Strange Testing Request.

[robdav99]

Hi Guys, this might be a bit long winded so please bear with me.

We got called to a job today by an Air Conditioning firm that we usually wire the supplies for.

The job was at a big industrial factory complex and they had their own sparks who had wired up the supplies to the units, nothing wrong with that and they had done a good job too.

So we wondered why we were there at all. I thought maybe they wanted us to do the test on the circuit they had wired, but that wasn't it as the factories own sparks where ok to test and certificate that work.

All they wanted us to do was test the 3core&earth SY cable that the AirCon guys had installed between the outside unit and inside unit.

Usually when we wire the supplies we just test up to the end of the flex leaving the isolator that is terminated into the external unit and this gives us a ZS reading for the circuit.

I wasn't really sure what they wanted of me but I took some readings anyway.

So I've taken the end to end resistance readings, the insualtion resitance readings and checked the polarity for all the cores in the SY cable but the on-site spark has said that is not enough.

here is part of the document I gave him:

I think he wants a full installation certificate but I can't really do one just for a single cable that isn't even connected to the origin (the cable goes from a PCB in the external unit to a PCB in the internal unit), they wouldn't even let me see the origin of the circuit.


Does that make any sense?

Would love to hear your thoughts on it?

Cheers

 

[Davey101]

Earth loop?

I dont know the kit the cable is connected to, but I'd be reluctant to, in case the test blew a fuse or caused other damage to the unit.
Why don't you just ask him?

Sounds a bit strange mate, do you think someone is trying to test you, or catch you out?

 

[robdav99]

I don't think anyone is trying to test me, I just think the guy who is in charge is a bit of a reg-book loving jobsworth to be honest.

I couldn't do the earth loop as the supply that they wired had not been powered up yet and like you said it goes through the PCB's in the AirCon units so could damage them.

I asked the guy what he wanted me to do and he bumbled and stuttered around saying about ZS and making sure the cable could carry the prospective fault current etc, that could all be worked out with the readings I've given him and with the readings they will have to take to test the circuit they have wired.

 

[solo2771]

I don't think anyone is trying to test me, I just think the guy who is in charge is a bit of a reg-book loving jobsworth to be honest.

I couldn't do the earth loop as the supply that they wired had not been powered up yet and like you said it goes through the PCB's in the AirCon units so could damage them.

I asked the guy what he wanted me to do and he bumbled and stuttered around saying about ZS and making sure the cable could carry the prospective fault current etc, that could all be worked out with the readings I've given him and with the readings they will have to take to test the circuit they have wired.

Zs = Ze + (r1+r2)
you got r1 + r2 just need Ze ( can you get reading with trip lock?) when they connect supply
PFC again you need Ze
cable calcs ?

 

[MartynS]

Is it a three phase Air-con unit or single phase unit. If three phase must be running a phase on the Blue core. Maybe this regs-Guy was looking to see if you think there is a problem with this.

 

[cornburn]

What type of split unit is it? I'd have thought they're normally classed as one unit and you'd just test from the origin to the fused spur or whatever's powering it. Never heard of anyone testing between the units as they're essentially one piece of equipment. Maybe they're getting into arguments over something with the aircon company so want a neutral third party to confirm something instead os using their own guys?

 

[robdav99]

What type of split unit is it? I'd have thought they're normally classed as one unit and you'd just test from the origin to the fused spur or whatever's powering it. Never heard of anyone testing between the units as they're essentially one piece of equipment. Maybe they're getting into arguments over something with the aircon company so want a neutral third party to confirm something instead os using their own guys?

its just a standard inside-outside aircon unit.

The outside unit gets the supply (rotor isolator) and then that is usually as far as I test too.

as far as I'm concerned any interlinking cables are part of the 'appliance', I'm not even certain they carry 230v, could be ELV.

I've managed to 'bodge' a periodic inspection report certificate with the cable details on which he seems happy with, most of the sections are just filled with NA.

He is just a bit of an idiot that like causing trouble with contractors I think.

Thanks for the help.

 

[cornburn]

its just a standard inside-outside aircon unit.

The outside unit gets the supply (rotor isolator) and then that is usually as far as I test too.

as far as I'm concerned any interlinking cables are part of the 'appliance', I'm not even certain they carry 230v, could be ELV.

I've managed to 'bodge' a periodic inspection report certificate with the cable details on which he seems happy with, most of the sections are just filled with NA.

He is just a bit of an idiot that like causing trouble with contractors I think.

Thanks for the help.

We normally test as far as the spur for the indoor unit, as the split units we put in are powered from the indoor unit. You then just connect the numbered wires to the outside unit under the waterproof cover and like you, I class this as part of the same applicance. I'm certainly not trailing leads up on the roof to test it any more than that anyway! Maybe just don't answer the phone next time he rings if he's that ---- about things