All-Pole disconnection switch

[Frimley]

I wish to install an Inverter Range split Room Air Conditioner. There are various sizes available,the smaller of which the instructions say can be plugged into the electrical supply via a 13Amp plug. The instructions state that the size of conditioner that I wish to install, 18k, requires a 20Amp Isolation switch capacity. The instructions state "An all-pole disconnection switch having a contact separation of at least 3mm in all poles should be connected in fixed wiring".
Taking a new cable back to the consumer unit would be very difficult and I had, therefore, proposed to take a spur off the ring main and install a 20Amp fused socket.
Questions:

1. Would this be safe and meet the wiring regulations?
2. Can anyone identify for me the required "all pole disconnection switch". I understand that I must not isolate the appliance earth and assume, therefore, that a 2 pole switch is all that is required. The electrical wholesaler that I tried was not able to help.
3. The ring main is protected by a main switch that is coded CD282U 80A and does not appear to be RCD protected, as these protected circuits are on the right side of the consumer unit whilst the ring main is on the left. That said the actual switch headed "RCD Controlled Circuits" seems to be identical to that referred to above i.e CD282U 80A. The cooker circuit is on the side of the unit labelled "RCD Controlled circuit". I provide this information as the spur would be off the ring main.
Any help would be much appreciated.

 

[plugwash]

1. Would this be safe and meet the wiring regulations?

The standard assumptions for the ring are that the largest single load is 13A. Putting a larger load on would take out of the realm of conventional circuits and into the realm of having to justify your design. If the other load on the ring is known to be very light AND the point where you add the additional load is close to the center of the ring it might be just about justifiable but it would still be considered very bad practice. You'd also need to fuse/breaker it somehow, standard fused connection units only go up to 13A so you'd have to use something else. Maybe a DP MCB in a modular enclosure.

For a load this size you should really have a dedicated circuit from the CU even if said circuit is a PITA to isntall.

2. Can anyone identify for me the required "all pole disconnection switch". I understand that I must not isolate the appliance earth and assume, therefore, that a 2 pole switch is all that is required. The electrical wholesaler that I tried was not able to help.

A standard 20A double pole switch made to UK standards will be fine for isolation.

3. The ring main is protected by a main switch that is coded CD282U 80A and does not appear to be RCD protected, as these protected circuits are on the right side of the consumer unit whilst the ring main is on the left. That said the actual switch headed "RCD Controlled Circuits" seems to be identical to that referred to above i.e CD282U 80A. The cooker circuit is on the side of the unit labelled "RCD Controlled circuit". I provide this information as the spur would be off the ring main.
Any help would be much appreciated.

Googling CD282U says it's a hager RCD.

 

[Taylortwocities]

A ring final can only support items that have a max load of 13amp so you are stuck with the 13A plug in option.
A 13amp plug is, by definition, an all pole isolator, when you unplug it!

Any load bigger than 13amp will require its own circuit, and therefore, an RCD at the consumer unit end.

 

[JohnW2]

... I had, therefore, proposed to take a spur off the ring main and install a 20Amp fused socket.

No-one seems to have pointed out, at least not explicitly, that there is no such thing as a "20A fused socket".

I certainly agree with others that it really would not be very appropriate to run a 20A load from a ring final circuit, but do we actually know how much current/power the proposed AC unit actually requires? - all you seem to have told us is that the instructions require a "20A isolation switch". What do the instructions say about the power requirements of the unit?

If the unit does take anything like 20A then I fear that, as has been said, and no matter however difficult it may be, you may have no alternative but to install a new dedicated circuit (back to your CU).

It sounds as if this unit might be pretty expensive to run!

Kind Regards, John

 

[Frimley]

The unit is the Ecoair "ECO1850SD"

The specification shows the following:
Cooling: Capacity 5.275kW; Btu 18,000; Input Power 1.62kW; Current 7.19A;
Heating: Capacity 5.275kW; Btu 18,000; Input power 1.6kW; Current 7.1A.

Rated Input 2.50kW
Rated Current 10.87A
Fuse Rating 20A

I understand that the 20A fuse rating is related to the start up load - but I may be wrong on this point. [The start up load is not specified]

 

[JohnW2]

The unit is the Ecoair "ECO1850SD" ... The specification shows the following:
Cooling: Capacity 5.275kW; Btu 18,000; Input Power 1.62kW; Current 7.19A;
Heating: Capacity 5.275kW; Btu 18,000; Input power 1.6kW; Current 7.1A.
Rated Input 2.50kW
Rated Current 10.87A

I'm not sure what the 'rated current' (higher than the stated currents for either heating or cooling) represents but, whatever, those running currents would, in themselves, theoretically be OK on a 13A plug.

Fuse Rating 20A
I understand that the 20A fuse rating is related to the start up load - but I may be wrong on this point. [The start up load is not specified]

That might be the case.

Kind Regards, John

 

[plugwash]

Personally given that the 20A only appears to be a startup current and given that portable heaters are unlikely to be used at the same time as an aircon unit i'd be reasonablly happy putting it on a ring. Others may not though, it's certainly a deviation from normal practice.

In such cicumastances I think i'd use a DP MCB in a modular box to provide protection and isolation.

http://www.rapidonline.com/Electric...eps&IncVat=1&gclid=CN_22aOM474CFWqWtAodc1IA5w
http://www.tlc-direct.co.uk/Products/MK5502.html

 

[JohnW2]

Personally given that the 20A only appears to be a startup current and given that portable heaters are unlikely to be used at the same time as an aircon unit i'd be reasonablly happy putting it on a ring. Others may not though, it's certainly a deviation from normal practice.

FWIW, I'm inclined to agree.

Kind Regards, John

 

[Frimley]

My sincere thanks to plugwash and JohnW2 for kindly responding to my query. Your responses were most helpful and I now have a clear view of what needs doing.

Once again my sincere thanks.