3 phase conundrum

[PatsPatter]

What I don't understand is why everything isn't all going into the lovely Schneider 12 Way TP+N board? And why that Sector POS is still there

This one?

Which rises another question:
Can the "lovely Schneider 12 Way TP+N board?" be used as a complete replacement for the whole distribution schebang, including providing supplies for TP machine tools? If so, no need for a replacement for the plastic consumer - unless you're meaning 'fit a single phase conversion kit' to it

The 'POS' is there temporarily supplying a 16 amp outside point to supply our motorhome - that we were living in whilst I did basic things like make the water system work and screw loo cisterns back onto the wall. It's also a temporary supply to the new garage roller door.

When it's done its job, it'll probably get consigned to a shed as an isolator

PatsPatter

 

[PatsPatter]

Possibly a time switch?

I believe it is for the off peak…………….

but would only appear to supply the off peak immersion.

PatsPatter

 

[Spark123]

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).

 

[Iggifer]

Can the "lovely Schneider 12 Way TP+N board?" be used as a complete replacement for the whole distribution schebang, including providing supplies for TP machine tools? If so, no need for a replacement for the plastic consumer - unless you're meaning 'fit a single phase conversion kit' to it

Nope I mean use just that, you can fit single phase ways to a TP+N board (assuming that leaves you with enough TP+N ways for your machines etc.

Whether or not there is now enough length on those cables and enough space to fit that board in that cupboard is another matter

 

[PatsPatter]

Nope I mean use just that, you can fit single phase ways to a TP+N board (assuming that leaves you with enough TP+N ways for your machines etc.

Whether or not there is now enough length on those cables and enough space to fit that board in that cupboard is another matter

My brain said it would upset any protection device on the supply side of the TP board if differing loads were applied to the phases. Happily, if I understand correctly, it won't.
All good news. Thanks
The TP board, fortunately, isn't in a cupboard, it's in the corner of the utility room and plenty of space. As you say, though, the existing cabling length may prove a bit of a challenge. Replacing the tails would probably give a bit more leeway.

PatsPatter

 

[Iggifer]

My brain said it would upset any protection device on the supply side of the TP board if differing loads were applied to the phases

It won't upset protection devices, as you'd use 3 x Single Pole devices per TP way, so they're separate. You would however, need to balance the loading regardless, you don't want to be pulling 60A on L1 and 3A on L3

 

[PatsPatter]

It won't upset protection devices, as you'd use 3 x Single Pole devices per TP way, so they're separate.

…… have I crossed my internal wiring/written the wrong thing?
Perhaps I should try asking the question in a bit better way:

Would you expect to see a RCD on the incoming ways to the cabinet - similar to this?

If the above is all correct, excellent! My original question/concern came from the worry that the RCD above would not be able to cope with differences in the individual phase loads - that are bound to occur in this situation.

PatsPatter

 

[Lectrician]

If you use the board for all circuits, you should use RCBO protection to the outgoing circuits. Having an RCD on the incomer won't comply, unless you had TWO TPN boards....

RCBOs for outgoing ways is going to prove expensive!

Spreading single phase circuits across a three phase board in perfectly normal.

 

[PatsPatter]

If you use the board for all circuits, you should use RCBO protection to the outgoing circuits. Having an RCD on the incomer won't comply, unless you had TWO TPN boards....

RCBOs for outgoing ways is going to prove expensive!

Spreading single phase circuits across a three phase board in perfectly normal.

OK. Ta.
Assume you use RCD/RCBO with the same meaning? Schneider et al seem to.

As you say, a RCBO on every outgoing circuit is going to be expensive. 3 smaller, decent quality, (Amd 3 compliant!) consumer units, fed from the TP board, each with a RCBO, instead of the present item, might be a better bet. It will also leave me 11 TP ways from the board for machinery.
That way I'll only waste the case of the current item, not all the MCBs/RCBOs. Whatever happens, it won't be a cheap solution.

As iggifer said, a fair bit of effort put into load balance as well.

At the moment the installation only uses one phase (L2) for all the domestic circuits and the 'outdoor' circuit for the motorhome. The off-peak-only unit. ie, the immersion is off L1 - which surprised me more than a bit………. I had a look and the split load part of the existing consumer unit is not split load anymore. It's bridged!!

Probably a large part of the reason for the bail-out. Out of depth/knowledge/experience.

PatsPatter

 

[flameport]

3 smaller, decent quality, (Amd 3 compliant!) consumer units, fed from the TP board, each with a RCBO, instead of the present item, might be a better bet.

That won't comply either, as there will be no discrimination between the RCBO and the MCBs in the consumer unit in the event of a short circuit fault.

 

[Lectrician]

An RCBO is an MCB and RCD combined in one unit, designed to go in place of an MCB.

An RCD is just an RCD. Earth leakage only, no overcurrent protection.

You get extension cabinets for the Merlin board. Perhaps look at fitting one, feeding it with a couple C63 MCBs, and then fitting a couple RCDs, each with a row of MCBs. Still pricey. You would need neutral bar kits etc.

 

[PatsPatter]

That won't comply either, as there will be no discrimination between the RCBO and the MCBs in the consumer unit in the event of a short circuit fault.

Please explain.
Please don't take offence, I'm only trying to understand but surely:

If there are 3 consumer units, each with RCBO and a MCB for each domestic circuit, isn't the short circuit option catered for? A MCB on the supply way to each consumer unit, within the TP board, would protect against any overload to an individual consumer unit. If the consumer unit side of it is tripled up, each with appropriate RCBOs/MCBs, the phase load of the domestic circuits is balanced as best as it can be.
The TP board has 63 amp provider fuses as is.
I can see that any TP load will have to have separate RCBO/MCB protection as well

Iggifer: I can see the necessity of the neutral balance link as well.

PatsPatter

 

[flameport]

If there are 2 MCBs (one in the 3 phase board and one in the smaller CU for the individual circuit), when a fault occurs it's anyone's guess as to which one will disconnect. Perhaps it will be the one in the CU so only a single circuit is disconnected. Or the main one in which case the entire CU has been disconnected because of a single fault.

 

[Iggifer]

If you shop around well enough, you can pick up schnieder RCBOs for MUCH less than the list price.

eBay is great, if you're careful. Only go for new ones, but you can get some good deals. Just had a quick look and there's 5x32A for £100, a 20A for £19

Much cheaper than the £87 RS want for the same thing

Make sure if you go that route to only buy the new style (with the curved white is test button around the toggle) or the old style (with a grey test button under the toggle) it'll look proper gash if you mix the two

 

[deadshort]

I believe it is for the off peak…………….

View attachment 106090

but would only appear to supply the off peak immersion.

PatsPatter

Eon obviously appreciate quality …… NOT

DS