EICR

[Grumps]

Hi, I've just had an EICR performed on a property that I let. I wasn't present during the test and my tenant has reported the following back to me (I'm too impatient to wait for the full report which might not be with me until the end of next week).

Apparently 4 16Amp MCBs need to be changed to 6Amp. Each MCB is connected to just one wall-mounted electric heater. The heaters are rated from 1500W to 2000W. The last time I had a look at the wiring (when I decorated some 4 years ago), I'm sure it was 2.5mm2 from the MCB to each heater's FCU.

2.5mm2 and 16A MCBs are a good combination, yes? Even 1.5mm2 should be good.

Surely if I get the 16A breakers swapped to 6A then that won't be sufficient for a 2kW heater, and probably not even for the 1500W ones?

What possible reason would the electrician suggest swapping to 6A MCBs? He has a good review rating and was booked via myconstructor web site. The sparks I've used before is on holiday (whatever one of those is) which is why I went to that web site. Ta.

[jon]

Perhaps he thought the heaters were 1kW.

[Scott]

I would just turn them on and if they trip out, phone the electrician and tell him there must be a fault with his work.

[ARW]

A 16A MCB and 1.5mm T&E may be fine but there are other factors to consider.

Length of cable and thermal insulation around the cable are two things that might affect the choice of MCB.

Of course if he fits 6A MCBs then they will trip (maybe not the 1500W ones).

Without knowing his reasons I could only guess.

Of course 10A MCBs are available which might be suitable (if 16A is for some reason not) and they would not trip with a 2kW heater.

Keep us updated.

[Brian Gaff (Sofa]

If they are the Infra red type they can be as low as750 watt, like the two I have, and I think they are wired into the upstairs lighting circuit. Brian

[Brian Gaff (Sofa]

Surely one could just assume they are what they are and act accordingly and let him know why you did not do the change. After all its not so adversarial is it? You don't want to upset him, in case you need him another time we all make errors.

Brian

[ARW]

I have a gut feeling that the tenant may be playing Chinese whispers.

They are not usually the most reliable people to pass on the correct information.

[Scott]

Not adversarial, just leaving the job to the professionals and not trying to tell him how to do his job. If you went to the doctor, you would describe the symptoms. You would not go in saying you should do this and this.

[ARW]

My mother would:-)

[charles]

The nearby village hall had an installed stage dimmer and lights fed off a

45A breaker. I was called in since fading up more than one light tripped the breaker. It turned out that the 'professional' who did their safety check changed the 45A breaker for a 6A one. "It's lighting, that only needs a 6A breaker!"

[Andrew]

Yorkshire lass ?

[ARW]

Yes and an ex nurse.

[ARW]

I switched off a 32A "Kitchen sockets" MCB yesterday.

All the lights over the ice rink went out and the microwaves in the kitchen stayed on.

[The Nomad]

I have been know :-)

I had one ask me what I wanted her to do re my 'condition'.

Younger ones may not be so keen I suppose ...

Avpx

[John Rumm]

It seems like you will need to wait for the proper report since something does not add up here.

[John Rumm]

+1

Yup too easy for nuance to get lost, or a subtle change of wording that has no real effect in plain English, take on a different meaning in technical lingo.

[Grumps]

So, I had a quick visit to the property (still haven't got the full EICR yet) and had a look at the wiring behind the FCU. Well would you believe it, it's almost certainly only 1.5mm2. I measured the cable (with my trusty plastic vernier) and it was a little more than 8mm but much less than 10mm.

I don't have any edition of the regs but I do see table 4D1A (which is probably for most domestic situations) that shows max capacity of 1.5mm2 cable as 14.5A (cable is plastered into the wall).

So the electrician was partly right I think. 16A MCB is too much, but his suggestion of 6A would be too little. When I get the report I'll have a chat and hopefully come to a compromise of using 10A MCBs.

The property was re-wired in 2004. Would (or did) the regs change or did the original installer make a mistake?

[Alan]

Are the heaters supplied by a Fused Connector? And, is each on its own cicruit? If so, no need to downrate the circuit breakers, as there is overload protection at the far end, via the fuse. Fault protection may need to be checked with a 1mm CPC.

[John Rumm]

I think you are looking at the wrong installation reference method. "Buried in masonry" is treated as method C, same as "clipped direct". So on current draw alone 20A would be a closer estimation. (there may be voltage drop issues if the cable is long) See:

I would argue that 16A is fine for a number of reasons. Primarily, the MCB only *has* to provide fault protection at the origin of the circuit, not necessarily overload protection - that can be done elsewhere (a spur on a 32A ring circuit being a prime example - the 32A MCB will not provide overload protection for a single length of 2.5mm^2).

You seem to have adequate overload protection via two means - firstly by selection of power consumption of the appliance - since this is hard wired you don't have to consider someone "plugging in" a too heavy load.

Secondly you mention a FCU. That kind of implies a 13A fuse is the highest that can be fitted there, and that will also prevent overload on the cable.

They have changed in that time (from the 16th to the 18th edition - so new rules on RCD protection, and maximum permitted earth loop impedance Cmin factiors[1])), but not in ways that would have a bearing here.

Not really - just engineered it to meet the requirements without any additional overspend or overbuild.

[1]

[Grumps]

Thanks for the wiki link. Very concise information. So the cable run leading to the FCU is method C (buried in plaster in this case), but perhaps the electrician has determined that some parts of the run are in the ceiling space and probably that would mean method

100 or 101 applies. Either way, the 13A fuse in the FCU should make any method acceptable except 103. Voltage drop would not be an issue either. Looks like I'll have to wait for the report.