Should RCD be used on AC?

[sighman]

It's a self explanatory question, but should a 30ma 100VA RCD be used on an AC system?

Someone has told me that there is too much earth leakage on the units after time and so they will trip out a lot.

[Argus]

Sounds like a fairy story to me.

The only acceptable earth leakage is NIL at any time, new machine or old.

30 mA is considered threshold for earth safety on a sub circuit. 60 mA RCD may be used on the main supply to a distribution board.
Please read the UK regulations on wiring BS 7671.

I would suspect any machine that 'leaks' to earth. If it trips a RCD it should be investigated, A/C unit or not.
________
essential vaaapp vaporizer

[frank]

Got to agree. Any earth leakage will trip and should trip an RCD - after all this is what they were designed to do. If your AC or cellar coolor is installed in a "wet" environment then it must be protected by a RCD or RCCD.

Some equipment is designed to "earth leak" and this type of equipment should not be fitted with a RCD. All is explained in BS7671. Lots of fridgies do not bother taking the 16th Edition but they should. It is an eye opener.

[chemi-cool]

we use over here two types of RCD,

one for residual use, 30ma.

two, for industrial use, 300ma.

the biggest "enemy" is heating elements used for drying and defrosting.

a good electric system well insulated and water proof up to IP 65 should do.

chemi

[sighman]

Hi Guys thanks for that one, I was thinking the same, but as I am new to this game then you have to listen to what people say who have been at it a while

[iceman007]

Hi Sighman,

I'd go with everyone on this. In addition, it's good practice to undertake an insulation resistance test and earth continuity test when installing. It's surprising how many install techs don't do any electrical tests when installing and commissioning.

Regards
James

[chemi-cool]

hi james,

insulation resistance test is one thing. I'm sure every tech Carry's a megger so no problems.

earth continuity test is a different story and if we talk about the same test, then its expensive piece of tool and not everyone knows how to use it.

I attach a picture of one. is that what you meant?

chemi

[iceman007]

Hi Chemi

I have a smaller tester than the one in the picture. The problem is that they are quite expensive. I would say about 50% of techs that I come into contact with here carry a Megger. I see alot rely on just a standard voltmeter.

Regards
James

[chemi-cool]

hi james.

being also an electrical contractor, I only use earth continuity tester after a project was finished and its only to make sure that the national electric company will not make any problems before connecting to main power. this is the only test they carry cause if results are bad RCD will not work and people can turn into charcoal before any one notice.

a good megger up to a 1000V is all you need after any installation.

if electric system equipped with RCD, the easiest way to check it is to bridge between "0" and ground. RCD sould trip.

chemi