Refrigerator Test

[rubicon327]

Originally Posted by cpaharley2008

Wow, most refers go to 5 in the rv, never seen one higher, is this the stock unit

Yes, older stock manual RM2510 fridge. No fancy digital controls. I did read that the unit thermostat is calibrated for an approximately 40F refrigerator cabinet temperature at mid-range. I'm right about there.

[padlin]

For milk

• Refrigerator temperatures should be between 32F – 39F, the colder the product, the longer it will last....AIM For 33 degrees
• Bacteria (spoilage) starts at 40 degrees

We rarely have dairy products other then cheese and butter, not much can spoil in our trailers fridge. The freezer on the other hand is usually full.

[rubicon327]

Originally Posted by padlin

For milk
• Refrigerator temperatures should be between 32F – 39F, the colder the product, the longer it will last....AIM For 33 degrees
• Bacteria (spoilage) starts at 40 degrees

We rarely have dairy products other then cheese and butter, not much can spoil in our trailers fridge. The freezer on the other hand is usually full.

Thanks. The temperature in our area is supposed to approach 95F on Tuesday. I will do another test on max and see how low I can get the fridge.

[rubicon327]

Still trying a few things to increase refrigerator performance in hot weather. Replaced the propane regulator AND adjusted pressure. Service literature for the fridge said to have 11-12 inches w.c. with no other loads and then with half of trailer BTU’s running it shouldn’t go below 11”. Used a digital manometer to dial it in hooked up to refrigerator test port. Started around 11.3” but it was dropping below 11 with load so adjusted regulator and ended with 12” at fridge test port. Flame looked real healthy and fridge has been performing better. I also recently cleaned the burner and jet.

I also bought an internal fan from RV Cooling Unit Warehouse. Since this is a single door model and the freezer is always very, very cold we removed the internal freezer door. I mounted the fan in the freezer opening to circulate cold air into the refrigerator compartment. This of course makes the freezer warmer, but still stays below freezing. This is just a test but may be a tactic we use in very warm weather. If this proves itself out as being needed I may mount the fan in a modified freezer door and run via a thermostat with a probe in the refrigerator compartment. Otherwise the fan unit will be clipped onto the fridge evaporator as it is designed for.
https://rvcoolingunit.com/Dometic-Ev...-P5444060.aspx

Overall I have now been able to more consistently maintain lower fridge temperatures with higher outdoor temperatures. Hoping this continues.

[MyronL]

How timely is this! It’s really hot out there. Like Rubicon, so hot my 4.3 RM 8551 needed a boost. A couple days ago I decided to add a little computer fan inside, attached to the freezer fins, connected to a rocker switch on the outside of the unit.

But I had to pull the fridge out, then (gulp) drilled a hole in the plastic face for my switch. Of course you could add the switch inside but that would mean opening the door just to turn the fan on. No thermostat involved, strictly manual control. My confusion with LED switch wiring was the bigger issue.

New fan uses a rocker switch with little red LED that’s on when the fan is running. A nice touch but that was my trouble. The switch has 3 poles for 3 wires.
You pull the fridge out, then you see the other trouble this seemingly simple mod just got you into. What an ugly plate of worms. Note, it might be that no two Dometic fridges look alike back there. The owner’s manual leaves plenty of room for guess work. If only I had known about that cooling unit Rubicon used!
Maybe this tutorial will help those who don’t get that.

So this switch has 3 poles for 3 wires.

• Center pole (red) wire goes through a fuse, to the (+) power source, the battery.
• Right brass pole gets wired (yellow) to the (-) negative ground of battery.
• Left silver pole (black) wire connects to positive wire of fan
• Negative wire from fan is connected to the same (-) negative ground of battery.

That’s it. Finding these end points takes a little deductive reasoning but it can be done. Up top on my RM8551 there’s a 5 amp fuse already there. I used existing interior hole to run my two new wires, out to the fridge back, and up top. You must remove the cooling fins. Used thin, but stiff telephone wire. Since it runs alongside the hot exhaust stack I covered the wires with heat resistant tape.

And it all works, but will it make a difference? I don’t know yet.

[rubicon327]

Originally Posted by MyronL

How timely is this! It’s really hot out there. Like Rubicon, so hot my 4.3 RM 8551 needed a boost. A couple days ago I decided to add a little computer fan inside, attached to the freezer fins, connected to a rocker switch on the outside of the unit.

But I had to pull the fridge out, then (gulp) drilled a hole in the plastic face for my switch. Of course you could add the switch inside but that would mean opening the door just to turn the fan on. No thermostat involved, strictly manual control. My confusion with LED switch wiring was the bigger issue.

New fan uses a rocker switch with little red LED that’s on when the fan is running. A nice touch but that was my trouble. The switch has 3 poles for 3 wires.
You pull the fridge out, then you see the other trouble this seemingly simple mod just got you into. What an ugly plate of worms. Note, it might be that no two Dometic fridges look alike back there. The owner’s manual leaves plenty of room for guess work. If only I had known about that cooling unit Rubicon used!
Maybe this tutorial will help those who don’t get that.

So this switch has 3 poles for 3 wires.

• Center pole (red) wire goes through a fuse, to the (+) power source, the battery.
• Right brass pole gets wired (yellow) to the (-) negative ground of battery.
• Left silver pole (black) wire connects to positive wire of fan
• Negative wire from fan is connected to the same (-) negative ground of battery.

That’s it. Finding these end points takes a little deductive reasoning but it can be done. Up top on my RM8551 there’s a 5 amp fuse already there. I used existing interior hole to run my two new wires, out to the fridge back, and up top. You must remove the cooling fins. Used thin, but stiff telephone wire. Since it runs alongside the hot exhaust stack I covered the wires with heat resistant tape.

And it all works, but will it make a difference? I don’t know yet.

Myron: Nice work. If that is the top of your fridge what stops the hot air from behind the fridge from coming over the top and surrounding the fridge? I had a 2” gap that I filled and it made a difference. Is there some type of divider or wall at the rear of your fridge?

These nicer interior units are made by the same company for the larger fridges. I have just enough room for one of these but opted to start with the smaller unit.
https://rvcoolingunit.com/Dometic-3-...-P5672097.aspx

For my fan testing I just ran the wire out through the door and grabbed 12V from an outlet. Going to wire permanently today. Need to figure out a pathway to the back of the fridge. The hole for the thermistor doesn’t look quite large enough.

Do yourself a favor and put a manometer on the fridge test port. Read your manual and adjust to get around 12” w.c. with no other loads. When they factory calibrate a regulator they don’t know the resistance of the system piping it is going on. You want the correct pressure at the fridge burner. I believe this is what made the biggest difference for us.

[MyronL]

When I first pulled the fridge back a few years ago to add my variation to Ron's baffle I added an insulation wall to cover the gap. That interior wire hole is tight but was able to force my solid 2-wire telephone wire through it. I also upgraded the propane regulator to the Marshall Excelsior MGR-253.

[Greg A]

Our fridge got whacked out when using the generator in May and switching back and forth from propane to 120. With the AC running when the Gen was on it caused something to happen and the fridge quit cooling on any mode.
It did recover and after three more trips it has returned to normal operation. Several things I learned from this interlude.
The freezer always worked throughout this period. So we now carry several compact freezer packs that if fridge performance is weak we rotate the freezer packs to the fridge. Works great in maintaining temps in the fridge if needed. Last week trip I did not need them as fridge ran strong the entire week in 95-105 degree heat.
Second thing I’ve learned is the Accurite wireless thermometer, at least mine, is not reliable. I’ve added manual thermometers in both compartments and sometimes the accurite was reporting 8-10 Degrees higher than the manuals. Normally about 2-4degrees higher. The Accurite has wild swings that made me think fridge was failing, it wasn’t.
I’m working on the switch override on the stock external fan, because it never seems to come on, and may add another. For the moment it seems like the fridge had something happen, but is back to normal.

[Patandlinda]

Originally Posted by Greg A

Our fridge got whacked out when using the generator in May and switching back and forth from propane to 120. With the AC running when the Gen was on it caused something to happen and the fridge quit cooling on any mode.
It did recover and after three more trips it has returned to normal operation. Several things I learned from this interlude.
The freezer always worked throughout this period. So we now carry several compact freezer packs that if fridge performance is weak we rotate the freezer packs to the fridge. Works great in maintaining temps in the fridge if needed. Last week trip I did not need them as fridge ran strong the entire week in 95-105 degree heat.
Second thing I’ve learned is the Accurite wireless thermometer, at least mine, is not reliable. I’ve added manual thermometers in both compartments and sometimes the accurite was reporting 8-10 Degrees higher than the manuals. Normally about 2-4degrees higher. The Accurite has wild swings that made me think fridge was failing, it wasn’t.
I’m working on the switch override on the stock external fan, because it never seems to come on, and may add another. For the moment it seems like the fridge had something happen, but is back to normal.

Hi Greg what refrigerator do you have ? Was wondering about the accurate not being accurate too. I think I will put another one for wine coolers in refrigerator . And yes our external Dometic fan never came on so I wired a switch to turn it on and off as needed. Pat

[MyronL]

Greg/Pat-- I do hope to see a picture of how you ran wires to manually switch on your Texas fans back there, overriding, I assume, the thermostat that like mine never seems to click them fans on. I would like my one external switch to run all the fans.

[Patandlinda]

Originally Posted by MyronL

Greg/Pat-- I do hope to see a picture of how you ran wires to manually switch on your Texas fans back there, overriding, I assume, the thermostat that like mine never seems to click them fans on. I would like my one external switch to run all the fans.

Hi Myron I pulled that little temp switch off . I ran wires from 12 volt source in back , over the top of refrigerator , removed carefully the top front refrigerator control panel .cut hole inside closet to put a switch on for fan that never came on ,also added another fan in back, wired from back over refrigerator . Give me a minute and I will find some pictures for you , it has been awhile . Pat

[Patandlinda]

Originally Posted by Patandlinda

Hi Myron I pulled that little temp switch off . I ran wires from 12 volt source in back , over the top of refrigerator , removed carefully the top front refrigerator control panel .cut hole inside closet to put a switch on for fan that never came on ,also added another fan in back, wired from back over refrigerator . Give me a minute and I will find some pictures for you , it has been awhile . Pat

here is some pictures more coming Myron . Pat

[Patandlinda]

Originally Posted by Patandlinda

here is some pictures more coming Myron . Pat

more will follow

[Patandlinda]

Originally Posted by Patandlinda

more will follow

more pictures

[Patandlinda]

Originally Posted by Patandlinda

more pictures

more pictures

[Patandlinda]

Hope these pictures help you Myron . Basically if I can remember ,pulled the refrigerator , insulated the heck out of that refrigerator cabinet . Took the stupid temp switch off . Wired the Dometic fan in the back to my own switch . Added another fan in the chase with a switch . Added a waterproof fan in refrigerator with the switch in the clothes cabinet . Later removed the thermistor and just let it dangle where it lands . All this about 4 years ago and not too much problems since . We can live with it . Oh one more thing bought the fridge guard and install if temps are up 95-pier 100's . I might remove freezer door too. Pat

[MyronL]

Wow, everything is so clean! Great shots, thanks, very helpful. And, I knew it:- no two Dometic fridge rear configurations are built alike. Must give more thought to adding a second switch for my 2 rear fans.

[Greg A]

Originally Posted by Patandlinda

Hi Greg what refrigerator do you have ? Was wondering about the accurate not being accurate too. I think I will put another one for wine coolers in refrigerator . And yes our external Dometic fan never came on so I wired a switch to turn it on and off as needed. Pat

Hey Pat,
I think our model fridge is RMD8555.
Thanks for the pics on the fan setup.

[rubicon327]

Originally Posted by rubicon327

For my fan testing I just ran the wire out through the door and grabbed 12V from an outlet. Going to wire permanently today. Need to figure out a pathway to the back of the fridge. The hole for the thermistor doesn’t look quite large enough.

Wired up the internal fan permanently. Thermistor hole was large enough to get wiring to the back of fridge and connect to 12V power. Left the wiring long enough inside fridge so fan can be easily removed and put in the freezer opening with door removed. It can be hung with two small pieces of gorilla tape. This will only be done if fridge needs a boost in really hot weather.

Myron: I noticed your model has a removable freezer. That’s a neat feature which could be leveraged in hot weather if you are ok with just a (hopefully colder) fridge.

[rubicon327]

Originally Posted by Greg A

The freezer always worked throughout this period. So we now carry several compact freezer packs that if fridge performance is weak we rotate the freezer packs to the fridge. Works great in maintaining temps in the fridge if needed.

Thanks for sharing this. I have thought about doing this exact thing as the freezer is always cold. I’ll try this if I don’t feel like removing freezer door and putting my fan in the opening.

Originally Posted by Greg A

Second thing I’ve learned is the Accurite wireless thermometer, at least mine, is not reliable. I’ve added manual thermometers in both compartments and sometimes the accurite was reporting 8-10 Degrees higher than the manuals. Normally about 2-4degrees higher. The Accurite has wild swings that made me think fridge was failing, it wasn’t.

Yes! I just figured this out too during my testing. I put two sets of sensors in fridge and freezer and a manual in fridge. I just looked at all my numbers and the Acurite averaged 5 degF high in the refrigerator and 3 degF high in the freezer. The worst it was off during one fridge reading was 7 degrees. So that was part of my problem all along. Never trust a cheap pair of temperature sensors!