Split Inverter Air Conditioning

[john2k]

Thanks for the replies guys, I'm having the system installed by a F gas engineer, only thing he won't do is the final connection from the outdoor unit to the electrics. He will place a exterior isolator and I have to get the connection to it made.

The supplier of the system has said that the power consumption of the system is 100 to 1510 Watts, so that technically should easily run of a fused 13A spur running off an existing 32A rings main right? Or I am assuming using 2.5mm flex cable suitable for outdoor use connected to a heavy duty plug with a 13A fuse should also be ok? Taking the outdoor cable through a conduit should be sufficient right?

 

[SimonH2]

A neater option would be a switched fused connection unit (FCU) inside, and the exterior isolator "back to back" through the wall from it - no wires showing. You drill through the wall (going from inside-outside through the back of the FCU backbox), push a bit of conduit through, and put the external switch on the end of the conduit. Ideally the conduit would be terminated with the correct adapters/bushes, but that's probably tricky to do inside (unless adding a new box).
Things need to be sealed to prevent water ingress - particularly at the entry to the external switch.
Technically you could just spur out the back of a socket IF the external switch is fused - but that would be a bad idea for several reasons. One of which is that if damp gets into the outside switch, it'll trip your RCD and you won't be able to isolate the fault easily (ie no double pole switch to flick off inside). Adding a new accessory box alongside a socket is generally not hard to do, and unless you've got hard to match paint or paper, making good afterwards shouldn't be too difficult.

 

[john2k]

Thanks. Is it safe to place the outdoor unit on a concrete slab? or does it have to be mounted to the wall?

 

[ban-all-sheds]

I suggest you ask the F gas engineer who is going to install it.

 

[john2k]

When the pipes come out instead of leaving visible insulated pipes, I want to put them in some neat trunking, what kind of trunking would be suitable that has a end cap too because as it runs vertically the top of it will need to be capped otherwise it will look a bit strange

 

[ban-all-sheds]

1) That's not an electrical Q.

2) You could try the plumbing forum, or you could ask the installer for ideas on neat installation.

 

[SimonH2]

Ask your refrigeration engineer. There is trunking designed just for that sort of thing - it's a common problem that pipes need to be hidden in offices etc.

 

[john2k]

I've got the correct trunking. Just a quick electrical question. If the system's spec sheet says: Power input (Min-Max) W: 100-1580W Does that mean the maximum power draw the system attempt to draw will be 1580W? If that is the case then it is way within 13A which means technically I should be able to run it off a 2.5mm flex cable wired to a 13 heavy duty plug?

 

[ban-all-sheds]

Good luck getting 2.5mm² into a plug. It's not actually impossible, but...

...But why 2.5mm²? How long is the flex going to be?

 

[john2k]

Good luck getting 2.5mm² into a plug. It's not actually impossible, but...

...But why 2.5mm²? How long is the flex going to be?

I've got 2.5mm² flex cable into heavy duty plugs in the past and goes in ok. But the run from the plug to the unit will be no more than 1.2meters

 

[ban-all-sheds]

So why do you want to use 2.5mm²?

 

[john2k]

So why do you want to use 2.5mm²?

Because I would think 2.5mm would be the safest option for 13A wouldnt it?

 

[SimonH2]

On that basis, 4mm² would be even safer, or even safer still 6mm² And if you're that paranoid, don't use a 13A plug with those pesky overheating problems - best put in a dedicated supply and hardwire it
1.5mm² should be quite adequate unless there's something we haven't been told about - the power quoted works out to only around 7 amps full load. You shouldn't even need to worry about startup current since this seems to be an inverter system (I've assuming from the variable power consumption) which will be inherently soft-start.

 

[ban-all-sheds]

If you needed a bookshelf to hold 67kg of books, would you put one up which could support 250kg on the grounds that it would be safer than one which could support 130kg?

 

[john2k]

Fair point guys I just wanted to make sure I have adequate cable to support the load. I dont want the cable to overheat or anything. Whats the maximum wattage and amperage a 1.5mm2 cable can handle?

If a 1.5mm cable is rated at 14A, then technically it's way higher than the 13A fuse that would be inside the plug anyway, so the fuse will blow before the wire has any issues. But does a 1.5mm cable rated at 14A get any hotter drawing 13A than a 2.5mm cable drawing 13A?