked on beermasters and sylensis units where the on-board isolator is behind a screw on panel - not much good for emergencies!

[LRAC]

I've worked on beermasters and sylensis units where the on-board isolator is behind a screw on panel - not much good for emergencies!

Hi Andy ac

On this one its between the devil and the deep blue sea, the bone of contention is, is the isolator for the customer to use or the service engineer to isolate before commencing work.

Iv'e been on quite a few call outs where the isolator on the outdoor unit has been switched off by somebody?

All the law states is that the unit can be isolated within 2 mtrs of the appliance, it does not state whether it should be behind a guard of some sort.

Very dodgy ground on all fronts no clear advice.

Lrac

[gwilliamson]

There is a regulation within BS7671 regarding isolation but I can't quote it at the mo because the book is in the office. From memory, local isolation with a separation of at least 3mm must be within 2 m of the equipment.

Even if the power is fed from the outdoor, the indoor is live when you are working on it.

Say you were getting an electric shock while working on the indoor, fell off the steps etc, passed out and still being electrocuted - would you want someone to have to run around to the outdoor to switch the power off?

Local isolation is there for a reason - not just because you want to change a pump.

The interconnect cable can be any type of cable so long as it is sized correctly for the current draw and provides mechanical protection. SWA has inherant mechanical protection, as does SY, and the metal sheaths must be earthed at one end. If you are using singles then the cable must be in mechanical containment (trunking, conduit etc)

Would you like to stand on a 3 core flex carrying 415v?

So would i be right with using SWA on all commercial jobs for safetys sake and on domestic run SWA if there is a chance of damage. ie . close to the floor/ in a garden and maybe use hightuff for use on a roof etc?. Or perhaps just use SY on all Domestic?

[Birds]

Hi
The type of cable that you use is down to the designer of the electrical installation. Yes the work that you are doing is an electrical installation, and if no one else is going to tell you which type of cable to use, then you are the designer. So you have to take into account all of the design criteria. Current capacity, volt drop, enviroment .Most of the electrical works described are for use with fixed wiring systems so flex would probably not be suitable.Swa is ok where there is a risk of damage .ie. low level in an industrial enviroment or maybe underground.but the armouring must be connected to earth,a lot of the time it is'nt.Look at the mess when people have to use Swa glands with an insulated isolator or enclosure .When you've designed the electrical installation, test it,record the results and issue a certificate stating that it complies with BS 7671.If it is a domestic, notify the local Building control.The best cable to use is a black multi core with tough outer sheath teminated with IP68 glands to external isolator etc.(Hituff is to hard)The isolator should be mounted on a wall not on the condensing unit.

Hope this helps

PS the best isolators are Salzer

[frank]

Requirements for Electrical Installations - BS7671

Chapter 13 Fundamental Requirements for Safety

Section 130-02 General

Sub Section 130-02-04
All conductors shall either
i) be so insulated and where necessary further effecively protected, or
ii) be so placed and safeguarded,
to prevent danger so far as is reasonably practicable.

Section 130-06 Isolation and Switching

Sub Section 130-06-01
Effective means, suitably placed for ready operation, shall be provided so that all voltage may be cut off from every installation, from every circuit thereof and from all equipment, as may be necessary to prevent or remove danger.

Sub Section 130-06-02
Every fixed electric motor shall be provided with an effective means of switching off, readily accessible, easily operated and so placed as to prevent danger.

[Electrocoolman]

Right guys.... lets talk cable...which was the original thread!

The regs say that "proper materials shall be used"..."all electrical conductors shall be of sufficient size and current carrying capacity"..."to prevent danger they shall be placed in such a manner as to be safeguarded, or insulated and where necessary, effectively protected"...."All joints and connections shall be properly constructed with regard to insulation, conductance, mechanical strength and protection"

They mention "non-flexible" and "flexible" cables. Non-flexible generally are "6xxx" series...with 1 or 7 strands, and flexible "3xxx" series....with 16 or more strands. Note that cables also have Voltage rating eg 300/500v, 600/1000v. The first figure is conductor insulation to ground and the second between conductors. Note: Some flexibles are designed for low voltage only and are not suitable for mains voltages.

The regs distinguish between sheathed and unsheathed, indoors and outdoors, Domestic, Commercial, Industrial and Agricultural situations.

For our puposes:
Unsheathed (e.g. conduit type) wire needs to be always enclosed by conduit, trunking or ducting, but cannot be run underground.
Single core and flat pvc insulated and sheathed can be used both indoor and outdoor (on exterior walls) and overhead between buidings. It can be run underground in conduit. Need to protect against severe mechanical stress.
Armoured cable can be used in most situations, but need to take precautions against damage when underground.
Pvc insulated / Pvc sheathed (FLEXIBLES) can be used on Domestic or Commercial premises both indoor and outdoor but NOT outdoors for Agricultural or Industrial applications.

So we can use multicore Flexibles for domestic and commercial situations...but always be aware of the need for mechanical protection...whether it be conduit (fixed / flexible), trunking etc., where appropiate.
The extra tuff hard pvc sheathed cable has its uses as does the "SY" type cable, but the glands (required to earth the braiding) for the SY do not have a high IP rating.

As a previous post mentioned it all comes down to the designer of the installation and their competency.
If you are the designer/installer are you competent?

If in doubt overspecify...use armoured .....or get an electrician in to do the work or advise.

[sinewave]

If exposed externaly then supply cables should be SWA, Domestic/Commercial/Industrial, makes no difference.

If you can terninate a supply cable straight in to the back of an IP56 Isolator mounted on an external wall then T/E is fine

Control cables are fine in SY/YY variations, however the braid must be earthed at source of supply which 99% of A/C firms don't bother doing!

There are proprietory gland kits for this, but due to all A/C manufactures having shyte designs for their condensor terminationations then a gland kit is awkward to use so a rougher approach has to be taken by twisting the braid and conecting directly to the Earth terminal!

[Birds]

If exposed externaly then supply cables should be SWA, Domestic/Commercial/Industrial, makes no difference.

Why?

[sinewave]

To comply with the various regs in BS7671.

Namely 522-01 (Ambient Temp), 522-03 (Presence of Water 7 Humidity), 522-05 (Presence of corrosive substances), 522-06 (Impact damage), 522-08 (Mechanical Stress), 522-11 (Damge by Solar radiation and Ultra-Violet radiation), that's why T/E should never be used outside.


So unless you want to install a suitable conduit system for all outside runs to a condensor then SWA/SY/YY is the way to go!

[Birds]

To comply with the various regs in BS7671.

Namely 522-01 (Ambient Temp), 522-03 (Presence of Water 7 Humidity), 522-05 (Presence of corrosive substances), 522-06 (Impact damage), 522-08 (Mechanical Stress), 522-11 (Damge by Solar radiation and Ultra-Violet radiation), that's why T/E should never be used outside.


So unless you want to install a suitable conduit system for all outside runs to a condensor then SWA/SY/YY is the way to go!

Just trying to compare SWA (exposed externally) and SY and YY (exposed externally) and the resistance to impact and mechanical stress. Surley they must be very similar otherwise you would'nt use them externally. I don't think they are!

Birds

[freezy]

Control cables are fine in SY/YY variations, however the braid must be earthed at source of supply which 99% of A/C firms don't bother doing!

There are proprietory gland kits for this, but due to all A/C manufactures having shyte designs for their condensor terminationations then a gland kit is awkward to use so a rougher approach has to be taken by twisting the braid and conecting directly to the Earth terminal!

What is wrong with twisting the braid? we always use SY as you can always earth one end by pulling out all the braid strands,twisting them, put on a 6mm earth sleeve, yellow ring crimp and connect to earth.

This is an easy way of doing it with small splits, people using SWA cannot do this

Also, a lot of companies only use 1.5 mm cable as there is not much current draw. Most manufacturers of splits recommend 2.5 as the earth cable needs to be larger and there could be volt drops.

Some splits interconnecting is linked directly from the mains terminals live and neutral terminals by the manufacturer and that may be fused at 30 or 40 amps at the distribution panel

Why we are on the subject, what about fusing condensate pumps as they are also going to be connected via the mains with a 30 or 40 amp fuse and they only pull 0.1 amps. Has anyone found a decent in line fuse to use........i'm a poet and I know it

[Birds]

Why we are on the subject, what about fusing condensate pumps as they are also going to be connected via the mains with a 30 or 40 amp fuse and they only pull 0.1 amps. Has anyone found a decent in line fuse to use........i'm a poet and I know it

Hi
Chilled Birds here

What about a fused connection unit with a 3Amp fuse fitted.Or is the pump to be used at the condensing unit i.e. external?

Birds

[freezy]

Hi birds

the problem with a fused unit is that if it has to go under the ceiling you end up with 2 isolators and it looks a bit unsightly. The easiest way would be to wire the pump to the unit with a in line fuse that is nice and small and can fit in the electrics compartment.

[monkey spanners]

We use Slidelock fuse holders and 1"1/4 fuses on control circuits/ cch's (fits in the contactor box a treat with units on pumpdown) they are quit small and im sure could be fitted somewhere.

[Electrocoolman]

Just trying to compare SWA (exposed externally) and SY and YY (exposed externally) and the resistance to impact and mechanical stress. Surley they must be very similar otherwise you would'nt use them externally. I don't think they are!

Birds

I would agree with you Birds.

SY / CY / YY cables are Flexible Control cables.
YY cable has NO braid or protection.
I have seen several references that suggest that SY is NOT suitable for outside use. The braid would not offer much MECHANICAL protection (ie against Impact, especially of a sharp object). After all you can cut it with normal sidecutters!

Hence the only options are either SWA or the mechanical protection offered by conduit or trunking.

Adrian