Help explaining power usage spikes

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Help explaining power usage spikes

Postby Thimsneb » Tue Dec 12, 2017 6:12 pm

Hi all,

Not sure if i've posted in the correct forum. I've recently had solar installed (6kw system, no battery storage) and am fascinated by the data produced each day from the system. I.e. energy produced, consumed, imported and exported. Although i have read these figures can sometimes be inaccurate.

Every morning at around 1:15-1:30 there is a spike in energy consumed, somewhere between 0.4 to 0.7 KWH. This occurs roughly every 3 to 4 hours over the span of the day.

We have a fridge/freezer in the kitchen and an upright freezer in the laundry. I'm guessing it's one of those 2 kicking in. I'm thinking perhaps the compressor in the freezer is cycling on for an unusually long period, perhaps a fault. The door is sealing correctly, there aren't any leaks, condensation or ice build up.

Anyway, my question is. Could this be something else consuming so much energy consistently across the day? Or if it is the freezer, are those consumption levels normal? If anyone can shed any light on the matter, it would be greatly appreciated.
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Re: Help explaining power usage spikes

Postby Gordon-Loomberah » Wed Dec 13, 2017 6:54 am

Hi Ben(?) welcome to the Energy Matters Forums :)

Can you post a graph to show how large the power increases are every 3 or 4 hours?

6 or 8 X say 0.5kWh is a very large amount for a fridge to use. Without knowing what other loads you are running, it is impossible to say what it might be, but a graph would be very useful.
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Re: Help explaining power usage spikes

Postby Thimsneb » Wed Dec 13, 2017 5:07 pm

Hi Gordon,

Thanks very much. I've posted an image of the graph, sorry but 100kb limits the quality of the image. This is the most typical and consistent instance i could find. Sometimes the spikes are 5 or 6 hours apart. I'll have a scout around and see if i can work out any other appliance possibly causing this spike. Hot water heater perhaps, although it's a heat pump and shouldn't be heating during the day anyway.
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Re: Help explaining power usage spikes

Postby Gordon-Loomberah » Wed Dec 13, 2017 5:29 pm

If your night time cost of electricity for the heat pump is more than your FiT, then you are better off only running it in the middle of the day. You could turn it (or any other suspect appliances, one at a time) off during the day to see if the peaks disappear.

For images with a limited number of colours, use GIF format for your images. 256 colours is more than enough, JPEG's 16.7million colours makes for unnecessarily large files, not to mention often blurry if too much compression is used.
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Re: Help explaining power usage spikes

Postby Thimsneb » Wed Dec 13, 2017 6:01 pm

I'm going to start turning individual appliances off day by day to try and narrow down the culprit, great advice thanks.

I've read about diverters which send your PV power directly to your hot water heater during the day, however I don't believe they work with heat pumps. Something to do with the currents or pulses being exchanged between the diverter and the hot water unit.

Is there an alternative way of having my hot water only heat during the day?
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Re: Help explaining power usage spikes

Postby Gordon-Loomberah » Wed Dec 13, 2017 6:40 pm

Diverters are generally only useful for resistive loads, such as water heaters with elements, similar to stove elements. Having the compressor in a heat pump turning on and off too frequently would likely burn the motor out pretty quickly.

Heat pumps can be run on a suitably rated time switch.
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Re: Help explaining power usage spikes

Postby Thimsneb » Wed Dec 13, 2017 6:48 pm

Correct me if i'm wrong, but there is no way of remotely controlling a time switch. So if it's an overcast day and my solar isn't producing, but my heat pump is running, i'll be paying through the nose?
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Re: Help explaining power usage spikes

Postby Gordon-Loomberah » Wed Dec 13, 2017 8:29 pm

If the heat pump has a 10amp plug on a cord, yes you can easily control it via a phone app, but it's rather more difficult if it is hard wired, as I'm not sure if there are any suitable remote control switches available. There may well be, but I don't know of them.
I use WEMO devices to turn on pumps and battery chargers, they are set up as timers, but can also be controlled remotely, wherever I have a phone signal or wifi access.
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Re: Help explaining power usage spikes

Postby Thimsneb » Wed Dec 13, 2017 8:35 pm

Good point, i hadn't thought about those Smart Plugs as an option. Do they make a weather proof switch for outdoors? Is that what you use for your pumps?
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Re: Help explaining power usage spikes

Postby Gordon-Loomberah » Wed Dec 13, 2017 9:02 pm

I just have the regular WEMO indoor switches controlling, one is on a cord under a plastic box in a greenhouse, until I figure out a better solution, the other is in a waterproof Aluminium box outside, both on aquaponics systems.
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