Many thanks for TT answers, and one more thing...

[NealHarman]

Many thanks to those that replied to my question about a new consumer unit on a TT supply. Sorry about the delay in replying - work just got insanely busy for a bit. Will probably go for the RCBO option (and as it happens yes I do have to dig a trench alongside the house )

Two other quickies (I hope).. My DNO (as far as I can get any sense out of them on the subject) won't fit an isolating switch between the meter and CU, so was thinking of getting one put in by whoever does the CU - any downsides? I guess the extra cost should be insignificant and we're basically talking about one of
these in one of these (or similar).

Second, for the number of ways we might (plus a few spare - I don't really want to have to do this again any time soon) we're likely to need a metal CU since the insulated ones aren't big enough (or at least it's tight). Is this a problem in a domestic install?

Regards and thanks again,
Neal

 

[andy]

Many thanks to those that replied to my question about a new consumer unit on a TT supply. Sorry about the delay in replying - work just got insanely busy for a bit. Will probably go for the RCBO option (and as it happens yes I do have to dig a trench alongside the house )

Two other quickies (I hope).. My DNO (as far as I can get any sense out of them on the subject) won't fit an isolating switch between the meter and CU, so was thinking of getting one put in by whoever does the CU - any downsides? I guess the extra cost should be insignificant and we're basically talking about one of
these in one of these (or similar).

Second, for the number of ways we might (plus a few spare - I don't really want to have to do this again any time soon) we're likely to need a metal CU since the insulated ones aren't big enough (or at least it's tight). Is this a problem in a domestic install?

Regards and thanks again,
Neal

since you have a TT supply, you cant use a metal CU unless protected by a RCD installed before it.

1: it may cost extra, since it has to be done live or by pullin the service fuse which will have to be resealed.

also, how many ways do you need. i have seen 24 way plastic CU's before

 

[Careful_Bodger]

Neal,

I took just this approach with a pre-CU isolator (...... howls of derision from the anti-DIY brigade and no I did not work live, and no I did not personally pull the fuse ......)

The only problem I found was manipulating the tails. The cable entries are a very tight squeeze for the 25mm2 L&N, and the turn radius to get from the enclosure entry to the isolator cable clamps is awkward (they are not directly in line - for MK at least). The plastic enclosure was not strong enough to lever against, so some care was needed to apply force where it was required i.e. to the cable.

But it all now fits. It all looks very tidy & I am very happy with it. And I have the advantage of being able to completely isolate the CU.

Cost of these components is trivial.....

Is this what you needed?

 

[NealHarman]

Thanks for the replies - I haven't seen a 24-way plastic I must admit, but I probably don't need quite that many any way.

Just for info:
1. Work's been ongoing for a year now, so Part P doesn't apply yet. The building inspector was pretty relaxed about it in any case when I brought the subject up.
2. However, I wasn't actually planning on doing this bit myself, since I don't have an earth loop impedence meter. (Having said that, getting someone to come and do it isn't proving that easy - everyone's busy.)
3. The DNO (WPD) upgraded the supply (it was a safety issue) and replaced the fuse - they did not put a seal on and explicitly told me that it was OK to pull the fuse (I haven't ): - and just to give them a call to come and seal it when all the work was done. I was pretty suprised.

I'm still a bit in two minds about an isolator - on the one hand I'm no big fan of doing working on the incoming side of a CU myself, and if I make sure I've got some spare ways I shouldn't need to mess with it. On the other hand, I've seen lots of places (including this one) with all sorts of extra bits added on...

Neal

 

[andy]

Thanks for the replies - I haven't seen a 24-way plastic I must admit, but I probably don't need quite that many any way.

Just for info:
1. Work's been ongoing for a year now, so Part P doesn't apply yet. The building inspector was pretty relaxed about it in any case when I brought the subject up.
2. However, I wasn't actually planning on doing this bit myself, since I don't have an earth loop impedence meter. (Having said that, getting someone to come and do it isn't proving that easy - everyone's busy.)
3. The DNO (WPD) upgraded the supply (it was a safety issue) and replaced the fuse - they did not put a seal on and explicitly told me that it was OK to pull the fuse (I haven't ): - and just to give them a call to come and seal it when all the work was done. I was pretty suprised.

I'm still a bit in two minds about an isolator - on the one hand I'm no big fan of doing working on the incoming side of a CU myself, and if I make sure I've got some spare ways I shouldn't need to mess with it. On the other hand, I've seen lots of places (including this one) with all sorts of extra bits added on...

Neal

i would recommend you put in an isolator between the meter and CU. makes it easier if you ever have a need to split the tails or disconnect the CU for whatever reason. how many ways do you want in the CU?

here's a link to the 24 way version
http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=PL03267&N=401

 

[securespark]

Careful, if you use a WF water resistant enclosure (or similar) there are no knockouts, the casing (although flexible) is quite rigid, and you can drill a hole of a suitable size directly opposite the terminal, then the tails go straight in - no need for bending.

I'd show you a piccy, but have mislaid the link.

STOP PRESS: FOUND IT!!

 

[NealHarman]

i would recommend you put in an isolator between the meter and CU. makes it easier if you ever have a need to split the tails or disconnect the CU for whatever reason. how many ways do you want in the CU?

here's a link to the 24 way version
http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=PL03267&N=401[/QUOTE]

OK - thanks. Had a bit of a rethink and currently (this isn't completely stable) the plan is:
-5 socket (attic, 1st floor, ground floor, kitchen, office) - could ditch the office but will be running several computers so... It seems a lot I know, but the house is quite 'rambling' and a lot of structural steel has gone it, which makes the cable runs long even though it's not that big. Also, I want to keep things logical.
-4 lights (attic, 1st floor, ground floor front + back halves)
-Heating
-Smoke alarms (I know this can go on the lights but the building inspector's thing is fire safety and I've been told he likes to see it even though it's not technically anything he has any authority about)
-Fridge/freezer
-Shower (don't plan on an electric shower at the moment, but don't wish to rule it out).
-Cooker
-Garage+Garden (Was going to have separate circuits for some combo. of garden and garage lights and power, but now think it might be better to run a separate CU in the garage for all that - has the advantage of meaning I don't have to think about something that isn't a priorty - just size the cable appropriately).

I make that 15 - and a few spares would be nice. I know I could shave it a bit, but it's a lot easier to do it properly now than later.

Neal

 

[ban-all-sheds]

I make that 15 - and a few spares would be nice. I know I could shave it a bit, but it's a lot easier to do it properly now than later.

Neal

So that 24-module one isn't overkill. Note that it's 24 modules, so taking off your incomer and 30mA RCD, you're left with 20. Now with your 15 that's 5 spare ways left. Not too many, IMHO.


BTW - does that unit have anything in it apart from a couple of DIN rails? I know it says it's a CU, but if you don't want to have to start buying and fitting your own neutral bars, earth bars, busbars etc, check before you buy it.