Connecting Air Con Unit to Socket Ring Main

[Damian30]

Hi,

I'm looking to install a Mitsubishi Electric inverter air con/heat pump in a domestic premises. The model I am looking to go for requires a starting current and running current of 4.4 amps.

I've spoken to the manufacturer and didn't get very far on the electrical requirements (I'm going to try them again though), although I understand it is preferred that they are connected via a rotary isolator.

I had my electrician round and he thought it wouldn't be an issue taking off an existing socket ring, rather than its own circuit. His suggestion was to take an internal FCO connecting into an adjacent socket, with a rotary isolator on the outside connected to the FCU. I don't have a problem with this, although it involves an extra accessory next to the existing socket.

I'd be grateful if anyone has any further experience or views on how this air con unit could be connected up and whether the way proposed by my electrician is the standard approach. My initial naive thought was to get an external IP66 socket installed (which I could use for other purposes) and plug the air con unit into the socket with a standard 13 amp plug. Then again, I'm not to sure what the benefits are of rotary isolators over an FCU, etc, but I'm sure someone will point out.

Many thanks,

Damian

 

[Taylortwocities]

At all times you must follow the makers instructions.

If an FCU is OK for their purposes, then I would suggest mounting an IP66 FCU outside as a spur from that socket, and wiring the aircon into that.

Something like this http://www.tlc-direct.co.uk/Main_In..._Accessories_Index/Masterseal_Spur/index.html

 

[ericmark]

I got caught out with AC units the bit that went in the room was quite a low power requirement around 4 amp, but the bit in our case that went on the roof was a real heavy user of power.

It is common to have two bits of an AC connected by pipes the bit with the compressor is rarely as low as 4 amps so do check.

I ended up (OK commercial not domestic) having to pull in a 150mm sq cable to feed the array of AC's on the roof of a shop in Chester.

 

[Damian30]

Hi All,

Thanks for the comments - forgot to say that the unit also states a fuse rating of 10 amps.

I've spoken to Mitsubishi again this morning and they said the electrical connections are basically up to the electrician in accordance with the appropriate regs and general practice is that it should have a means of isolation in close proximity. When discussing further, they didn't seem to have an issue with connecting using a 13amp plug. In which case I'm guessing we could probably extend the ring to an external Masterseal double socket and plug it in.

Does this seem a big no no ?

Thanks,

Damian

 

[Taylortwocities]

Sockets are designed for portable items to be plugged in.
Your proposed aircon item is not a portable item like a lawn mower.
The socket (and the plug) reply on a good contact by the process of item(s) being plugged in and out. The contact of the plug, left in place in moist conditions (like your wall) will deteriorate over time.

Your socket will be outdoors in frost, hail, rain,snow, sun and pestilence and will rely on there being a 100% seal on the lid when the plug is in place.

Your aircon unit is a fixed appliance - PLEASE use a fused spur as i have already posted. It is designed to do the job.

 

[ericmark]

There are times when we use plugs and sockets for fixed equipment so that we can unplug for maintenance it was at one time common to use a 15A socket for immersion heaters so the plumber could change it without needing an electrician to disconnect. However we would not normally use a 13A socket for this as the fuse generates heat so it would be a FCU supplying a 15A sockets and since it is cheaper to connect direct into the FCU that would seem a strange way to do it.

Open many bits of equipment and you will find multi-pin plugs and sockets and edge connectors again for easy maintenance so we can change a board. But the 13A socket is considered as for portable appliances and using it for anything fixed means you may find it has been unplugged to use something else.

It is normally considered that 2kW is the limit for items which are fixed using a 13A plug although the 13A plug is nearly 3kW. One reason is the fuse produces heat the other is if using that power for an extended time it could reduce the power available to other items enough to mean a fuse/MCB opens.

You are right on the limit and I would not want to normally use an existing circuit. However with for example my mother who uses very little it may be OK but not as a general rule.

 

[JohnW2]

it was at one time common to use a 15A socket for immersion heaters so the plumber could change it without needing an electrician to disconnect. However we would not normally use a 13A socket for this as the fuse generates heat so it would be a FCU ...

The fuse will obviously generate the same amount of heat (for the same load) whether in a plug or FCU. Some claim that the heat is better dissipated from the fuse in an FCU, but I don't know whether (or even necessarily why) that is actually true. It's probably best to avoid the 13A fuse altogether and rely just on the 15/16A MCB/fuse of a dedicated circuit.

Kind Regards, John

 

[viewer]

Is this the machine? If so the pictures show the rotary switch to the external unit and the help line was talking about the internal unit which could be fitted with a 13A plug so that isolation for cleaning would be foolproof (?).

http://www.youtube.com/watch?v=cxpjIUeHM_c