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 > absorption refrigerator out of level, boiler temp control

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otrfun

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Posted: 11/16/22 11:05am Link  |  Quote  |  Print  |  Notify Moderator

SJ-Chris wrote:

. . . I would guess the Fridge Defend is designed such that you can adjust those temperature settings for detecting high temp . . .
-Chris
The Fridge Defend high-temp cut-off is adjustable (at least on v4 and v5). Instructions how to adjust it can be downloaded at the FD website.

The FD logs the maximum boiler temp and number of times the high-temp cut-off has activated (since the last user reset). The boiler temps on our Dometic DM2663 typically hover between 185-190c/365f-374f (on propane, 120vac, and 12vdc). After a year or so of travel with zero effort to make sure our truck camper was level, the FD logged a max boiler temp of 207c/405f (we reset it). Just to be on the safe side we also reset/lowered the factory default high temp cut-off from 217c/423f to 202c/396f. After another two years of travel, max boiler temp has only risen as high as 197c/387f. Lastly, just to make sure all was well after all these resets, we manually heated the FD boiler sensor above the high-temp cut-off. The FD cut-off 12vdc power to the fridge control board and logged it.

SJ-Chris

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Posted: 11/16/22 11:48am Link  |  Quote  |  Print  |  Notify Moderator

dougrainer wrote:

Chris, My comments come from 43 years as a RV technician. ALL are solid based on MY travels and what I have seen about RVer parked at roadside areas and eateries and even in neighborhoods. TRAVELING on slopes and inclines does NOT cause an out of level problem as the movement overcomes the problem of the Ammonia system. The overheat disc is a SAFETY install. Has nothing to do with stopping a potential blocking problem. IF the out of level or even a large blockage happens, running the Refer, can cause a burst of a cooling unit at its weakest points. IF on LP, the flame can ignite the spewing ammonia and cause a fire. So after lawyers sued Dometic and Norcold 25 years ago, both installed overheat disc's. There was a massive recall over 20 years ago for millions of refers to have the overheat kits installed. ALL new refers since then had the kits installed at build. Doug


Good stuff. I'm happy to hear that out of level problems are not an issue while driving because of the movement. One less scenario to worry about.

Regardless of HOW OFTEN parking off-level happens, we can both agree that it does happen.

I understand that the overheat discs are to help with a catastrophic overheating situation. Just seems strange to me that they would let the boiler get 300*F-400*F OVER the "normal" operating temperature. Why? Why don't they cut off the power at 100*F over the normal operating temperature? 750*F-800*F just seems like it is asking for trouble.

Just curious...Do you agree that a high temp thermostat (or Fridge Defend) is a reasonable modification to add some protection against overheating (and set it to cut power at something like 410*F-420*F, and turn it back on once the boiler gets down to ~330*F)? I'd be interested to hear if you think it is worthwhile. My DIY fix will cost me ~$25.

Regards,
Chris


San Jose, CA
Own two 2015 Thor Majestic 28a Class C RVs

SJ-Chris

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Posted: 11/16/22 11:58am Link  |  Quote  |  Print  |  Notify Moderator

otrfun wrote:

SJ-Chris wrote:

. . . I would guess the Fridge Defend is designed such that you can adjust those temperature settings for detecting high temp . . .
-Chris
The Fridge Defend high-temp cut-off is adjustable (at least on v4 and v5). Instructions how to adjust it can be downloaded at the FD website.

The FD logs the maximum boiler temp and number of times the high-temp cut-off has activated (since the last user reset). The boiler temps on our Dometic DM2663 typically hover between 185-190c/365f-374f (on propane, 120vac, and 12vdc). After a year or so of travel with zero effort to make sure our truck camper was level, the FD logged a max boiler temp of 207c/405f (we reset it). Just to be on the safe side we also reset/lowered the factory default high temp cut-off from 217c/423f to 202c/396f. After another two years of travel, max boiler temp has only risen as high as 197c/387f. Lastly, just to make sure all was well after all these resets, we manually heated the FD boiler sensor above the high-temp cut-off. The FD cut-off 12vdc power to the fridge control board and logged it.


Thank you for providing your data! Very interesting to read.

FD default is set to 217*C...good to know. On their video it looks like making sure the boiler doesn't get over ~220-225*C is important.

Your max of 207*C over a 3 year period is good to know. It is also pretty reassuring in general for all those absorption refrigerators out there (especially since you didn't do anything extra to try to keep things level).

I will likely set my high temp thermostat to 210*C (410*F) to turn off.

-Chris

dougrainer

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Posted: 11/16/22 05:48pm Link  |  Quote  |  Print  |  Notify Moderator

Yes, a ARP type device in my opinion is a MUST HAVE modification. Until they were developed years ago, there was no device to help prevent cooling unit destruction. Doug

JBarca

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Posted: 11/16/22 09:37pm Link  |  Quote  |  Print  |  Notify Moderator

Chris, I have been following your post.

I did review the ARP system a while back, just never made it to installing any, yet. I called and talked with them today. They are very down to earth, and they are a, know what they are doing company.

I am going with the Fridge Defend V5.11 with the fan control. I want to add the defrost fans inside the fridge and to cycle them you need the fan control version. The V5.11 has an alarm, so you know when you have a problem and you and tweak the settings as needed. Since most all the fridges I work on are older, there may be some level of coolant damage from prior owners, so the fridge may have limited life, but having the fire safety part is a big plus.

Since I already have a fan up on the roof vent and a thermal disk switch to turn it on and off, I may switch the roof vent fan to the Fridge Defend. You just parallel the inside defrost fans with the roof vent fans. The ARP fan relay is rated at 20 amps, plenty for the milli amp fans I use, and the ARP defrost fans.

Another reason for the Fridge Defend not yet mentioned is cold weather. I know you may not camp in cold down to freezing, and below, but in our area, freezing temps are here and we do winter camp.

If you want to get close to 32F outside or go below, the fridge as it stands in the stock configuration will slow down and may stop working. The heating may not stop, but the fluid can slow down flowing from what I have read. It seems Dometic does offer a lower vent hood that has some blocked off vents to lower the amount of cold air entering.

This Dometic lower vent is made for cold weather, just they do not list much else or fit the older Dometic vent frames. Norcold sells a cold weather kit to heat up a certain return tube on the cooling coil. Here is one of them. https://www.amazon.com/Norcold-634913-Cold-Weather-Kit/dp/B00T36VI30

I have not been able to find Dometic offering that heat strip. By using the heat strip on the Norcold and helping to reduce the cold air intake, it is reported you can go down to 0F. Some folks use an incandescent light bulb in the outside compartment.

The ARP system will help to shut off the boiler heat if the coolant stops flowing due to the cold weather for any reason.

Doug may be able to add some more to this and if he knows if Dometic offers a cold weather kit or do you just use the Norcold one? Most all of the older campers I restore have RM2652 fridges that I service.

Thanks

John

* This post was edited 11/16/22 09:57pm by JBarca *


John & Cindy

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SJ-Chris

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Posted: 11/16/22 11:15pm Link  |  Quote  |  Print  |  Notify Moderator

Hi John. Good post.

JBarca wrote:

Chris, I have been following your post.

I did review the ARP system a while back, just never made it to installing any, yet. I called and talked with them today. They are very down to earth, and they are a, know what they are doing company.


I have visited the ARP site and seen many many posts from the makers of Fridge Defend on some online forums. It seems like they have a good product AND they seem to be genuinely passionate about safety. Very knowledgeable. Seem like nice people. Seems like they want to help people.


JBarca wrote:


I am going with the Fridge Defend V5.11 with the fan control. I want to add the defrost fans inside the fridge and to cycle them you need the fan control version. The V5.11 has an alarm, so you know when you have a problem and you and tweak the settings as needed. Since most all the fridges I work on are older, there may be some level of coolant damage from prior owners, so the fridge may have limited life, but having the fire safety part is a big plus.


If you are looking for an integrated system that controls the boiler temp, the fan(s) behind the refrigerator, and fans inside the refrigerator, then the Fridge Defend is definitely for you.

I'm not anti-Fridge Defend...I think they have a great product. But I'm a DIYer and I enjoy tinkering with modifications. I personally believe that from a safety standpoint, the most important thing on these absorption refrigerators is to keep the boiler under 220*C. I believe a simple high temp thermostat can easily accomplish this task, and they only cost $20. If I only had 1 RV I would probably still just buy a Fridge Defend. But I've got 3 RVs. So if I can implement this DIY fix it will save me 3x the money.

JBarca wrote:



Since I already have a fan up on the roof vent and a thermal disk switch to turn it on and off, I may switch the roof vent fan to the Fridge Defend. You just parallel the inside defrost fans with the roof vent fans. The ARP fan relay is rated at 20 amps, plenty for the milli amp fans I use, and the ARP defrost fans.



I'm not sure why you would want to tie your roof vent fan to your inside defrost fans. They aren't related in function. The Fridge Defend has a feature to control fan(s) that are placed behind the refrigerator to provide extra cooling to the coils behind the fridge and it seems like you'd want to use these controls for your vent fan.
(Side note: I'm also planning a DIY modification for putting fans behind the refrigerator controlled by a separate thermostat.)

JBarca wrote:


Another reason for the Fridge Defend not yet mentioned is cold weather. I know you may not camp in cold down to freezing, and below, but in our area, freezing temps are here and we do winter camp.

If you want to get close to 32F outside or go below, the fridge as it stands in the stock configuration will slow down and may stop working. The heating may not stop, but the fluid can slow down flowing from what I have read. It seems Dometic does offer a lower vent hood that has some blocked off vents to lower the amount of cold air entering.

This Dometic lower vent is made for cold weather, just they do not list much else or fit the older Dometic vent frames. Norcold sells a cold weather kit to heat up a certain return tube on the cooling coil. Here is one of them. https://www.amazon.com/Norcold-634913-Cold-Weather-Kit/dp/B00T36VI30

I have not been able to find Dometic offering that heat strip. By using the heat strip on the Norcold and helping to reduce the cold air intake, it is reported you can go down to 0F. Some folks use an incandescent light bulb in the outside compartment.

The ARP system will help to shut off the boiler heat if the coolant stops flowing due to the cold weather for any reason.

Doug may be able to add some more to this and if he knows if Dometic offers a cold weather kit or do you just use the Norcold one? Most all of the older campers I restore have RM2652 fridges that I service.

Thanks

John


I will admit, I had not thought about ultra cold weather usage. I have been camping down to ~30*F and didn't have any issues with the refrigerator/freezer temps. I don't have immediate plans to camp down to 0*F. I'm guessing that the boiler getting hot to the touch does a fair job heating the cavity/space behind the refrigerator. But I can see how if it were 0*F outside and that cool air is being pulled in then maybe it could affect the cooling unit functionality. If I was going to camp in such temps I think I would consider putting something along the back side of the rear vent to limit the amount of air that could enter. That seems like it would allow the heat of the boiler to keep the air behind the refrigerator warm enough for proper operation. Not sure if that is true or not, but I'd start there.

I am big on safety. I do think it is important for safety and also to help protect your cooling unit from overheating damage to have some sort of high temp thermostat (either DIY or Fridge Defend) on your boiler to keep it below 220*C (428*F).

-Chris

dougrainer

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Posted: 11/17/22 08:04am Link  |  Quote  |  Print  |  Notify Moderator

The best way in sub 20 (F) weather is just a 120 volt 40 watt incandescent light bulb installed in the area behind the refer. In sub 20 degree weather the Refer will not cool at all. The sub cold weather kits I have never seen or ever needed. Texas is not an area that would require them. Doug

otrfun

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Posted: 11/17/22 10:47am Link  |  Quote  |  Print  |  Notify Moderator

SJ-Chris wrote:

. . . I'm a DIYer and I enjoy tinkering with modifications . . . I believe a simple high temp thermostat can easily accomplish this task, and they only cost $20. If I only had 1 RV I would probably still just buy a Fridge Defend. But I've got 3 RVs. So if I can implement this DIY fix it will save me 3x the money.
Have you found a suitable 200c sensor and control board combination that operates on 12vdc? IMO realworld temperature accuracy and overall, proven reliability may potentially be the biggest hurdle.

Who wouldn't love a reliable, low-cost alternative to the $200+ FD?! [emoticon]

SJ-Chris

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Posted: 11/17/22 11:39am Link  |  Quote  |  Print  |  Notify Moderator

otrfun wrote:

SJ-Chris wrote:

. . . I'm a DIYer and I enjoy tinkering with modifications . . . I believe a simple high temp thermostat can easily accomplish this task, and they only cost $20. If I only had 1 RV I would probably still just buy a Fridge Defend. But I've got 3 RVs. So if I can implement this DIY fix it will save me 3x the money.
Have you found a suitable 200c sensor and control board combination that operates on 12vdc? IMO realworld temperature accuracy and overall, proven reliability may potentially be the biggest hurdle.

Who wouldn't love a reliable, low-cost alternative to the $200+ FD?! [emoticon]


I bought this high temp thermostat to try out.

https://www.amazon.com/gp/product/B09TT7VWCK

Cost was $20. One thing that looked interesting is that it has an app so you can track things on your phone, export the data, etc. I'm not sure, but I don't think Fridge Defend does that. If the app works, that will just be a bonus (...I couldn't find it in the app store and I was paranoid about scanning their QR code).

I bought a tiny clear plastic box for it to go in. The screw in probe housing was easy to slide down the wire so that there is just a cylinder probe end. I will attach it to the boiler tube with a hose clamp like this:
https://www.homedepot.com/p/Everbilt-1-2-1-1-4-in-Stainless-Steel-Hose-Clamp-6712595/202309385

I hope to get to this project in the next couple of weeks. I'll keep you posted.

-Chris

* This post was edited 11/17/22 12:15pm by SJ-Chris *

Vintage465

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Posted: 11/18/22 07:45am Link  |  Quote  |  Print  |  Notify Moderator

I guess today I'm going to "be that guy"........I grew in a family that owned an RV sales and repair shop.....in the days that if you ran your fridge out of level(propane or electric)it would lockup in 20 minutes. The law was "not level, don't light". The repair was to remove the fridge turn it on it's head for 24 hours, reinstall and fire it up...level of course. 99% of the time it fixed it. So my question is, why hypothetically set your self up to do damage to your fridge when it just needs to be level. Yes I get it that driveways and streets aren't level, but.........I'll stick by "not level, don't light".


V-465
2013 GMC 2500HD Duramax Denali. 2015 CreekSide 20fq w/450 watts solar and 465 amp/hour of batteries. Retired and living the dream!

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