Mains RCD for Workbenches 6 or 20mA? - Page 1
Forum section: electronics / projects

author: mrpackethead
author_rank: Super Contributor
timestamp: December 03, 2018, 07:48:03 am
content: Hi, I'm in the process of setting up some new workstations in our new workshop. ( horrah! space! ).. I'm going to have a goodly number of AC Sockets along the bench, as there is nothing worse than running out of places to plug stuff in.I'm able to put some individual RCD's in at the Workstation, and i'm contemplating if i put 6 or 20mA ones in. 6mA may trip and be annoying. 20mA may allow just enough current to seriously hurt or kill someone. We do assemble items with AC power supplies, and sometimes have items 'open' while they are powered up.Thoughts?

author: capt bullshot
author_rank: Super Contributor
timestamp: December 03, 2018, 07:51:43 am
content: Just read my signature

author: Berni
author_rank: Super Contributor
timestamp: December 03, 2018, 08:06:22 am
content: 4mAIf a single device trips that then it is faulty,The reason that the less sensitive RCDs are used is that they tend to supply an entire house. The leakage currents of everything adds up with the many devices plugged into it so it has to be more tolerant to not false trip. This is the reason why bathrooms in a lot of countries are required to have a dedicated RCD. It allows for the use of a more sensitive one by minimizing the amount of stuff connected.

author: Zero999
author_rank: Super Contributor
timestamp: December 03, 2018, 09:45:45 am
content: Yes, use the lower tripping current. From memory, the leakage current should be below 1mA anyway.

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 03, 2018, 10:02:12 am
content: I got the lowest I could get (which is 10mA).Rule of thumb is:1 mA can be felt10 mA you'll feel all day100 mA: if it takes the scenic route you'll feel no moreI thought 2mA was permissible (think: EMI caps to earth and such). So if you're attaching several PSU's on a 4mA line you'll run out quickly.

author: 001
author_rank: Super Contributor
timestamp: December 03, 2018, 10:13:48 am
content: Why not to use simple isolation transformers?

author: Zero999
author_rank: Super Contributor
timestamp: December 03, 2018, 12:54:25 pm
content: Quote from: 001 on December 03, 2018, 10:13:48 amIsolation transformers can make it more dangerous, under some circumstances. For example, if a device is connected to an isolation transformer, one might think it's safe to touch a part of the circuit or connect it to an oscilloscope's ground lead, but another part of the circuit is earthed, due to a fault, then bang!

author: amlu
author_rank: Contributor
timestamp: December 03, 2018, 02:02:10 pm
content: how about adjustable earth leakage relay?something like that, for examplehttps://www.ebay.co.uk/itm/Broyce-Control-True-RMS-Earth-Leakage-Relay-8A-2P-230VAC-ELRV-30-1-30000mA/123511614271?hash=item1cc1ddab3f:g:YQAAAOSwtc9b0Huq

author: 001
author_rank: Super Contributor
timestamp: December 03, 2018, 04:38:39 pm
content: Quote from: Hero999 on December 03, 2018, 12:54:25 pmWhat about transformer AND leakage relay?

author: Zero999
author_rank: Super Contributor
timestamp: December 03, 2018, 04:53:54 pm
content: Quote from: 001 on December 03, 2018, 04:38:39 pmWhat good will that do? The isolation transformer will prevent the earth leakage relay from working.