Refrigerator real consumption versus energy guide estimate

[dmholmes]

Nice work. What do you guys think of overriding the thermostat/compressor powering off and on?

I've seen in gas generator forums it is common to suggest running the fridge for an hour and then not run it for 4 hours.

For a battery/inverter I've also seen suggestions to use a programmable outlet timer to set the fridge to run for only 15 minutes out of the hour. Does this actually save you power and keep the food safe, or does it simply make the fridge work harder when it is on?

 

[Mcgivor]

Remember it is only your nighttime usage that you need to factor into your battery consumption, assuming a decent size array. And nighttime is the lowest consumption part of the day as it is cooler and you don't open it when sleeping.

True, the night time consumption was actually less than the inverters standby consumption , search mode wouldn't be woken up so I overcame that problem by using a second more efficient idle inverter, programed to switch over by the main inverter's invert block feature and an auto transfer switch.

 

[Short_Shot]

I'd have to see what the internal temp does vs power consumption.

I'd be willing to bet the savings are negligible.

 

[John Frum]

Nice work. What do you guys think of overriding the thermostat/compressor powering off and on?

I've seen in gas generator forums it is common to suggest running the fridge for an hour and then not run it for 4 hours.

For a battery/inverter I've also seen suggestions to use a programmable outlet timer to set the fridge to run for only 15 minutes out of the hour. Does this actually save you power and keep the food safe, or does it simply make the fridge work harder when it is on?

One thing the outlet timer does is make your loads predictable.
You can prevent the fridge compressor from causing an overload while you use the kettle for example.

 

[Hedges]

For a battery/inverter I've also seen suggestions to use a programmable outlet timer to set the fridge to run for only 15 minutes out of the hour. Does this actually save you power and keep the food safe, or does it simply make the fridge work harder when it is on?

Fridge works longer. There is some difference in power consumption and AC current draw power factor depending on delta-temperature.
I'm pretty sure it won't save much if any on kWh consumed by fridge.
Results could differ for an inverter fridge that has variable power consumption. Question would be at what power level it is most efficient (BTU transferred vs. watt-hours consumed.)

Whether food stays safe depends on how warm it gets in 45 minutes.
The goal would be to save on inverter or generator no-load consumption.

 

[Hedges]

One thing the outlet timer does is make your loads predictable.
You can prevent the fridge compressor from causing an overload while you use the kettle for example.

A power strip with priority switch controlled by current sensor would be convenient for van life or other underpowered inverter (and generator) situations. Could be implemented as a current transformer and amplifier driving a relay.

A spring-wound timer with SPDT switch could turn on your kitchen gadgets for a limited time, then return power to loads like refrigerator and A/C.

This one says SPDT and 2500W (another said 20A but only 875W).
"SPDT" only mentioned in title, not listed under specs. But picture of bottom describes as has diagram, so should be good.
This one goes to 12 hours, which could mean you thaw your frozen foods by mistake. Or, you avoid battery drain at night, return to operation in morning.

TORK 125-277-Volt 12-Hour SPDT Indoor Spring Wound Mechanical Twist Timer, Ivory A512H - The Home Depot

A series spring wound auto off in-wall time switch. Application includes whole house fans, indoor/outdoor lighting, bathroom fans and lights, self-storage. Features variable timing: twist knob for time

www.homedepot.com

 

[Mcgivor]

Nice work. What do you guys think of overriding the thermostat/compressor powering off and on?

I've seen in gas generator forums it is common to suggest running the fridge for an hour and then not run it for 4 hours.

For a battery/inverter I've also seen suggestions to use a programmable outlet timer to set the fridge to run for only 15 minutes out of the hour. Does this actually save you power and keep the food safe, or does it simply make the fridge work harder when it is on?

A timer on a refrigerator is a bad idea for 3 reasons, it can increase the internal temperature thus encouraging bacterial growth, it can prompt additional unneeded defrost cycles, interrupting a cycle will prompt a delay in restart of the compressor until the pressure drops, which could result in short interrupted cycles.

 

[boondox]

True, the night time consumption was actually less than the inverters standby consumption , search mode wouldn't be woken up so I overcame that problem by using a second more efficient idle inverter, programed to switch over by the main inverter's invert block feature and an auto transfer switch.

What is the standby consumption of your inverter? I think my Magnum is about 25 watts. Not very much in the grand scheme of things. I can't use search mode as my power draw is always well above the minimum. I don't think you should have the fridge on a timer, food safety and interrupted cycles and all. Just size the system to be able to handle it. IIRC, you got about 33kWh in a month? Let's say half of that was a night, although it is actually less. So 16.5kWh/30 nights = 550wH a night. In reality less. Just size the system to work with that and be done with it.

When I was first off grid I tried several schemes to bring down fridge and freezer consumption. At one point even had a system that would lower the set temperature of my chest freezer as soon as the battery went to float. So during the day it would pump the freezer way down and then as soon as I was out of float set it back to its normal temperature. A whole lot of extra dog, more possible things to go wrong, more run time on the compressor, since one gets into diminishing returns as you lower the temperature. And I could never come up with numbers that proved it saved any considerable amount of energy. The juice just wasn't worth the squeeze. So I tore out the custom thermostat that I built, re-connected the stock thermo and have been happy ever since. Just a year or so ago I gutted the custom thermo for parts. I did have fun building it and programming it but that is all I really got out of it.

 

[JimmyL]

We have a Panasonic inverter fridge. It uses around 1.2kwh/day but really struggles in the summer to keep the fridge cool and the temp inside varies a lot. We noticed milk and dairy not lasting on the usual midpoint setting. I measured the temp in a few locations and some spots were 8 degrees c, so had to turn it right down. I will stick to an standard fridge next time.

 

[Mcgivor]

We have a Panasonic inverter fridge. It uses around 1.2kwh/day but really struggles in the summer to keep the fridge cool and the temp inside varies a lot. We noticed milk and dairy not lasting on the usual midpoint setting. I measured the temp in a few locations and some spots were 8 degrees c, so had to turn it right down. I will stick to an standard fridge next time.

Can't say I've experienced the inability to maintain temperature even in 40°C ambient, it is important to have sufficient clearance on both sides and above, this would apply to non inverter types as well if they use the outer skin as a means of heat transfer, mine is in open air with a minimum of 1 meter on both sides and ceiling.

 

[JimmyL]

Ours is in a typical double fridge sized spot in the kitchen but definitely not heaps of room as preferred. In summer our house is 29 degrees inside and the fridge runs flat out most of the time to keep up. Can be rather noisy too. I can't remember the model number but i checked a product review page and others had the same issue. The wide ranging internal temp is the biggest concern and you wouldn't know without measuring.

 

[Mcgivor]

What requirement dose it use, perhaps that may have something to do with it, mine uses R600A, I have measured the temperature to ensure its set correctly at 4°C, just over might point on the adjustment slider.

 

[JimmyL]

I think mine has the same refrigerant.

 

[JimmyL]

What requirement dose it use, perhaps that may have something to do with it, mine uses R600A, I have measured the temperature to ensure its set correctly at 4°C, just over might point on the adjustment slider.

Model is

Panasonic NR-BY552XSAU​

 

[Mcgivor]

Looks to be the model up in size bur otherwise identical to the one I have, I'll have to recheck the temperature to make sure, only use powered milk so no early warning system.

 

[JimmyL]

Ours has 9 temp setting for the fridge and i originally set it 1/2 way but ended up using 7-8. Another thing is no matter what i do at that 7-9 the meat section is just below zero and freezes meat after a day or 2. Great place to store beer though.

 

[Mcgivor]

At least it's able to perform the most important task, keeping the beer cold!

 

[Hedges]

Bottom freezer.
Is there an air path between fridge and freezer?
See if you can set up a fan (or switch on the built-in one) to draw cold from freezer compartment into fridge.

Frozen food turns soft at some temperature.
Ice melts at 32F, too high to keep food frozen.
Brine can be made of a concentration which will melt at some temperature cold enough to keep food frozen.

Your fridge gets too warm. Use a thermocouple or something to measure temperature of freezer over time. Settings may help.
Any chance you have a problem with dust on radiator coils, or icing up of the cooling coils?

Top and side freezers work by turning on compressor whenever fridge gets too arm, but compressor cools freezer. Air spills between the two. Not sure for bottom freezer.

Bottom Mount Refrigerator: NR-BY552XSAU | Panasonic Australia

This award-winning bottom mount refrigerator features a vegie crisper with nutrient boosting technology and ECONAVI sensors to reduce wasted energy.

www.panasonic.com

 

[wattmatters]

I tested our main fridge some months back and it was averaging 1.46kWh/day (~534kWh/year). During a duty cycle it would draw at ~110-120W, on idle 2.3W and with door open 5.7W due to the light opening.

~500l Fisher & Paykel with bottom drawer freezer. Nearest models I can find with stated energy ratings are between 412 and 467kWh/year. We are mild to hot climate. Our owners manual will be filed somewhere but not going to dig it out.

Choice of fridge type can help if energy consumption and power draw are constrained. e.g. Having the freezer on top uses a bit less energy than with freezer on bottom. Inverter models also have low power draw on start up and are pretty efficient. Good door seals matter.

Lowest energy consumption freezers are chest freezers as opening the lid door doesn't lead to all that much heat transfer into the compartment. Less convenient but energy savings are there.

 

[JimmyL]

In case anyone is interested our inverter panasonic draws about 60w when under a high load and does taper down to 30-40w and will also cut out when everything is stable. At 60w the maximum it can draw for 24hr is still only 1.44kwh

Also the freezer is always very cold so no issues there. There is also a slide in fridge compartment that can adjust how you want to split thr flow between fridge and freezer. We always have it at max fridge. The vegetable section is also great and find fresh produce lasts a long time.

We are just about to move 2,000km south, so it will be interesting to see how the consumption changes and a cooler climate. In saying that the house temp might not be too much cooler as the heater will be on!