Data Logs: Current Draw and Temp from a Norcold 630C

[TreeTopFlyer]

The weather has actually become a little more normal lately. This week has been in the 80s. Today I decided to to some more data logging with the fridge.

At around 2 I started the logger, I was recording the amp draw from the fridge as well as the temperature inside the Ex. I cracked the windows to give the fridge a bit of a break. But I wanted to see the worst case scenario...a hot truck with the fridge on.

From 2 till 5 the fridge ran a low draw of around 1A. Not sure what this means. It did need time to get the inside cold, but why the low draw, why not more like 2 or 3.5. When it was 40 degrees outside, I was having draws of 3A. Can the fridge only cool so much? If the outside air temp is too high, the delta T too great, it only can cool a certain amount, so it draws very little current? You can see in the graph that as the interior temps drop, the current goes up as well as the time between cycles increases.

I got in the truck and left work at 5. You can see the temp start to drop as the AC cooled the truck off. I stopped at Home Depot for some parts, the temps climbed accordingly. Then I stop off at another store, then proceeded with my 30min drive home. Stopped at a buddies house for a beer, then came home and unhooked the logger from the 12V socket.

After unhooking the CT from the socket, I put the temp probe into the fridge for a minute just the get a temp of the inside, it shows about 70 degrees. This was on the 2.5 setting. I grabbed two beers and walked in the house, everything still plugged in, you can tell because the current draw is zero but the temp is still going. I touched the beer can to the probe, it was about 75 degrees.

With the inside of the truck about 80 degrees, the compressor was cycling every 10 mins or so. To compare, when the temp was about 40 outside last week, the compressor was cycling every hour. When I was driving home in 40 degree weather, I had the heater on, at that point the compressor was cycling about every 30 mins. I don't know the interior temp from last week because I didn't have a temp probe hooked up at the time. I would guess it was maybe 60ish inside the truck, extrapolating btwn the 40 and 80.

The attached graph should give some insight into how much these types of fridges will draw on a hot or cold day.

My next logs, I think I will put the temp probe into the fridge and see how long it takes to get to each numbered setting; 1-5. Okay, enough geeky number stuff.

Data Logs

 

[BigJim]

Nice

Are you using Hobo data loggers or some other?

 

[TreeTopFlyer]

Loggers

Hobo. I have some ACRs but they are in PITA. Hobo is was easier. If I could only integrate the HOBO inputs AND my Autoenginuity scanner into a carPC software I could have RTA of everything going on.

 

[08whitex]

Are you saying that your fridge is kept at 70 degrees?

 

[ExpoMike]

Are you saying that your fridge is kept at 70 degrees?

That's my thought... Shouldn't it be down in the 40* range for a fridge setting and below 32* as a freezer.

Kind of confused with a 70* inside fridge temp.

 

[08whitex]

I run my fridge at 37 degrees and when I use it as a freezer it is at 0 degrees

 

[UK4X4]

Current spikes on startup depend on what position of the cycle the compressor stopped in.

once its up and running the current draw drops and stabilises as the compression cycle and flow sorts its self out

75 deg beer where's the vomit smily

So during the day with the truck sat in the sun, the compressor was struggling to cool the fridge sufficiently with the compressor permanently on.

when you leave at 5 the temp in the vehicle cycles downwards, the compressor works more efficiently and is able to disapate sufficient heat and starts to cycle on and off.

Yes a Fridge of any type will work more efficiently when the exterior radiator can disapate more heat.



Ie the hotter the place where the fridge is the harder the fridge needs to work in order to cool the inside.

The process has a fixed heat exchange capacity once your outside its range
your done.

If your fridge is empty the fridge will work harder

if its used as a freezer and full of frozen items the compressor only has to keep topping up, as the thermal mass is larger.

I love this info, being an engineer diagnosing and looking at test data to me is an interesting challenge

 

[TreeTopFlyer]

Inside temp

The inside temp was only taken for about 30 seconds, the logger records every 8. The temp may have been lower, I just didn't leave the probe in log enough. I am going to run some more testing today with the probe inside the fridge and see how the temperature settings on the dial correspond. I'll post back this evening.

 

[TreeTopFlyer]

New Temp Tracks

Data File

Okay, so today I logged the inside temp of my fridge. I ran thru settings 1-4. Didn't get to #5 because I only had two beers in the fridge and by 4 I was ready to have a couple.

I woke up this morning, setup the logger and turned the fridge on. The temp inside the truck was around 72 degrees. It stayed in that range all day, I think we got up to around 76 today. I left the windows and back hatch open while I worked on my poorman's maxaxe.

Every 2hrs or so I would lower the temp setting. You can clearly see the stagger in the excel chart. But what is interesting is that the colder I ran the fridge, the lower the current draw. The compressor was running for about 15mins, off for 10, then kicking back in.

A few times, the inrush current spiked. I had one spike up to 3A, the rest were much more normal. Not sure how to interpret this except that maybe the motor was hungup for a second and cause a higher draw.

I turned off the fridge after a while so that I could see how the temperature climbed back up with the compressor off, it rose pretty quick.

I think my settings can be interpretted as such regarding beer temp:

1-snooty brewhouse room temp (back story to that)

2-Rodeo Cold

3-Cold

4-Perfect

5-Slushee

If I ever find a transit bag for cheap or borrow one, I would like to see if the fridge gets colder quick and or how fast the temperature rises with the when the compressor shuts off. The curves should be a lot flatter. Didn't someone make a poorman's bag with some type of home depot insulation. I remember seeing it on a recent post somewhere.

Well, time for some dinner. All this geeky data acquisition works up an appetite.

 

[UK4X4]

mm quite neat, the compressor seems happier at the lower set temperatures

although the temp shifts more at the lowest temp

The return back to hot is surprisingly swift.

two things will effect that- empty fridge- and lack of insulation.

Repeat the test with a full fridge, even bags of water will do.

I'm really interested in the effects of thermal mass within the fridge
as its something thats often not considered.

Geeky data tests are cool if the have value...........

Ie when I get a chance I'll do the calcs for average consumption over time for each setting-

This should help you choose your power requirements.....

Full fridge please one last test !

As I'm expecting the time between cycles to extend out significantly and the return to ambient temperature much slower, ie less power consumption, over time

 

[TreeTopFlyer]

Yah, I was going to do an area under the curve thing for power consumption. But waiting till I got back to work. I have some spreadsheets saved from when we did an energy audit for a golf course. We wanted to see the charge time and frequency of the charges for the carts so we could get a cost per round for the carts.

I agree with the thermal mass. It was only loaded with 2 beers. One of the reasons I am doing this, other than for the fun, is because I have a 55Ah trd battery in the back and was unsure of how much capacity I would need. The 3rd batt will have other accessories of course but the fridge is one that will be running the most. I am hoping to not have to put in the 110Ah batt because it's quite a bit heavier and I will need to weld up a new bracket mount.

I will probably head down to the lake today, I'll get a flat of water and some beer to fill the cooler up with and see how temp swings relate.

 

[teotwaki]

For the sake of the experiment phase you could fashion a quick transit bag with bubble wrap.

 

[UK4X4]

"For the sake of the experiment phase you could fashion a quick transit bag with bubble wrap"

man I'm sounding like a geek.............right now we have real world external temps, with a 2 beer fill

and I'm sorry a two beer fill is not realistic, even with no drinking on the trail rules

Next step 3/4 full fridge which should be pretty normal usage

ie stuff you used gets replaced with warm spares as you go along.

agree if he has the time and money a transit bag or aluminised bubble wrap will help...actually anything to help either heat disapation from the radiator or the insulation / shade ambient temperature around the fridge.

Thats why fridge manufacturer's never state the efficiency specifications or average consumption due to so many external variables effecting the process.

Hence my interest in the tests as I don't have the tech here to log the tests myself.

 

[JIMBO]

:sombrero: Transit bags are as expensive as you want them to be

"For the sake of the experiment phase you could fashion a quick transit bag with bubble wrap"

man I'm sounding like a geek.............right now we have real world external temps, with a 2 beer fill

and I'm sorry a two beer fill is not realistic, even with no drinking on the trail rules

Next step 3/4 full fridge which should be pretty normal usage

ie stuff you used gets replaced with warm spares as you go along.

agree if he has the time and money a transit bag or aluminised bubble wrap will help...actually anything to help either heat disapation from the radiator or the insulation / shade ambient temperature around the fridge.

Thats why fridge manufacturer's never state the efficiency specifications or average consumption due to so many external variables effecting the process.

Hence my interest in the tests as I don't have the tech here to log the tests myself.

My cooler bag from offroadtrailtools . com cost $39.50

Worksfine

:smiley_drive::safari-rig::safari-rig: JIMBO

 

[TreeTopFlyer]

1/2 full fridge

Well, the results are in for the 1/2 full fridge. I thought I had more beer at the house, but I only had a case. Next time I will to 3/4. Not very impressed with the results. But there was one factor that came into play that was never in any of the other test....Angle.

Around noon I started the fridge up. The outside temp was in the mid 70s, right before I stuck the probe in the cooler, i sampled the in-cab temp it was 72. I cranked the frige to #4 and let'r rip. You can see some jump in current, I am attributing this to the vibration while driving. The current draw levels out when I parked and did some grinder work on a little project I was working on. After I was finished and packed up and headed down to the water, again you can see the jump in current.

Once down at the water, I backed up, open the windows and rear hatch/barn doors and proceeded to relax and enjoy the day. I figured with the 10-15mpg south breeze, the fridge was well ventilated. You can see the temperature peaks when I would open the lid to get beer out. Some swings were as much at 10 degrees.

You will immediately notice one glaring fact, the compressor never stopped running. One variable that has changed in my not so scientific laboratory testing conditions is ANGLE. I don't know what the angle was, it was slight, but there was a slope to the shoreline. I am going to harbor freight today and pick up one of those magnetic angle finders and figure out what the angle was I was at yesterday.

Around 6pm, we packed up and went up to the house, here the car was level. Note the flat current curve and the downward slope of the temperature. The temp started dropping once the vehicle was level. Around 7:45 I left to go run and errand, hence the jump in current that I can only attribute to movement of the vehicle. The compressor starts to draw a little more power, the temp drops again by about 7 degrees.

So, a couple of things have me pondering. Does angle really create such a drastic change in temp? Is my compressor acting up? At temp setting #4 it only wants to draw around 1A unless I the vehicle is moving around. Is this the equivalent to hitting a TV on the side of it to make the reception better?

From previous plots I have seen the compressor work just fine. It cycled as expected. On temp setting #4 it was cycling every 10-15 mins. Yesterday's test, the thing ran all day long. Albeit only drawing about 1A/hr it still never shut off. Disturbing. The glass half empty guy(me) says this doesn't seem right. The glass half full guy may say well start and stop on a compressor kills the motor faster than constant running. That's why we have VFDs, soft start controllers, etc.

I don't know the exact age of the unit. I found an online scan of the 630C manual that was dated 1989. So they were at least in production then. I am guessing it was made in the early 90s. The guy I bought it from can't remember, however it was hardly ever used, maybe 2-3 times. The cords still were tie-wrapped.

If the compressor is working properly, as it seemed to have been in Saturday's test, I can only point to the angle variable being throw into the mix. Norcold's site says the compressor can "operate" at an angle up to 30degrees. To me, operate and run the exact same as on level ground are two different things. My fridge did operate at the unknown angle it was at, but it didn't operate like it typically has in the past.

I will repeat the 1/2 to 3/4 full test this afternoon when I get home. But the truck will be level. If it still doesn't cycle, maybe the thermostat switch is faulty, or the compressor may not be up to par. We'll see.

1/2 Full Test