Discuss Panel with Relay and SPD, Installation? in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

Reaction score
0
Hello and thanks for the interest. I have a little dilemma and was unable to get an answer anywhere.

I'm trying to fit a SPD and an over/under voltage protector to my existing "Main Switch" and "RCD" setup. my question: is the location of the SPD and surge protector correct? thanks
 

Attachments

  • Panel with Relay and SPD, Installation? meters3 - EletriciansForums.net
    meters3.jpg
    122.5 KB · Views: 31
Hello and thanks for the interest. I have a little dilemma and was unable to get an answer anywhere.

I'm trying to fit a SPD and an over/under voltage protector to my existing "Main Switch" and "RCD" setup. my question: is the location of the SPD and surge protector correct? thanks
What is the current rating rating of your surge protector? I have fitted Dehn SPD’s at a factory this year and to simplify matters the units are rated for 125A with big terminals so you can fit them without going through a Mcb first and Just off the main switch. If you use smaller cable to connect them then they come off a suitable rated mcb. Panel with Relay and SPD, Installation? 232EBF9E-9FA7-4C35-93CD-9B69FA8D68D0 - EletriciansForums.net
 
thanks for the message. mine is rated some 40 - 60a. wiring goes to the spd after the main switch as per diagram, thanks
 
It looks like your main switch is in fact a double-pole MCB, is that correct?

Nothing wrong with doing that provided it is appropriate for the load, etc, but it would make selectivity with any down-stream MCB/RCBO very difficult to achieve (unless its instant trip point is above the PFC/PSSC of your supply at that point).

As already said above, many of the SPD are designed to be safe with supply fuses of up to 125A (or more) so you can normally get away with the supply's own fuse and use a simple DP switch. However, if your choice of SPD specifies a smaller breaker then you need to look at the design more carefully.
 
It looks like your main switch is in fact a double-pole MCB, is that correct?

Nothing wrong with doing that provided it is appropriate for the load, etc, but it would make selectivity with any down-stream MCB/RCBO very difficult to achieve (unless its instant trip point is above the PFC/PSSC of your supply at that point).

As already said above, many of the SPD are designed to be safe with supply fuses of up to 125A (or more) so you can normally get away with the supply's own fuse and use a simple DP switch. However, if your choice of SPD specifies a smaller breaker then you need to look at the design more carefully.
thanks for the detailed explanation. yes the diagram is of a double pole mcb but as per the text its just a main switch (a manual on/off). the switch is rated as 40a and the spd is rated at up to 60a. the spd is the one below:
 

Attachments

  • Panel with Relay and SPD, Installation? 1pc-AC-SPD-1P-2P-3P-4P-20-40KA-30KA-60KA-385V-House-Lightning-Surge-Protector - EletriciansForums.net
    1pc-AC-SPD-1P-2P-3P-4P-20-40KA-30KA-60KA-385V-House-Lightning-Surge-Protector.jpg
    79 KB · Views: 16
That is 60kA peak surge current, almost certainly for a 8/20us waveform.

You need to look up the data sheet to see what the maximum over-current protection is, and check that is above the incoming supply fuse.
 
That is 60kA peak surge current, almost certainly for a 8/20us waveform.

You need to look up the data sheet to see what the maximum over-current protection is, and check that is above the incoming supply fuse.
thx for the reply. yes the spd is as you said. the incoming supply is 40a, so it should be enough. may i ask if you can advise if the components are positioned properly in relation to one another? (in particular the rcd position and the relay? should their position be swapped maybe?)thanks
 
The basic layout is OK, though you would get slightly better protection by having the power cables connect through the SPD (known as as Kelvin or V-wiring).

However, doing they way you have drawn is fine so long as you keep the cable lengths to the SPD down to a reasonable minimum, no more than 25cm for each live wire and ideally less for the earth wire to the main earth terminal bar of your enclosure. Also it is better if the cables are run close together to reduce inductance (i.e. less total "area" formed by the loop of switch L or to SPD and back to switch N).

Check the SPD data sheet for the minimum wire size. It should be at least 4mm section, but more often is specified at 10mm minimum so in the event of a fault in the SPD it can safely take out the supply fuse. However, if you have say a length 16mm wire for the rest of the power wiring and the switch terminals can properly clamp 2*16mm then just use the same 16mm size for all.
 

Reply to Panel with Relay and SPD, Installation? in the Electrical Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock