Hi All

 

I am using hisense fridge and want to add it on the battery backup. Can someone assist with the wattage it may take per hour and if I have to use one circuit breaker for fridge, what should be the minimum amp circuit breaker? Would something like 2amp or 3amp circuit breaker work?

 

 

A 3A circuit breaker will be fine for the fridge. However, if it is running on a domestic plug, you should consider a 16A circuit breaker.

Wattage is instantaneous power. The fridge switches on and off ever so often. My fridge uses 1kWh of energy per day on a rainy summer day.

2 minutes ago, Superfly said:

Thanx but I'm not convinced a Rated current of 1 amp?

My fridge draws 130W while running. So 1 A seems plausible. The only concern would be the startup current of the compressor.

1kw per hour on rainy days, that sounds too high unless I am missing something.

Can you please help me understand what do you mean by domestic plug? The fridge is in the granny flat. I see you mentioned 130W in the second message, I also had similar number in mind about 100w per hour.

No Superfly, I disagree.  If your fridge still uses a 7A lamp, well then you can flood light the whole of Soweto with it.  Then you need to get a real fridge.  LOL.  Modern fridges should and normally do use LEDs and a 1.5W LED is ample for a 300L fridge.

To answer the question, or at least a part of it:

It says the Rated current = 1.0A.   Power:  P = I * V    so it is 1.0A * 230V = 230 Watt.

Please note that these are always the worst case conditions.  In all likelyhood your fridge will run a fair number of percent below this rating.  HOWEVER, this excludes the start-up / inrush current which can be expected to be 10x running current.

The 230 W is consumption during compressor run time.  If you want the Watts per hour then I can't help you.  Simply because I don't know for how many minute in the hour your compressor will run.  That depends on the outside temperature, how well the fridge is isolated, how much you have placed into the fridge.  If your teenage son makes sure to close the door properly, and about 10 other factors.  Perhaps one could assume a 50% duty cycle?  So 30 minutes compressor runtime in the hour?  What do other guys think.  (I plan to soon find out, but I first need to get my Arduino datalogger running...)

I think the smallest general circuit breaker would be 5A.  Note that CB are specced for different curves.  I am no electrician and can't remember the domestic SA curve used.  I think it's curve C.  The curve rating has to do with a over current of x10 and x100 of nominal rated current before the thing trips.  Short inrush current will not trip it.  If the over current is maintained it will thermal trip.  Each CB has two trips, a thermal trip and a magnetic (max current) trip.  A 5A CB will be fine for your fridge, as long as it doesn't use the same 7A bulb as in Superfly's fridge.

4 minutes ago, Modina said:

No Superfly, I disagree.  If your fridge still uses a 7A lamp, well then you can flood light the whole of Soweto with it.  Then you need to get a real fridge.  LOL.  Modern fridges should and normally do use LEDs and a 1.5W LED is ample for a 300L fridge.

To answer the question, or at least a part of it:

It says the Rated current = 1.0A.   Power:  P = I * V    so it is 1.0A * 230V = 230 Watt.

Please note that these are always the worst case conditions.  In all likelyhood your fridge will run a fair number of percent below this rating.  HOWEVER, this excludes the start-up / inrush current which can be expected to be 10x running current.

The 230 W is consumption during compressor run time.  If you want the Watts per hour then I can't help you.  Simply because I don't know for how many minute in the hour your compressor will run.  That depends on the outside temperature, how well the fridge is isolated, how much you have placed into the fridge.  If your teenage son makes sure to close the door properly, and about 10 other factors.  Perhaps one could assume a 50% duty cycle?  So 30 minutes compressor runtime in the hour?  What do other guys think.  (I plan to soon find out, but I first need to get my Arduino datalogger running...)

I think the smallest general circuit breaker would be 5A.  Note that CB are specced for different curves.  I am no electrician and can't remember the domestic SA curve used.  I think it's curve C.  The curve rating has to do with a over current of x10 and x100 of nominal rated current before the thing trips.  Short inrush current will not trip it.  If the over current is maintained it will thermal trip.  Each CB has two trips, a thermal trip and a magnetic (max current) trip.  A 5A CB will be fine for your fridge, as long as it doesn't use the same 7A bulb as in Superfly's fridge.

Thank you. I will start with 5A. Does it mean that average wattage would be 5 * 230 = 1 150. Is it possible for the tenant to unplug the fridge and run microwave or heater etc if someone decides to misuse the facility during load shedding. To avoid the misuse, I was originally thinking of 3A circuit breaker. So if someone runs non fridge item, the breaker should trip. That's what I was trying to achieve.

Well then my Kill-a-Watt meter is busted. I am sure my double door fridge uses more power but I have no reason to doubt the 130W reading for the combo fridge.

I have reported on some of my recent findings regarding my newly purchased 157L Defy "solar hybrid" in another thread.  I can just recap here that the maximum power was measured with an effergy plug-in power meter and it reported a Max of 108W.  This is a special fridge that uses an inverter driven 3-phase compressor.  The inverter has not only soft start, but seems to also reduce the compressor speed at times.  It's maintenance current (compressor running at low power) is about 45W and at high power normally under 100W, occasionally peaking at 108W.

 

4 minutes ago, PB15 said:

Thank you. I will start with 5A. Does it mean that average wattage would be 5 * 230 = 1 150. Is it possible for the tenant to unplug the fridge and run microwave or heater etc if someone decides to misuse the facility during load shedding. To avoid the misuse, I was originally thinking of 3A circuit breaker. So if someone runs non fridge item, the breaker should trip. That's what I was trying to achieve.

Your calculation is right at a power factor of 1.

5A won't be enough for most heating appliances but it also depends on what system you have.

This OP fridge uses between 100 and 130W while running. 130W being less than a minute after starting and then drops to 100W. Expect the fridge to run about 14.5h out of each 24. This is not thinking but actually measured on an identical fridge. On days like the last 2 the use was a bit lower due to cooler weather. 

Picture shows the usage during December up to the 24th.

Edited February 17, 20233 yr by Scorp007

I would expect Circuit Breakers to have a bit too much of a spread to use them as a reliable abuse avoider.  But in case you do NOT want your tenant to use heating devices such as kettles and microwaves it can work.

Thank you all.

Cheap SA fridges are old school and super simple.  Good for our country.  As soon as you go for Bosch and Samsung the nightmares begin.  My Samsung double door is now off for the 4th day, waiting for yet again a defrost.  It has too much brains and now refuses to co-operate.  These fridges have defrost heaters.  Mine uses a 140W fridge defrost element, and I am not sure, but I think the freezer might have another heater as well.  I am foaming at the mouth, with having to deal with icing up every two weeks.  Some Samsung fridges have 240W heaters.  However the heater and compressor are not run in unison.  But the blik-brain does run the compressor longer and over-cools the fridge, before then going into a defrost cycle with heaters blazing.  I am convinced my fridge never turns on the heater, thus the investment into a current/power Arduino datalogger to find the truth.

Point is, you get a very wide spread of fridges. 

28 minutes ago, PB15 said:

Thank you. I will start with 5A. Does it mean that average wattage would be 5 * 230 = 1 150. Is it possible for the tenant to unplug the fridge and run microwave or heater etc if someone decides to misuse the facility during load shedding. To avoid the misuse, I was originally thinking of 3A circuit breaker. So if someone runs non fridge item, the breaker should trip. That's what I was trying to achieve

Rather use a dedicated socket with dedicated plugtop to avoid misuse of that curcuit CB are used to protect the wire not the appliance the compressor is protected by a Ptc overload. Example how to calculate approximate power consumption:

Refrigerator wattage = 130 Watts
Estimated usage = 8 hours per day (33% duty cycle)
Total energy = 130W x 8h = 1040Wh = 1.04kWh/day.

6 minutes ago, TaliaB said:

Rather use a dedicated socket with dedicated plugtop to avoid misuse of that curcuit CB are used to protect the wire not the appliance the compressor is protected by a Ptc overload. Example how to calculate approximate power consumption:

Refrigerator wattage = 130 Watts
Estimated usage = 8 hours per day (33% duty cycle)
Total energy = 130W x 8h = 1040Wh = 1.04kWh/day.

A duty cycle of 33% was good 15 years ago. Most cheaper fridges use smaller compressors to make them look good on paper with a low current draw but they might have a 60-75% duty cycle as can be seen in my actual power used pic posted earlier. 

Edited February 17, 20233 yr by Scorp007

The defrost element must also be considered in the calculation that could be activated a few times a day to clear the evaporator from frost that will add another 150w to the consumption

6 minutes ago, Scorp007 said:

A duty cycle of 33% was good 15 years ago. Most cheaper fridges use smaller compressors to make them look good on paper with a low current draw but they might have a 60-75% duty cycle as can be seen in my actual power used pic posted earlier. 

That is debatable all depends on ambient temp, how many times the door is opened, position of your fridge,door seals, how much food is inside your fridge, how dirty your condensor is. Compressors are designed for the size of the fridge/ freezer combo(litres) so 75% duty cycle is not due to derated compressors but rather to above mentioned conditions.

Yes, Samsung with LCD display.  Youtube is full of people complaining and they all have the same problem I have.  However there are many points of failure.  Heating element could be open circuit, mine is OK.  Then there is a thermal fuse, checked that, that's OK.  It could be a temperature sensor.  My frost temp sensor is working, but I know there is another sensor inside the cooling ducts and THAT sensor doesn't seem to want to change....  heating the panels with a hair dryer makes nothing to the measured resistance.  Not sure what to do about it.  And then you have a A4-sized controller PCB.  What a nightmare.  Obviously the relay or SCR or MOSFET that switches the heater could also be faulty.  My fridge must be about 10 years old.  You  are looking at 18K replacement cost.  So there is a strong urge to fix it.  Even if I do a McGyver on it.  (implement a small uP timer that ignores all sensors and manually switches the heater on every 12 hours).

Ha, Superfly.  Good luck with disassembly.  It would take a hundred years.  The control board must have about 50 wires.  A lot of logic will be used to drive the ice-maker and cold water pump/disperser.

In my younger years I tried to reverse engineer a IDS 1200 alarm panel based on a 8051.  the decompiler allocates random, meaningless labels...  anything is possible....  breaking one's finger in you-know-where too.  No, disassembly on such a complex board with many other main functions is not worth it.  There is a UK company that fixes fridges.  They have developed their own power logger to debug the fridge's behaviour.  These guys sell kits to take over the defrost cycle.  But I don't need kits.  First I need to try and fix it properly.  If unsuccessful I will give it the McGyver treatment.  One can buy simple programable timers and I need to see if they do the trick.  Or maybe buy such a timer and re-write the timing loops from scratch.  These sort of devices normally run on a little PIC.  It will still consume a few hours...

Why do you want to change original Samsung firmware?  Surely firmware that was working for many years should be good for a few more?    Yes, you can MASK a failing sensor in software and create some bypass.  But rather find the misbehaving sensor and replace it.

9 hours ago, TaliaB said:

That is debatable all depends on ambient temp, how many times the door is opened, position of your fridge,door seals, how much food is inside your fridge, how dirty your condensor is. Compressors are designed for the size of the fridge/ freezer combo(litres) so 75% duty cycle is not due to derated compressors but rather to above mentioned conditions.

New and old. My old Samsung with all the bad conditions o ly run 50% of the time with 8 min cycles between on and off. 

Yes opening does play a part and one can actually see it on my daily graph. When we at home the power used is lower. Then my 60% time in my graph is for a 2 year old Hisense. 

I would say the largest variance will be due to make. Defy for instance use the same model of compressors than Hisense but they do have thicker insulation and that is key. Modern fridges do not have a very good insulation unless you go to the more expensive ranges. 

They are miles apart between the economy range and A+ or A++. 

Having young children that are always looking at something to eat or drink you will find the fridge could perhaps use 50% more power due to opening on a regular basis. 

What we try to do is put things in a box as all systems and equipment perform the same. The same with how much power can a 5kw system save/produce. Countless variables so no size fits all. 

Edited February 18, 20233 yr by Scorp007

Modern appliances are remarkably more efficient than those of 10, 20 years ago. 

I have 2 fridge/freezer combos and an upright deep freeze. There are backed up, and since they are pretty much all that runs at night, I can monitor the steady load. This seldom gets above 300W. Obviously they don't all run at the same time, but still, the load is not great and so I think the 1A draw is plausible. For steady running. The momentary load on startup of the compressor will be higher.

I've seen lots of chat about Samsung fridges recently. We had a 2nd hand example with LCD display and upright freezer section. I didn't like that. It worked and kept stuff properly cold, but it drew a lot of current. Especially once it had been to the repaid shop. It seemed to run all the time, and eventually I put it on a timer so that it ran for an hour, was disconnected for an hour. Which helped but is unsatisfactory really.

I think a lot of appliances have proprietary, closed parts that are difficult to work on and expensive to replace, so repairers just bypass them and in doing so bypass some of the circuitry that gives a better owner experience.

We have two much newer Samsungs (one bought last year) and they do very well for us. The older of the two is at least seven years old now and has never given us a day's trouble. (And now I've posted that I wait for it to pack in, be taken away, and come back with all the clever gubbins bypassed).