energy saving quest - how to trace < 300w background load

[sandyman44]

hi
I have a "your loop" energy monitor on my electrical supply. Its been pretty good at helping me find things that are using energy in my house. It shows the at-rest load of my house (everything switched off / unplugged that can be) around 350W constantly, which is working out around £1 a day just for the background load, more than I would like.
However, when I last went on holiday I did something different - I switched power off using the MCB's to all circuits, other than the one that has the freezer on it. Using this method, and working out meter readings, the freezer is using a few 10's of watts only. So, the problem is I can't work out where the extra 300 or so is coming from.
I have already been round every room and unplugged / switched off everything .so I now think there must be something somewhere hidden by the previous owners that I don't know about , or had not considered as taking always on power, e.g an outside sensor light . I am currently mystified as to what it might be, so need to start a process of tracing to find it.

I can shut down circuits using the MCB one by one to see what happens to the load at the meter tails and I am quite happy to pop in the loft / under floors and trace cables to try find the miscreant as well.
To do this I will need something to tell me the real time power consumption level focused on the lower end of the spectrum (1.5 amps or less), clamped on to wiring.

Is there a clamp on meter with good enough low-end (<1.5A) power resolution in a DIYNOT'ers price bracket anyone can recommend?

 

[Taylortwocities]

Boiler/heating system? TV distribution stuff? Power to external items?
Often forgotten when doing this sort of thing.

Only you know how your place is laid out/wired.

Screwfix have a clamp meter for not much more than £20
http://www.screwfix.com/p/lap-digital-clamp-meter-600a/8906f?_requestid=122123

 

[sandyman44]

Boiler/heating system? TV distribution stuff? Power to external items?
Often forgotten when doing this sort of thing.

Only you know how your place is laid out/wired.

Screwfix have a clamp meter for not much more than £20
http://www.screwfix.com/p/lap-digital-clamp-meter-600a/8906f?_requestid=122123

been round killed all that "house infrastructure" stuff such as boiler, loft tv amp etc already.
hence why my method now is to shut down by ring , trace and then I will find it and either go "d'oh" or "eeenteresting...."

looked at the screwfix one, annoyingly min current 2amps... I assume pro-grade kit will go less, but don't want to spend a fortune.

 

[bernardgreen]

To do this I will need something to tell me the real time power consumption level focused on the lower end of the spectrum (1.5 amps or less),

Using this method, and working out meter readings,

If something is using 350 watts then you electricity meter will be indicating that usage. Either the wheel will be turning ( old mechanical meter ) or the lamp will be pulsing ( modern electronic meter ).

 

[big-all]

its to do with inaccuracy
they are renowned for not being accurate you will always get a reading error so dont worry about it

 

[sandyman44]

its to do with inaccuracy
they are renowned for not being accurate you will always get a reading error so dont worry about it

so are these devices untrustworthy at the low end / too much error margin?
and thus need to do a meter reading maths method on the the low load point to get valid reading?

 

[JohnD]

its to do with inaccuracy

Yes, I use Owls, one of them connected to the PC, they are not accurate at low loads.

there is a tiny drain overnight from a couple of lamps, fridge freezers, TV on standby, PC asleep, clocks and timers. The Owls usually display 250-350W during the night, never less.

They are accurate enough for me to see if lights have been left on, and if you care, you can watch the reading go up and down with the thermostat if there's a heater running. At higher loads they are more accurate, you can see it go up by 3kW with a kettle or 2kW with a fan heater, almost exactly. It even detects the extra load from CH pump and fan when the boiler starts.

When I replaced the old fridges and freezer with modern ones, the drop in average daily usage was quite striking (but that was before I got the monitors).

 

[big-all]

as johnd says its low end where the problem is

 

[winston1]

For at start those things do not measure power consumption. They measure current. They take no account of voltage or power factor.

In my opinion they are not fit for purpose and trading standards should take them off the market.

 

[sandyman44]

thats all great. however still the same question remains - is there a reasonably priced clamp on meter that will give accurate readings at low (< 2 amp) current levels on household circuits?

 

[big-all]

not that i know off
you need a plug in monitor to get any sense off a use able comparison
https://en.wikipedia.org/wiki/Current_clamp

"direct currents, and very low AC currents (milliamperes) are more difficult to measure."

 

[stillp]

looked at the screwfix one, annoyingly min current 2amps

That's the maximum on the lower range. It will give a reading down to a few mA, but the accuracy is a percentage of 2A, so it won't be highly accurate. If you want high accuracy you need to look at £150+.

 

[sandyman44]

looked at the screwfix one, annoyingly min current 2amps

That's the maximum on the lower range. It will give a reading down to a few mA, but the accuracy is a percentage of 2A, so it won't be highly accurate. If you want high accuracy you need to look at £150+.

hmm ok thanks. for 20 quid I'll give it a shot then.
I guess the best tool for the job is the electricity meter itself. however mine is a type with a digit readout only so no indication of realtime, which I assume I would get from a smart meter... have asked my energy supplier when they plan to upgrade me to smart metering - answer "no short term plans only by 2020".

 

[EFLImpudence]

You probably don't want a smart meter.

Your meter does flash in relation to current usage.

is there a reasonably priced clamp on meter that will give accurate readings at low (< 2 amp) current levels on household circuits?

Probably not what you would call reasonably priced.
http://www.test-meter.co.uk/earth-leakage-clamp-meter/