3 phase conundrum

[PatsPatter]

My advice would be to utilise single phase before your domestic wiring. Having three phase in a domeati installation is pointless. Furthermore it is likley to cost more and perhaps more worrying more dangerous due to the elevated fault currents in a three phase system.

Consider this. If somehow you cause a fault in your home on a single phase you only have 230V between phase and ground. Do that on a three phase system and you will have up to 415V, depending on how you are wired.
415V is an entirely different ball game in terms of potential damage that can cause!

Continue to use the three phase before your workshop only and stick to standard single phase for your domestics.

scubadog.
I understand the dangers, the potential for damage and I much appreciate your concern - but I don't exactly have a choice.
My first post on the matter maybe wasn't clear enough.
The TP supply incomers/meter/fuses, etc, are in the utility room of the domestic side of things. The photo attached to my second post shows the whole, grim, set-up.
It is also the site of the Three Phase powered central heating system for the domestic side. Moving it somewhere else isn't really an option. It's ducted, blown, warm air. I didn't opt for it, it was here when I bought the place - and it works well.
I'm trying to make the best I can of a less than ideal set-up. I also want to utilise the three phase for my machine tools which will be located apart from the domestic property, about 6 - 8 metres away.
It would be a Very expensive option to have the incomers moved out of the house - and I still need it for the heating anyhow.

PatsPatter

 

[Scubadog]

scubadog.
I understand the dangers, the potential for damage and I much appreciate your concern - but I don't exactly have a choice.
My first post on the matter maybe wasn't clear enough.
The TP supply incomers/meter/fuses, etc, are in the utility room of the domestic side of things. The photo attached to my second post shows the whole, grim, set-up.
It is also the site of the Three Phase powered central heating system for the domestic side. Moving it somewhere else isn't really an option. It's ducted, blown, warm air. I didn't opt for it, it was here when I bought the place - and it works well.
I'm trying to make the best I can of a less than ideal set-up. I also want to utilise the three phase for my machine tools which will be located apart from the domestic property, about 6 - 8 metres away.
It would be a Very expensive option to have the incomers moved out of the house - and I still need it for the heating anyhow.

PatsPatter

I agree....so use the three phase for your heating and workshop..

Then just use single phase for domestics.

 

[PatsPatter]

I agree....so use the three phase for your heating and workshop..

Then just use single phase for domestics.

……… so leave it as it is, just replace the non-Amd 3-compliant CU and fit the Acti 9 panel as an isolator and supply point for the TP?

I guess it is the easiest and simplest option.
Currently:
L1 supplies off peak immersion (through a provider time switch)
the temporary supply to the garage/workshop/outbuildings
the heating system
L2 supplies the whole domestic side through the CU
the heating system
L3 supplies the heating system

As far as I can see, the off peak immersion would then be best kept as is but through a new isolator and RCBO. It's under the control of the provider's contacter, which is in turn controlled by the meter.
If the Acti 9 is installed for the TP loads, I'm then left with the question of what method of protection to apply to the TP cabinet, considering there are currently only the provider's fuses. The loads will be TP (heating and machines) plus SP for lighting and SP tools/machines/etc in the workshop. If it's individual RCBOs on every output way, what about the input to it? TP MCB only?

PatsPatter

 

[PatsPatter]

Yes, it is a contactor for the off peak supply. The time switching will be done by the meter (switching the neutral wire on the left).

Spark123:
a question based upon the above (and the attached picture)
First, I can see the purpose of the neutral switch line to the off peak contactor but there is a second connection to that output terminal from the meter.

It goes from the meter to the neutral terminal (Henley?) block sited just below the bottom lefthand corner of the Sector CU, ie the same block as the neutral from the meter.
The only other connection to that block goes up to another block, immediately left of the Sector CU, and is the connection point for all other neutrals AND anything supplied by L2 - which is the domestic CU and the TP heating unit
That meter has only been there a couple of months, so I'd guess re-connected deliberately. Is it/was it for some other switching signal purpose?

PatsPatter

 

[RF Lighting]

I really wouldn't be concerned at all by having your domestic supply over more than one phase.

It never causes any problems anywhere else, and I don't see what the perceived issue is with using it in a domestic property.

It's probably worthwhile using a commercial electrician who is used to working on larger installations, and will know how to balance phases etc.

 

[PatsPatter]

I really wouldn't be concerned at all by having your domestic supply over more than one phase.

It never causes any problems anywhere else, and I don't see what the perceived issue is with using it in a domestic property.

It's probably worthwhile using a commercial electrician who is used to working on larger installations, and will know how to balance phases etc.

Sorry for a lack of perception but do you mean it's not necessary to use more that one phase?
I guess a lot of this arose because everybody (me included) wanted to tidy up and modernise the mess that's currently there.

 

[Scubadog]

I really wouldn't be concerned at all by having your domestic supply over more than one phase.

It never causes any problems anywhere else, and I don't see what the perceived issue is with using it in a domestic property.

It's probably worthwhile using a commercial electrician who is used to working on larger installations, and will know how to balance phases etc.

Even in most industrial installations the domestics are single phase.

 

[Iggifer]

Sorry for a lack of perception but do you mean it's not necessary to use more that one phase?
I guess a lot of this arose because everybody (me included) wanted to tidy up and modernise the mess that's currently there.

No, RF means it doesn't matter if you have different phases in use in your house, i.e. your cooker on L2 and your upstairs lights on L3. So long as it's designed properly, so say your upstairs lights and downstairs lights are on the same phase so you don't end up with 400v inside the same light switch, then it's not really a concern.

PLENTY of houses have 3P+N in use for their supplies and it's not a problem.

 

[Iggifer]

Even in most industrial installations the domestics are single phase.

What does that even mean?

 

[PatsPatter]

………..so say your upstairs lights and downstairs lights are on the same phase so you don't end up with 400v inside the same light switch, then it's not really a concern.

Iggifer:
Could I correctly expand the above with the following?
…………. because if the lighting circuits were on different phases, as in the case of, say, a two gang light switch at the bottom of the stairs, one switch for the downstairs hall light (off the downstairs cct L1) and another switch for the upstairs landing light (off the upstairs lighting cct L2), phase-to-phase would be 400 volts.

 

[Iggifer]

Iggifer:
Could I correctly expand the above with the following?
…………. because if the lighting circuits were on different phases, as in the case of, say, a two gang light switch at the bottom of the stairs, one switch for the downstairs hall light (off the downstairs cct L1) and another switch for the upstairs landing light (off the upstairs lighting cct L2), phase-to-phase would be 400 volts.

Exactly. 400v isn't a problem in a domestic installation, but it's definitely not a good idea to mix phases inside the same enclosure, but it's simple enough to design the installation so that doesn't happen.

Even if you had 4 lighting circuits you could keep them all on L1 and still have enough 3-Phase ways in your board for the rest of your stuff (I would have thought)

 

[PatsPatter]

Even if you had 4 lighting circuits you could keep them all on L1 and still have enough 3-Phase ways in your board for the rest of your stuff (I would have thought)

36 to go for and only 12 (4 x TP) required for machinery
The following questions remain:
1. I've still not got a clear idea in my head regarding what sort of protection to use on the incoming side of the TP board.
2. I can see and am happy with the reasons for using individual RCBOs on all the outgoing ways to SP circuits but do the TP outgoing (machinery/heating) ways need individuals as well - assuming the continued use of the Acti 9 board? (I could add another bit here but might5 cause confusion, so will leave it for later)

 

[Iggifer]

Protection on the incoming side of the TP board? How far away is it going to be from the meter to the board? If over 3m then use a switchfuse & SWA. Without knowing the details, probably 25mm² 4-core and an 80A TP+N switchfuse.

Schneider do add on RCDs for TP circuits, should you need them for the TP outgoing ways, but they take up more ways in your board, so something to bear in mind. If the cables are installed in such a way that the cables do not need RCD protection, then you should be fine (depending on what machinery it is)

 

[PatsPatter]

Protection on the incoming side of the TP board? How far away is it going to be from the meter to the board? If over 3m then use a switchfuse & SWA. Without knowing the details, probably 25mm² 4-core and an 80A TP+N switchfuse.

It's less than 2 metres - as in replacing the position of the ancient MEM isolators in the original picture

Schneider do add on RCDs for TP circuits, should you need them for the TP outgoing ways, but they take up more ways in your board, so something to bear in mind. If the cables are installed in such a way that the cables do not need RCD protection, then you should be fine (depending on what machinery it is)

The aim is to have all the TP cables in trunking/conduit - unless there's a better option.
Each TP machine has its own internal overload trip in the starter box. They are all induction motors, the biggest is 4 horse - a shade under 3 Kw.

 

[Spark123]

Spark123:
a question based upon the above (and the attached picture)
First, I can see the purpose of the neutral switch line to the off peak contactor but there is a second connection to that output terminal from the meter.


View attachment 106370

It goes from the meter to the neutral terminal (Henley?) block sited just below the bottom lefthand corner of the Sector CU, ie the same block as the neutral from the meter.
The only other connection to that block goes up to another block, immediately left of the Sector CU, and is the connection point for all other neutrals AND anything supplied by L2 - which is the domestic CU and the TP heating unit
That meter has only been there a couple of months, so I'd guess re-connected deliberately. Is it/was it for some other switching signal purpose?

PatsPatter

I'm not 100% sure with this but likelihood is the meter has a relay in it (with dry contacts*) for the off peak switching so when the off peak is active the relay is closed thus completing the circuit. The link to the neutral block will complete the circuit.
The advantage being with dry relay contacts the type of meter can be used (by the supplier) for various differing purposes and they don't need to stock loads of variations of them.
Maybe someone who deals with meters can confirm?

*Dry contacts are those with no supply to them, they need to be "wetted" with an external supply