Electric Questions

[andy82]

Please excuse my lack of knowledge in electrickery, looking to see if i am safe plugging my machine into 3 phase sockets.

Just signed a lease on a new workshop, the property is spilt into 2 units and has 2 supplies. The main workshop has 3 phase, the 3 phase comes into 3 Meters marked 240v (old style meter with the spinning disc).. Sorry dont know the name of them. At the bottom of each meter is marked 1-2-3 however only 1&2 meter is working.

1st question - Why have 3 meters

2nd question - Only 2 of the meters seem to work, having not plugged my machine into the sockets i am worried about causing damage to my welder.

There is a lever type (safety cutoff thing) at the other end of the workshop for the 3 phase and has been disconnected, Because this is disconnected is it a possibility these switches complete the circuit for the 3rd meter.

Sorry for the confusing question i will try and get pictures, i need to be sure the 3 phase is working before plugging in my machine....might need to get the landlord to get an electrician out.

 

[rtbcomp]

One meter per phase. You may have single phase equipment connected to phases 1 & 2 but not 3, which is why #3 isn't registering.

Try a bulb between each phase and neutral in turn, or even a fan heater - you should see the meter disc move with a decent load on it.

 

[andy82]

Thanks 1 meter spins when office lights are on and 2nd meter spins when standard sockets are used in the workshop, i have tried all standard sockets and lights to try and get the 3rd meter to move.

Putting my hand on the meter (even with all electric off) i can feel vibration from the 2 working meters and nothing from the 3rd.

 

[Feanor]

I had this kind of set-up in the workshop back in the 80s when I moved in. I re-wired the whole building in 1993 and Norweb (as they were then) came and fitted a single brand new meter of decent size and in fact renewed all the primary wiring from the meter to the connection underground just outside (where it comes into the building). From the meter they wired, with 4 x 100 amp cables, into a new 3 x 80 amp isolater that I supplied.

This is how it used to be and sounds like you could be wired the same:

Meter No 1 - 240v single phase powering all the lights (through a fused isolater just after the meter). Two-wire meters (Live and Neutral)

Meter No 2 - 240v single phase powering all the 3 pin sockets - scattered everywhere and added to over the years and not in a ring-main set up. They still worked of course. Also a fused isolater just after the meter to shut that circuit off if desired. Ditto with the lights of course. Again a 2 wire meter.

Meter No 3 was 415v three-phase (four wires into and out of it) that powered a circuit of that voltage. Again added to and a bit higgeldy-piggeldy over the years though never too bad.

Look carefully if you can, to see how many incoming mains wires are entering the building. There should be four if you have 3 phase. Each live phase (and maybe the neutral too) will be fused with an Electricity Board main fuse (tamper proof) somewhere before the meters.

See how many and which of these wires enters the Meters, particularly Meter 3 which you haven't seen spinning and similarly how many wires emerge and become workshop circuitry.

Obviously be extremely careful and get someone in if you aren't sure.

 

[andy82]

Thanks, I cant see the wiring coming into the property. there is 4 wires going into each meter. All wires lead to the breaker box with old looking breakers.... i have 3x 3 phase red plugs (16a) 2 of them are 5 pin and 1 is 4 pin

There are 3 compartments in the breaker box, Each compartment supplies 1x 3phase plug and other things like lights etc.

 

[sparky_col]

a picture is worth a thousand words.

 

[rtbcomp]

there is 4 wires going into each meter - is that 2 in and 2 out? Did you say all 3 meters were 240v?

 

[KemppiFrog]

Don't the meters have it written on them what they are rated for? If the old disc type: 3phase 30amp or somesuch?
KF

 

[the snooper]

if you need 3phase get it sorted if you dont, then get everything connected through one meter and get the power company to de energise the meters you dont use that way you dont get a standing charge for the meter on each bill

 

[Feanor]

Yes it seems strange to be getting 3 phases by having three separate meters with the one phase from each to achieve this. And we've ascertained that 2 of the meters each also provide separate 240 volt supplies (lights and sockets). You also have to presume that the three meters (and so phases) are truly separate from the sub-station - ie: one is the Red, the other the Blue and the 3rd the Yellow (or whatever colours they now use). You would think this is the case.

It seems that maybe meter No 3 doesn't have a supply going to it. Maybe the main incoming fuse on that phase has blown? In which case there are only 2 live separate phases currently at work on the premises. Andy - you need to check this out, but you need an electrician or even the power company to check.

It might be worth contacting your supplier anyway (or the landlord do it) about a modern new meter. Via H & S and regulations they are duty bound to do it, almost certainly in this case, because like I was, it's probably an ancient set up that has been overlooked. When I re-wired 19 years ago, they came out no problem and spent half a day removing all the scrappy old main wiring and main fuses and the 3 meters. What they replaced was 100 times better and neater and there was no charge. Everything up to and including the meter is of course still their property. Since then they have anyway (last year actually) been out again and put one of these new Smart meters in - I had no say in the matter.

You may then though have to upgrade or renew some switchgear and/or distribution board.

 

[rtbcomp]

I've seen loads of places with one meter per phase, they were older premises though.

 

[andy82]

thanks for the replies, i will get some pics.

So who would be responsible (or pays for) for updating the old system. (electric company or landlord or me) Is it a legal requirement to have an old system updated.

Being a new tenant to the property i am yet to meet the landlord (done through a letting agent) and still dont know who the electric supplier is. I am going to note down the meter numbers and find out.

 

[madkayaker]

upload some photos so that us that can assess the work can tell how old we are talking. by rights if a main fuse has blowed then it is the local DNO that has to change it (Scotish electricity in your case) they then reseal the meter etc so that there is no question of tampering. Changing the fuse is not a difficult job for a decent spark but the equipment is owed by the DNO so its illegal to do and i do know that scottish electrical are very hot on prosecution. Sperate meters is not an issues and is still often fitted as new but combined one are more commonly fitted these days.

as for the rest of the installation then it depends on what is in the lease agreement as to who pays for what.

 

[Feanor]

Yes pics will help. You would think, surely, that it would be better with one modern combined meter, not only for neatness but as someone said, for less standing charges they may levy against the user?

Do suss it out first though just in case you start something off that you have to then see through, only to find out this means spending a blob of money on new switchgear, etc.

I was fortunate because at the time, all the coal mines were being closed in Lancs. I knew lots of soon to be redundant miners who were then employed on winding down the collieries. The amount of brand new, and as-new armoured cable, switchgear, fuses, connectors, etc, etc, that was going into skips was typically criminal. I managed to appropriate enough stuff to rewire an entire premises with lots left over. Quite a bit of stuff was recycled from closing down cotton mills too.

Obviously there are even more regulations now to prohibit some of this kind of thing so get some advice as well first. I had my re-wire fully tested by a sparky and the primary switchgear was approved by Norweb, before the new supply was hooked up. There hasn't been a problem in 19 years anyway.

At the same time I enquired about the strength of the supply and Norweb freely told me it was 80 amps per phase. It's a useful thing to know for free.

 

[andy82]

OK Here is some pics

Also added a pic of the welder that will be used on the 3 phase

 

[madkayaker]

other than the face there rewireable fuses (with abstedos backing in as well) and the hand;e is snapped off the isolator that desont look so bad. there not DNO meters there sub meters that the landlord has put in to split the bill up. looks a good size unit!

 

[andy82]

What do you mean to split the bill up, i have a second supply in the other unit as seen on the pic below the second supply is in the room behind the door at the rear, that supplies the sockets and lights in the 2nd unit and sockets upstairs.

I am installing a powder coating oven and will have an electrician out to install that and whilst he is here i will get him to re route the wiring to the main board and get the electric company to disconnect the other supply.


What would happen if i plugged my welder in and turned on and was found to be 1 phase down would it cause any damage to the welder or would it just not turn on.

 

[madkayaker]

those meters are not the main meters there must be taking a supply from somewhere else and those meters are so the landlord can tell how much each bit has used a bill aproperatly. get a spark in before starting anything.

 

[andy82]

hmmm thats different, it used to be a whole complex with multiple units owned by one company. Like i was saying there is another fuse box and meter at the back of the workshop. Its one single meter and looks a more modern unit however it only spins when using certain parts of the workshop and does not appear to link anywhere near the other meters.

With the setup i have does this mean i have a supply thats branched off from a supply that not located in the workshop. This may get confusing.

 

[madkayaker]

thats it in a nut shell. somewhere there will be a master fuse and meter set and then a set of fuses and supplies that go to the different units. so you will need to check how many amps your supply is before putting in loads of big kit