Just installed Reflectix over the original thin fiberglass batt insulation. I also painted the fridge coils black to have them dissapate heat better. I'll update once it's back together and has run for a couple of days.
Hmmmmmmmm.....
Won't black paint make the coils absorb heat?
Larry
Quote from: brainpauseHmmmmmmmm.....
Won't black paint make the coils absorb heat?
Larry
No, black radiates heat, hence why wood burning stoves, and alot of air cooled engines are black. Also, look at the coils on the back of a modern fridge....black. Car radiators and A/C condensors.....black.
They also use special heat conductive paint. Just spraying anything with regular off the shelf black paint does insulate rather than promote heat transfer.
Back in the day when it was more economical/possible to repair auto radiators than replace them I can remember the radiator shop guys bitching about morons that would spray paint radiators and them wonder why they didn't cool as well.
Quote from: mike4947They also use special heat conductive paint. Just spraying anything with regular off the shelf black paint does insulate rather than promote heat transfer.
Back in the day when it was more economical/possible to repair auto radiators than replace them I can remember the radiator shop guys bitching about morons that would spray paint radiators and them wonder why they didn't cool as well.
Well, being one of those morons who's repainted a lot of radiators black and never once had a problem with overheating, even in the vintage stuff that I regularly restore, I have to say.............never had a problem with it.
While I understand the theory that coating bare metal would at some miniskewl level "insulate" it; but how much insulative or heat transfer blockage do you think you get from a layer of paint bonded directly to the surface that's maybe .0001" thick?
Sometimes theorey gives way to real life.
Quote from: austinado16While I understand that theory that coating a bare metal would at some miniskewl level "insulate" it; how much insulative or heat transfer blockage do you think you get from a layer of paint bonded directly to the surface that's mayb .0001" thick?
I wouldn't be surprised (talking strictly auto radiators) if the real problem was putting enough paint on to significantly reduce airflow, which could cause
huge cooling problems.
Austin
Fired up the fridge at 8pm last night. Digital fridge thermometer was reading 72*F inside the fridge. About an hour later, it was reading 42*F. This morning, with a low of 57*F on the outside digital, the fridge had cooled down to 33*F and change. Right now it 85*F outside in the shade on the digital, and the fridge is holding steady at 34*F and change.
We'll see how the temp progresses as the afternoon wears on. It's 12 noon right now. Also, I'm not using the cube fan inside the fridge. I just wanted to see what the fridge would do on it's own.
Of course this isn't a super accurate test because I'm not at any sort of elevation (if that makes a difference) and I'm not opening the door every once in a while to get something out.
Quote from: austinado16Also, I'm not using the cube fan inside the fridge. I just wanted to see what the fridge would do on it's own.
My understanding with the fan in the fridge wasn't to make the fridge colder, but to make the cold more even. I can easily believe that in a prked pop-up with the fridge door closed all the time that it could get to 33
I guess with the cube fan, I'm also thinking that there's some cooling enhancement due to the fan moving air across the evaporator fins.
Okay: 2pm. Outside air temp in the shade, 87*F. Inside the PUP it's 101*F. Inside the fridge, 40*F. (The digital fridge temp sensor is mounted mid-way deep, and mid-way up, the fridge wall inside)
I guess this is where the little fan on the condensor fins would start to be a benefit. My fridge's louvered panels are in the shade.
I'm going to fire up the cube fan inside and see if that does anything or not at this point.
Opened the fridge a couple times very briefly. 6pm now, cube fan running for about 3-4hrs, 76*F outside and 45.5*F inside the fridge.
I'm going to let it run all night and see where it's at in the morning and what it does tomorrow.
This has been the pattern during camping as well, so obviously my insulation and black paint did nothing. It's always nice and cold after the first night of pre-cooling and then slowly creeps up during the next several days of camping.
Maybe tomorrow's test will be how it performs with a little fan moving heat through the exterior coils and condensor fins.
Have you tried a small box fan blowing over the coils on the back of the fridge? I used one out of an old pc until we got a new and larger fridge. It seemed to cool the fridge down faster, but I didnt have a prob of it getting warmer after running.
Quote from: skamper75Have you tried a small box fan blowing over the coils on the back of the fridge?
No, not yet. That's what I'm going to test out tomorrow. I wanted to take it sort of one mod at a time in order to see what helped and what didn't. I had to take the fridge out to switch which way the door opened (it was on wrong for some reason), so I figured I'd do the insulation and black paint trick first and test it out, before doing the external fan.
Just went out to check temps. It's 7:30pm, 69*F outside and the fridge has dropped a full 5 degrees to 40.5*F in 1-1/2hrs.
I think the fan may be the solution since the fridge's temp is so effected by outside air temp.
Quote from: austinado16It's always nice and cold after the first night of pre-cooling and then slowly creeps up during the next several days of camping.
By chance, do you live where it is very humid? This sounds like what I would expect if the fins in the fridge were becoming coated with frost.
Austin
I'm about 10mi from the Pacific Ocean as the crow flies, with a low set of hills that seperate our weather from the coastal weather. I think my humidity gauges on the digital weather station are typically reading around 45%.
But yes, you're right, the fins and main cooling tube under the little ice cube box do get very frosty. I was thinking last time we were camping, "I wonder if I should either get that frost build up off of there." The other part of this whole fridge performance equation has been that we've only been on 2 camping trips and each time we've left the "normal" weather here and travelled umpteen hours in 100+*F weather and then been at 7,000' and 85-95*F days.
I need to go camp locally for a couple of days and see what it does for real in our weather at basically sea level.
But back to the frost question: With the door switched to swing open from the correct side, I've paid good attention to how the door seal closes and even spent some time yesterday going over the seal itself with some good cleaner because it was all nasty down in the folds at the bottom. Seems like it's closing tight all the way around though.
9:30pm, 62*F outside, 35.2*F in the fridge. Actually, just a small amount of frost on the center cooling tube and fins in each side. Not too bad really.
Quote from: austinado16No, black radiates heat, hence why wood burning stoves, and alot of air cooled engines are black. Also, look at the coils on the back of a modern fridge....black.
That is because all of the coils you mention are
not exposed to sunlight. Black absorbs heat. Being black does not make it
radiate heat any better than being white, grey, blue or purple. Being black makes all of your examples merely
LOOK better than a colored device.
Thus, if your new fridge coils
never see daylight, then black will not help them, and they will look "cool".
But, if your coils see daylight, you want them to be as non-absorbing as possible - so, silver or white.
Frost on the cooling plate will be familiar to anyone old enough to remember before there were frost free home fridges. Just opening and closing the door would/will cause moisture laden air to enter and the plate is a nice icy cold surface for that mositure to condense on and freeze.
I can remember as a kid my mother spending hours with pots of boiling hot water in the freezer trying to loosen up the ice/frost that would build up....mainly from me standing there with the door open staring at the food figuring out what I wanted....LOL
Quote from: zamboniThat is because all of the coils you mention are not exposed to sunlight. Black absorbs heat. Being black does not make it radiate heat any better than being white, grey, blue or purple. Being black makes all of your examples merely LOOK better than a colored device.
Thus, if your new fridge coils never see daylight, then black will not help them, and they will look "cool".
But, if your coils see daylight, you want them to be as non-absorbing as possible - so, silver or white.
Sorry zamboni, but that's not correct. All sorts of mechanical devices are painted black for heat disappation and few if any of them ever see the sun. Refer to my list, and then look around you in the real world. In this scenario, we're talking about metal that's hotter than it's exterior surroundings on one side, and painted black on the other side to promote heat transfer.
Yes Mike, I'm familiar with those refrigerators. I've restored a 1952 Philco Advance Design and it's been in use full time as our only refrigerartor for 14 years (gloss black painted condensor coils on the back and gloss black painted compressor underneath, just as the factory built it.) I defrost it about every 3-4months.
Fridge performance testing update: 7:45am and a huge thunderstorm has been raging since about midnight with rain off and on and a low of 37*F on my digital thermometer! 63*F outside right now and the fridge is 34*F inside. Also, no leaks in the newly rebuilt roof or canvas.
1:30pm 87*F outside and 41.5*F in the fridge.
Quote from: austinado161:30pm 87*F outside and 41.5*F in the fridge.
Which most people would find unacceptable. The "danger zone" for uncooked food is between 40
Quote from: AustinBostonWhich most people would find unacceptable. The "danger zone" for uncooked food is between 40
Check out this website: http://www.rvmobile.com/Tech/Trouble/vent.htm (//%22http://www.rvmobile.com/Tech/Trouble/vent.htm%22)
scroll down the page to "almost good venting".
It shows how a PU fridge should be vented and baffled.
We found over 1/2 the fridges we've looked at over the years to be installed incorrectly according to the fridge makers installation instructions.
Missing or inadaquate baffling is the main problem. Improper placement of the upper vent that allows hot air to pool at the top of the fridge compartment (we've seen it bad enough to blister counter top material). Door seal is another cause check it around the perimeter using a dollar bill, and damaged or missing insulation around the box a distant fourth.
Thanks Mike,
Yes, that's an excellent website. I actually called and talked to "T.J." who owns it. Super nice guy and very knowledgeable.
After seeing that page on his site about 2 months ago (before our first trip) I added the lower baffle like you see on his page there at the bottom. The fridge already had the nicer "ramped" baffle at the top that goes out to contact the condensor fins. It even has a baffle at the very top so hot air has no choice but to go out.....it's a big sheetmetal flashing.
To all this I added the reflectix and filled in the space between the lower and upper baffles with reflectix so it would be less of a pocket. The fridge body insulation is perfect and the door seal seems to be good all the way around.
I guess it's just time to add the little 12v fan and be done with it. Or step up and replace the fridge (and that's not happening).
Quote from: austinado16Agreed. During the afternoon "heat soak" it's now up to 46.9*F with an outside temp in the mid 80's.
I know I've got a good flame and clear chimney, etc. so the only thing I can think of, is that just like a car's A/C system, this fridge is low on refrigerant and at higher outside air temps it just can't tranfer enough heat. Bummer.
How much food/product do you have in the fridge? An empty fridge works very harder to maintain temperatures than a full/stocked fridge.
Try putting in a bunch of water bottles/soda or the like then check the temperatures again tomorrow.
Good Luck.
Well I can pretty much assure you it's not "low refridgerant". You'd notice a yellow pollen like substance (a chrome addative) around the back of the fridge and a definite ammonia smell.
Both Dometic and Norcold recommend mounting any suplimential fan so it blows out the upper vent.
And don't forget to check out the entire perimeter of the door seal. Only a couple of inches of "gap" where you don't get resistance from a dollar bill (we use them as they are really good quality heavy tear resistant paper) can have a fridge temp up 10 or more degrees.
Quote from: mike4947Well I can pretty much assure you it's not "low refridgerant". You'd notice a yellow pollen like substance (a chrome addative) around the back of the fridge and a definite ammonia smell.
Both Dometic and Norcold recommend mounting any suplimential fan so it blows out the upper vent.
And don't forget to check out the entire perimeter of the door seal. Only a couple of inches of "gap" where you don't get resistance from a dollar bill (we use them as they are really good quality heavy tear resistant paper) can have a fridge temp up 10 or more degrees.
Okay, just checked it with a bill. The seal is tight all the way around. I've had the temp dial set to "max" since about 4 today and right now the fridge is at 28.4*F......not that it really matters because it's still getting into the hight 40's during the afternoon heat.
There's definately no yellow staining or ammonia smell. Maybe it's damaged internally from age (it is 20 years old) or from being operated when not level.
Time to quit talking about it and mount that fan, as you suggest. I appreciate your input! Oh, and here's how I baffled the bottom air intake...
Here's how the 2 upper bafflers were installed by Starcraft. The upper horizontal one fits right on top of the fridge. The angled white one rests about in the middle of the condensor fins so all air has to go through the fins before hitting the horizontal baffle and going outside...
Quote from: austinado16Here's how the 2 upper bafflers were installed by Starcraft. The upper horizontal one fits right on top of the fridge. The angled white one rests about in the middle of the condensor fins so all air has to go through the fins before hitting the horizontal baffle and going outside...
The lower baffle looks fine, but on the upper baffle, there is a gap (on the right in the picture) of about 3/4" that would allow warm air to escape into the space between your reflectix and the fridge. Surrounding the firdge with warm air (and then effectively insulating that compartment to keep the heat
in when you menat to keep the heat
out) may be a contributing factor.
Also, knowing it is a 20 year olf fridge makes me feel better; I was really thinking "he should be getting much better performance than that," but that was when I though you had a relatively new fridge.
Austin
Okay, day 3:
Fridge is has cold food in it as of about 8:30am......thanks for that suggestion, I was wondering if the temp swings would level out some if there was stuff inside acting as a cold storage.
Pulled the upper louver panel off and an laid in a "baffle" of Reflectix against that metal upper baffle. Cut the Reflectix to span the full width of the wood framed opening, so there is no longer a gap (to the right in the photo) or to the left (which was there because of how the chimney comes up in that corner). So that should take car of improving the passive convective air flow.
Heading over to Radioshack right now to pick up a fan. Inside of fridge is sitting at 35.5*F right now with an outside temp of 70*F.
One thing I have noticed is how sensative the system is to having the louvered panel and louvered door off. It actually came up in temp while I was working on it with the panels removed. With them back in place, and while typing this, it's come down a point.
Quote from: austinado16Okay, day 3:
Fridge is has cold food in it as of about 8:30am......thanks for that suggestion, I was wondering if the temp swings would level out some if there was stuff inside acting as a cold storage.
Pulled the upper louver panel off and an laid in a "baffle" of Reflectix against that metal upper baffle. Cut the Reflectix to span the full width of the wood framed opening, so there is no longer a gap (to the right in the photo) or to the left (which was there because of how the chimney comes up in that corner). So that should take car of improving the passive convective air flow.
Heading over to Radioshack right now to pick up a fan. Inside of fridge is sitting at 35.5*F right now with an outside temp of 70*F.
One thing I have noticed is how sensative the system is to having the louvered panel and louvered door off. It actually came up in temp while I was working on it with the panels removed. With them back in place, and while typing this, it's come down a point.
You may want to hold off on the fan ... you'll be surprised how much the addition of food will make a difference. Any heating/cooling device works a lot better when there is already product in unit. Without product ... it has nothing to cool but itself and nothing to hold that cold air making it always working.
Let us know what that does (the addition of food) to the temperatures. I think that you'll find it maintains a lot better temps.
Quote from: mykwalker1You may want to hold off on the fan ... you'll be surprised how much the addition of food will make a difference. Any heating/cooling device works a lot better when there is already product in unit. Without product ... it has nothing to cool but itself and nothing to hold that cold air making it always working.
Let us know what that does (the addition of food) to the temperatures. I think that you'll find it maintains a lot better temps.
You are correct sir!
87*F outside and the fridge temp was in the mid 36's before pulled the louvered panels off and installed a little 1-9/16"x1-9/16" 12v computer fan from Radioshack. I decided to install the fan regardless of what the fridge temps did today because I wanted the option of additional cool if needed.
Fridge got up to 38.7*F during the installation of the fan. During the time it took to snap a couple photos and right this, the fan has dropped the fridge temp to 38.3*F.
Fan is part number: 273-240
6,500rpm
.13amp (130mA) of current draw
1.56watts max
7.7CFM (cubic feet per minute) air flow
29dB noise level (can't hear it unless my head is right next to the louvers)
I installed the fan at the very top of the opening right up front next to the louvers, and centered on right grill opening which is where the majority of the heat lives and exits due to the chimney being there. As you can see, I ran 2 galvanized sheetrock screws in along each side of the fan and then ziptied the fan housing to the screws using the 4 holes in the fan housing. Fast and simple.
The switch is in the upper left corner of the lower opening, and wired in to break the ground circuit. Radioshack part number: 275-730 and came with it's own mounting surround that screwed right into the upper wood crossmember. Again, fast and easy. Wiring is as you'll see in the next photo.
Here's a shot of the switch installation.
There is a noticeable "soft breeze" out the upper louvers with the fan running and I figure at just under 8CFM, it's probably changing the entire air in the cabinet about 2-3 times per minute.
Expense: Fan and switch came to $17.22 with tax.
Addition parts: 2 female spade connectors and 2 16ga butt splices, 6 small zip-ties, and 3 plastic wiring holders with screws.
Time invested: Maybe 30min including taking the louvers of and putting them back on again.
Well, day 3 of fridge testing is about over and the temp peaked at 40.3*F, about 7.5*F cooler than the highs of the last 2 days. This with food on board, temp setting all the way to "9" and the fan running for the last 4hrs.
Still not great because this was with the door remaining closed all day. Had it been opened for lunch and later for snacks (I opened it in the morning to put the cold test food inside) It would probably be up another 3-5 degrees.
Any suggestions on how to improve this are certainly welcome!
Quote from: austinado16Well, day 3 of fridge testing is about over and the temp peaked at 40.3*F, about 7.5*F cooler than the highs of the last 2 days. This with food on board, temp setting all the way to "9" and the fan running for the last 4hrs.
Still not great because this was with the door remaining closed all day. Had it been opened for lunch and later for snacks (I opened it in the morning to put the cold test food inside) It would probably be up another 3-5 degrees.
Any suggestions on how to improve this are certainly welcome!
One thing I heard of someone else doing was putting a small shade awning over the fridge on the outside. If your fridge is on the sunny side of the pop-up, providing it with shade could help. Just make sure there is plenty of room for the warm air you just blew out with the fan to clear away freely.
Another option is to make sure you always camp with the back of the fridge facing north.
You could get an a/c for your pop-up, and install a duct from the a/c output to the base of the fridge, cooling the fins with a/c air.
Looking at your pics, it looks like there may be significant air gaps between the fridge and the Reflectix. If there is, try to find styrofoam or other foam insulation that will completely fill that gap. The thin foam that is used under vinyl siding may work; you could layer it until you have the best fill possible.
I think these are all long shots, but they are all (ok, all but one) cheaper than a new fridge.
Austin
Good suggestions.
For this test, the fridge louvers were in the shade and on the north side, so this is probably as cold as it's gonna make......unfortunately.
You're right about the reflectix not filling in completely. Actually, it did on the top and on the left side in that one photo, but on the right there was about a 1" gap. I filled that in with some ceramic wool insulation that I happened to have. So, the fridge is packed in solid right now.
It may just be that it's "damaged" internally either from age and a million hours of run time, or from being run while not level.....or both. Bottom line is, it's just not as efficient as it should be and that's too bad.
Quote from: austinado16Well, day 3 of fridge testing is about over and the temp peaked at 40.3*F, about 7.5*F cooler than the highs of the last 2 days. This with food on board, temp setting all the way to "9" and the fan running for the last 4hrs.
Still not great because this was with the door remaining closed all day. Had it been opened for lunch and later for snacks (I opened it in the morning to put the cold test food inside) It would probably be up another 3-5 degrees.
Any suggestions on how to improve this are certainly welcome!
What are you using to take the temps? Is it just ambiant air temp or is it the temperature of the product inside? The reason that I ask is that when I worked in the food service industry we always put our probes in a gel in the fridge. That told us more accurately what the temp was for the food inside and aleiviated the high spikes that you would see with the ambiant temps. :eyecrazy:
I don't think opening the door for 5 minutes at lunch a few (3) to pull out the food and a couple (2) to replace the food that wasn't used and 2 minutes or so at a later snack time would not affect the temperature of the food more than .5 of a degree -- but would affect the ambiant temp drastically (probably a 10 degree swing) and would be corrected within 15 minutes of a closed door situation.
Maybe your temps aren't that bad when looking at it from the standpoint of what the food temps are throughout the day.
What was the outside temps on day three? Was there any change from the day before?
These are excellent points! In fact, I went out last night and grabbed a big nectarine out of the fridge just to see how it was doing......it was very nice-n-cold. There are some yogurts in there and I was going to poke my digital temp probe into one of them (which is attached to my $350 Tectronics digital volt/ohm meter).
Right now I've tried 3 different temp sensors. One is the digital fridge thermometer that I bought at the local RV place. It has a sensor that's stuck to the inside wall of the fridge about midway back and midway up the wall. As you say.......it's extremely sensative. Open the door and bam, the temp starts to creep up almost instantly. Of course I know the food isn't doing that. The other temp sensor is the remote unit that came with my Acu-Rite weather station. That reads the same as the fridge thermometer. I also put the probe from my Tectronics meter in there and it agreed with the other 2....as far as ambiant temp goes. The final temp sensor is one of those metal spike style appliance thermometers that are mechanical and you can adjust the nut on the back to make them accurate (at least at freezing). So, it's calibrated to 32*F and it actually reads lower than the other thermometer, and more stable.....as if it were the food.
Day 4 and air temps peaked today at 96*F in the shade, inside the pup was well over 100*F and the fridge is showing 43.6*F inside, but the ice cubes in the little freezer are still frozen.
Guess I'll go poke a hole in yogurt cup and see what's goin' on.
Thanks for the tip!
Okay: yogurt temp test. It was actually 37*F inside the yogurt when I first put the temp probe in. Meanwhile the fridge thermometer was reading 43 and change. So, I feel pretty good about this, especially after the 96*F day we've had today.
Day 7 and time to bring the fridge testing to a close.
Following Day 4 with 96*F weather, on Day 5 we had a blistering day of 105*F. Fridge air temps inside maxed out at 51.8*F and cooled to the low 40's during the night.
Day 6 came and went with outside temps back in the 80's and the more normal fridge temps in the mid 30's in the morning and low 40's in the late afternoon. Cooling down to 35*F last night.
One final food temp test this morning showed the yogurt was 30*F inside, but not frozen.
The fridge cube fan ran for 5 days and was still running this morning...and that's after 5 days to and from the Grand Canyon, 2 days to Kings Canyon, and all the other pre-cooling and other testing I've done with the cube fan running. Pretty good on the same set of D-cells.
So for what it's worth, here's what I learned:
1) It's important to have food (and probably ice cubes in the ice cube tray) in the fridge when doing temp tests.
2) It's important to take the temp of the food because it is typically 5 or more degrees below the temp of the ambient air in fridge.
3) Painting the fridge coils/fins may not do anything to help cooling.
4) Redoing all the insulation with Reflectix may only help marginally.
5) Installing an external fan to help pull or push air out of the rear fridge cabinet does have some benefit.
Mods for the future?
1) I noticed during hot days that the face of the refrigerator door was getting really warm. Basically the whole PUP inside was really warm. I'm wondering if there can be some heat transfer through the front door. I've got a spare fridge and if it looks like the doors come apart easily, I might take a quick peek inside to see what they have for insulation. If there's room to stick in a layer of Reflectix, I probably will.
2) Keep my eye out for a 12v fan that uses less than the 1.5amps my radioshack one uses, or that moves more than 7.7cfm for the same amps.
Quote from: austinado16Day 7 and time to bring the fridge testing to a close.
It would be interesting to see tabulated into a list the various fridge/outside temperature readings you have made.
Austin
Quote from: AustinBostonIt would be interesting to see tabulated into a list the various fridge/outside temperature readings you have made.
Austin
I think it would be more interesting if I'd put more "controls" in place before and during the test, so I could have more results where I could honestly say, "This resulted in that."
But, the temps last week and this weekend were all over the place from lows at night to 53*F and highs during the day up to 105*F. That helped the fridge temps swing all over the place too.
But the pattern I saw was that nightime air temps 65*F and lower would allow the fridge to cool into the high 20's if I left the dial on 9 or higher. Then during the day, no matter where the fridge was at night, or what the dial was set to, the fridge temps ran at about 40*F until the outside air temps got up into the 90's and above. Then it was mid to high 40's and for a brief time, as much as 52*F.
The first couple of days were inaccurate because there was no food in the fridge. Adding food and letting it make ice cubes in the little freezer box brought the air temp of the fridge down almost 7 degrees.
So:
Night time outdoor temps(min)..........
Night time fridge temps(min) 53-65*F ...................................................27-33*F
Day time outdoor temps(max)...........
Day time fridge temps(max) 85-105*F...................................................40-53*F