Cooling performance of fridges (Engel etc and 3 way) - some numbers

[e9999]

I got curious about the relative performance of the compressor-type fridges (electric Engel, Norcold etc) and the absorption types (3 way, propane etc).

I went out and did a bunch of measurements in the 3 way fridge we have in our little trailer. I put in a thermocouple inside the empty fridge with an outside display and recorded that temp as a function of time, as well as the ambient temp in the trailer (should have also done the outside since the condenser is exposed to the outside air but oh well...). This since I really had no idea how fast this fridge would cool things down and how cold it would keep things under high ambient temps. Of course, measurements with an empty fridge does not tell the full story about how fast one could cool things down if they were placed hot in the fridge. Did not open the door during the measurements.

The fridge is a 1.5cuft inside volume (about 45qts). Dometic built-in.



Too much data to post here now, but the basic lesson seems to be the following:

- the mode used (12V, 110V, or propane) did not seem to make much difference as far as cooling .
- Generally speaking it takes about 2 hours to cool the inside down from about 70 F to freezing with ambient temps of the order of 80F.
- the lowest temp it could maintain at around 65F or so ambience was of the order of 25F. That was evening and early am. Have not checked in the middle of the night, but don't think it would go too much lower.
- at higher ambient temps, say 80F or more during the day, the fridge seems to be limited to maintaining temps around 32F.

So it seems that we are not talking here about technology that can do deep freezing during the day. Obviously, though, the big advantage of the propane mode is that you can run the thing for a month off a smallish tank vs a few days off 2 truck batteries (I guess). Admittedly, though, if you were to camp for an extended time with an Engel you could use a generator or turn on the truck every day. But then you need extra gas...

Now, I don't know much about portable compressor types a la Engel, but suspect they can probably go colder faster. This is based on some data I saw on the i-m-d site. But no idea if these are true in real life.

Sooo, anybody has any figures on how cold and how fast one can cool things down with a compressor fridge?

[firetruck41]

Get me a thermocouple and I will try it in my 1st 30qt Norcold, if you wait till next week to get it for me I can try it in my 2nd 30qt Norcold which ships today

[NorCalDoug]

It gets cold enough fast enough to start freezing my diet pepsi and beer if I'm a dunce and set it to 2.5 rather than 2 overnight.

No fancy measuring equipment...sorry.

[e9999]

Originally Posted by NorCalDoug

It gets cold enough fast enough to start freezing my diet pepsi and beer if I'm a dunce and set it to 2.5 rather than 2 overnight.

No fancy measuring equipment...sorry.

it don't take no fancy equipment, just stick a container of water in there and see how long it takes to freeze... So you can plan for beer cooling much more effectively!

[e9999]

well, tried the above.
Put in a container of water, about 1 qt or so in it overnight. Ran at less than 29F all night. Morning showed no trace of ice yet! Bummer! Not a fast freezer for sure!

Engel?

[e9999]

still no ice!
Dang, looks like that is that for freezing stuff....

[Cruiserdrew]

Eric-Do you want me to put a cup of water in the Engel and see how long it takes to freeze? I'll bet it's just a few hours. I'll start it now and check hourly.

[firetruck41]

I just stuck a 1 qt tupperware container of tap water, into the ~15 yr old, 30qt Norcold, chest type, AC/DC, compressor driven, freezer/fridge. It started unplugged at room temperature, then I plugged it in to 120V AC, and turned it on to "Freeze" at 15:08 PST. I'll check back on it later.

EDIT: Found a indoor/outdoor thermometer with remote sensor to use, ambient temp is 74 F

freezer/fridge air temp, center of freezer
15:18 - 54 F
15:26 - 31 F (freezing)
15:38 - 20 F
15:48 - 15 F
15:59 - 10 F
16:10 - 7.9 F opened freezer and checked the water, not freezing yet
16:28 - 6.1 F
16:39 - 4.6 F
17:12 - 1.8 F opened freezer, relocated probe into water

water temp
17:15 37.8 F
17:48 33.8 F
18:04 31.8 F top of water is iced over
23:50 31.8 F water is progressively freezing
07:50 17.8 F solid ice, just woke up so not sure when it "froze solid" over night
Expirement Ended!

[e9999]

Originally Posted by Cruiserdrew

Eric-Do you want me to put a cup of water in the Engel and see how long it takes to freeze? I'll bet it's just a few hours. I'll start it now and check hourly.

that would be interesting to see. Might be better to let it stay for a while without opening it too often or you'd be lengthening the process. Although, it's not as bad with a top opening as with a side opening like my trailer one.

[e9999]

Originally Posted by firetruck41

I just stuck a 1 qt tupperware container of tap water into the 30qt Norcold, which started unplugged at room temperature, I plugged it in to 120V AC and turned it on to "Freeze" at 15:08 PST. I'll check back on it later.

EDIT: Found a indoor/outdoor thermometer to use, ambient temp is 74 F

15:18 - 54 F

15:26 - 31 F (freezing)

thanks. Darn, that's fast. Takes a couple of hours with mine to get down to 32F...

I think I'm resigned to the fact that my absorption one is a fridge, not a freezer...

[firetruck41]

Originally Posted by e9999

I think I'm resigned to the fact that my absorption one is a fridge, not a freezer...

That may be the case, but that's not too bad as long as you plan accordingly, could still be better than a cooler full of ice. If you can keep it below freezing you should be able to keep frozen stuff in there for a while.

[Cruiserdrew]

Ok-I'm giving into the madness. Here are a few pic of my now more scientific fridge test. I have a thermometer with a remote digital read out. The tip is in 500ml of water. At 3pm it was 68 degrees F. It seems to be cooling fairly quickly. The fridge interior started at warm ambient and was 29 degrees F after about 20 minutes. edit-this is the 45 quart version of the fridge.

Initial data points (water temp):
3:00 68F
3:30 64F
4:00 53F
4:15 48F
4:30 42F

Went to Borders

5:30 33F
5:45 32F Ice Forming, experiment ended.

Eric-arn't you an engineer? You should have all sorts of gadgets for gathering this sort of info, but it won't change the basic fact that you need an Engel fridge. Propane fridges suck in comparison.

[firetruck41]

Originally Posted by Cruiserdrew

Ok-I'm giving into the madness.

Awesome, I am curious how my old Norcold (same manufacturer as ARB/Engel I think) measures up to a new model.

[e9999]

Originally Posted by Cruiserdrew

Ok-I'm giving into the madness. Here are a few pic of my now more scientific fridge test. I have a thermometer with a remote digital read out. The tip is in 500ml of water. At 3pm it was 68 degrees F. It seems to be cooling fairly quickly. The fridge interior started at warm ambient and was 29 degrees F after about 20 minutes. edit-this is the 45 quart version of the fridge.

Initial data points (water temp):
3:00 68F
3:30 64F
4:00 53F
4:15 48F
4:30 42F

Went to Borders

5:30 33F
5:45 32F Ice Forming, experiment ended.

Eric-arn't you an engineer? You should have all sorts of gadgets for gathering this sort of info, but it won't change the basic fact that you need an Engel fridge. Propane fridges suck in comparison.

errr.... 123F is not freezing, you know!

and why did you stop, pray tell, we wanted to see how long it'd take to freeze over...

[Cruiserdrew]

Originally Posted by e9999

errr.... 123F is not freezing, you know!

and why did you stop, pray tell, we wanted to see how long it'd take to freeze over...

123F was the temp the thermometer was set to beep last time we cooked a rib roast! I ended the experiment because it was 32 and had iced over. I cleaned it all up at 6pm and the temp probe was frozen into the water, but not solidly.

It looks like Ben's data is proving the same thing. THese fridges cool fast and well. When I opened up to end the experiment the air temp was not readable with my food thermometer-I think it can only read to 15F. That's pretty outstanding performance for a device this efficient that can go with you anywhere.

If the spirit moves me, I'll repeat the experiment with 1000ml of water starting from ambient, then a whole fridge full of cans of beverages starting from ambient.

[FirstToy]

when I first got my engel, I put a ice cube tray w/ tap water in it. It started to freeze within 45 min.

[e9999]

Originally Posted by Cruiserdrew

123F was the temp the thermometer was set to beep last time we cooked a rib roast! I ended the experiment because it was 32 and had iced over. I cleaned it all up at 6pm and the temp probe was frozen into the water, but not solidly.

It looks like Ben's data is proving the same thing. THese fridges cool fast and well. When I opened up to end the experiment the air temp was not readable with my food thermometer-I think it can only read to 15F. That's pretty outstanding performance for a device this efficient that can go with you anywhere.

If the spirit moves me, I'll repeat the experiment with 1000ml of water starting from ambient, then a whole fridge full of cans of beverages starting from ambient.

wow! so at 3pm it was ambient and at 6 it was close to having almost fully frozen a qt of water?
that is really good indeed!

there is indeed a big difference between these and my (maybe all) absorption device. No comparison!

[firetruck41]

Originally Posted by e9999

wow! so at 3pm it was ambient and at 6 it was close to having almost fully frozen a qt of water?
that is really good indeed!

Not even close to freezing through, my sensor is at the bottom of the quart container which is the last to freeze, it is freezing over the top first. The sensor continues to read 32 F as it is still surrounded by water (not ice), if it were ice the sensor would start going back down in temp. the top started to freeze over fairly quickly but with a large container which will freeze into a block (as opposed to an ice tray) it will take a while to freeze through. We do know it will freeze, with temps as low as 1 F in my fridge/freezer, it is just a matter of time. I will check it in the morning, I kinda think it will be frozen through by then.

[firetruck41]

TEST CONCLUDED

I updated post #8 above with my observtions. Apparently a ~15 yr old Norcold still works like new, and the absorption type (3 way) does not have close to the same performance.

[surfpig]

Hello, I've been shopping for one of these fridges for quite awhile now. I have been working on a competent solar charging system, so we can stay awhile somewhere... Anyway, I've just put most of the pieces together, and today received my new(to me) ARB 43qt fridge. Here's what I got, out of the box(Ebay ) 6pm arrived home, anxiously opened box: looks good...

6pm: 92 ambient temp. Turned on (110V), 1 pt water inside.
6:15: 80 degrees, air feels cool inside
6:30: 60 degrees...
6:45: 40 degrees...
7:00: 30 degrees...
7:15: 25 degrees, no ice forming yet...
7:30: 20 degrees...
8:00: 15 degrees...
8:45: 12 degrees...
9:15: ~10 degrees, ice film on top of water container (etched glass Medocino Brewing Company pint glass)...
9:30: 10 degrees, same...
9:45: 10 degrees, substantial ice throughout container... I think I'll give the guy good feedback! Oh yeah!

OK, now off to Reggae on the River, Aug 4,5,6,7

Nial

Update, 6:20 8/4: 10 degrees, reset to 4 previous night...

[spressomon]

Surfpig, Does your new fridge have the built in thermometer? I saw, somewhere, the new model ARB/Engel has a digital thermometer now...

Also if you get the solar charger thing figured out please post the info up!

[Landpimp]

my ARB goes down to 0, I kept 3 gallons of Baskin and Robins ice cream in the back of the 100 series on a 90 deg day, stayed at 0 all day long.

[surfpig]

spressomon said...

Also if you get the solar charger thing figured out please post the info up!

Will do, I'm putting my first version to the test this weekend... ARB and party lights will be plugged-in 24/7 in 100 degree heat for 4 days...

[surfpig]

spressomon said...

Oh yeah, I was going to post results of my trial run with the solar panel... Well. New post? Not quite yet... Lets just say camping in the redwoods is not conducive to solar power. I had about 2 hours of sun a day, my battery was dead (for starting) after a day. I moved the truck to a sunny spot (almost full day) on day two, still couldn't start it. So, for my trial run, I'd say it was pretty much a flop. Things to consider: I ran party lights off an inverter most of day(night) one, as well as the stereo (low draw) and my ARB. My battery is old, but still "good". Through all this (four days...), the fridge ran fine, beer and perishables were cool and delicious, just couldn't start the truck. So the draw is minimal, and a small solar panel can probably handle the drain from a ARB/engel, etc, refrigerator if it gets full sun for at least 4-5 hours a day. My next step is to figure out if a "deep cycle" Optima-type battery will help with the constant (small) draw this type of appliance needs, and what can still start the truck. I'd rather not do dual batteries, but if that's what it takes...

Anyone else got any ideas?

nial

[Cruiserdrew]

Originally Posted by surfpig

Anyone else got any ideas?