I'm tempted to contact him before he publishes his report as I believe a copy of a failing report also goes to the Local Authority. It might be less embarrassing for all if you explain why in some instances 6A MCB wouldn't be suitable.
Also check if a 10A is available for your CU.
I have sent him a text. It is a bank holiday so won't call him and won't expect a reply until tomorrow. I wanted to get some of my facts right before questioning his reasoning for the MCB change. I now have the wiki to refer to (thanks John Rumm) so won't sound like a complete idiot!
Yep, I'm sure the report will go to the LA, but eventually if work needs to be done, or he needs to make a correction, then that will also go to the LA.
And yes, 10A MCBs are available for this CU at just £3 each.
That was what used to happen with hay fever medication before it was taken off prescription. It started as 'I see last year you had A and B. Did this work? Good. I'll give your the same again this year' and eventually evolved to 'I always get A and B and it works well'. No further questions - prescription in hand.
I have the full report now.
All circuits have been deemed to be reference method 100. The 5 heaters are on 1.5mm2 cable with 16A MCB.
The failures are listed as:
3x 1.5mm cable in a 6A breaker (these are lights and smoke detectors). Incorrect breaker sizes for heater circuits.Recommended solution: Downgrade MCBs to 10A C type for inrush protection of 1.5mm cables. Split the doubled up 6A circuit.
So my quick questions are: Are you not allowed to have 3 circuits in one breaker? Can you not protect 1.5mm2 ref method 100 wiring with a 16A breaker?
The electrician quote to "mend" this is £205 inc VAT. Ta.
If they're on one breaker they *are* one circuit.
It is permitted to have 3 cables on one breaker, typically ring final and a spur socket from the breaker. I can't see that 3 x lighting cables would be too big for the terminals.
The problem is splitting the lighting circuit at the consumer unit may also need the smoke detectors rewiring as wired-interlink smoke detectors MUST all be on the same circuit (because the interlink is 240V)
If you combine the 3 x 1.5mm in a junction box outside the CU they all become one "circuit" anyway.
I woudln't regard 2kW domestic heaters having much inrush current. It should be calculable if you know what type of heaters they are eg nichrome, the temp coefficient of the element, and run that against the adiabatic for cable heating.
I'd leave it to someone better than me to do the ackchewul sums.
Owain
Just for clarity, is it 4 MCBs for 5 heaters?
Assuming the MCB is rated to take 3 x 1.5mm cables (and I can't think why it wouldn't be) I wonder if the argument is that there is insufficient resilience (Reg 314's "314.1 Every installation shall be divided into circuits, as necessary, to: (i) avoid danger and minimize inconvenience in the event of a fault...").
Which lights are on that MCB and which on separate circuits?
I wonder if that "Method 100" will become a typo for "Method 101" in response to questions :(
5 MCBs; 4 are for heaters and one for a towel rail.
Bathroom lights are on that MCB.
Yep, I think it might ;)
Maybe I should just say "sod it" and pay the £205. Although I do like a bit of a discussion/argument if I have some firm facts on my side.
And finally, from the electrician...
6242Y PVC/PVC COPPER CABLE is rated at approx 13amps it is therefore good practice to downrate the mcbs from 16a to 10a to protect the cableBy replacing the mcbs from B type to C type this will reduce the risk of nuisance tripping when the heaters click on and off at full load
It is poor electrical practice to have more than 1 circuit fed from 1 mcb to multiple circuits especially if not in the same location , therefore with a spare way on the board the circuit can be successfully split
Well spotted Robin. It has to be method 101!
I wouldn't mind if it was written 101 on the report, but he wrote 100.
Your electrician meant (assumption) to say 1.5mm 6242Y cables is rated at 13A using installation method 101. The CCC of 1.5mm using method 100 is 16A.
I can see why he has flagged it but there is nothing unsafe as long as the end load only consists of a 13 fused spur. So yes it is good practice to downrate the MCB if there is a chance someone uneducated might alter the circuit.
It's probably better to get the MCBs swapped than have C3's or comments on your EICR.
Note that the OSG does not give a guide for a 1.5mm 16A 101 installation method radial circuit as it assumes a terminal load of 16A.
ok might be true...
So 1.5mm^2 should be fine (so long as they have a cable each, and not one shared between the lot :-)
No sure what that is that supposed to mean? You don't size cables for inrush current anyway. You might choose a MCB type to allow for loads with excess inrush.
(what kind of heaters are they?)
You don't have three circuits on one breaker, you have just one radial circuit that happens to have two branches at the origin. Nothing wrong with that IMHO.
Can't see why not.
Even at 101, I still can't see a problem if the FCU has a 13A fuse, and there is a single hardwired appliance...
As it's hardwired it should only be changed by someone with a clue, that is not going to try and stick a 4kW heater on it. Even if they did, the fuse would save the day. The 16A MCB will more than adequately provide fault protection for the cable unless its ridiculously long.
Yup, either that or someone is going cross eyed looking at the table, or can't measure insulation depth. :-)
Yup, from an engineering PoV, it's fine as it is, but from the pen pushing PoV it's less hassle to swap them.
They're Atlantic wall heaters. Don't know if that brand is common. I'd assume nothing special, mainly resistive and not a significant inrush. But what do I know!
Looks like the path of least hassle is to pay him his £205 ransom.
I am afraid it looks likely.
Or set him up on a date with T i m 's daughter.
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