Anyone Running a Dometic Fridge? 12 or 24v?

[KamikazeKunze]

Hey guys,

i’ve got a lot of my pesky issues taken care of and the interior almost built out on my 1010. I am having one weird issue with my new Dometic CFX95DZ.
it runs great off of 110v using a 24v 3000w inverter. It runs great when the truck is running (compressor kicks on and stays on) either with 12v from cig socket or 24v from the back box.
it will not start or the compressor won’t kick on unless the truck is running.....kind of defeats the purpose of a low voltage fridge.
currently running it off the starter batteries but also hooked up a second 24v “battery” effectively doubling my ah’. Still the same result.

I’m trying to determine if it’s a crap compressor in the fridge or if I have another issue. Not sure how these would run if a person overnighted in their car or truck with one battery.

thanks again for any and all input.

 

[chevymike]

Check your battery voltage without the engine running. It could be below the low battery voltage cut off set point on the fridge. With the engine running it is likely getting a voltage that is high enough to allow it to start the compressor.

Not familiar with that model to know if you can adjust the low voltage cut off. I know some fridge models are adjustable.

Edit: looking it up, appears it has a phone app that will allow you to adjust that cut off point.

 

[Bill Nutting]

I don’t run any accessories off my main 24 volt batteries unless I’m driving . I don’t want to run them down and not be able to start the motor.
My fridge runs on 120 v ac or propane . I lived in
my truck for six weeks last summer. I ran on propane almost all of the time. If I had a place to plug in, i would run it on 120 v. I used 1.5 20 lb bottles of propane for the whole trip. I was concerned about running propane while driving but the flame is a little bigger than a pilot light. There are folks that say never use propane while driving others say it’s ok. I am going to install a 24 volt inverter to run on ac while driving, but I had no issues last summer. I was even able to make ice with it.

 

[SCSG-G4]

Check your voltage when it tries to start. The compressor starting draw is high and I think the Dometic supplied 12/24 V cable is a bit flimsy (IMHO) at 16 ga wire. The fuse in that cable is rated at 8 amps for 12 volts or 96 watts, the higher the voltage of the batteries , the lower the ampere draw will be. Don't check at the battery, check where it goes into the unit - that is where the load is at.

 

[KamikazeKunze]

Check your battery voltage without the engine running. It could be below the low battery voltage cut off set point on the fridge. With the engine running it is likely getting a voltage that is high enough to allow it to start the compressor.

Not familiar with that model to know if you can adjust the low voltage cut off. I know some fridge models are adjustable.

Edit: looking it up, appears it has a phone app that will allow you to adjust that cut off point.

ChevyMike - my 12v circuit shows 12.67v my batteries show 25.5 alternator bumps it to 27v, my investor indicates 25 and goes to 27.1 when running

 

[KamikazeKunze]

Check your voltage when it tries to start. The compressor starting draw is high and I think the Dometic supplied 12/24 V cable is a bit flimsy (IMHO) at 16 ga wire. The fuse in that cable is rated at 8 amps for 12 volts or 96 watts, the higher the voltage of the batteries , the lower the ampere draw will be. Don't check at the battery, check where it goes into the unit - that is where the load is at.

SCSG-G4 - I believe we had the truck running and the fridge running and compressor off. Then we shut the truck off and adjust the temp to kick on the compressor. The app would show voltage at 25 and change, then get pulled down to 23.2 and start the compressor “bare;y” and shut off when set to low battery safety About 2-3m later.

 

[KamikazeKunze]

I don’t run any accessories off my main 24 volt batteries unless I’m driving . I don’t want to run them down and not be able to start the motor.
My fridge runs on 120 v ac or propane . I lived in
my truck for six weeks last summer. I ran on propane almost all of the time. If I had a place to plug in, i would run it on 120 v. I used 1.5 20 lb bottles of propane for the whole trip. I was concerned about running propane while driving but the flame is a little bigger than a pilot light. There are folks that say never use propane while driving others say it’s ok. I am going to install a 24 volt inverter to run on ac while driving, but I had no issues last summer. I was even able to make ice with it.

Bill - I hear you. I am trying to stay away from using any propane in this build. I will be running additional batteries with a manual disconnect to separate the starting batteries, solar in the future as well.
I’m thinking I am either under batteried or the compressor is “faulty” and is pulling more amps than it should. Going out to test it again while temping up a third 24v battery system as well as running four 12v batts in parallel.

 

[SCSG-G4]

SCSG-G4 - I believe we had the truck running and the fridge running and compressor off. Then we shut the truck off and adjust the temp to kick on the compressor. The app would show voltage at 25 and change, then get pulled down to 23.2 and start the compressor “bare;y” and shut off when set to low battery safety About 2-3m later.

That sounds like low voltage, no load should be closer to 27 volts and that compressor should only drop it down to 24.5-25 volts on startup. If it's a new unit from Dometic, contact them! I have a small (CC40) unit and so far no problems.

 

[chevymike]

Yeah, it doesn't sound like a capacity issue, since that is related to how many hours you can run it. Voltage is the main issue and if it is dropping down to 23.5, that is likely tripping the low voltage cut off. If you're dropping below 24 volts, you batteries are low on charge, especially if the fridge works fine with the engine running.

 

[KamikazeKunze]

Yeah, it doesn't sound like a capacity issue, since that is related to how many hours you can run it. Voltage is the main issue and if it is dropping down to 23.5, that is likely tripping the low voltage cut off. If you're dropping below 24 volts, you batteries are low on charge, especially if the fridge works fine with the engine running.

I think you’re correct. The fridge has been in my Ram Cummins all night unplugged and is at 23°. It fridge starts with the truck off and shows 14v. When the compressor starts it pulls all the way down to 9.6v then shuts off.

In retrospect, others on YT running this unit have solar and a house battery bank. Both of which I have yet to be installed (funds).
my GF jus6 bought the fridge for use and we thought it would at least make it through the night on 12 or 24v running two house batteries and having the starter batteries isolated. We may have to go to a smaller unit ( smaller compressor) maybe. Not sure yet. I’ll call Dometic tomorrow and see what they say.

 

[cruzer747]

I have that fridge, just run it off a leisure 12v battery and have never had any issue.

This sounds like it could be a wire gauge issue as mentioned above. How many total feet of wire are you running from the fridge to the power supply and what gauge? I cut the stock wire as close as I could and ran to a dedicated fuse about 14' of 10G wire. If you want to test the theory you can supply a parallel wire from the same source (jumper cable would work fine). It could also be a bad connection if you are using crimp fittings. I am almost positive I erred on the side of caution and soldered this as well as crimped.

Also this is a great amp chart for quick reference.

Part 1: Choosing the Correct Wire Size for a DC Circuit - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

edit: I also know that at my length is overkill but it is not going overboard.

Since you are pulling 24v the amps should be half but the distance to your batteries is probably double so it would be worth while getting a jumper cable to give you a temporary bigger wire and if it cures your problem you can know pulling a bigger wire is the solution and not just throwing $ at the problem.

 

[Bill Nutting]

I agree with cruzer747. I use 10 awg Wire for my 12 and 24 volt feeds to fuse panels or accessories with high current demands. It’s just good insurance. I buy 10 or 12 awg extension cords and cut the ends off. I like using wire that is flexible in my truck because there is a lot of vibration . All of my 120 v ac outlets are wired with 12 awg wire. I was surprised to find 14 awg Romex used in a trailer I stripped for appliances. Solid copper wire in a moving vehicle just doesn’t make sense to me. To see if your wire gauge is the problem, measure the voltage at the source and at the load when it starts up. If you see voltage drop at the load, your wire is too small.

 

[Tow4]

I think it's fairly common to use Romex in RVs for the AC wiring. I have a 2005 Airstream classic and it has solid copper wire for the AC circuits.

I used Romex in my M373 build. It's easy to work with and inexpensive. As long as you have the proper strain relief you should not have any vibration related issues.

 

[SCSG-G4]

So, why do I use 10 ga extension cords? Because i can't find anyone who makes 8 ga ones and sells them locally! This is a re-hash of the AC/DC argument of over a century ago. DC voltage is heavily dependent on wire size, AC not nearly as much. New 12 volt car batteries should read about 13.5 volts, at the terminals, a dozen feet away on 16 ga wire the reading might be 12 volts or less under load. That is why battery to starter cables are so big (and usually fairly short).

 

[CARMAN]

You may want to research on the expedition portal. They are big time on this subject.

 

[KamikazeKunze]

I have that fridge, just run it off a leisure 12v battery and have never had any issue.

This sounds like it could be a wire gauge issue as mentioned above. How many total feet of wire are you running from the fridge to the power supply and what gauge? I cut the stock wire as close as I could and ran to a dedicated fuse about 14' of 10G wire. If you want to test the theory you can supply a parallel wire from the same source (jumper cable would work fine). It could also be a bad connection if you are using crimp fittings. I am almost positive I erred on the side of caution and soldered this as well as crimped.

Also this is a great amp chart for quick reference.

Part 1: Choosing the Correct Wire Size for a DC Circuit - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

edit: I also know that at my length is overkill but it is not going overboard.

Since you are pulling 24v the amps should be half but the distance to your batteries is probably double so it would be worth while getting a jumper cable to give you a temporary bigger wire and if it cures your problem you can know pulling a bigger wire is the solution and not just throwing $ at the problem.

So, the power junction block in the box on the drivers side is where I’m hooking to. I used 6 or 8 gauge jumper cables cut and run from there through the floor drain holes and up the other side to my kitchen cab. About 8’ long. I’m tapping into that power before I hit my 24v to 12v converter for all other 12v needs. I’m running solid wire 14 gauge to the socket for the fridge. I could see how the added length would strain things on start up just blow away by how hungry the fridge is when the compressor kicks on.


i was able to consistently get good start up and run time results yesterday with hooking up two more 12v deep cycle batteries in series to boost the starting batteries but still only mana 10m of compressor running on medium battery saver mode before it quit. Pulled down too 23.6 volts and shut off. Yet there was enough battery left to fire up the inverter and run it off a/c as well as start the truck.

still really baffled.
on a side note. We decided the unit was ever so slight.y too big for where we want it to live in the rig. We may return it and get the cfx75dz or the ICECO 63DZ which uses the Danfoss compressor

if anything I feel better about things, I’m just under batteried.

I’ll checkout the EP sight as well.

 

[KamikazeKunze]

I agree with cruzer747. I use 10 awg Wire for my 12 and 24 volt feeds to fuse panels or accessories with high current demands. It’s just good insurance. I buy 10 or 12 awg extension cords and cut the ends off. I like using wire that is flexible in my truck because there is a lot of vibration . All of my 120 v ac outlets are wired with 12 awg wire. I was surprised to find 14 awg Romex used in a trailer I stripped for appliances. Solid copper wire in a moving vehicle just doesn’t make sense to me. To see if your wire gauge is the problem, measure the voltage at the source and at the load when it starts up. If you see voltage drop at the load, your wire is too small.

yes sir. I’ll use bigger gauge multistrand wire for the final connection as well.

 

[cruzer747]

Pulled down too 23.6 volts and shut off.

That is 11.8v per battery. Where and how are you taking this measurement? If you draw your batteries down past that you are starting to harm them. I would say that even this is too low. Is this reading taken under load? (sounds like it) if so what do they come up to after 30 seconds of no load? It really sounds like the fridge is operating as designed at this point.

I just took some measurements for you....my 100ah AGM house battery is at 12.6v. It has a short run to a fuse panel and then to a switch, and then the run to the fridge. Fridge on the house battery drops to 12.4v (at the battery) The amps the compressor is drawing is about 3.5A (probably a brief spike at startup but my DVM could not detect it so that would be VERY brief) Also doing this amp test with my DVM inline at the fridge the extra resistance sent the fridge into a low voltage shutoff..(could have been my ground jumper was also adding resistance). At my switch I am seeing 12.2v(running). Running at the fridge with my normal plugin I spiked in to the power there and see 12.1v (motor running). The switch and fuse panel are obviously points of resistance but I am still able to feed the fridge above what it deems safe as far as my batteries health.

Ultimately you need to look at what your batteries are at no load and load (at the batteries) and then check loaded voltage "at the fridge" 3.5A is pretty dang good for a fridge and on 24V you would likely see about 1.5-2A.

You should sort your stuff out before you install another fridge with a under par setup (maybe a bad connection somewhere, maybe tired batteries... either way the fridge needs to see 12v or better under load or it will protect your batteries. 23.6 is 11.8. If that is taken at the source your batteries are tired. Maybe consider taking them and having them individually load tested. A bad one can cause havoc like this. Also I am sure you are planning on it but a house battery is great insurance for not getting stranded somewhere camping way out in the boonies!

 

[KamikazeKunze]

That is 11.8v per battery. Where and how are you taking this measurement? If you draw your batteries down past that you are starting to harm them. I would say that even this is too low. Is this reading taken under load? (sounds like it) if so what do they come up to after 30 seconds of no load? It really sounds like the fridge is operating as designed at this point.

I just took some measurements for you....my 100ah AGM house battery is at 12.6v. It has a short run to a fuse panel and then to a switch, and then the run to the fridge. Fridge on the house battery drops to 12.4v (at the battery) The amps the compressor is drawing is about 3.5A (probably a brief spike at startup but my DVM could not detect it so that would be VERY brief) Also doing this amp test with my DVM inline at the fridge the extra resistance sent the fridge into a low voltage shutoff..(could have been my ground jumper was also adding resistance). At my switch I am seeing 12.2v(running). Running at the fridge with my normal plugin I spiked in to the power there and see 12.1v (motor running). The switch and fuse panel are obviously points of resistance but I am still able to feed the fridge above what it deems safe as far as my batteries health.

Ultimately you need to look at what your batteries are at no load and load (at the batteries) and then check loaded voltage "at the fridge" 3.5A is pretty dang good for a fridge and on 24V you would likely see about 1.5-2A.

You should sort your stuff out before you install another fridge with a under par setup (maybe a bad connection somewhere, maybe tired batteries... either way the fridge needs to see 12v or better under load or it will protect your batteries. 23.6 is 11.8. If that is taken at the source your batteries are tired. Maybe consider taking them and having them individually load tested. A bad one can cause havoc like this. Also I am sure you are planning on it but a house battery is great insurance for not getting stranded somewhere camping way out in the boonies!

So my initial voltage reading is in the Dometic app itself. So it reads it accurately at the start. At the batteries I read 25.5 when running it’s 27v.
at the box in the back it reads 25.5 and where I’m tapping into the power it reads the same. Even at the unscrewed plug end at the factory 12v24v socket wire.
I’ll have to test again and take amp readings as well. I agree addressing my last leg of wire is mandatory. I’m using smaller gauge solid wire for the last leg. I’ll test it again today but using jumper cables. Albeit they’ll add an additional 10-12th in length to the equation.
that for all the input.

 

[cruzer747]

At the batteries I read 25.5 when running it’s 27v.

I hope I was clear in my post that my "running" measurements were the fridge running, I never started the truck at all.

That said Id be curious to see what the voltage was if you spike in to the cord near the fridge. It should stay above 24v at that point (truck off fridge on) and then unplug it, cobble up a short ground (top prong, I just used a bent spade connector) and use your DVM to connect between the bottom prong and cord and get a read on amps.

And since your problem is when the truck is not running all your tests should be truck not running as well. As far as the jumper cable.... no need to disconnect existing wire, you can just clip it on and add more path to power. Also grounding it sooner than later is good (mine is grounded at around 2' with the existing cable.