New Circuit. Help please guys.

[domsta72]

Hi guys. Recently passed ELECSA assessment, woohoo. I'm after a bit of advice. I've been asked by a local firm to test & certify there air source heat pump wiring. To date they've fitted 16 that need doing, already commissioned. I've been told that they've all been put on a dedicated circuit, but getting confused as to wether I should ensure rcd protection regardless of cable installation method.
Thanks in advance.

 

[MDJ]

Could be a bed of nails an RCD covering these, I see all types of trouble with nusience tripping, are they wired in armoured and have they got rotary isolators on the ends and final question are the units caged?

 

[domsta72]

Hi Mike, thanks for prompt reply. I think I need to have a longer chat with the installer to confirm but, I'm sure it's rotary isolators on the ends, I don't think they're wired in armoured. What do you mean by caged? Metal cage around them on the external unit?
This firm has suddenly got a conscience and wanting all previous work tested, last week! Just creating a headache for me.

Cheers Dom

 

[MDJ]

yeah, caged as in are the units protected from interference due to being caged fella?

 

[domsta72]

I need to find this stuff out.
My initial query was on the basis that a new circuit needs to be rcd protected? Or am I ust being overly simplistic?

 

[MDJ]

RCD Protection is the last thing I would be looking at for a air handling unit with a heat pump in it, if the unit is caged and only accessable by competent people and has proper cabling and suitible IPX rated Local isolation combined with the right sized MCB I would be happy with it myself, Unless of course the factory has a TT system which is very unlikely, theres a place for RCD protection and air handling units isn't one of them IMO, JMO, Tin hat on.

 

[domsta72]

Thanks for the advice MDJ. I haven't had any experiance with these air source heat pumps, I didn't know they could be so troublesome with RCD's. These are domestic installs rather than factory though.
Anyway thanks for your help, I've been thrown in the deep end a bit with 16 units to check, but from then on I'll be doing the wiring install for them as they occur, I hope.

 

[plugsandsparks]

Domestic !!! - Would ring Elecsa tech and ask their opinion but i suspect its going to end up on an RCD or RCBO (probably better) - Also check manufacturers installation instructions to see i they state that it must not be on an RCD, either way make sure the earth to the unit is very good.
cheers

 

[Knobhead]

A seperate RCBO if needs be. But for gods sake not on a shared RCD.

 

[Engineer54]

What sort of system are these domestic air source heat pumps working with???

I wish you would have stated these heat pumps were for domestic installations, it would have saved MDJ giving sound advice on a commercial/industrial set-up....

 

[MDJ]

Yes this is a different matter, when you mentioned 16 units I assumed we were talking commercial or industrial, Check out the manufacturers suggestion first and report back to us will you?

 

[Plonker 3]

Also why are you being asked to test them? Is it because they need a Part P certificate and the company installing doesn't have that facility?

 

[domsta72]

That's exactly it Dillb.
Sorry to everyone for not giving enough info. New to this awesome site, still learning how to drive it.

 

[Plonker 3]

You do know part P doesn't allow the certifying of 3rd party works don't you?

 

[glasgospark]

oh dear