Mains energy monitor - power fluctuating

Black_Knight

I just got an efergy elite energy monitor for the house, and attached the CT clamp to the mains live at the meter box.

I've been keeping an eye on it over the evening and noticed the power jumping from ~320W to 1kW and back again over the space of about 30 seconds. It's been doing this for about the last 30 minutes I've been throwing an eye on it. I've other power sensors on specific plugs around the house, and right now the draws I know of are the washing machine (it's finished heating) taking ~90-170W, TV @80W, office taking ~120W, but nothing that can explain the ~600W fluctuations I see.

Any thoughts?

brightspark

water pump?

Black_Knight

brightspark wrote: »

water pump?

Nope. Mains fed, boiler would be the only thing pushing water around and that was off at the time, unless of course water pump extends to the washing machine.

brightspark

Black_Knight wrote: »

Nope. Mains fed, boiler would be the only thing pushing water around and that was off at the time, unless of course water pump extends to the washing machine.

The washing machine would be starting and stopping the drum motor often at various stages of the wash cycle?

Black_Knight

brightspark wrote: »

The washing machine would be starting and stopping the drum motor often at various stages of the wash cycle?

This is up and down every 10 seconds, though the washing machine is finished now and the monitor is pretty steady at 280W. Odd, because I've a plug energy monitor on the washing machine and that says it never went above 170W after the water heating cycle. Unless that plug averages it out a bit more than the mains monitor I have does

alan4cult

Immersion thermostat clicking on and off? Seems a little too frequent and regular though.

Black_Knight

alan4cult wrote: »

Immersion thermostat clicking on and off? Seems a little too frequent and regular though.

No immersion.

Seems to sync up with the washing machine being on, but the size of the fluctuations don't really add up.

brightspark

Black_Knight wrote: »

No immersion.

Seems to sync up with the washing machine being on, but the size of the fluctuations don't really add up.

Way too big for an immersion anyway (2.5-3kw)

I have limited experience watching washing machines, but I have observed some of them turn in one direction for a few revolutions, stop, then turn in the opposite direction.

The 600-700w would be around the typical wattage of the drum motor.

John.G

I have one of those cheap (but quite accurate) plug in monitors that displays volts, amps, watts and power factor,
plugged the w/machine into it and while the motor is running it consumes ~ 120 watts BUT the amps are 2.7 with a PF of 0.2 so the apparent power is 230*2.7, 621 watts, real power, 230*2.7*0.2, 124 watts. Your clamp meter is possibly measuring the apparent power as probably can't measure the PF??.

Black_Knight

John.G wrote: »

I have one of those cheap (but quite accurate) plug in monitors that displays volts, amps, watts and power factor,
plugged the w/machine into it and while the motor is running it consumes ~ 120 watts BUT the amps are 2.7 with a PF of 0.2 so the apparent power is 230*2.7, 621 watts, real power, 230*2.7*0.2, 124 watts. Your clamp meter is possibly measuring the apparent power as probably can't measure the PF??.

Interesting. Never knew about power factor.

The mains power monitor I have does mention compensating for power factor:

The Efergy true Power Meter monitor shows you the real time usage in Watts and the cost per hour (or kWh if preferred), based on true power consumption. It follows the utility voltage and measures phase angle to compensate for power factor.

Though their site is a bit vague, and that might be a different version than I have. Very hard to tell, lots about their site and device fall short

NeuralNetwork

If the washing machine is still on the wash cycle, it may be bringing the heater in and out to maintain the wash temperature. They usually keep the wash temp steady for the wash part of the cycle. That heater could be about 1 to 2kW

Modern machines only contain a relatively small amount of water so the element will definitely cycle on and off as the sensor detects a need to warm the water and it’ll go off again quit quickly if you’re just running a 40° wash.

So you might see short busts of heating.

The other thing might be a big motor load of the machine does the odd rapid semi-spin tumbling sequence. A lot of them do bursts of high speed tumbling, enough to stick the clothes to the walls of the drum during the wash cycle to force water though them. That’s likely to draw a substantially higher load than just tumbling.

Black_Knight

NeuralNetwork wrote: »

If the washing machine is still on the wash cycle, it may be bringing the heater in and out to maintain the wash temperature. They usually keep the wash temp steady for the wash part of the cycle. That heater could be about 1 to 2kW

Modern machines only contain a relatively small amount of water so the element will definitely cycle on and off as the sensor detects a need to warm the water and it’ll go off again quit quickly if you’re just running a 40° wash.

So you might see short busts of heating.

The other thing might be a big motor load of the machine does the odd rapid semi-spin tumbling sequence. A lot of them do bursts of high speed tumbling, enough to stick the clothes to the walls of the drum during the wash cycle to force water though them. That’s likely to draw a substantially higher load than just tumbling.

All perhaps true, but odd that the power monitor plug I have doesn't show this, but the CT clamp at the mains supply does.