Freezer to Fridge Conversion: Good performance or shitty Freezer Selection

[Paul_B]

Hello,

I am new to the forum. I have deep respect for the generous folks I see posting their experience and assistance. Thank you.

We live on the grid, in a rural area just west of Algonquin Park, in Ontario, Canada. For a long time, I have been keen to reduce our dependency on grid power. This includes our energy usage for refrigeration. Medium term plans are to add PV and batteries to safeguard DC freezers and fridges.

I’d like to share some energy usage numbers for chest fridges / freezers. In the past, I experimented with the “home-brew” external thermostat conversion approach on several freezer units; Over time, I purchased several Sundanzer units. I have collected Kill-a-Watt usage figures each month over the past 4 to 6 years for these units.

RF_DCRF is in the kitchen where ambient temps stay between 16 deg to 24. Other units were/are in an attached garage (modestly insulated, but no direct heating). Summer inside ambient temps can reach 25 deg. Celcius. Winter inside ambient temps get down to -1 on very cold days (-30). Obviously, ambient temp plays a major role in energy consumption of a fridge or freezer.

F_CF	Amana/Maytag	AC Chest Freezer	14.8 cu ft
F_DCF	Sundanzer DCF 390	DC Chest Freezer - 12VDC power supply	14.7 cu ft
F_SCF	Danby Compact	AC Chest Freezer	3.6 cu ft for fallback use
R_SCF (converted)	Danby Compact	AC Chest Freezer	3.6 cu ft for fallback use
R_UF (converted)	Large upright	AC Upright Fridge	Approx. 18Cu ft No longer used - RIP
R_DCR	Sundanzer DCR 225	DC Chest Fridge AC power option, DC compressor	7.9 cu ft
RF_DCRF	Sundanzer DCRF 450	DC Upright Fridge/Freezer - 12VDC power supply	15 cu ft

Takeaways / Comments

- The usage figures for the DC units include power supply consumption (approx 6W), so those WHr/Day values are conservative.

- “Personality” of DC appliances is different than AC. AC freezers can cool quickly. DC freezers cool a bit slower, compressor runs longer each day, but lower overall power consumption.

- Chest Fridges have no drains, or defrosters. Condensation needs to be mopped up regularly.

- With a chest fridge, stackable baskets are very useful. With no shelves for horizontal access, you use the refrigerated space differently than an upright unit. It’s do-able, not always convenient.

- Thicker Insulation on Sundanzer units than brand-name AC units; I suspect a unique blend of insulating foam.

- Usage figures in marketing material can look great, but probably don’t reflect opening/closing multiple time in a day during normal use. YMMV – mine certainly does.



Best regards,

Paul

 

[No Idea]

Hello,

I am new to the forum. I have deep respect for the generous folks I see posting their experience and assistance. Thank you.

We live on the grid, in a rural area just west of Algonquin Park, in Ontario, Canada. For a long time, I have been keen to reduce our dependency on grid power. This includes our energy usage for refrigeration. Medium term plans are to add PV and batteries to safeguard DC freezers and fridges.

I’d like to share some energy usage numbers for chest fridges / freezers. In the past, I experimented with the “home-brew” external thermostat conversion approach on several freezer units; Over time, I purchased several Sundanzer units. I have collected Kill-a-Watt usage figures each month over the past 4 to 6 years for these units.

RF_DCRF is in the kitchen where ambient temps stay between 16 deg to 24. Other units were/are in an attached garage (modestly insulated, but no direct heating). Summer inside ambient temps can reach 25 deg. Celcius. Winter inside ambient temps get down to -1 on very cold days (-30). Obviously, ambient temp plays a major role in energy consumption of a fridge or freezer.

F_CF	Amana/Maytag	AC Chest Freezer	14.8 cu ft
F_DCF	Sundanzer DCF 390	DC Chest Freezer - 12VDC power supply	14.7 cu ft
F_SCF	Danby Compact	AC Chest Freezer	3.6 cu ft for fallback use
R_SCF (converted)	Danby Compact	AC Chest Freezer	3.6 cu ft for fallback use
R_UF (converted)	Large upright	AC Upright Fridge	Approx. 18Cu ft No longer used - RIP
R_DCR	Sundanzer DCR 225	DC Chest Fridge AC power option, DC compressor	7.9 cu ft
RF_DCRF	Sundanzer DCRF 450	DC Upright Fridge/Freezer - 12VDC power supply	15 cu ft

Takeaways / Comments

- The usage figures for the DC units include power supply consumption (approx 6W), so those WHr/Day values are conservative.

- “Personality” of DC appliances is different than AC. AC freezers can cool quickly. DC freezers cool a bit slower, compressor runs longer each day, but lower overall power consumption.

- Chest Fridges have no drains, or defrosters. Condensation needs to be mopped up regularly.

- With a chest fridge, stackable baskets are very useful. With no shelves for horizontal access, you use the refrigerated space differently than an upright unit. It’s do-able, not always convenient.

- Thicker Insulation on Sundanzer units than brand-name AC units; I suspect a unique blend of insulating foam.

- Usage figures in marketing material can look great, but probably don’t reflect opening/closing multiple time in a day during normal use. YMMV – mine certainly does.

View attachment 103746

Best regards,

Paul

F_CF and F_DCF chest freezer comparison helps me. I see how all AC vs DC diverge more as ambient temps increase favouring DC so I can see in my case with a freezer indoors in a long term power failure in Thailand (so mid 30degC ambient due to no aircon) the DC would truly stand out in terms of efficiency. Good info.

I have been in two minds on keeping my AC chest freezer with UPS or going DC. I like having redundant power sources so mains AC with DC backup made me stick with AC freezer. Having DC only and potentially shutting down to troubleshoot issues from time to time made me shy away from it but I can see this efficiency difference might justify DC primary source and an AC to DC converter for backup.

Certainly got me thinking again...

 

[Paul_B]

There are many excellent comments provided about efficiency of AC chest freezers vs. DC, aspects to consider about the power these units draw, and how to get the best from them.

I agree with @Xhumeka, to get the numbers quoted for the Samsung vertical fridge/freezer, someone might have tested it in an igloo, with the doors kept tightly closed.


For a comparison, I suggest a quick look at peak values for usage curves in the chart I posted earlier:

F_DCF	14.7 cu ft	12VDC	July	830 wHr/day
F_CF	14.8 cu ft	AC	July	1,210 wHr/day
F_SCF	3.6 cu ft	AC	July	1,350 wHr/day

These units were next to each other in the same location. Treat readings as representative only, based on my situation (models, climate / ambients). Values for each unit were taken at roughly the same time in any month, but not the same days, then averaged together over 4 to 6 years.

F_SCF is ugly inefficient on a usage / cu ft basis. It is compact, apartment size. I suspect mfr decided to cut some corners re: insulation thickness, compressor efficiency, lid sealing. It consumes more power than an AC chest freezer with 4x the capacity.

DC is more efficient than AC freezer for equivalent size.
- lid seal on that freezer is much better (closing it creates suction if I try to open lid again quickly)
- insulation thickness (wall/lid width) is 25-30% more.
- mfr’s insulation foam uses special sauce (NASA research?)

 

[MattiFin]

I agree with @Xhumeka, to get the numbers quoted for the Samsung vertical fridge/freezer, someone might have tested it in an igloo, with the doors kept tightly closed.

Mentioned Samsung is about same level as others with A grade in new european energy scale.
IIRC standard test is performed at close to 30 Cel /85F and the actual measurement results what I have seen in various magazines or consumer test reports have been mostly in line with the results, typically showing even lower than rated consumption when ambient temperature has been closer to 25cel.

 

[Hedges]

Does the defrost timer require power to advance?

That aside, it seems pretty easy to put a user-controlled relay in there somewhere.

Older refrigerators simply use a compressor time mechanical timer powered by the thermostat. When it reaches one revolution it switches from compressor to heating element. The element thermostat turns off when it is up to temperature and when the timer times out it goes back to compressor run. Find that little timer motor and break the connection. Or the heater connection, timer will continue to run and fridge won't work in that time period. Use a relay to close only in daylight hours with a nearly full battery charge.

If the old motor-driven timer cycles once per 24 hours, could adjust to desired time. My upright fridge-freezer has a plastic button on control panel over screwdriver slot. Freezer it is underneath in rear. Hook up an indicator light to observe when it cycles (in case it changes due to power outage.)

I'm digging into mine again today. I previously replaced defrost thermostat (interrupts power to heater above a certain temperature), but still not defrosting. Must be an intermittent connection I didn't track down last time.

What I have done is convert side-by-side to all freezer.

Converting a refrigerator/freezer to freezer only

My upright Frigidaire deep-freeze wasn't freezing anything more concentrated than ice cubes any more. Things were mushy and spoiling. Maybe it just needs a refrigerant recharge; I'll look into that later. Went to the store and found they all have 60 or 90 day delivery. Only come out of China...

diysolarforum.com

 

[Checkthisout]

Does saving .3kwh per day really matter?

Your total daily energy consumption must be incredibly low?

Also, what about doing weird experiments like dripping water over the condenser or putting the whole fridge or freezer inside a box and then filling it with spray foam?

I thought chest freezers were more efficient for no reason other than less cold air escapes when the lid is opened.

What happens to real-world consumption if the doors on the appliances are opened and closed several times throughout the day?

 

[Checkthisout]

Also, knowing what I know. There must be differences in compressor types in regards to efficiency.

Reciprocating would be the lowest with a vane type being the highest?

 

[Hedges]

Many different perspectives on this.

I joined this forum because it is geared towards a robust and safe build that avoids the system becoming an ignition source. In the fridge / freezer threads I have not come across discussions on considerations for their selection to avoid them too being an ignition source.

I would like to contribute by sharing a link here to include some perspective on other important safety considerations when getting into the details of specific brands / models / features that are well worth your awareness before committing to a specific purchase.

Causes, Consequences and Prevention of Refrigeration Fires in Residential Dwellings : LSBU Open Research

Open Research at LSBU | A repository of internationally recognised and world-leading research generated by our staff and students

openresearch.lsbu.ac.uk

Thanks for the link.
Interesting - foam burning, flame ignition? Defrosters - mine has a thermostat, hopefully also over-temp cutout; will check.
A number of electrical components which failed as ignition sources.
Water, "pyrolysis", flammable gasses, electric spark.
Older (> 20 year) units with failed cooling fan and bimetalic strip switch fails after repeated cycles. Spark or arc-tracking of insulator (carbon based plastics do that more than Teflon or silicone)
Possibly U.S. U.L. testing results in safer models.

 

[efficientPV]

They are probably all vane. The big difference is in the past the AC use fractional HP shaded motors which tend to be inefficient. The DC are actually 3 phase motors which are more efficient. Some newer AC fridges are inverter now for efficiency.

 

[Paul_B]

Mentioned Samsung is about same level as others with A grade in new european energy scale.
IIRC standard test is performed at close to 30 Cel /85F and the actual measurement results what I have seen in various magazines or consumer test reports have been mostly in line with the results, typically showing even lower than rated consumption when ambient temperature has been closer to 25cel.

Samsung European upright unit: 4 cu ft freezer and 9 cu ft fridge totalling 295 Wh per day or mere 12w average.
That is a fantastic power usage, compared to my experience with Sundanzer's DCRF450 (15 cu ft) that used approx. 1.4kWh / day over 5 months of warm weather in our kitchen. I look forward to hearing more about consumers' actual experience with the Samsung unit.

As for DC being more efficient than A/C, it definitely seems that way. In another thread, it was mentioned "Unique said that when you use the AC converter on a DC fridge, it consumes just as much energy as a regular AC fridge": https://diysolarforum.com/threads/using-dc-fridge-with-ac-converter.36916/post-467597

Whether AC or DC, an upright unit can't hold the cold air so well when the door is opened. I do think that DC freezers are designed to reduce power consumption. That's how I explain my own readings, anyway.

But if using the AC converter with Unique's product causes it to consume just as much energy as a regular AC fridge - that's a yellow flag for me. I interpret that as meaning most of the energy saving is from the DC compressor, not due to improved insulation. When I purchased the Sundanzer DCRF450, Unique had a similar-looking upright fridge/freezer. I can't say the current models are directly comparable.

 

[MattiFin]

They are probably all vane. The big difference is in the past the AC use fractional HP shaded motors which tend to be inefficient. The DC are actually 3 phase motors which are more efficient. Some newer AC fridges are inverter now for efficiency.

99% of fridge compressors are piston compressors. I can find some small chinese 12vdc rotary compressors but I'd say those are the 1% exeption.
Newer inverter driven fridges can be 3-phase squirrel-cage motors, brushless dc (BLDC, 3-phase) or permanent magnet ac motors(3-phase)
LG has also few linear driven piston compressors

 

[Hedges]

I'm digging into mine again today. I previously replaced defrost thermostat (interrupts power to heater above a certain temperature), but still not defrosting. Must be an intermittent connection I didn't track down last time.

Here's a fridge/freezer defrost thermostat, L140-30F off at 140F on at 90F

GE WR50X10068 Defrost Thermostat (AP3884317) - AppliancePartsPros.com

Specs: L140-30F. Limits how warm the freezer section can get during the defrost cycle., WR50X10068 / AP3884317 made by GE

www.appliancepartspros.com

L50-30F, off at 50F on at 20F

Whirlpool 4387500 / WP4387500 Refrigerator Bi-Metal Defrost

Shop Whirlpool 4387500 / WP4387500 Refrigerator Bi-Metal Defrost online. We help you to fix your broken appliance at lowest prices & with fast shipping.

www.partsimple.com

My original was L60-32F, replaced when refrigerator didn't defrost with L55-30F.
Still having problems. Maybe it will work better relocated to the middle of most iced portion, where refrigerant line enters freezer. Otherwise, I'll try L140-30F.

Now I understand why placing it in an ice/water bath didn't cycle it back on. Bypassed with a jumper for manual defrost & temp limit for the moment.

Do some refrigerants tolerate 140F better, others want to remain under 60F?
I also see L140-30F for furnace thermostats.

 

[Paul_B]

Does saving .3kwh per day really matter?

Your total daily energy consumption must be incredibly low?

Also, what about doing weird experiments like dripping water over the condenser or putting the whole fridge or freezer inside a box and then filling it with spray foam?

Don't know if this was addressed to me, but I suspect 0.3kWh / day would matter to @no idea who is using a beefed up UPS as his fallback for grid outages. Pretend 0.6kWh was the current power offered by the UPS. Dropping consumption by 0.3 kWh means longer run time with the same UPS.

I seriously like your idea about experiments.

I was told multiple times that the power consumed by a freezer is proportional to the square of the temperature differential (outside unit vs. inside). So adding insulation board on the unit can have a good impact on keeping the inside cooler, and result in lower power draw, since the compressor won't need to run so much. Obviously, I'd need to ensure heat isn't trapped behind any insulation, maybe use a small computer fan (2-3w) to move heated air away from the condenser area.

 

[Paul_B]

Shame they don’t have 48v

Sundanzer DCRF450 (fridge/freezer, 15 cu ft) has a 48v option, in case it suits your need. 12v/24v is standard.

 

[sparrowhawk]

Many different perspectives on this.

I joined this forum because it is geared towards a robust and safe build that avoids the system becoming an ignition source. In the fridge / freezer threads I have not come across discussions on considerations for their selection to avoid them too being an ignition source.

I would like to contribute by sharing a link here to include some perspective on other important safety considerations when getting into the details of specific brands / models / features that are well worth your awareness before committing to a specific purchase.

Causes, Consequences and Prevention of Refrigeration Fires in Residential Dwellings : LSBU Open Research

Open Research at LSBU | A repository of internationally recognised and world-leading research generated by our staff and students

openresearch.lsbu.ac.uk

Here's a fridge/freezer defrost thermostat, L140-30F off at 140F on at 90F

GE WR50X10068 Defrost Thermostat (AP3884317) - AppliancePartsPros.com

Specs: L140-30F. Limits how warm the freezer section can get during the defrost cycle., WR50X10068 / AP3884317 made by GE

www.appliancepartspros.com

L50-30F, off at 50F on at 20F

Whirlpool 4387500 / WP4387500 Refrigerator Bi-Metal Defrost

Shop Whirlpool 4387500 / WP4387500 Refrigerator Bi-Metal Defrost online. We help you to fix your broken appliance at lowest prices & with fast shipping.

www.partsimple.com

My original was L60-32F, replaced when refrigerator didn't defrost with L55-30F.
Still having problems. Maybe it will work better relocated to the middle of most iced portion, where refrigerant line enters freezer. Otherwise, I'll try L140-30F.

Now I understand why placing it in an ice/water bath didn't cycle it back on. Bypassed with a jumper for manual defrost & temp limit for the moment.

Do some refrigerants tolerate 140F better, others want to remain under 60F?
I also see L140-30F for furnace thermostats.

View attachment 103955

View attachment 103956

I would not put the defrost termination thermostat in the middle as it will cycle the heater off sooner because of being closer to to defrost heater and likely leave some frost unmelted. Clipped onto the top right evaporator tube would be the best place. Also use what the manufacturer calls for as a replacement thermostat. And make sure you melt off any ice that is still leftover before you close everything back up and restart the refrigerator.

 

[Hedges]

I just went through many cycles using jumper wire to bypass defrost thermostat for 5 minutes, circulate air for 20 minutes, until the ice was gone. Had to keep rotating the timer to disable compressor for a few hours.

Thermostat had originally been toward the left, I think. I just clipped it on the tube going into back wall on the right, where ice had lasted longest. I'll double-check that it has finally closed now that freezer is operating again. If it does function, could be it kept switching off when left side thawed, leaving frost building up more an more on right.

I've been having water drip through fridge, rather than out rear drain to evaporation pan. Could be drain airlock got plugged. I made sure to clean it a previous time. Could be just ice dam causing problems.

I thought I ordered thermostat by part number or fridge model. At least what I got was close, within about 5 degrees. I was concerned about the 140F ones overheating something (refrigerant or plastic). Phosgene gas, anyone? That would require flame temperature.

GE fridge top freezer
defrost thermostat, open at room temperature
TOD 37T31 30625 L60-32F
467326P011 J9239 Mexico
"32F" sounds like temperature, 0C, freezing. No, 60 - 32 = 28F close.
Ordered new OEM replacement 6/19/21
WR50X10010
TBHW18ZRFRWH	model

 

[sparrowhawk]

I just went through many cycles using jumper wire to bypass defrost thermostat for 5 minutes, circulate air for 20 minutes, until the ice was gone. Had to keep rotating the timer to disable compressor for a few hours.

Thermostat had originally been toward the left, I think. I just clipped it on the tube going into back wall on the right, where ice had lasted longest. I'll double-check that it has finally closed now that freezer is operating again. If it does function, could be it kept switching off when left side thawed, leaving frost building up more an more on right.

I've been having water drip through fridge, rather than out rear drain to evaporation pan. Could be drain airlock got plugged. I made sure to clean it a previous time. Could be just ice dam causing problems.

I thought I ordered thermostat by part number or fridge model. At least what I got was close, within about 5 degrees. I was concerned about the 140F ones overheating something (refrigerant or plastic). Phosgene gas, anyone? That would require flame temperature.

GE fridge top freezer
defrost thermostat, open at room temperature
TOD 37T31 30625 L60-32F
467326P011 J9239 Mexico
"32F" sounds like temperature, 0C, freezing. No, 60 - 32 = 28F close.
Ordered new OEM replacement 6/19/21
WR50X10010
TBHW18ZRFRWH	model

Your refrigerator looks like the type that has the defrost water draining from the freezer into the refrigerator before it passes outside to a tube that runs down the back wall into the condensate pan at the bottom. If you are having water drip into the refrigerator you have an obstruction somewhere along the drain path, most often it's ice where it passes from the freezer but it could be debris further down. What I do is use compressed air to blow out the line through the drain hole in the freezer so the time to do it is when the freezer is opened and everything is defrosted.
Oh and the first thing to do is check for ice in the defrost drain and if present then it needs to be defrosted/cleared.

 

[Hedges]

Thanks, I'll check whether it is draining now (or rather after it does some defrost cycles). I blew out the line before, but might still be iced up after today's defrost.

I checked out temperatures and found defrost thermostat is working as expected. Tubes were 5F, enabled defrost and heater came on. Tubes rose to 32F, paused until frost disappears at thermostat (where I placed the thermocouple), rose to 60F and heater came back on switched off. I then set defrost timer for approximately 9:00 AM, assuming it is 24 hour.

Freezer gets coolant tubes down to 5F, thermostat on end where refrigerant enters:



Thermostat did turn on, heating now, hit 32F and paused until frost melted:



At 60F, thermostat turns off heater:



Seems to be working.
Cooled down, then warmed up significantly despite compressor operating. Cleaning off dust bunnies (cat hair) from condenser seems to have it cooling again ...

 

[sparrowhawk]

Thanks, I'll check whether it is draining now (or rather after it does some defrost cycles). I blew out the line before, but might still be iced up after today's defrost.

I checked out temperatures and found defrost thermostat is working as expected. Tubes were 5F, enabled defrost and heater came on. Tubes rose to 32F, paused until frost disappears at thermostat (where I placed the thermocouple), rose to 60F and heater came back on. I then set defrost timer for approximately 9:00 AM, assuming it is 24 hour.

Freezer gets coolant tubes down to 5F, thermostat on end where refrigerant enters:

View attachment 104012

Thermostat did turn on, heating now, hit 32F and paused until frost melted:

View attachment 104013

At 60F, thermostat turns off heater:

View attachment 104014

Seems to be working.
Cooled down, then warmed up significantly despite compressor operating. Cleaning off dust bunnies (cat hair) from condenser seems to have it cooling again ...

I still recommend you move the termination thermostat to the top of the evaporator. The reason for that is to insure that the heater doesn't shut of before the temperature of the evaporator from bottom to top has warmed enough to melt all the ice.
Also if the defrost drain keeps icing up then you will need to install a defrost drain kit. It consist of a thin flat piece of aluminum that wraps around the defrost heater at the top and then extends down into the defrost drain hole about an inch. It works by allowing enough heat transfer from whenever the heater is on down to the drain to defrost any ice that might accumulate there.

 

[Hedges]

I'll see if it gives me any more trouble. The ice buildup was on the right hand side, bottom to top and several inches wide & thick. So I put thermostat in the middle of where ice block had been, figure the thickest part will have to be completely melted before thermostat turns off.

I thought thermostat was supposed to cycle on and off to maintain an optimum defrost temperature, but original (and replacement) won't turn back on until below 32F, next cooling cycle. The others I've seen L140-30F would run much hotter and could cycle.

I've had this unit since the late '90's, no issue (except hair on cooling coils) until just a couple years ago. Maybe the defrost thermostat failed; that's what I thought and replaced it one year ago. Think it was between upper & lower coils toward the left.

Air enters compartment top rear and exits bottom front, passing between freezer and fridge. Previously I could feel ice there.

Wasn't down to temperature last night but compartment has now reached 15F, have put frozen items back in now.

This GE unit appears to have retained (at least most of) its refrigerant, uses good old R12.
My Frigidaire deep freeze started melting things at half the age of this one, needed recharge of R134A.