Spike in power consumption when shutting off LCD TV

In addition to whole house monitoring, I have a CT on the (USA) branch circuit feeding my living room. I can reliably see a surge of an extra 500W for just over five minutes when I turn off my LCD TV (Sony XBR52HX909). I’m not familiar enough with electric theory to identify the cause (capacitors discharging once power is removed, perhaps). Any thoughts as to where that power is going?

This is not problematic, just surprising to see such a marked jump in power when shutting a device off. Education is greatly appreciated!

That does not make sense. How are you monitoring - real power or apparent? What does that circuit read when no load is connected?

How do you “turn off” your TV - do you mean standby mode or do you pull the plug? If standby, do you see the same when you pull the plug?

N.B. The TV normally consumes 184 W working and 0.12 W in standby. The possibility of capacitors discharging causing a 500 W load is something I can’t get my head around.

Hi, Robert. Thanks for trying to help out here!

Definitely doesn’t make sense to me! :laughing:

This is with the TV going to standby mode. I’ll test out a full plug pull as well (a bit awkward due to how my cables are run, but I’ll get it done). There’s not much else on this circuit besides a Roku media player and a couple of lights. This is monitored with a single CT connected to an emonTX with the OpenEnergyMonitor voltage reference (and power supply) on the same phase, making this…apparent power, if I have that right?

Here’s a sample plot from the feed:

voltage reference (and power supply) = the a.c. adapter? If yes, that’s real power. On batteries or a USB supply and no a.c. adapter gives apparent power.

That doesn’t mean much without telling me what happened when. According to the data that I found, the TV on its own should show 180 W when ‘on’, and I can’t see that there.

Yes, the AC adapter, so real power. Thanks for the correction! :bow:

The only event in the graph is putting the TV to standby at approximately 21:16. Two LED lights would have turned off at roughly the same time. It’s very odd.

I’ve done no calibration apart from ensuring the US values are selected in the various sketches. A similar CT on a different branch circuit works without any unexplained spikes and matches up closely with some KillAWatt readings I made a while back. The wiring in this older house is a bit odd in spots, but I thought I had tracked down all the circuits carefully (and there are no other significant home events at this time frame). Apart from doing a full time log of events and fully pulling the plug on the TV, is there anything else I could/should do to try to debug this?

Does the same thing happen every time you put it into standby?

Not really - the first step is to prove it’s the TV. The only thought I had is it’s (a) updating itself or (b) phoning home, and for something taking ~100 W (that’s why I queried the calibration - it’s supposedly more than that), I can’t see it pulling 400 W - 4 times - more to do some Internet stuff.

that odd- i would think you have a UPS on the circuit-- i have a similar issue but it no where near five minutes in length . when something on one circuit in my house powers off the resulting spike causes my instant hot heater to fire momentarily causing a much big momentary spike plus you hear the water heater kick on for a 1/2 second

As I wrote, David assumed it was the TV. Let us prove it first, and if it is not, he can start hunting for the real culprit. There is no point in acting on hunches, more than likely it has a logical explanation, so the best course is to follow logic to isolate the problem.

In your case, it sounds as if the instant water heater requires a filter to remove the interfering spike.
I fitted a high power TVS to a friend’s house after the spike from a neighbour’s machine blew up (separately) his TV, his Ethernet powerline extender and another neighbour’s central heating boiler; a device similar to this.

thanks robert i will give that a try-- the only reason i mention the UPS is because if his tv gives out a spike that triggers the USP to power condition its line (can be anywhere in the house) … that would create the issue he is having - first the UPS would trigger run off battery for a few moment . then after it resets the battery would begin to charge again to top itself up-- well just a thought

It could be central heating, or pretty much anything that has a control circuit (not just an on/off switch).
David’s got to find out how to trigger it on demand, then go round isolating things until it doesn’t happen. One thing I’m almost certain - it’s not going to be the TV. But funnier things than this have proved me wrong in the past, so I don’t rule anything out nor in until proven.

A quick update on this - I’ve been busy with other pressing projects, but I can reliably reproduce this recorded surge of high consumed power whenever I turn the turn off (move to standby) after the unit has been on for a time (1-2 hours). I’m going to test out yanking the power lead to the TV itself and see what effect that has, then report back.

you say you have a killawatt meter does it show the same 400w consumption right at the tv cord? curious it it 2 prong or 3 prong cord on the tv perhaps your outlet is wired wrong and when your tv shuts off there a trickle charge escaping – but 400w is very high for that something would usually burn out something especially for such a long duration … but good luck hope you find your source- as it does not seam normal-