TT and RCD

[sblakey1]

having just converted from been a Military Spark to civilian one can you guys help me out,

TT installations are one that i am always bit edgy about,

however im getting my Elecsa site assessment done on this property, "friends house" excellent access to CU etc..!! its only a 5 way so not to bad, but they are 1x lights (house) , 1x extension socket & wall light, 1x sockets (house), 1x immersion heater , 1x shower

right my question

Can i get away with a 100a main switch and dual 30ma RCD similar to this
http://www.tlc-direct.co.uk/Products/CPDS088P.html
or would i require to fit a time delayed 100ma as the main incomer???

may seem a simple question but rather ask now than later.

steve





[/url]

 

[ban-all-sheds]

Think about why CUs for TT installations used to have the 100mA-S/30mA split.

Think about what the 17th requires for RCD protection.

Think about what you would do in a TT installation with the 2 ways in that CU which have no RCD protection at all.

 

[sblakey1]

oh sorry im not using the 2 ways that are not protected!!!!

 

[sblakey1]

unit im using is similar to this

http://www.tlc-direct.co.uk/Images/Products/size_3/HGVC712C1.JPG

total protection

 

[ban-all-sheds]

oh sorry im not using the 2 ways that are not protected!!!!

Why not?

 

[ericmark]

The RCD has to be two pole and able to trip with current which will flow under fault conditions to earth.
The one selected in picture second web site would do that, but one selected on first link would not.

 

[ban-all-sheds]

Those Contactum RCDs are dual pole, surely?

 

[sblakey1]

i would not be using the 2 unprotected ways due to no need..!!!

the circuits i have would all be on RCD for various reasons..! sockets , shower, not 50mm deep etc etc..

covering my ass

 

[ban-all-sheds]

i would not be using the 2 unprotected ways due to no need..!!!

Could they be used in some way?

the circuits i have would all be on RCD for various reasons..! sockets , shower, not 50mm deep etc etc..

What type of RCD is needed?

 

[sblakey1]

personally i would shift the rcd module along to take up the ways....

or remove the ability to fit mcb/rcbo.... by chopping the pin off the busbar. (not professional)

chance are i will get a unit with NO unprotected ways..

30ma for sockets , shower, etc.

 

[ban-all-sheds]

personally i would shift the rcd module along to take up the ways....

That's one method.

or remove the ability to fit mcb/rcbo.... by chopping the pin off the busbar. (not professional)

Why would you want to remove the ability to fit MCBs or RCBOs in those ways?

30ma for sockets , shower, etc.

So back to your original question, what do you think about using a time-delayed RCD incomer?

In what circumstances would it trip?

 

[sblakey1]

original question answer,

the way i look at it then is that if i was to use the board with the 2 unprotected ways then i would use a time delay rcd to give me protection on them but ultimately not at same time level as a standard RCD to ensure that discrimination can be achieved on the non delayed circuits.

but if i was to use a CU where all final circuits were protected by RCD then i would not require the incomer to be a time delay RCD device,

is it possible that the time delyed RCD incomer can also provide protection from any faults that my develop on the board.?????

 

[ban-all-sheds]

if i was to use the board with the 2 unprotected ways then i would use a time delay rcd to give me protection on them but ultimately not at same time level as a standard RCD

Would that comply with the regulations?

to ensure that discrimination can be achieved on the non delayed circuits.

Is there another way you could do that?

is it possible that the time delyed RCD incomer can also provide protection from any faults that my develop on the board.?????

What faults are you thinking of?

 

[sblakey1]

defo got my mind thinking..!


(1)100ma time delay would not give me the 0.4 disconnection time required by the regulations..!

(2)yes discrimination can be achieved with use of an rcbo on non protected circuits. or by incorporating them into the RCD protected side.

(3) i was thinkking along lines of protection against fire?? but would that not be 300ma??. however i found this link

http://www.voltimum.co.uk/consult.p...set=&id=1045&universe=consult.index.questions

getting a lot of contradicting answers.....!! from sparks also....!!

then this link.....

http://www.voltimum.co.uk/consult.p...set=&id=6727&universe=consult.index.questions

then finaly this one which has thrown me off!!!!!!!

http://www.voltimum.co.uk/consult.p...set=&id=5467&universe=consult.index.questions

 

[sblakey1]

please help