Water Heater Questions, Important To Connect A Water Heater Electric System To Ground ?

[stgrhe]

You are welcome! Which type did you buy?

[frenchFARANGbkk]

Gi,

Can you confirm that it's not useful to install a breaker in the bathroom as the sale person adviced when you already have a breaker in the consumer unit (box with many switches inside to cut electricity at different place of the condo). (one of this switch already cut electricity at every plug in the bathroom and also at the previous water heater).

I don't mind to pay 400 thb more to install the water heater but the kind of breaker box they want to add (just a switch ?) is quite ugly !

Thanks again.

[lopburi3]

Any breaker should be outside the bathroom - there should be a breaker/rcd built into the shower unit itself. Then the panel breaker. But make sure there is a ground - if in any doubt install another RCD outside bathroom. You are in a very bad position taking a shower if something goes wrong.

[Gulfstream]

You are welcome! Which type did you buy?

Sorry for the delayed reply, bought the ABB RCD and will have it all installed shortly.

Why are so many posts advising to ground; I thought the RCD breaker would cut off in the event of a problem? Why RCD + Ground?

[elkangorito]

RCD protection is considered to be "Secondary" protection. "Primary" protection is earthing.

RCD's are electronic devices, which can fail. This is why they MUST be tested monthly by pressing the "test" button.

Conversely, a hard wired earthing system is less likely to suffer damage from surges in the electrical supply etc. As such, it will provide more reliable protection.

On a further note, there is not just one type of RCD...there are about four types. See the attached picture.

[David006]

Thanks for that...interesting... wonder what the logic/safety aspect the design is based upon...

I was repairing our cheapie Panasonic Plastic dual tub washer (only has a two flat prong plug) and noticed both motors have ground bonding connected which go no place....same with our the fridges...ah well!

Not being experienced in HT distribution AC theory....anyone know what the resistance to ground of the "neutral" standard is? I suppose theoretically it should be the same as local ground since it is effectively that at the source. Also I noticed there is always a few ac volts to "ground" on the neutral ...ie a pd.( I have seen this in several locations in Thailand)! Suspect this is induced voltage only..the source of ground hum..?

The Schuko is a very safe design, the outlets are shuttered and the plug fits into a recess, it is impossible to contact live metalwork whilst inserting/removing the plug from the correct outlet, in both versions the ground connects first / disconnects last. As to why we get these on Thai appliances, who knows.

The neutral-ground connection at the transformer should be a few ohms if it has a proper earth mat. Your local ground spike will likely have a few hundred ohms, which is why an RCD is necessary, a L-E fault will not pull enough current to drop the MCB.

The N-E potential you're seeing is the volt drop along the neutral under load, the ground is at the same potential as the neutral at the transformer.

thanks for that mate...I have installed parallel ground rods and would hope that the ground should also be nearer the neutral . I which were have seen "paralleled" ie multiple rods in electrical room grounds in Canada which produced an effective ground resistance of less than 3 ohms.

Interesting story re grounds...I was managing the installation of an early electronic telephone exchange which kept getting a corrupted database every summer . turned out it was the system/building ground which had been driven into the land fill on which the building was placed. On the recommendation of one of our power engineers who had "meggered" the ground for me... had to get a drilling rig in to sink and drive 100m long copper clad carbon filled rod!! Ground dried out every summer...

[lopburi3]

You are welcome! Which type did you buy?

Sorry for the delayed reply, bought the ABB RCD and will have it all installed shortly.

Why are so many posts advising to ground; I thought the RCD breaker would cut off in the event of a problem? Why RCD + Ground?

One thing the RCD will not prevent is a hot to neutral fault - that will require the overload breaker to trip. Not good if your left index is on neutral and right on hot.

In your water heater the ground wire will trip the breaker if the chassis/metal tank becomes hot. Without it you would be the ground and if the RCB failed could lose your life.

Have both. Please.

[stgrhe]

You are welcome! Which type did you buy?

Sorry for the delayed reply, bought the ABB RCD and will have it all installed shortly.

Why are so many posts advising to ground; I thought the RCD breaker would cut off in the event of a problem? Why RCD + Ground?

One thing the RCD will not prevent is a hot to neutral fault - that will require the overload breaker to trip. Not good if your left index is on neutral and right on hot.

In your water heater the ground wire will trip the breaker if the chassis/metal tank becomes hot. Without it you would be the ground and if the RCB failed could lose your life.

Have both. Please.

Isn't that one of the reasons why one should chose a RCBO before a RCD?

[lopburi3]

RCBO says it is a RCD and a breaker combined but in home use I have never seen them not combined here regardless of what they are called (although I am not in that business). The RCD trips the breaker as does an overload. But you really should have overload breakers of lower ratings than the Safe-t-Cut and main panel RCBO 50-60 amps. In most overload situations the circuit 15 amp breaker trips long before the RCBO breaker would trip for overload.

[Gulfstream]

You are welcome! Which type did you buy?

Sorry for the delayed reply, bought the ABB RCD and will have it all installed shortly.

Why are so many posts advising to ground; I thought the RCD breaker would cut off in the event of a problem? Why RCD + Ground?

One thing the RCD will not prevent is a hot to neutral fault - that will require the overload breaker to trip. Not good if your left index is on neutral and right on hot.

In your water heater the ground wire will trip the breaker if the chassis/metal tank becomes hot. Without it you would be the ground and if the RCB failed could lose your life.

Have both. Please.

Thanks all for the wise info, just ordered earthing/grounding. A major job but prefer safety.

I had always thought the RCD was so sensitive it would trip before I got "fried", looks like it's not the case.

[lopburi3]

It is not a matter of not being sensitive - when set properly they are. But they can fail and it is always best to prevent touching a hot chaises (which is what the ground will do - short to ground/chaises will trip the overload breaker before you have a chance to touch it).

[Gulfstream]

It is not a matter of not being sensitive - when set properly they are. But they can fail and it is always best to prevent touching a hot chaises (which is what the ground will do - short to ground/chaises will trip the overload breaker before you have a chance to touch it).

Got it, and thanks again. Will have all grounded.

[Gary A]

My condo has no ground (earth) available. Most hot water showers have an ELB built in but some don't. Turbora is one that doesn't. I'd make sure that the unit you buy has the ELB.

[Thaifan2]

My condo has no ground (earth) available. Most hot water showers have an ELB built in but some don't. Turbora is one that doesn't. I'd make sure that the unit you buy has the ELB.

The model i just bought has a ELCB ( same as ELB ?) .Turbora model ,DZ-3500E

[ronz28]

Getting it right is a common problem elsewhere too. There needs to be a plug-in LED device that anyone can use to quickly determine if the wiring is proper since some of it isn't in Thailand and elsewhere.

KBR recently Lost $24.1 Million Fee Over Green Beret’s Death due to this type of electrocution:

KBR Loses $24.1 Million Fee Over Green Beret’s Death (Update1) - Bloomberg.com