Do I need an isolator?

[cornburn]

Need to get a feed in ready for an aircon unit, which will be on its own circuit. I'd usually put a rotary isolator in ready, but as the aircon guys will be there when I'm working it there a problem with taking the lead off the unit and putting it straight into the RCBO, with that used as the isolator if needed? The CU is only 2 foot away from where the aircon unit will be so sticking another point of isolation directly next to the CU seems a bit pointless!

Cheers

 

[malcolmsanford]

No not really as long as you don't need double pole isolation for instance if the system is a TT.

 

[Paul.M]

I see your dilemma with the cu only 2 foot away and that we can use the mcb/rcbo as a functional or isolation switch. I would put a rotary isso in just to make the install idiot proof for the users. Big red switch next to the aircon is better than finding a switch in a large board imho.

 

[truckster]

Agree with Malcolm

Although Paul has a point but evolution states that if you make something idiot proof, nature just evolves a better idiot

 

[malcolmsanford]

I agree with Paul to be honest I would put a switch in just out of false of habit I suppose.

 

[Paul.M]

Agree with MalcolmAlthough Paul has a point but evolution states that if you make something idiot proof, nature just evolves a better idiot

We then install a bigger red button

 

[cornburn]

Thanks for perfectly demonstrating my dilemma Nice to see none of you can agree either! The rotary isolator would need to go outside so I might just see if I can get an outdoor one at the ready and then see on the day.

The system is TT, but as it can be isolated from the DP main switch on the 5 way unit we're installing the isolator for this piece of equipment (or any other for that matter) can be single pole can't it?

 

[malcolmsanford]

You can if you wish utilise the main DP switch as your means of isolation for that unit, but you would have to use that switch and not the single pole MCB all the time for isolation, which would means you isolate those other 5 circuits every time you want to isolate your unit, not a good design point really is it.

As it is TT use a double pole switch you could fit a double pole 20amp grid switch, won't need to be lockable if it's close by, or for extra safety a key type one.

 

[Hawca]

remember that an MCB / RCBO is an 'off load' device and not designed for full load switching, I would put in an isolator as a mater of principle, if only for local isolation for the untrained. mechanical switching.

 

[netblindpaul]

Check PUWER98 it's statute and will require the isolator regardless of 7671, thus you have to install it.

 

[cornburn]

Thanks guys, I've ordered the usual crabtree rotary so will put that outside next to the unit and let the aircon guys take it from there. It seemed like a bit of a waste but better safe than sorry, especially as it's a TT.

Cheers

 

[mogga]

iv has same argument with a gaffer years ago He didnt want to fit isolator near db I argued that Onload and double pole He was stuffed when he checked the scope of works it said Every air conditioning unit shall have point of isolation next to it even indooor units fed from outdoor so the AC guys couldnt make mistakes turning off stuff
BIG RED BUTTON all the way

 

[malcolmsanford]

remember that an MCB / RCBO is an 'off load' device and not designed for full load switching, I would put in an isolator as a mater of principle, if only for local isolation for the untrained. mechanical switching.

Most likely the rotary switch that will be fitted would be to BS 60947-3 which is also a non switchable device on laod

 

[truckster]

remember that an MCB / RCBO is an 'off load' device and not designed for full load switching, I would put in an isolator as a mater of principle, if only for local isolation for the untrained. mechanical switching.

I can't see as that is right, the MCB/Rcbo is designed to break a fault current which would be several times the flc. Table 53.2 lists a 60898 for isolatin, emergency and functional switching