AC Fitting Question/mains conditioning

[Gunslinger]

I'm about to have a daikin wall mounted split AC unit fitted to the house, the outside unit that requires the main power supply (it then supplies the indoor unit) is planned to be connected to the garage ring main circuit.

This in itself is not an issue, or dificult.... however, the AC unit is an inverter type and capable of heating fuctions as well, now, as i understand it there is a small/slim possibility that due to the way the inverter units work, it may trip the RCD in the main supply line.

The manufacturers guidence is that the units should not be connected through an RCD for this reason, however as the house wiring is old, the RCD that is fitted is an "after thought" and fitted in the line after the meter before the consumer unit, so there is no easy way to wire the unit in before this (its also seperated by about 40 odd feet !)


ok, thats the info, now.... is there any small mains conditioner/filter that i can use (consumer unit rail fitting would be ideal) to filter the mains and ensure nothing is fed back onto the ring main that could cause the RCD to trip ??

thanks for any help/suggestions

 

[sparkydude]

What is the power consumption of the unit? if its over 2kw then the new 17th edition regulations do not allow you to connect it directly into a ring main and it must have its own dedicated supply. It is very unusual to have a split air con unit supplied form a ring main , i have never seen it done before due to the loading it imposes on the circuit. As for the rcd protection, if you have whole house rcd protection then its probably time to get the electrics checked and look into the possibility of solitting the circuits up over several RCDs to prevent nuisance tripping.

 

[jj4091]

Given that you say that the house wiring is old, I think there are more things to consider than you are awair of, but the easiest way to achieve what you require, I would think, is to fit a Henley block between the meter & the rcd, but depending on how it is to be supplied electrical regs may dictate that you have to have it rcd protected no matter what the manufacturers say. I would think your best bet is to call in an electrician to advise you on site.

 

[Gunslinger]

thanks for the very speedy responces, the unit is being professionally fitted, so they will do the electrics not me, so if the ring main is not suitable, then they will have to run the full distance to the electrical cupboard,

Yes the main house wiring is old, hoever the extension where the unti is being fitted into is only about 15 years old.

I was simply trying to pre-empt a possible problem


EDIT.
the outside unit is FVXS35FV1B if i remember correctly, and here are the tech specs (beware this lists other models too) and shows 1.22Kw under heating mode

http://pmd.daikineurope.com/Consultation/Internet/Display2/techdata.jsp?id=11208&locale=en


@sparkydude
Yes you are right, the whole system is due to be re-evaluated, however we also have some extension work underway, and with the latest regulations being such a pain in the ar*e in relation to what i am allowed to do, i have a physical cost limit on how much i can afford to have redone at once, the final plan is to have a split as you suggest and also a second consumer unit in the garage area to control that end of the house, and that will eventually have a dedicated supply line for the AC


(and sorry, i forget to explain well, it's a single room split unit)

 

[Adam_151]

I'd reckon it would be alright on the RCD and the daikin are just trying to cover themselves, I'd imagine it has some filters connected to earth in the same way a computer does (the input stages of the inverter will work in a similar way to the input stages in the computer power supply)

I'd run it on a separate circuit to the fuseboard though and avoid chopped in T+E cable etc, so if your fuseboard is eventually changed, then it can go on a non rcd circuit (assuming TN supply)... this should be simple enough, the standard way of wiring aircon units is SWA from the fuseboard and to a rotary isolator near the unit outside (and normally the aircon installers will take care of fitting the flex from the iso to the unit), use 3C SWA and CW glands

 

[ericmark]

If I am reading correct 3.5Kw then not able to power from ring main but also worth pointing out that the RCD that was fitted to allow the use of a TT earthing system was normally 100ma but to protect personal they are normally 30ma from what you say I would guess fitted with 100ma S type RCD which is unlikely to be tripped by the AC unit.

As to heating when the AC is reversed it is likely to freeze and in general not suitable for UK use with out damp weather. So in the main just heating elements are used.

 

[Adam_151]

If I am reading correct 3.5Kw

You're not, you are reading the cooling capacity field, the electrical input is listed as either 0.87 or 0.96kw depending on whether the device is in heating or cooling mode

I'd still recommend a separate circuit for it though

 

[ban-all-sheds]

Yes you are right, the whole system is due to be re-evaluated, however we also have some extension work underway, and with the latest regulations being such a pain in the ar*e in relation to what i am allowed to do

The "latest regulations" do not impose any prohibitions on what you may do - only a requirement to notify some types of work, but as it's part of a project requiring Building Regulations approval anyway the extra notification will cost you nothing.

If you truly are competent enough for it to be right for you to DIY the electrics then there is nothing standing in your way.

 

[Gunslinger]

ok, i need to clarify a couple of things, as i seem to have not been too clear

1. the extension work, is at the other end of the house, nothing to do with this.

2. the rating i read for that model was 1.22Kw in heating mode.

3. I am not planning to do the wiring myself (Although that said, i am not concerned about my copentency in doing it, but do understand there are certain limitations legally as to what i can do, i do not want to cause myself issues in the future when other things are inspected)

4. running a seperate feed for it now from a henley block as suggested may be the route we go, if that is what the installer recommends, however, it will will have no bearing to the later swtich in consumer units and seperation of the zones, because the consumer unit supplying it eventually will be in the garage, rather than the other end of the house.

5. As for notifying work, yes the replacement and reconfiguring of the wiring i am sure will eventually need notifying for completion inspection. As will any work carried out in relation to the extension work that is shortly to begin.

6. I'm not at home right now so can't check, but that S Type 100mA trip sounds awfully familiar

 

[Taylortwocities]

What is the power consumption of the unit? if its over 2kw then the new 17th edition regulations do not allow you to connect it directly into a ring main and it must have its own dedicated supply.

You couldn't connect it

directly into a ring main

in any event. it would have to be via a device limiting the current (a 13A fuse in an FCU eg).

More to the point, can you tell me where you found the reg that says you must have a dedicated supply for loads over 2KW??

Appendix 15 details a number of ways in which possible overloads in ring finals can be eased and it suggests that one way this can be achieved is to use a separate feed for loads over 2KW. This is a long, long way from a regulation that says it is not allowed.

 

[Gunslinger]

yes, the unit will have the regular isolator fitted normally with these, and the line will be fused/mcb as required, when i said "directly into a ring main" i was meaning using the ring main as the supply.

 

[ban-all-sheds]

3. I am not planning to do the wiring myself (Although that said, i am not concerned about my copentency in doing it, but do understand there are certain limitations legally as to what i can do, i do not want to cause myself issues in the future when other things are inspected)

Your understanding is flawed.

There are no legal limitations on what you may do - only on what you may do without notifying.

If you truly are competent enough for it to be right for you to DIY the electrics then there is nothing to prevent you.

 

[Gunslinger]

ah ok, thanks for clarifying that

I know i will have to notify some of the work thats for sure, especially the effective rewire stuff later, so i am assuming that when those things are inspected then the rest will get an eye cast over it.


Further inspection of the wiring in place and consumer units/MCB/Isolators for that area of the house, i have, seem to have revealed a flaw in the original idea, and it looks like they will need to run a new line because there is simply too much linked through one small consumer unit, without sufficent separation of the circuits as it is, without adding an additional item to it.