L1, L2, L3 on my cooker - does order matter?

10 Nov 2007
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United Kingdom
I'm here in Austria and I've got a three phase electric cooker and I'm new to 3-phase but I've done a fair bit of rewiring before. I've had to replace the cable from the distribution board (DB) to the cooker because we're moving the cooker to another location and the existing cable was not in the right place and was too short (by about 1m). I've replaced all the cabling using 2.5mm H05RR-F cable (this is a high spec rubberised cable, with 5 cores, strangely with two black cores, 1 brown, 1 blue and 1 green/yellow - no grey as I expected for 3 phase). The cable I replaced was exactly the same as this one with two blacks, a brown, a blue and a green/yellow. Again no grey.

Anyway, on closer inspection - at the distribution board - I can see three live cables coming (all brown with no obvious markings) coming in from the supplier, each fitted to screw in 40A fuses. There's a big fat earth cable as well doing the obvious thing. I'm assuming the 3 x brown cables are L1, L2, L3 but which one is which is not obvious. Each phase then goes into a 3P+N RCD, with the phases splitting out to power various circuits around the house via MCBs. The electricians who originally did the work, wired a connection into three individual MCBs (via type B 16A). , each of which then goes off to the cooker (with blue(N) and green/yellow (E) connecting to the appropriate DB connection blocks/strips). Ok, so far so good, easy to understand.

I've already connected this new installation and checked all the voltages at the connection points and the new cable is all OK and as expected. But now I've hit a bit of a snag. I took the back off the cooker and I can see three connections at the back for L1, L2, L3 (and the usual PE (N) and Earth). Unfortunately, I don't know which phase is which from the DB as there are no labels on the cables - they are all the same there (brown).

I am wondering if I need to be concerned about which phase I connect to which terminal since they are all carrying 230V with respect to N and 400V with respect to each other. My primary concern is if there any safety issues from connecting the phases in potentially the wrong order (e.g. could something get 400V instead of 230V?).

Any ideas on whether I should be concered about which phase goes where?
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On heating equipment the order of phases in normally not critical.

It is 3 phase motors that must have the phases connected in the correct order otherwise they are highly likely to rotate in the wrong direction.

So unless there is a large motor using 3 phases in the equipment connecting the phases in any order should be OK.
Thanks for that.

There's a fan in it (fan oven) and a light but I'd expect those to be 230V and not really relevant. Apart from that, it's just heating elements for the hob and the oven itself.

I'm still wondering why my cable has two blacks, one brown (the blue and green/yellow obviously don't raise any issues). I think this must be "old standards" or multi-use cable for other installations.
The cable is quite common in industrial use. You may find the blacks have faint markings of 1 and 2 printed on them about 6 inches apart along the wire but not always.
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I've connected it all up and it works just fine - I tried to guess on L1/L2/L3. Maybe I just got lucky. However, at least we can have hot food again! Thanks for all your help!
That type of cable is common. It is intended for the brown and the two blacks to be used as the three phases. Blue for neutral