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FlyingPete

112 posts

Master Geek


#178976 21-Aug-2015 11:23
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Hi,
I have been trying to figure out a mysterious drop in power usage at home everyday.

I have a Effergy Engage power meter with the sensor on the main phase cable going into the meter outside, the usage it is reporting reflects what the meter is saying on the occasions I have checked.

There are a number of gadgets and stuff running 24x7, no electrical heating though (gas heating and hot water).  Idle load sits around 400w, which is a little high for my liking but seems to ring true to my IT and comms stack (about 100W), two aquariums with 100W heaters (not on all the time though) plus fridge and other idle stuff.

The screenshot below is fairly typical of power use, shows the idle then a jump when I get home from work and turn stuff on, there is often a peak in the morning too if I have time for a coffee :)

 

The strange thing is the 11am drop.  If I am not home it lasts from 11am to 9pm and is about 100W.  The only thing that I can find that changes in that time is the one of the aquariums, its lights turn on at 11am and switch off at 9pm, but that should result in an increase in power.  The lighting is 36W of fluros and 7.2W of LEDs.  I haven't measured real usage at the point yet on that though.

Now for the kicker.  I unplugged the timer and lights this morning to see what happens.  11am has been and gone and the power hasn't dropped today!

Now how on earth do those lights reduce power usage?  Surely they are not heating the aquarium more efficiently than the heater?  Probably worth pointing out that the heater is in the external filter so not exposed to the lights in anyway so doubt its the lights messing with the thermostat.

This is all very weird.




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frankv
5680 posts

Uber Geek

Lifetime subscriber

  #1371458 21-Aug-2015 11:27
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The only logical thing seems to be the timer... maybe its burning up a whole lot of power when the lights aren't on?




  #1371459 21-Aug-2015 11:28
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There will be others with a better knowledge of this, but from what I understand without a voltage sensor you are not able to measure real power, accurately. Those current-only sensors only measure power on resistive loads (i.e. filament lights, HWC elements etc). Anything with a reactive load will not be measure correctly and you could quite possibly see a drop in the reading - even though you are using more power.

Hopefully someone with more know-how can explain it a bit better!

FlyingPete

112 posts

Master Geek


  #1371460 21-Aug-2015 11:29
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frankv: The only logical thing seems to be the timer... maybe its burning up a whole lot of power when the lights aren't on?



I have wondered that too, but the timer is disconnected a the moment and there was no corresponding drop when I did that.



FlyingPete

112 posts

Master Geek


  #1371476 21-Aug-2015 11:31
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SumnerBoy: There will be others with a better knowledge of this, but from what I understand without a voltage sensor you are not able to measure real power, accurately. Those current-only sensors only measure power on resistive loads (i.e. filament lights, HWC elements etc). Anything with a reactive load will not be measure correctly and you could quite possibly see a drop in the reading - even though you are using more power.

Hopefully someone with more know-how can explain it a bit better!


Hmmm my electrician was telling me about power factors the other day as some new LED lights I had were particularity bad.  I wonder if its a situation like that?  I think there is another option to put a reader that reads the IR LEDs on the meter itself which is supposed to be more accurate.

Aredwood
3885 posts

Uber Geek


  #1372640 23-Aug-2015 19:06

In short - it is to do with power factors. As different devices can have different power factors that can partially or fully cancel out. This is why you see an "apparent" drop in power consumption. You need to get a power measuring device that can measure power factors.

Also have you compared your monthly consumption as reported by your Effergy. With the consumption recorded by the power company meter. Due to the Effergy not being able to measure power factors. It should report higher than the meter. Also can you have a look at the power adaptor for the engage hub. Does it output DC or AC? As if it outputs AC it suggests that it is using the AC as a means of picking up the mains voltage waveform for power factor calculations.





FlyingPete

112 posts

Master Geek


  #1374603 26-Aug-2015 13:44
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I haven't managed to get a full month of monitoring yet on my Effergy.  My power company does not provide day by day usage or hour by hour usage so I wanted something to fill the gap, hence the Effergy box.

Pretty sure the engage hub is using DC but will check again...

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