Install a SPD

[Max Brok]

I wish to install a SPD in a existing CU. This CU is equipped with a Main MCB 50 A, RCD 0.03mA and 6 breakers 16 and 20 A. The unit have a good earth, a rod of 2.7 mts and wire 10 mm square with MEN system on Neutral. The main is 1 phase 1 Neutral.

Which SPD I have to buy? I have 2 pictures of SPD Type2 as example

How to install them and what is the difference between them?

?

[bodga]

get the second one, I got one for N&L

[Max Brok]

5 minutes ago, bodga said:

get the second one, I got one for N&L

I need more info. See my questions.

[Crossy]

If you are definitely MEN and have a good solid ground rod then the first one connected L-N on the controlled side of your 50A incomer would do the trick. They are internally fused so you don't realy need an MCB for the SPD itself.

 

I would however go for one of at least 60kA or more if you can find one. 

 

I would also scatter some good quality plug-in units on your critical technology, I also bought a bag of the individual 6kA units which are installed in our LED light fittings.

 

A note about using the naked units. They can fail in a spectacularly pyrotechnic manner, so make sure they are in a non-flammable box (such as a metallic light fitting).

[RichCor]

a somewhat recent Surge Protection Device topic thread:

Do these surge protectors work?
By tomas557, August 15, 2017 in The Electrical Forum

+73 posts

[Metropolitian]

4 hours ago, Max Brok said:

I wish to install a SPD in a existing CU.

This CU is equipped with a Main MCB 50 A, RCD 0.03mA and 6 breakers 16 and 20 A.

The unit have a good earth, a rod of 2.7 mts and wire 10 mm square with MEN system on Neutral.

The main is 1 phase 1 Neutral.

 

Which SPD I have to buy? I have 2 pictures of SPD Type2 as example

As replied by Crossy that you have a MEN system and you are sure that you have good earth, then indeed the first one is enough.

It's not really overkill to go for the second one, it depends on the space still left in the CU.

Even with good earth, it is still possible to have a spike on the neutral, especially if the rod and CU are not close to each other there will still be a resistance in the 10mm wire.

 

The one you found the L and N has different characteristic, it IS for situation with men.  The SPD for the Neutral will catch all spikes above 255 volt while the L part starts conducting above 275 volts.

 

You even can use both L and N, on the same line. It works then as double protection, the same as in Crossy's reply 'I would also scatter some good quality plug-in units on your critical technology'.

But the one you found , with the N side reacting on 255 volt is made for neutral that has a link to earth in the CU.

 

I use SPD's which catchs spikes at 385 volts and 420 volts in the sub panels and 275 volt in the main unit.

 

 

Quote

How to install them and what is the difference between them?

Difference is explained above, and installation is depending on the situation in your CU.

 

If you post a picture of your CU, also opened with the wiring visible, I/we are able to draw it out for you.

 

The question is like where the live bar is, and how the main breaker is wired and if there is an rcbo behind it.

 

Roughly explained, the bottom, earth terminal need to be connected to the earth busbar, the L to the live busbar that's coming out the main breaker and the N to the Neutral busbar which is not the main incoming neutral but is the one which is connected to the RCBO if that is there.

And that is where the story can be complicated without knowing the situation, if in the same CU the earth and neutral is bonded there is really not much use of the second style SPD when there is no RCBO behind the main breaker, but it is in sub-CU's.

 

 

Edited August 31, 2020 by Metropolitian
dots

[jastheace]

yeah what they all said^^^^^^.

2nd one in a separate suitable box if main CU getting crowded.

belt and braces, do it right first time. or if you have a problem with a surge, you'll kick yourself for doing it with just the L side.

[Max Brok]

Thanks all. I am still at home in the Netherlands and can not make a picture of the present situation. I will do it as soon I can go to Thailand.

Speek you soon if possible