Monitoring for maximum demand

[Leigh Winspear]

Hi yall,
A customer has bought this -

https://www.amazon.co.uk/KETOTEK-Vo...ltifuction/dp/B095LYZWYV?ref_=ast_sto_dp&th=1

I am usually against amazon electrical purchases, historically, but he is adamant that it is approved and recommended by his electrician neighbour. Hhmm.....

I did an EICR on his property last month and he now wants 4 types of ovens in his kitchen, so therefore I questioned maximum demand. It is a 4 story building just to explain, so many circuits already.

I did a basic/usual calculation and luckily he has an 80amp main fuse, but his twin rcd board seems already pretty well potentially, loaded to be fair on 1 phase.

Then I mentioned the possibility of monitoring energy/load over an actual time and that is why he purchased this device.

So, what alternatives, as in quality approved products should I mention? or is this supposed - 2000+ amazon positively recommended item, worth installing?

Also is there a portable/temporary device I can install for a duration, get a result then move to the next job?

The latest EFIXX video is worth a watch also, as it focuses on the very topic of maximum demand......but it is still a very grey area to me still to be honest. I do my best..........but appreciate any input/guidance I can get as you know.



Cheers n stuff

L

 

[Murdoch]

What is his typical weekly usage?

I’d be really surprised if the house got anywhere near 80A unless it has electric space heating

 

[SPECIAL LOCATION]

Maximum demand metering is more of a need for commercial / industrial applications..
e.g. https://www.businessenergyuk.com/knowledge-hub/maximum-demand-meters/

But similar problems to yours in residential (private and/or rental), are not uncommon..
e.g. this article.. https://www.test-meter.co.uk/blog/maximum-demand-the-understated-benefit-of-power-energy-loggers

I suspect what you need is a bit more expensive than a £20 Amazon purchase...???
Maybe give this link to your client and ask if they are willing to purchase a proper power logger instead...
https://www.test-meter.co.uk/chauvin-arnoux-pel104-power-energy-logger-contractors-kit

I can't see how that little DIN rail power meter can offer any useful max demand values..
Isn't it just measuring cumulative power over time? Which is not Maximum Demand!

I try to evaluate max demand in relation to how many loads are simultaneously on during a single one hour time period..
i.e the max Kilo-Watt-Hours consumed during 1 hour.

e.g. Consider an 8.0kW shower.. if it was running for 1 hour it would be 8kWh..
However if it was only on for 6minutes (10% of an hour) it would only be 0.8kWh!!

So lets imagine a hypothetical installation with three 40A MCB circuits supplying three 8kW loads and one 10A circuit supplying a 1kW load over a 24hour period...

Just adding the MCB values together = (3x40) + (1x10) = 130A
or using the 100% largest 40% of the rest rule of thumb calculation = (1x40) + (0.4x((2x40)+10)) = 76A which is still probably wrong..

So imagine:-
Day 1 the 1kW load is on for 24 hours: Cumulative meter reads 1kW x 24hrs..
24kWh over one day. But.. Max demand = 1kW (4.35A)

Day 2 the three 8wW loads are on for three individual non-overlapping 1hour periods: Cumulative meter reads 8kW x 3hrs..
24kWh over one day. But.. Max demand = 8kW (34.8A)

Day 3 two 8wW loads are on for the same overlapping 1 hour period, the 1kW load is on for 8 hours not overlapping with the 8kW loads... Cumulative meter reads 8kW x 2hrs + 1kW x 8hrs..
24kWh over one day. But.. Max demand = 16kW (69.6A)

Hence why maximum demand is a bit of a grey-art, not a simple calculation.. and requires someone with a comprehensive understanding of the full installation composition.. and the realistic simultaneous usage of the various circuits.. Or an expensive power logger... Not a £20 amazon purchase!!

 

[johnb2713]

Thanks for sharing the video, a lot has changed since the start of my electrical apprenticeship in the Steelworks. I also watched the linked video of meter tails above 3 metres which is relevant to me at the moment, I'm converting the upper floors of my retail premises into flats and the distance from the flats to the incoming supply is around 40 metres. So I now have some info to go with for my planning, I do intend to use an experienced sparky for the install with me running cables and doing 2nd fix etc.

 

[Leigh Winspear]

What is his typical weekly usage?

I’d be really surprised if the house got anywhere near 80A unless it has electric space heating

Me too......Questions have been asked!

 

[mort2376]

Ive used this in the past. Simple to setup and comes with software for you to get the data off.

That's the company I hired from, they do deliver, but you may find a local supplier you can collect from.

You don't need an energy monitor you need an energy data logger. So what your customer has got won't work unless he sits there and records the data showing on the display.

 

[Leigh Winspear]

Ive used this in the past. Simple to setup and comes with software for you to get the data off.

That's the company I hired from, they do deliver, but you may find a local supplier you can collect from.

You don't need an energy monitor you need an energy data logger. So what your customer has got won't work unless he sits there and records the data showing on the display.

View attachment 16809

looks a good solution. Im sure the customer claims that the amazon device can store peak values, which I guess is part of what we are after.

 

[binky]

looks a good solution. Im sure the customer claims that the amazon device can store peak values, which I guess is part of what we are after.

Yeah, but that needs an enclosure and tapping into the meter tails to work

 

[SPECIAL LOCATION]

looks a good solution. Im sure the customer claims that the amazon device can store peak values, which I guess is part of what we are after.

From reading the info on the Amazon link, I cannot see where is states Peak values?

 

[kerching]

Hire one I bought one. Years ago, second hand. Brilliant bit of kit Got it for one client and saved them 10s of £k a year by getting them to change their systems ".lifestyle". This included fitting a IMI Pactrol system with a weather compensator and a time clock to,switch off NS heaters on Friday and Saturday night
Only issue is that it
is an MSDos operating system