Power supply for domestic air conditioning split system

[powerbooksub]

Hi

I will shortly be purchasing a split system with 1x outside unit and 2x inside units for my house (domestic).

The aircon company will do the refrigerant circuits and want the electrical circuits ready for when they arrive.

I will do as much of this as possible as well as employ a sparks and have some questions please.

Q1. For the external aircon unit I will need a separate circuit rated to 20A. My consumer unit is the old type with cartridge fuses. Do I need to upgrade the CU to a 17th edition complaint one with MCBs? If so I would get the sparks to do this!

Q2. Re. cable to external aircon unit, can I install Hi-Tuf or does it have to be SWA? I was going to use cleats to fix to outside of brick wall. Is this OK or do I need to use conduit and if so what spec please?

Q3. I did the Vd and EFLI calcs and 2.5sqmm will be fine however for belt and braces I will install 4sqmm. I was planning on doing the donkey work (routing the cable thru the walls) and leave the sparks to terminate the cable in the isolator/CU. Am I allowed to do this in terms of building regs?

Q4. Re. inside aircon units, I was advised by aircon firm that these units can be run off ring main circuits provided FCUs are used. Am I allowed to do this in terms of building regs? I've spurred off bedroom sockets in the past but never really knew if I was allowed to do it!

Thanks!!

PB

 

[ericmark]

All the real work is done by unit outside and it will be that supply which will likely cause you the problem.

Yes you can DIY but likely you will need to go through building control under the Part P regulations so likely it will be cheaper not to DIY.

If not using local authority building control then you may not be able to use multi-signature installation certificates as the scheme operators limit what their members can do. So you need to select an electrician first before you start and agree with him what he is happy for you to do.

Since you it seems don't have RCD protection then you may have to use SWA depending on the run. It is not a simple answer.

Unless the indoor units are going in the kitchen or bathroom then likely you will have no problems with in doors side.

However as a ball park figure I would allow around £200 for LABC fees and meter hire if going down DIY route. With that in mind I would get a quote for getting the work done by a scheme member electrician then decide if it is really worth all the hassle to DIY. That is assuming you have the required skill anyway. Remember if you don't inspect and test the LABC can now charge for that as well. So if you don't understand what earth loop impedance is for example then I would advise against DIY.

 

[holmslaw]

..

 

[powerbooksub]

Hi ericmark

Thanks for the reply. I have some questions if thats OK.

Q5. Are you saying that the CU will or will not need to be updated? I would like to avoid a CU upgrade if this is possible/permitted?

Q6. Are you saying that if I do upgrade the CU I can use Hi-tuf but if I don't upgrade the CU I need to use SWA?

Q7. I was not planning on terminating the cable to the outside unit but due to the layout of the house I was planning to route it myself. It will need to go up in to the roof and then back down in to the centre of the house in to a cupboard under the stairs. This will probably take the best part of a day which I thought I would do it myself. Would a sparks normally be content for me to do this?

Q8. No the indoor units won't be in kitchen/bathroom, just bedrooms. If I provide the FCUs myself, ie DIY, do I need LABC sign off? Because if I do I will get a sparks to do it and all I will do it chase out the plaster and create the cable route.

Thanks again
PB

 

[Wontdothatagain]

All the questions you are asking, come down to the electrician that you employ as he will be the one signing off the work.

I would get 3 quotes and explain that you would like to keep the costs down by doing some of the work yourself and see what they say. As long as the cables that you install are visible for the electrician to check, i cant see a problem.

Remember, the electricians will need the spec for the units so he can do the calculations for himself.

 

[powerbooksub]

OK thanks I will speak to the electrician.

However I was kindof hoping someone on the forum could answer my first question, i.e. is it permitted to run a new circuit in to my old CU with it's old style cartridge fuses? Or do I need a 17th Edition CU.

Maybe electricans read this forum or is just DIY peeps?

Thanks
PB

 

[Wontdothatagain]

I personally do not like adding new circuits to re-wirable fuses. New circuits are required to be RCD protected unless certain conditions are met, like in a previous post where SWA was mentioned but even then, you will be going outside of the property so RCD's will come into play.

How many spare slots do you have on your existing fuse board?
Is the bonding and Earthing up to standards?
When was the last time that you had an condition report carried out on the property?
Have any alteration been done on the electrical installation?

Could you take a picture of you fuse board and post it here? may give us a better idear.

 

[powerbooksub]

Hi

Photo attached.

Its a 6-way, I have at least 1 unused way.

Its got a installation sticker dated 1993, I dont imagine its been looked at since then.

No alteration have been done on the electrical installation and on that basis I would say I believe the bonding and Earthing up to standards.

Regards

PB

 

[powerbooksub]

Untitled

• powerbooksub
• 3 Jul 2011
• 1

 

[Wontdothatagain]

The big black sticker on the fuse board answers your questions. I would of preferred if it said "Electrical equipment outside of the property".

 

[powerbooksub]

Thanks.

Do I need to replace the whole board or is there way of taking a feed off the single unsed way in to a "mini RCD", Just seeking the cheapest solution, Thanks

 

[ban-all-sheds]

You say you will be using a spark, in which case all the details will have to be agreed with him.

All the questions you are asking, come down to the electrician that you employ as he will be the one signing off the work.

 

[flameport]

is it permitted to run a new circuit in to my old CU with it's old style cartridge fuses?

Yes.
It is also permitted to install a new fusebox containing cartridge fuses. Or even rewireable ones.
The point is - whether it is permitted or not depends on the circuit which is being installed, not the type of protective device.

A circuit being installed outside does not automatically mean an RCD is required either.

As for building regulations, you can legally build an entire house and install all of the services and equipment contained within - provided you are competent to do so and follow the relevant procedures for notification.

 

[slup]

The big black sticker on the fuse board answers your questions. I would of preferred if it said "Electrical equipment outside of the property".

Why would a permanently fixed air conditioning unit fed by SWA cable need an RCD? The fact that it is outside is irrelevant?

 

[JohnW2]

Why would a permanently fixed air conditioning unit fed by SWA cable need an RCD? The fact that it is outside is irrelevant?

Regulations aside, I would personally have thought it wise to have RCD protection for an item of electrical equipment that could possibly fill up with rain water.

Kind Regards, John.