Neff appliances discrepancy watts vs amps

[seanmcinnes]

We have Neff appliances and ran into an excessive energy bill recently. As such I started troubleshooting what might be the cause and by process of elimination and with the help of an energy device monitor it told me the built in microwave was using 50 to 60w even when not in use. A similar problem seemed to exist on the induction hob (using approximately 170w when not in use). Conversely the ovens and coffee machine are all fine and register 2 to 4w when idle. I called Neff and the engineer visited and used a plug in socket meter and demonstrated that the reading for him was only 2w - so in theory it was my meter that appeared to be the issue. So he left. I bought a similar meter (probably cheaper than his) but when I use it to check the readings I do get a much lower watt reading as he saw (1.4w on 242.4V), but what is odd is that the Amps readings is 0.271. If I multiple 242.2 x 0.271 I get 65watts? This correlates with the first energy meter, but why with the plug in meter would it display only 1.4w?

This still says these appliances are still consuming a lot more than they should? The manuals suggest they should only use 2w or so when idle.

I have not been able to reach the electrician who did the original install for comment but I expect he would confirm the amps readings and therefore that power is being consumed or does anyone have an opinion otherwise as to the discrepancy?

I should note that testing a 50w led floodlight confirms the 50 watts and 0.2 amps as expected on the plug in meter - so again it confuses me why the Neff appliances don't show up what you would expect.

Any constructive comments appreciated.

 

[bernardgreen]

Almost certainly the power factor of the device on Standby is poor, the current and voltage are not in phase with each other. This will confuse a basic Watt meter that does not have power factor correction and hence expects them to be in phase.

Quoting from FLUKE

Power factor is an expression of energy efficiency. It is usually expressed as a percentage—and the lower the percentage, the less efficient power usage is.

Power factor (PF) is the ratio of working power, measured in kilowatts (kW), to apparent power, measured in kilovolt amperes (kVA). Apparent power, also known as demand, is the measure of the amount of power used to run machinery and equipment during a certain period. It is found by multiplying (kVA = V x A). The result is expressed as kVA units.

 

[seanmcinnes]

Thanks for the reply. On that basis I am correct to assume there is some fault to these devices that requires attention, but any idea what proof I should take to Neff as their engineers are not knowledgeable enough in this area and their test equipment appears to be no better than my own. I shudder to think how many appliances are out there over the expected consumption. Would you expect all electricians to have equipment that would test and pick up this discrepancy and be able to report on it accurately so we can use that as evidence to take back to Neff or is there anything specific I should ask for?

 

[bernardgreen]

There is almost certainly no fault with the appliance. With a lot of modern appliances ( from TV to ovens ) the circuitry of the standby system does not have a good power factor. It would make the standby circuit more expensive if it was designed to have a "perfect" power factor

 

[seanmcinnes]

Thanks again. So assuming 'no fault' don't you consider this very misleading when they say it only uses 2w in standby but actually it is using 170w - that's a massive difference to the electricity bill!

 

[bernardgreen]

It is not using 170 Watts in standby, the meter is not giving an accurate reading because it is not correcting for the power factor of the standby circuit.

If it was using 170 Watt continuously then it would always feel warm to the touch.

 

[seanmcinnes]

My theory though is that if I run the hob circuit as the only live circuit overnight my meter on the wall will tell me I have used 1kw overnight. I am going to test this and will report back. Appreciate your input and appreciate what you are saying so will check what the results are in the morning.

 

[Harry Bloomfield]

Thanks again. So assuming 'no fault' don't you consider this very misleading when they say it only uses 2w in standby but actually it is using 170w - that's a massive difference to the electricity bill!

No, you are NOT paying for the 170w. If you were then the appliance would be quite hot where it was dissipating that 170w. It is just errors in your method of measurement.

If you still have doubts and your electricity meter is reasonably modern one, with a flashing red LED - turn everything off but your two appliances, then count the pulses over ten minutes. Multiply by six, then from that you can decide what you are being charged for the items on standby. One Kwh will either be 1000 pulses, or 800 pulses, from that you should be able to work out the actual wattage you are being charged for. It will say on the meter IMP 800 or 1000.