Disconnection times for 30mA RCD at 5 times current.

[volers]

Hi guys ths is my first time on here and relatively new to electrics. I was asked to find the times of disconnection needed for 5x and 1x. I was wondeering if anyone could give me a push in the right direction by pointing out where i could find such useful info inthe BS 7671 or onsite guide. THank you. Volers

 

[IQ Electrical]

seems to be some confusion over trip times of MCBs and RCDs. RCD times are 300msec.@ x1. 40msec.@ x5. ( TT systems it's 200msec.@ x1. )

Lol, there's more confusion:

Don't forget Note 2 of table 41.1 whereby the TT disconnection time of 0.2s is for fault currents 'significantly higher than the rated residual operating current of the RCD'
In other words, the 0.2s disconnection time does not apply to 1 X IΔn tests.

 

[telectrix]

Lol, there's more confusion:

Don't forget Note 2 of table 41.1 whereby the TT disconnection time of 0.2s is for fault currents 'significantly higher than the rated residual operating current of the RCD'
In other words, the 0.2s disconnection time does not apply to 1 X IΔn tests.

note 2 says typically 2xIdelta n. how are we supposed to test that when all testers test at 1x and 5x?

 

[IQ Electrical]

note 2 says typically 2xIdelta n. how are we supposed to test that when all testers test at 1x and 5x?

The official line is that if the disconnection times for the BS are met on 1X and 5X then it can be taken that the 2X will be met.

One of my suggestions at the Guidance Note 3 amendment meeting was for a better explanation of this process-I've even heard some that didn't understand this advocate the use of a BS4293 device to meet the 200ms time!

 

[truckster]

thanks Goody ii didnt read your post before replying... thats great help. i think my main problem is trying to locate where to extract info from in the holy 7671 book.

One of the best skills to learn is how to find your way round the BRB. Why oh why can't they make it easier??

 

[ezzzekiel]

One of the best skills to learn is how to find your way round the BRB. Why oh why can't they make it easier??

because plumbers could read it and call themselves sparks

 

[truckster]

Plumbers can read????

 

[FatBob]

The official line is that if the disconnection times for the BS are met on 1X and 5X then it can be taken that the 2X will be met.

The only way to test a component function at 2xIΔn is to sample at 2xIΔn

A sample at 1 and 5xIΔn are samples at 1 and 5xIΔn

Component manufactures specifications for performance at 2xIΔn cannot be assumed because the component functions within an acceptable tolerance at any other measured value previously ascertained by the manufacturer and in agreement with measured values by the tester.

 

[topquark]

All disconnection times are listing in the On-Site Guide page 92. If you are taking your 2330 302/303 make sure you label your On-Site with post-its so you can access the information quicker.

Post it's are good. Don't shoot the messenger but when you do your 2382 (17th) you are no longer allowed to have an "annotated copy" of BS7671 to refer to (C&G rule).