6.16.7.3

[Isetech]

6.16.7.3 Earth leakage protection shall be provided for the circuit that
supplies an electrode water heater, steam generator or boiler. This protection
shall be set to operate in the event of a leakage current exceeding 10 % of the
current consumed by the appliance under normal conditions of operation. The
characteristics of the circuit and of the earth return path shall be such that the
earth leakage device will operate before the potential between earth and the
shell of the steam generator or boiler exceeds 50 V, including under
short-circuit fault conditions

A formula is required, or must just have normal earthing and bonding like a geyser?

[Dylboy]

Formula for me would be on a 30mA example....

50V ÷ 0.03 A= 1667ohm.

So the resistance of the earth cable can be 1667ohm and then the ELU will trip at 50Volts.

Now 10% of a boiler I have no clue how many mA or Amps that is but that is how I see that statement

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[GCE]

6.16.7.3 Earth leakage protection shall be provided for the circuit that
supplies an electrode water heater, steam generator or boiler. This protection
shall be set to operate in the event of a leakage current exceeding 10 % of the
current consumed by the appliance under normal conditions of operation. The
characteristics of the circuit and of the earth return path shall be such that the
earth leakage device will operate before the potential between earth and the
shell of the steam generator or boiler exceeds 50 V, including under
short-circuit fault conditions

A formula is required, or must just have normal earthing and bonding like a geyser?

You need to size the earthing correctly and double check it .
On a Electrode boiler there is a high earth current . On a 800KVA boiler at 1 200Amps you will get 120 Amps flowing down to earth - If your earth mat and earthing depending on distance is not correct that boiler to touch will give you a a nice wake up.

I used to measure the earth current to help make the decision on service intervals for the electrodes and clean out the boiler.

When you start getting to 8MVA boilers at 11KV the earth current can get scary - If the water is contaminate it also becomes a problem.

[Dylboy]

How would one design the correct protection for such a situation ?

I don't think you get an Earth Leakage Device that trips at 120Amps haha.

I would love to learn how if possible

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[GCE]

How would one design the correct protection for such a situation ?

I don't think you get an Earth Leakage Device that trips at 120Amps haha.

I would love to learn how if possible

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You do get -
Is general refer to as a Adit unit - You can set percentage of current and it uses a CT to sense imbalance
Often used on main incoming supplies, and at one stage was a bylaw to fit on supplies over 500Amp if I remember correctly

[Isetech]

You need to size the earthing correctly and double check it .
On a Electrode boiler there is a high earth current . On a 800KVA boiler at 1 200Amps you will get 120 Amps flowing down to earth - If your earth mat and earthing depending on distance is not correct that boiler to touch will give you a a nice wake up.

I used to measure the earth current to help make the decision on service intervals for the electrodes and clean out the boiler.

When you start getting to 8MVA boilers at 11KV the earth current can get scary - If the water is contaminate it also becomes a problem.

This could explain why the other unit earth wire is burnt blue and broken, there is no bonding and the earth wires dont even go to the same earth bar, and no leakage current detector.

[Dylboy]

You do get -
Is general refer to as a Adit unit - You can set percentage of current and it uses a CT to sense imbalance
Often used on main incoming supplies, and at one stage was a bylaw to fit on supplies over 500Amp if I remember correctly

That is so cool thank you !

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