Electrical Problem

[rude]

Hope the people that are good with electrics can help me with this. Actually just need something explained to me.

Basically went to 2 panasonic E18GKR/HKR High wall splits today and the complain was from the sparky wiring them up.

basically he tested the earth wire for power for some reason like so:

http://i35.photobucket.com/albums/d193/123MMM/Pana.jpg


Now he was getting 108V between the earth on the Condensing unit and the earth coming from the Main Earth at the board.

So i did the right thing and checked all components with a megger and found nothing down to earth. To my understanding this 108V is only a potential voltage that isnt really there and can be caused by the 240V and earth's being run close together within the boards or something?

I did end up running one of the units and didnt get zapped from touching the unit. But the problem is this sparky has called our power company and has requested them do a site visit to see if its illegal or whatever.

Now i know theres nothing wrong with the units and it is electrically safe, but the problem was i didnt know how to explain to the sparky that he was wrong.

So any help with explaining this voltage to me so i can explain it to him as well would be greatly appreciated. Or am i wrong?

[marincarl]

Did you do your measurement with a digital meter? The input impedance is generally around 10 Mohms and internal capacity in the ref units can easily cause some voltage to appear at the casing. As soon as you touch it, you'll short this voltages out, as you can check with the meter, currents are neglegable, all is fine.

[dogma]

I've seen a similar problem with an industrial condensing unit. The problem was a fan capasitor wired wrong in manufacture.

[paul_h]

Was this a domestic or commercial install?
A/Cs do filter a lot of the mains and dump it to earth, but the only time I've encounted voltage that high was a commercial install on a MENs system. Changing the PCBs didn't help so it was a building wiring problem, faulty earth.

Those voltage pens are handy for this, not the screwdriver contact type, but the plastic ones that light up when near voltage. Odds are it wouldn't do anything when near the earth/chassis of the unit, but would light up on the disconnected earth cable from the mains. Proving the detected voltage comes from the building mains earth cable via neutral, not the a/c

[frank]

Why isn't the earth from the Dist board not connected to the chassis??

this needs to be done to ensure that all earth potential is at the same level.

From your drawing, it would appear that your chassis is not earthed

[rude]

Why isn't the earth from the Dist board not connected to the chassis??

this needs to be done to ensure that all earth potential is at the same level.

From your drawing, it would appear that your chassis is not earthed
Yeah your right, the electrician tested with his meter between earth and earth, for some unknown reason. Well his reason was thats how you test these things.

I told him he was wrong and the units were fine and left site. But the poor old customer had no A/C because he refused to connect power to them.

[Electrocoolman]

This voltage is probably due to the mains filter. These can result in a potential on the earth (chassis) and a very small current to earth.
A lot of electronic equipment has filters.
Problems can arise when multiple units (eg computers) are all fed from one mains plug. These small currents add together and can exceed the allowable (regulation) earth current.
In the UK this means either a dedicated industrial supply or supplying via an isolating transformer, but in this case I can see no problem.

Get a different electrician who knows a bit more!

[ianybeany]

yea seen it before,
its a bad earth, check that the earth at the board is properly connected and the cable is good and if that fails check other items of machinery in the building to cross check that it is singled out as just the ac unit what manufacturer by the way?

[rude]

yea seen it before,
its a bad earth, check that the earth at the board is properly connected and the cable is good and if that fails check other items of machinery in the building to cross check that it is singled out as just the ac unit what manufacturer by the way?
All earth's were connected and fine.

There were 2 units on site and both had this same voltage. One was a Panasonic E18GKR and the other was the newer Model E18HKR

[rude]

This voltage is probably due to the mains filter. These can result in a potential on the earth (chassis) and a very small current to earth.
A lot of electronic equipment has filters.
Problems can arise when multiple units (eg computers) are all fed from one mains plug. These small currents add together and can exceed the allowable (regulation) earth current.
In the UK this means either a dedicated industrial supply or supplying via an isolating transformer, but in this case I can see no problem.

Get a different electrician who knows a bit more!
Yeah im convinced the units fine. I did tell the customer to call out another electrician to connect up, as our license here doesnt allow us to and after hearing the electrical board was notified i didnt want to touch anything.

[install monkey]

This problem occurs if the cabling to the condenser is run in trunking with other cables.typical sparks making problems!