EN 61000-3-11 and EN 61000-3-12

Something that takes >16A and <=75A and is likely to cause disturbances to the supply if it's not beefy enough .... heat pump perhaps?

  - Andy.

A Triton 5.4 kW instantaneous under sink water heater.

So do you think I phoned the electric supplier?

I'm guessing the answer might be no., you didn't call the DNO.

However, assuming the question is "Do we need to contact the DNO?" ... it's rather open question without knowing some more detail, eg. what kind of installation, size of supply and earthing arrangement, perhaps the measured (or otherwise determined) prospective fault current and Ze, etc?

There was another electrician at the same house at the same time,  I was in a bathroom and he was in the kitchen. 

He read that and said "if that's a required loop measurement it's not going to happen".

This seems to be above my paygrade. 

Its obviously a water heater designed for installation in substations. Those DNO operatives need clean hands just like you and me!

The issue appears to only affect larger units > 9 kW. The installation instructions say:

1 The water heater must only be connected to a
230-240V ac supply. If you are installing a
water heater with a kilowatt rating above 9kW,
it is advisable to contact the local electricity
supply company.

I said to the other electrician that there's times I read manufacturer instructions and think "what the hell are they going on about?".

I think the issue about informing the DNO about showers and heaters above 9.0 kW is the increased maximum demand.

Is there a requirement for a low live neutral loop reading to avoid dimming the lights next door?

Is there a requirement for a low live neutral loop reading to avoid dimming the lights next door?

I think that's the general idea - I've seen requirements expressed in that sort of way for heat pumps - basically voltage drop but written the other way around (and possibly in a way that's easier to verify on-site).  I'd always presumed the issue with heat pumps and the like was the starting currents rather than rated demand (lights flickering every time the heat pump started up rather than continuous low voltage).

I would have thought that resistive heating elements would have had much less of an issue on that score though (OK the elements will have lower resistance when cold, so will have a somewhat higher 'starting current', but not that much surely?)

In any event the 0.031776Ω figure seems ridiculously low to me (unless I've completely understood what it means) - that would match a PFC of around 7.2kA and be impossible to meet in the vast majority of installations, especially domestic ones. I might suspect the Manufacturer has put the decimal point in the wrong place.

    - Andy.

Found this guidance  61000-3-3__-3-11_voltage_fluctuations__flicker.pdf (emcstandards.co.uk) which agrees it concerns light flickering and inrush currents. It also states, in the overview on page 4, it is illegal to connect an item if the power supply does not conform to the requirements

for 61000-3-12 the manufacturer's instructions state "it is the responsibility of the installer or user..." so you could pass the buck on this one;)

Perhaps a typo with the decimal point in the wrong place?