3phase question

paul_h · Jan 2, 2013

Hi guys, I'm mainly a housebasher but done a few bigger jobs when serving my time. In past two years I've wired my dads pals car garage. Nothing major just wired an office some extra lights etc also wired 3 3phase car ramps.

Now the problem/question I have is when testing circuits everything was fine also checked phase rotation everything was great. But when actually testing the ramps 2out the 3 ran backwards ( up was down /down was up) when this happens I was always told to rotate the last two phases ( l2/l3) so i done this and ramps worked. Tested the phase rotation and it was showing up 321 instead of 123 on my fluke mft? So obv this would be classed as the phase rotation being reversed? Now I'm abit stumped because as I said my tests showed all rotation going same way and correct etc but yet still ramps ran backwards?

Am I missing something? :sad_smile:

paul_h · Jan 2, 2013

I did the phase rotation at load side of isolator in db then feed side at 20a rotary isolator. Then once ramps had been installed Load side at 20a isolator then again at the ramp. ? Plus the other zs tests etc. if the service head ( which I would call cable head?? Same thing I'm presuming) was round the wrong way I would probably have phoned Scottish power out as its there gear and surely would be there problem to fix? Same as if someone's house cable head had a fault I'd phone them? Had that a few times and once had to full the main fuse cause it was arcing that badly it was melting/charring it. Thot the sp guy woulda been abit dodgy with me pulling it but he said the general consensus was that as long as it was a spark pulling the fuse ( for a reason, fault/new tails etc) and aslong as the meter was still sealed (apart from the connections) they didn't care? Anyway side tracking abit here. Lol

Knobhead · Jan 2, 2013

Try phoning them, see what they say (after they've stopped laughing).

plugsandsparks · Jan 2, 2013

I almost did that when i was doing an EICR for two adjacent factories owned by same Company as one supply was 123, the other 321. Then i counted up how many TP circuits there were and how many DBs and thought bloody hell that will take some sorting, not to mention the downtime. Sod that !
Anyway, ended up marking all the boards as phase 321 so the next poor sod who tries to connect up a machine the right way round has a chance.
It was funny as they were a little down on the previous spark for always connecting up the machines backwards. He was clearly just following the colours - bless.