Watts and Amps is my maths wrong?

[ericmark]

I was taught Watts = Volts x Amps x Power factor correction.

So a 32 litre freezer has the volts 220 - 240 and watts 50 and amps 0.45 so that would mean with my maths PF = 0.505 which seems rather low. Used 220 volt as with 240 even worse.

Actually measured volts 241 watts 28 amps 0.15 and PF 0.83 does not quite line up but some where near.

Do manufactures really expect such a poor power factor or is my maths out?

 

[Chris61]

There's nothing wrong with your maths and the mfr doesn't expect that power factor either.

Measuring the power consumption of refrigerators isn't easy. You are supposed to measure the maximum value of current averaged over any five minute period in an hour - a right pain. In reality you just look for the maximum value when the appliance has stabilised.

The power rating is not supposed on there (unless it's the rating of any defrosting heaters), only the current rating.

I suggest the stated ratings are very approximate and not accurately related. The standard only stipulates that current measured during the ratings test should not be more that 20% greater that the rating marked on the appliance. It is common on fridges and freezers for the current rating to be much greater than the actual current consumed...

 

[ericmark]

Thank you I did note with my larger units there were two very different current consumptions clearly one is heaters the other is the motor but with cheaper units the maximum current is with motor start so unless I happen to see the reading when heater cuts in then impossible to monitor heater power with a standard energy meter.

With the better quality freezer and fridge/freezer using inverter control for the motor the maximum is heater size so you can easy see heater wattage. Also the motor run power varies much more than with non inverter control I would guess due to which solenoids are open be it cooling fridge or freezer or both.

Until inverter control I never saw a temperature display built in and although we had high med low settings we did not have the option to set temperature of fridge and freezer independently.

Also with inverter control PF either 1 or 0.99 never any worse. The inverter does not control the temperature like in commercial freezers it is just a soft start for the motor.

The problem I have encountered seems to be due to a faulty thermostat and the energy meter identified a problem in that it was running 24/7. Recorded time x Run Watts = watt hours used where it should have been less than watt hours used if the motor had turned off.

The next problem was how to measure temperature I tried every shop I could think of to buy a thermometer to measure -18°C Maplin showed them on web site but local shops had no stock. In the end I used salt. I knew freezing point of brine is -18°C so I made up a saturated sample of salt and water and placed it in the freezer and it froze solid and when removed took a few minutes to melt so I was 99% sure it was thermostat fault.

So now just a wait for new parts to arrive. Plus doing the same exercise on all other fridge/freezers in the family but I think with a fridge/freezer we would have had frozen stuff in the fridge it was being a freezer only which was the problem.

Did not note any freezer burn, but did find ready meals cooked as per instructions were cold in the middle. But since in the main stand alone freezer was a back-up on top of the fridge/freezer with food being moved from top freezer to bottom freezer before use which allowed time for temperature to rise to -18°C before use.

Still can't believe no local shops sell thermometers which go below -10°C tried the digital thermometer it showed LLL which it seems is what they show when too cold to work.

 

[JohnW2]

The next problem was how to measure temperature I tried every shop I could think of to buy a thermometer to measure -18°C

IME, fridge/freezer thermometers are available 'everywhere' Did you try Tesco ( click here - albeit that is for Tesco Direct - they may well be available in-store )?

Kind Regards, John

 

[Spark123]

I was taught Watts = Volts x Amps x Power factor correction.

Less the correction, Watts = V x A x PF

 

[ericmark]

I did the lot Asda, and Tesco were first. Did the local shopping mall every shop which sold pots and pans was tried plus pound world. Then Wrexham expected to buy in Maplin but not expected in until after Christmas. Even tried the manager of local Aldi but he says built into the telemetry so they can call him out in middle of night so could not lend me one.

Minus 10C not a problem minus 18 just no where even though every cooking establishment must have them.

Anyway once my Andoer 200-240V Digital Temperature Controller Thermocouple -40 °C to 120 °C with Sensor arrives I should be able to use that to check the temperature. Then after I can use it to keep my beer at 18 - 20 degrees which is more important.

I did not order a box I though could get one of them local. That's another thing which is proving harder than expected. A box is easy one at reasonable price with requires a key or tool to get into is something else.

This are of course the items which would have in the past so easily fallen into my lunch box!

 

[JohnW2]

I did the lot Asda, and Tesco were first. Did the local shopping mall every shop which sold pots and pans was tried plus pound world. Minus 10C not a problem minus 18 just no where even though every cooking establishment must have them.

Homebase do one (which has a fancy name, hence ~£11) which goes down to -35°C: (click here)
B&Q do one (for £3) which goes down to -20°C (click here)
eBay has hundreds, such as this one (£1.99) which goes down to -40°C: (click here)

Kind Regards, John