Grounding AC's

[r136dg]

I'd like to clarify something from the questions & answers seen here. I've been under the impression anything getting power from your distribution/consumer unit/breaker box, should be grounded from a ground that's bonded to that ground pole in that box.

I have a pole in the front of our property with a small distribution box to power anything around the front gate. Put a ground rod in @ the pole which goes up to a ground bar in that box, than wired all the way back to the house & bonded to the ground bar there.

Is this the correct way to do it?

If so, when an appliance has directions to put in an independent ground rod for it, or one was to ground something in the trusses that wasn't bonded to the ground bar at your power source, what could the consequences be? 

Note: The 2nd ground rod in the pic is for a SPD also in the pole box.

[Crossy]

Multiple independent ground rods are not hazardous per-sé.

 

However in the event of a close lightning strike there could be significant difference in the "ground" potential at the two locations. This could get big enough to fry electronics or even (it would have to be very close) cause a side-strike.

 

Multiple linked rods that are a significant distance apart could have similar issues with very large currents flowing in the link cables (they are specifically prohibited by Aussie regs for this reason).

 

I can see absolutely no reason to independently ground an appliance if you already have a satisfactory grounded 3-pin system.

 

Linking your building steel to a rod may improve your ground resistance, certainly isn't going to do any harm.

 

[r136dg]

2 minutes ago, Crossy said:

Multiple linked rods that are a significant distance apart could have similar issues with very large currents flowing in the link cables (they are specifically prohibited by Aussie regs for this reason).

You got me thinking again Crossy. lol

My pole ground to house distribution box is about 40-50 meters & I believe 25 or 35mm aluminum wire was used to make that link. Is this nearing the significant distance threshold? If so would I be better off severing the link & using an independent ground for anything out front near the pole? (gate motor, outlet, lights, ect.)

There is an SPD in that pole box that should take some of a surge, hopefully... Also, I'll be using an RCBO to power anything out there if that's relevant.

Thanks!

[Crossy]

I would put 40-50m in the "significant" box.

 

Get a rod in at the house. Personally I would break the link to the other rod, but unless you have a high likelihood of close strikes it probably won't hurt.

[Dazinoz]

1 hour ago, r136dg said:

 

If so, when an appliance has directions to put in an independent ground rod for it,

 

I have never seen an independent ground rod required for an appliance. What type of appliance have you seen this on?

 

Maybe products specifically for thailand where they know that the running of ground wire in houses not common.

[Dazinoz]

I have had another interesting thing happen as regards to a hot water heater.

 

My friend is in a condo and her hot water heater failed. The owner lives in Pattaya so I offered to buy and instal new heater to save time and pay that much less in the next rent payment. He agreed.

 

Bought new heater from HomePro and took it to the condo. Removed old one. I had removed the cover before and had seen ground wire so I thought ok (stupid me). The ground wire was attached under one of the mounting screws which was screwed into a plastic wall plug. So NO ground. Anyhow I noted on new heater the internal wiring had small wire going from ground connection the PCB. Also noted that the heater had an "iSafe" light. Did some checking and found this protects from no ground. Took it back to HomePro and told them will not work can I get heater that does not need ground wire to work. I was told all heaters now require 3 wires to work. OK, contacted owner who has agent in Chaing Mai. Agent later called and said he could not get an electrician to instal  as condo has no ground wires.

 

Ok, next step. I mounted the heater, plumbed and wired with a short length ground wire for a later connection. Her room is on second floor at back of condo so I though i could drop a ground wire out window down to the ground and drive in earthing rod and connect. Turned on water and, out of curiosity turned power on. IT WORKED. So much for the safety circuits.

[r136dg]

I am seeing a lot of this in online Daikin Inverter installation guides/manuals;

 

"3) Be sure to install an earth leak detector. (One that can handle higher harmonics.) (This unit uses an inverter, which means that it must be used an earth leak detector capable handling harmonics in order to prevent malfunctioning of the earth leak detector itself.)"

 

?1- Can someone define this?

?2- Should our AC's be on an RCBO circuit? If so does the locally available Shcnieder 30ma qualify to handle higher harmonics?

?3- Most refrigerators are inverter models now, would they need this earth leak detector handling higher harmonics also?

 

Sorry but instructions are in Thai & I'm finding confusing things on the internet.

Thanks!

[StevieAus]

On 7/22/2017 at 4:48 PM, wpcoe said:

By any chance was the "two pin" plug a Schuko plug?

 

 

I think these are less common in Thailand these days, but maybe worth asking?

No it was a two pin sealed plug , logic would suggest that they provide a three pin plug and a separate earth wire from the frame for those houses without three pin sockets but then again than means more cost.

[StevieAus]

23 hours ago, Dazinoz said:

 

I have never seen an independent ground rod required for an appliance. What type of appliance have you seen this on?

 

Maybe products specifically for thailand where they know that the running of ground wire in houses not common.

It was a Samsung refrigerator which has an invertor bought about one year ago

[Crossy]

1 hour ago, r136dg said:

I am seeing a lot of this in online Daikin Inverter installation guides/manuals;

 

"3) Be sure to install an earth leak detector. (One that can handle higher harmonics.) (This unit uses an inverter, which means that it must be used an earth leak detector capable handling harmonics in order to prevent malfunctioning of the earth leak detector itself.)"

 

?1- Can someone define this?

?2- Should our AC's be on an RCBO circuit? If so does the locally available Shcnieder 30ma qualify to handle higher harmonics?

?3- Most refrigerators are inverter models now, would they need this earth leak detector handling higher harmonics also?

 

Sorry but instructions are in Thai & I'm finding confusing things on the internet.

Thanks!

 

Any modern RCD / RCBO will be fine, the instructions are a spot of a** covering by the manufacturer.

 

Up to you if you RCD / RCBO your aircon, but we usually say that the manufacturers instructions should be followed.