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Is it really necessary to have the 60A MCB as the main switch in the DB?


hoohloc
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Hi Guys

My installation has the 60A MCB between my load and the Earth Leakage. I'm out of space and want to install a contactor so that I can isolate my geyser and stove during load shedding and use N/c contact to power a pilot light so that I can be aware when there is no mains supply. The only way I can achieve this is by removing the 60A MCB and my question is, is it ok to remove it and use the E/L as main switch? I honestly don't see the need for it

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1 hour ago, hoohloc said:

is it ok to remove it and use the E/L as main switch?

Hang on, not so fast... 🙂

You must have both 1) overcurrent protection, and 2) residual current (aka earth leakage) protection. You do get combination overcurrent/rcd devices, but they are quite costly, so in most cases your house will be fitted with individual breakers, a 60A main breaker for overcurrent protection, followed by a 30mA RCD. It is unlikely that you have overcurrent protection on that RCD (due to cost factor), so it is NOT as simple as just removing one of them.

Edited by plonkster
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5 minutes ago, plonkster said:

Hang on, not so fast... 🙂

You must have both 1) overcurrent protection, and 2) residual current (aka earth leakage) protection. You do get combination overcurrent/rcd devices, but they are quite costly, so in most cases your house will be fitted with individual breakers, a 60A main breaker for overcurrent protection, followed by a 30mA RCD. It is unlikely that you have overcurrent protection on that RCD (due to cost factor), so it is NOT as simple as just removing on of them.

Eish! that means I will have to replace my Earth leakage with one that has both overcurrent and earth leakage protection 😞 

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56 minutes ago, Louisvdw said:

See the last image in this post 

So I did that... last time I saw that image I ignored it, assuming you had the overcurrent aspect covered. I looked up the spec sheet for the KRC3... it's has no overcurrent protection. You better fix it... 🙂

ABB makes some nice RCBOs (that do both).

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11 minutes ago, Louisvdw said:

Hmm interesting. I wonder how they got an COC for that.

Oh, when I moved into this house it was the same. Note the CBI breaker to the right. If it has two green levers, it is a switch. It must have green+white combination to have overload protection. The previous owner spent over 10k to get things right, and then got CoCs for all the DBs (three of them)... and this was still overlooked.

84336362_10157735091375619_1420454467718873088_o.thumb.jpg.b96ee7ad3b8c80c9da8c675232db30ab.jpg

 

Edited by plonkster
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48 minutes ago, plonkster said:

So I did that... last time I saw that image I ignored it, assuming you had the overcurrent aspect covered. I looked up the spec sheet for the KRC3... it's has no overcurrent protection. You better fix it... 🙂

ABB makes some nice RCBOs (that do both).

I think Growatt has overcurrent protection 🙂

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14 minutes ago, hoohloc said:

I think Growatt has overcurrent protection 🙂

It probably does, in the sense that if you overload it it will switch off. But when it is in bypass mode (passing through the grid) I'm not so sure. Most inverters require that you install external overcurrent protection. Besides, it still won't pass a CoC.

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58 minutes ago, plonkster said:

It probably does, in the sense that if you overload it it will switch off. But when it is in bypass mode (passing through the grid) I'm not so sure. Most inverters require that you install external overcurrent protection. Besides, it still won't pass a CoC.

Thanks for the help, much appreciated. Will have to go with the ABB Earth leakage the, I have no choice 

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11 hours ago, hoohloc said:

Thanks for the help, much appreciated. Will have to go with the ABB Earth leakage the, I have no choice 

The one I linked is just an example (an only 32A) and it is rather expensive. But the CBI combination breaker is usually around the 1.5k mark, and the last ABB RCBO I bought was around the 1k mark, so that's where you're looking. It doesn't have to be that one of course, shop around a bit 🙂

 

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