"Changing a consumer unit" this time:
Any obvious bits missing, unclear or misleading?
Should more or less detail be included in the live working section?
I feel there ought to be more words on dealing with a substandard TN-S earth provision (i.e. skinny bit of uninsulated rusty wire connection incoming cable sheath to old fusebox etc). Thoughts?
Any pictures needed?
Hi John,
I would propose another reason to change:
- To rationalize or simplify an existing existing which is complex (either just to reclaim space, or to make use of the system less prone to errors).
Under Planning->Split Load Vs Multiple, it wasn't clear to me from the text why you can get away without a time delayed RCD in a TT system if you have multiple CUs. I think you mean this is because both CUs are to be wired in parallel with each other, so one can have the 100mA RCD and the other a
30mA, and because they're in parallel the 100mA isn't behind (or in front of depending on your view!) the 30mA. I think this could use clarification.Under Starting Work-?Disconnecting the power, I thought there were cases where is was legal to pull the main supply fuse - for example to avoid (or put out) an electrical fire. In any case I think this could use a statement that you can ask the supplier for permission which they should grant (although perhaps for a fee), and may even come out and reinstall the seal. Perhaps also a suggestion that now might be a good time to try and persuade the supplier to come out and install a breaker for you (using mutterings about safety to try and get a freebie).
Your link to VIR rubber cable link in Removing the Old CU is broken.
In Installing new CU->Prepare the new CU, your cable_crimping link is broken (an extraneous _crimped I think).
Finally, I wonder if the various sections that refer (sometimes implicitly) to extending circuit lengths shouild note that voltage drop may need to be consider.
Cheers, Piers
You don't mention testing the RCD(s) after installation (and making sure your punters are out of the way when doing live testing before you've proved your safety devices are OK!) Maybe you need to put in your prerequisites that one should have the various bits of test kit (or a multifunction tester) to do the job.
In general I might suggest that anyone contemplating changing a CU might consider doing it according to the 17th ed (though I couldn't tell you off the top of my head all the implications of that)
It would be lovely, but it probably bring the diy writing from hobby status up to 'job' status.
Comments: Really helpful. Well done.
Suggestions:Are the tails meant to be 25mm² even if the suppliers fuse is less tan 100A? If the tails are in the meter then probably you will need to use those ones anyway. Although if they are very old breaking the meter seal to upgrade the tails is the lesser "crime".
There is no mention of the legal/regulatory aspect. We all hate the Prat P, but I think it could do with a mention. Obviously some people are into compliance paperwork etc.etc.
Not too much of a job since I am aware of some CU upgrading work that needs doing shortly somewhere or other ;-)
Ta
It was my understanding that they can be less than 25mm^2 with lower capacity supplies, although obviously there is no harm is using more than the minimum especially as it allows for a future upgrade to the service without incurring extra work.
yup
Well it gets a mention as the very first bit of the article, in a boxed out section ;-) how much more did you want?
There did not seem to be much point in describing how the building notice procedure is supposed to work since each of the LAs seem to make up their own rules.
Yes, good point frequently the case in real life.
Yup, that is what I was trying to say ;-)
(having said that, now TLC stock time delayed RCDs a sensible price it is less of an issue!)
Yes there are procedures to have then disconnect and reconnect officially. I presume they will want to see signed off papers showing that the installation passed testing prior to reconnecting.
ta, will fix.
Possibly, although you would need to have a very marginal design in the first place... I suppose you could move the CU by 4m without need for additional protection for the tails.
is the big master on/off switch you mention the same as an isolator switch?
I cant find one at Wickes or Screwfix of CPC, but think I should get one for my house before I do much more electrical repairs...
is this the kind of isolator for a house?
Since when? About mid-Feb I looked and they only had 'normal' 100mA RCDs. Ended up getting a TD unit from Harbro(?) for about 70 notes.
A link to
Down the bottom of the list...
A bog standard two pole switch as used for the incomer of a CU:
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