EEVblog 1652 - Why is my Lab Switchboard Wired Like This? - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: November 15, 2024, 01:36:40 am
content: Why is my lab power switchboard wired like this?

author: andy3055
author_rank: Super Contributor
timestamp: November 15, 2024, 02:20:53 am
content: What is your capacity? If it is below a certain minimum, they may not give you a 3 phase supply. The white and blue phases may be not energized. The cables may not be connected at the other end.

author: temperance
author_rank: Super Contributor
timestamp: November 15, 2024, 02:50:10 am
content: I see a few things wrong with this box. Without digging any further the following things are forbidden where I live:-Unequal wire sections used in the same clamp.Two wires with unequal cross sections in one clamp are forbidden.-The two white wires going into the same clamp is probably also not allowed.The white wire cross sections probably exceeds the manufacturers recommendation if the component is specified for the application of two wires into the same clamp.

author: EEVblog
author_rank: Unknown
timestamp: November 15, 2024, 03:17:22 am
content: Quote from: andy3055 on November 15, 2024, 02:20:53 amMy pinned comment:Mystery SOLVED!I went and checked the meter room and sure enough my unit only has a single phase meter. Lots of others have 3 phase (3 different meters). So the units must all have 3 phase wires pulled to them as standard for futureproofing, but not all have 3 phases connected and metered. There are only two spare meter slots on the board for my level, so only one single phase unit could upgrade to 3 phases without having to bodge anything.My panel is 3 phases because it would be a standard design for the entire building regardless of how many phases you get installed.

author: nctnico
author_rank: Super Contributor
timestamp: November 15, 2024, 05:50:42 pm
content: I can't say I like this setup with those exposed busbars in the middle. Your new switchboard at home is nicer with the inputs connected with a busbar at the bottom and the loads connected at the top. A similar setup can be used for 3 phase installations as well but then using 3 busbars. I also note that the RCDs used in this switchboard need a seperate neutral connection which is just messy. Personally I prefer to use the dual pole (Line + N) RCD / circuit breaker units so both neutral and line are disconnected for a circuit:For safety reasons I treat neutral the same as the phase. You can't know if somebody wired it wrong and crossed phase and neutral (and other, more horrible wiring errors).Last but not least, if this is a standard switchboard, then it highly surprises me that there is such a wide variety of different brands & models in there. There must have been replacements / additions done over the years.

author: Monkeh
author_rank: Super Contributor
timestamp: November 15, 2024, 06:05:57 pm
content: Quote from: nctnico on November 15, 2024, 05:50:42 pmUnless you go in there with a knife they're no more exposed than any others.Neutral flyleads on RCBOs is pretty common as it removes the need for two or four pole busbars. Two pole in single width is tight, and four pole means lost density in 3-phase boards.

author: EEVblog
author_rank: Unknown
timestamp: November 16, 2024, 02:34:06 am
content: Quote from: nctnico on November 15, 2024, 05:50:42 pmThey are insulated with a rubber coating.QuoteOnly on has been added since I've owned it.Maybe the builder just got bulk lots of various types.

author: thm_w
author_rank: Super Contributor
timestamp: November 18, 2024, 10:03:08 pm
content: I don't like the white wires being used for earth connections, looks like a bit of a hack job there. Otherwise looks good.Though the stranded earth is interesting, it seems to loop through the bars on the left, and be held in place with two screws for redundancy?Here its mostly solid core uninsulated for earth.

author: nctnico
author_rank: Super Contributor
timestamp: November 18, 2024, 11:16:51 pm
content: Now you mention it, it looks like all the wires are stranded. Using ferrules would be a nice upgrade for the wires clamped directly under a screw

author: Monkeh
author_rank: Super Contributor
timestamp: November 20, 2024, 05:27:37 am
content: Quote from: thm_w on November 18, 2024, 10:03:08 pmYou mean the cream functional earths from the RCBOs? Bit hard to change those..

author: thm_w
author_rank: Super Contributor
timestamp: November 20, 2024, 09:41:30 pm
content: Quote from: Monkeh on November 20, 2024, 05:27:37 amDidn't know they just came with white wire by default, ok nothing could be done there.