Electrical Earthing/Bonding....

[les1]

Do we have any qualified electricians who can give good advice. Recently I was told that a particular electrical system to a condominium swimming pool needs Earth bonding.

When the point was put to a Thai electrical Technician he said that the whole building is Earth Bonded up on the roof. I personally do not follow that but I am no electrician.Any comments on this would be helpful..    thank you..............

[ubonjoe]

Moved to here where you should get some good answers.

[Crossy]

What is the "particular electrical system", pumps, lighting, something else?

 

In general the building / pool structural steel will provide a good structural bond all the way to ground, but it will need to be verified that there is indeed a low impedance path.

 

Normally your pool electrics are SELV (Separated Extra Low Voltage) for lighting and your mains powered pumps are well away from the pool itself on the end of plastic pipes (so no shock risk). Obviously both need grounding in the conventional sense at the supply.

[les1]

2 hours ago, ubonjoe said:

Moved to here where you should get some good answers.

Thank you Ubonjoe I looked for an appropriate forum but obviously didn't find it.

 

Thanks again,                           

[les1]

2 hours ago, Crossy said:

What is the "particular electrical system", pumps, lighting, something else?

 

In general the building / pool structural steel will provide a good structural bond all the way to ground, but it will need to be verified that there is indeed a low impedance path.

 

Normally your pool electrics are SELV (Separated Extra Low Voltage) for lighting and your mains powered pumps are well away from the pool itself on the end of plastic pipes (so no shock risk). Obviously both need grounding in the conventional sense at the supply.

 

Thanks for your reply, it is pool pumps (2) & lights (3) Don't follow the "low path impedance. This system has been in for the past 23 years. I understand the low voltage lighting. Also pumps are run off plastic piping. So possibly when they say that the building is grounded but at the roof it may well be OK.

 

Thank you,                        

[elektrified]

Probably means the ground buss terminates at the steel frame of the roof. Our house is like that. Probably not the best system, but better than nothing.

[les1]

8 hours ago, elektrified said:

Probably means the ground buss terminates at the steel frame of the roof. Our house is like that. Probably not the best system, but better than nothing.

 

Thanks for your input....

[Crossy]

A system that old may well have mains powered pool lights. These must be disconnected at the source in order to guarantee safety. As an absolute minimum the lighting circuit must be protected by a 15mA RCD. We read of too many electrocutions in pools! Replacement by SELV lighting should be a priority.

 

Also the earthing of the pool pumps needs to be verified (which is probably what was being referenced in post #1). The easiest way would be by an earth-loop impedance test, you'll need a man with the relevant kit and knowledge of how to use it.

 

As this is a public space safety is paramount.

[les1]

9 hours ago, Crossy said:

A system that old may well have mains powered pool lights. These must be disconnected at the source in order to guarantee safety. As an absolute minimum the lighting circuit must be protected by a 15mA RCD. We read of too many electrocutions in pools! Replacement by SELV lighting should be a priority.

 

Also the earthing of the pool pumps needs to be verified (which is probably what was being referenced in post #1). The easiest way would be by an earth-loop impedance test, you'll need a man with the relevant kit and knowledge of how to use it.

 

As this is a public space safety is paramount.

 

 

Thanks, Do you know of anyone who could do this?

[Crossy]

Where are you located?

 

Someone may well know a local sparks who can do the job.

[les1]

Location is Nong Hoi,  Chiang Mai

[shaemus]

I am not quite sure what you want to know. Please ask a specific question. I am an electrician. But fundamentally the earthing system of the installation should be continuous and be permanently connected to conductive surfaces to prevent "touch potential". Examples of things may include metalic casing of pumps, Structural steel, re bar in concrete, hand rails etc etc.  You want to create a farriday cage. Your cabling and protective devices should be chosen and i stalled so they operate in the correct manner. E. G trip times of an rcd.  Google eath loop impedance and fault loop impedance. 

 

Hope this helps 

 

Shaemus

Chapter 20 Earthing Regulations.pdf

[Crossy]

3 hours ago, shaemus said:

I am not quite sure what you want to know.

 

He needs to know if there is someone in his area with the equipment and knowledge to verify that the pool and its associated electrics are safe.

 

[sappersrest]

There is no such thing as direct  mains powered pool lights, never has been.

They are  12 volt, the original pool lights were PAR type ,( car headlamp).

Most modern lights are either LED or Halogen.

 

There could be issues with the transformer and of this of course must be suitably earthed. as should be all electrical equipment  in the pump room.

 

All decorative lights and general lighting around the pool side should be SELV especially  within 3m of any water, taps ., showers pool tank, etc.

[Crossy]

Agree 100% sappersrest, except that mains pool lamps were in common use in the past even in the nanny state UK.

 

US pool owners can still buy mains (OK 120V) pool lamps and fittings, example http://www.intheswim.com/p/hayward-replacement-lights

 

Many pools in Thailand had mains lamps and many people have died because of faulty ones with no RCD protection.

 

Anything built here in the last 20 years or so ought to have SELV lighting, but one never knows, better to be safe than sorry.

 

[elektrified]

My pool in the USA had 120V lamps. The building code was for triple grounding. I believe (but could be wrong) that it is still common practice in the USA.

[sappersrest]

Incredible that anyone can still install mains voltage lights in a pool??