SPD's Why Are Some 1 Way & some 2 Way?

[thomp1983]

Hi all,

My question is as the title really, why are some SPD's made to fit in a 1 way slot and others are 2 way sized?

Is there any advantage in an spd being 2 way sized?

Thanks,
Chris.

 

[ericmark]

I have two modules, one line to earth the other neutral to earth, but not sure how they help so not sure if there is really any difference, I was convinced there were the reason my LED bulbs lasted longer than my sons, then when I came to do some work, found wire disconnected so not doing a thing.

 

[Gonsa]

The main difference is usually down to the design of the SPD and the way it needs to be connected rather than any innherent advantage of having a two-module device.

A single-module SPD can be useful where space in the consumer unit is limited, while a two-module version may simply provide more room for the internal components, terminals or associated protection. Some manufacturers also use a two-module format because the SPD is designed to work alongside a separate protective device or has additional functionality.
So I wouldn't assume that a two-module SPD provides better surge protection just because it takes up more space. The important things are its specification, maximum discharge current, voltage protection level, earthing arrangement and compatibility with the particular consumer unit and installation.

In other words, the physical size isn't really an indication of how effective the SPD is. I'd choose based on the manufacturer's specifications and the requirements of the installation rather than the number of ways it occupies.