Calling all D-Square 'museum' buffs ...

[sparc]

Can anyone help me with anything about this Square D board please? It - and one connected one above, covering only lights - are in a very large house that is mainly early 1990s. If there are any older bits they are well hidden.

I was called out because the main RCD had tripped, taking everything out. It had been reset, but owner couldn't get outside stuff back on again. That was because there was a 30mA RCD between this board and the outside stuff - pumps, fountains in ponds, outside lights, etc.

Once I'd done IR test on outside side and reset 30mA RCD all back to normal.

I'm assuming because 30mA RCD had tripped that circuit is protects was source of fault, and this was big enough leakage current to take out the main board RCD. Whatever that problem was, it is no longer showing up as an IR fault.

So, here's the thing: I was really surprised when I took cover off main board and found the main switch is a 300mA RCD. Everything else is on standard MCB. So if main switch goes, everything goes.

Does anyone know anything about this model of Square D - such as: would it have been installed in early 1990s? It seems way to old for that - maybe that was in 1990s, or maybe it was 're-cycled' from any earlier part of property on that site.

Why a 300mA RCD - not a 30mA - or at least a 100mA? It's a TN-S system, btw.

 

[Guest111]

Given that the breakers are all 32A it's possible that it started life in an office block or something similar,loads of rings feeding computers,lots of leakage so 300mA RCD to avoid nuisance tripping.Lot's of people "borrow" things from work to use at home,or it could be a car boot special!

 

[sparc]

Could well be a builder taking a short cut .... This is a big expensive property, seems odd to skimp.

On side of RCD it says Quik Gard QO200RCDX 300. I've search online but nothing for these showing - the 30mA comes up being sold second hand. Must be ancient.

 

[Andy78]

I believe that pattern of MCB is the Square D QOE pattern. You should be able to get MCBs and RCBOs for it still, although they will mostly be second hand. Any compatible new ones will be megabucks as it's all discontinued now.
It's no way as old as you think though. The second from right is a BS60898 for example.

 

[GLENNSPARK]

I believe that pattern of MCB is the Square D QOE pattern. You should be able to get MCBs and RCBOs for it still, although they will mostly be second hand. Any compatible new ones will be megabucks as it's all discontinued now.
It's no way as old as you think though. The second from right is a BS60898 for example.

yeah they are...

3871s....the RCD will be to BS4293....

and they made the similar pattern MCBs to BS60898...

 

[GLENNSPARK]

the board + MCBs and RCD will date from the 80s...apart from the 60898 thats in there...

i`v got loads of these...RCBOs as well...

 

[sparc]

I was thinking it looked like the old black bakelite Crabtree RCCB from 70s - so over 40 years old. It looks like supply cables go into bottom of the RCD, then MCBs plug into a live bus bar on backplane, like a Crabtree Starbreaker?

 

[ipf]

Given that the breakers are all 32A it's possible that it started life in an office block or something similar,loads of rings feeding computers,lots of leakage so 300mA RCD to avoid nuisance tripping.Lot's of people "borrow" things from work to use at home,or it could be a car boot special!

Seeing as it's a 'very large house' and has another board above, maybe it was intended to feed power circuits only.

 

[telectrix]

QO board. 80's. bought a 3 phase MCB for one a year ago cost £126 inc. vat. the single phase stuff is also megabucks.

 

[Engineer54]

I'm assuming because 30mA RCD had tripped that circuit is protects was source of fault, and this was big enough leakage current to take out the main board RCD. Whatever that problem was, it is no longer showing up as an IR fault.

An actual earth fault can be of many tens or hundreds mA's or even much more!! Which is why a time delay (S type) RCD upstream is always required to assure discrimination with the same or lower value RCD's downstream....

Only with a gradually increasing leakage, will a standard RCD (30mA) device discriminate with a higher value upstream standard RCD (100/300mA)...

 

[Guest55]

square D stuff is rubbish imo.
wouldnt bother trying to source anything for it , just recommend replacing it ,
if customer moans then tell him he'll just have to live with the tripping instead.

 

[telectrix]

have to disagree, biff. got 2 RCBO boards in a pub kitchen. greased up to the eyeballs, but they all trip within limits. lol.

 

[Guest55]

have to disagree, biff

how dare you !
when say its crap then thats it , no reprieve , cased closed.
court is adjurned.

;-)

 

[telectrix]

i appeal to a higher court, -- eng54. LOL.

 

[sparc]

An actual earth fault can be of many tens or hundreds mA's or even much more!! Which is why a time delay (S type) RCD upstream is always required to assure discrimination with the same or lower value RCD's downstream....

Only with a gradually increasing leakage, will a standard RCD (30mA) device discriminate with a higher value upstream standard RCD (100/300mA)...

Thanks, E54. I think I understand your point. What I was saying was all the other circuits in house are ONLY protected by the 300mA main switch, while only the outside (better protected!) light and fountains circuit has both the 300mA and 30mA in series.

So I'm assuming that the fault must have been on the outside circuit - evidenced by both the 30mA and 300mA having tripped - because if it had been on any other circuit only the 300mA would should tripped.

Still trying to get my head around why someone would have installed a 300mA RCD as a main switch ....

 

[Richard Burns]

So I'm assuming that the fault must have been on the outside circuit - evidenced by both the 30mA and 300mA having tripped - because if it had been on any other circuit only the 300mA would should tripped.

Correct.

Still trying to get my head around why someone would have installed a 300mA RCD as a main switch ....

If you were trying to make an installation safer but did not want a lot of nuisance tripping then you could install a 300mA RCD as a main switch (segregation of circuits to prevent danger might stop this now). Rapid and backed up tripping on an earth fault.
Most of the references in BS7671 are to an RCD and not to a specific mA of RCD.
It is only if you are aiming for additional protection (i.e. protection of persons and livestock) that you would need to drop to a 30mA RCD.

 

[Engineer54]

i appeal to a higher court, -- eng54. LOL.

Sorry Tel , i have to agree with Biff on early Square D stuff, ...Crap with a capital ''C''!!... lol!!!