TT CU with One 30mA RCD as a main switch.

[Megaohm7]

I have been to look at a job today that is a TT System and the CU is a fairly modern looking Wylex with a 30mA RCD as a main switch. and BSEN 60898 b typemcb's. I've been asked to add a radial and ring final to the spare ways on the board. Am I right in thinking that all circuits must have protection of a 30mA rcd which this has but my concern is that should a fault occur on any one of the circuits it would knock everything else out. I was thinking of rcbos on the circuits that I will be adding. I'm sure that I've read that a device on a TT system must be capable of switching both poles.

 

[Andy™]

waste of time adding RCBO. you wont have any discrimination. many houses have only 1 RCD and dont have many problems with it. i would just get on with it.

 

[Evans Electric]

I'd say the same as Andy , just get on with it .

Don't create problems , altering their board is another expense they may not want to go with.

 

[wozz]

Sounds like a safe set up to me. I think alot is made if this single fault scenario, after all what happens if there is a power cut? In certain parts they are alot more likely than a genuine fault!

 

[Megaohm7]

Sounds like a safe set up to me. I think alot is made if this single fault scenario, after all what happens if there is a power cut? In certain parts they are alot more likely than a genuine fault!

Power cuts!! reminds me of the 70's

 

[steptoe]

you are not making it any less safe, and your circuit is provided with the 30mA protection it requires under 17th.

it is a DI board I assume?

 

[Megaohm7]

you are not making it any less safe, and your circuit is provided with the 30mA protection it requires under 17th.it is a DI board I assume?

I take it you mean a plastic one Steps. Yes it is.

 

[steptoe]

no problemo then.

 

[Megaohm7]

no problemo then.

Cheers mate. At least I'll be able to do the EIC, the Schedules and notify and sleep soundly now.

 

[steptoe]

you are welcome

 

[batty]

What are the extra circuits for personally I would not be happy adding to the board should not have been done that way in the first place.

 

[steptoe]

but it is, and you cannot change what is done,

how did you do stuff under 16th batty? did you make people change CU then? everything was either on one RCD or it wasnt on any, so what is the massive issue now.?

 

[kme]

Why not............put the RCBos before the RCD - hang on - did you say there were only the two spare ways? No, you said "the spare ways",

I`d be tempted to fit a main isolator up front; then RCBos for your new ccts, THEN the RCD & its circuits.

You could even move existing ccts to the RCBos, and put your new `uns on the pre-existing RCD - I`d prefer it that way, if I was doing it TBH

 

[batty]

Even in the 16th I would have more than one RCD in boards. I generally would use contcatum and have a 16th edition with one RCD on the split and then put an RCBO for some of the sockets before it and in them days they were double pole.

 

[steptoe]

in them days batty,?

you trying to say they are not DP now, or that people just wont install DP now?

KME, this is why I wouldnt go the RCBO route, perhaps only my preference mind, but DP RCBOs are not plentiful, and IMHO the regs for TT require DP disconnection,

BUT,

everyone to their own,

how will we ever win jobs if all we ever want to do is load the price with extras, albeit beneficial, but nonetheless, more costly and unwanted by the client.

 

[Andy™]

Even in the 16th I would have more than one RCD in boards.

same here.

on TT i sometimes made my own dual split (before they were popular) instead of the 100mA TD

 

[Megaohm7]

Went along to that job today and did a Ze ( Ra ) and got 13.7 ohms. PFC 1.07Ka Trip times of RCD 1/2x no trip 1x 48.0 mS 5x 15.0 mS RCD type 100a 30mA BSEN 60439-3 . Had a cuppa too. THE job is 10mins away from me. I had a look at the Earth rod and shouldn't they be in a pit or something to protect the connection? Apart from that it all looks fine to go.

 

[NozSpark]

Nice one

However,,, BS EN 60439-3 is not for RCDs, it's for Distribution boards

BS EN 61008-1 is for RCDs

---------- Post Auto-Merged at 15:53 ---------- Previous post was made at 15:52 ----------

P. 236 BRB

 

[Megaohm7]

Oops!! What plonker I am!! I was reading the label underneath the RCD. The board is a NH type Wylex With the RCD as the main switch. I could not see any BS/EN number on the device I was thinking main switch and thanks for the BSEN number of the board Noz. I'm going back to the property anyway so I'll make sure I have the correct number on my paper work.

 

[NozSpark]

Thought that you did,,,

It's a common mistake if you're not familiar with the BS numbers