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DIN Panel KwH Meter on Circuits

Postby naesk » Fri Oct 22, 2010 10:13 pm

I'm in the process of researching to make my home intelligent using various "smart" technologies. The initial stage I will be adding meter monitoring using devices such as CurrentCost etc...

Whilst these types of devices monitor overall consumption, I was wondering can DIN panel KwH meters for consumer units be placed on individual circuits (light, sockets, heating, shower, cooker) to monitor usage on said circuits, or are these modules limited to cumulative monitoring?
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Postby ericmark » Sat Oct 23, 2010 11:31 pm

There is no limit as long as your willing to pay.
Where I worked we were told we were claiming for cranes that were not being used as time laps photography had caught the cranes in same position on numerous shots.
We fitted monitors which produced a graph of exactly how much power and when was used showing the cranes were in use.
However each unit was expensive to hire and in domestic unlikely it would be cost effective.
So let me list some items to look at.
1) The florescent lamp uses far less power than the tungsten but it is very voltage dependent. If the voltage raises by just 10% the current raises by something like 30% and if the voltage falls by 5% they stop working. Using HF florescent fitting will correct this problem but they cost around 6 times the equivalent induction unit. A meter that records the max voltage therefore will held deciding if worth the extra expense.
2) The fridge freezer use power according to how often the door is opened and how good the insulation is. Unseen damage to insulation can allow water to enter which will allow far more heat to enter the unit and so increase running costs. Measuring and recording usage will assist in identifying when insulation has been damaged. A simple plug in recorder will do this.

Other items are so hard to measure. Take for example a tumble drier. It sucks air in from inside the room and blows it out outside so not only are you paying for electric being directly used you are also paying for extra central heating power to heat the new cold air being drawn in from outside. Putting the unit in an area which is well vented from outside and unheated can save money. The same applies to any other device blowing hot air outside for example bathroom extract fan. There are special heat exchangers but these are not cheap.

Then there is the sneaky power users. The Sky box powers the LNB at all times so uses about 15W all the time it is switched on but a free to air box powers down the LNB's when in standby so uses that little power most plug in units will not measure what it uses. Less than 1W. So to use a timer or remote to switch off a free to air box will use more power than the box uses but with a Sky box they will really save money. Again the little plug in units will identify this type of problem.

Transfer of power from one source to another is a problem too. Remove all tungsten lamps and replace with discharge lamps and the electric use will go down. But gas use goes up as you were heated from the bulbs the power was not waisted. Also since the heat from a bulb is both radiated and convected the radiated part does not heat air but heats you directly so air changes will not remove as much heat as with the pure convected heat of the central heating so in real terms in winter tungsten bulbs could save energy compared with discharge. It would depend on number of air changes.

The interaction between parts is so often missed when manufactures make their claims. I have tried to compare the two types of tumble dryer but all the data forgets the ducted type sucks the heated are out of the house and blows it outside where as the heat pump type dries not only the cloths but the air in the house so reduces the air changes required to stop the house getting damp. Plus little consideration is given to the chance that it could draw flue gases into the house instead of them going up the flue.

My parents had cavity wall insulation fitted. This stops the natural breathing through bricks so they also added vents so house colder after than before until vents were blocked up.

Hence I have become sceptical as to energy saving and although I will use energy saving items when natural replacement is required I consider in the main it just a way of generating more trade and has nothing to do with saving energy.
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