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 > absorption refrigerator out of level, boiler temp control

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SJ-Chris

San Jose, Ca

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Posted: 11/11/22 07:21pm Link  |  Quote  |  Print  |  Notify Moderator

Safety is important!


Consider a scenario where someone parks for the night (or for several days) on a steep driveway or side of the road on a hill and they are very unlevel. Assume they have their absorption refrigerator on. Without some form of temperature protection (ie. Fridge Defend, or DIY thermostat solution) this seems like it could be a dangerous situation (fridge damage and/or fire). I sometimes let others use my RVs. I tell them the refrigerator needs to be level, but most non-RVers don't really understand the importance, or they don't care because the RV isn't theirs.


I have seen from multiple posts and websites, that under "normal" operation of a "level" absorption refrigerator the boiler temperature will be ~180-190*C with either propane or plugged in.


I understand that when your refrigerator is out of level by too much (more than 3% refrigerator side-to-side or 6% refrigerator front-to-back) then the gravity functionality of some of the internal liquids in your cooling unit can stop flowing where they are supposed to flow. This can cause (blockage?) the boiler temperature to increase. Once it gets "too hot" (...I've seen on Fridge Defend's video that value is around 225*C) boiling can happen and damage can occur.


Q1: Is it accurate to say that as long as the boiler temperature is kept under some value (220*C? 210*C? 205*C?) your cooling unit will not get damaged/corroded and it will unlikely cause a refrigerator fire?


Q2: If your refrigerator is out of level (more than 3% / 6%) and continues to run, but a thermostat (or Fridge Defend) keeps the boiler from going over say 210*C, what will happen? Imagine a thermostat that cuts off refrigerator power at 210*C but then turns the refrigerator back on at 170*C and the boiler temp floats back and forth between 170*C and 210*C but the refrigerator is well out of level. What will happen? Does cooling stop because the liquids cannot flow where they need to flow? Does pressure in the system keep the fluids flowing even if off level? Does the internal temperatures of the interior of the freezer/refrigerator climb to ambient outside temperatures?


Q3: Does anyone have any examples of when their boiler got up to 300*C, 400*C, etc. Can it get that hot under some strange scenarios?


What I'm planning on doing is a DIY modification where a high temp thermostat will turn off the refrigerator once the boiler temp hits some value (ie. 210*C) and then turn it back on once it drops back down to 170*C. This will act as a high temperature protector on the boiler. Under normal operation, the boiler temp will likely not get over 190*C so things will work as they should. In the event that the refrigerator gets unlevel (or some other problem) and the temps start climbing, the thermostat will shut it off before it gets dangerous. Does anyone see anything wrong with simply cutting off refrigerator power if it hits 210*C and then restoring power once it has cooled back down to 170*C? Seems reasonable to me. Just want to check to see if I'm missing anything.


For safety reasons, I think most people with an absorption refrigerator should have something to cut off an overheating boiler situation (either a Fridge Defend or DIY thermostat) to reduce the risk of damaging their cooling unit and/or starting a fire (worst case scenario). Maybe the risk is small(?), but my DIY fix will likely only cost me $25 and an hour of time.


Thoughts?
Chris


San Jose, CA
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QCMan

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Posted: 11/11/22 07:48pm Link  |  Quote  |  Print  |  Notify Moderator

Another route that may help your issue is to put electronic levels in the unit and set them so the fridge will not get power unless it is within the limits for operation.


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SJ-Chris

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Posted: 11/11/22 08:06pm Link  |  Quote  |  Print  |  Notify Moderator

QCMan wrote:

Another route that may help your issue is to put electronic levels in the unit and set them so the fridge will not get power unless it is within the limits for operation.


I considered that option. But it occurred to me that the refrigerator boiler can possibly overheat for reasons not related to being unlevel. Therefore, having protection (thermostat) on the boiler itself seemed like a catch-all for any type of overheating.

-Chris

RickLight

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Posted: 11/11/22 08:25pm Link  |  Quote  |  Print  |  Notify Moderator

You might double check your manual.

Mine says 3/6 degrees not percent. In another spot it says "comfortable to live in" which can be misinterpreted but I think is easily understood.


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SJ-Chris

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Posted: 11/11/22 08:59pm Link  |  Quote  |  Print  |  Notify Moderator

RickLight wrote:

You might double check your manual.

Mine says 3/6 degrees not percent. In another spot it says "comfortable to live in" which can be misinterpreted but I think is easily understood.


I'm not worried about refrigerator operation anytime someone is actually CAMPING in the RV. Because when someone is camping in the RV they will naturally try to make the RV somewhat level for sleeping and walking around. Most campsites are not off by 3 or 6 degrees. 3 or 6 degrees is actually quite a bit of an angle.

I think the most likely scenario to avoid would be one where someone parks on a steep driveway or parks on a road on a hill. In those situations, the refrigerator can be wildly off-level as people aren't necessarily parking there to camp/sleep but it could be there for a day or more. Or maybe driving up a long steep grade, or break down on such a grade. Most people wouldn't think about their refrigerator in such a situation.

I'm curious to know....if someone was parked significantly off-level and the boiler temperature was cut off at 210*C then back on at 170*C, what would happen to the temps inside the freezer and refrigerator?

-Chris

MFL

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Posted: 11/12/22 08:04am Link  |  Quote  |  Print  |  Notify Moderator

Chris...that is an interesting read.

My thought...this is an example of over thinking things.[emoticon]

As mentioned, while camping, likely never a problem, due to comfortable level needed.

I've often noticed campers parked along the street, in front of owners home. I see the 100' 16ga cord running out to it. I think most likely to run fridge, while preparing for upcoming departure. While 2 wheels are at the crown of the street, and the other 2 next to curb, quite a bit off/level. My other thought is how much electric are they trying to pull through that length of light duty cord? Is the converter/charger operating at peak? Are they trying to run the AC also? Many people don't have a clue! Somehow most seem to get by without issues.

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dougrainer

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Posted: 11/12/22 08:51am Link  |  Quote  |  Print  |  Notify Moderator

Out of Level and overheating will do just 1 thing---DESTROY(block) the cooling unit. There is NO way for a fire to happen. Both Dometic and Norcold have installed overheat temp disc's for the past 23 years. So, if it overheats, the unit trips the disc and shuts off all power to the refer. BUT, the damage to the cooling unit has already happened. If I had a rental or was dumb enough to let friends and family use my RV, I would install the ARP device . This keeps anybody from operating the refer when it starts to overheat. Doug

opnspaces

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Posted: 11/12/22 09:14am Link  |  Quote  |  Print  |  Notify Moderator

The problem with out of level is the refrigerant can pool and then cool in the upper tubes. Once cooled it can harden and block off the passage. Once hard there is no way to dissolve the deposits and you have to replace the cooling unit. This is typically not a one and done damage issue. It is usually cumulative and happens over time with repeated operation of the refrigerator off level.


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SJ-Chris

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Posted: 11/13/22 12:28am Link  |  Quote  |  Print  |  Notify Moderator

MFL wrote:

Chris...that is an interesting read.

I've often noticed campers parked along the street, in front of owners home. I see the 100' 16ga cord running out to it. I think most likely to run fridge, while preparing for upcoming departure. While 2 wheels are at the crown of the street, and the other 2 next to curb, quite a bit off/level. My other thought is how much electric are they trying to pull through that length of light duty cord? Is the converter/charger operating at peak? Are they trying to run the AC also? Many people don't have a clue! Somehow most seem to get by without issues.

Jerry



I agree with the "long extension cord to the house" comments. In each of my RVs I have a heavy duty extension cord to try to limit problems. I think running the AC or microwave could/would be the biggest risk in the scenario you mention above (large current = large voltage drop potential). If the voltage drops enough, it could damage those items. Everything else in the RV is probably fine though.

Crown of the street vs curb is likely okay (less than 6 degrees assuming fridge is mounted along a side of the RV). I saw the calculation in another post and I believe it showed the RV would need to be off level by 8 inches in this direction to hit 6 degrees. If in doubt, put a block or two under the gutter side tires.

The troublesome scenario I am imagining in this post is one where the RV is parked (or stopped) on a hill or steep driveway for a length of time and what impact that could have on the boiler temp and refrigerator function. I *think* that as long as something (thermostat or Fridge Defend) cuts off the heat before 220*C no boiling/damage will occur. My initial thought is to have the thermostat set to turn off the system at 205*C and then go back on at 170*C. Just trying to see if any experts here can confirm my assumptions.

-Chris

SJ-Chris

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Posted: 11/13/22 12:44am Link  |  Quote  |  Print  |  Notify Moderator

dougrainer wrote:

Out of Level and overheating will do just 1 thing---DESTROY(block) the cooling unit. There is NO way for a fire to happen. Both Dometic and Norcold have installed overheat temp disc's for the past 23 years. So, if it overheats, the unit trips the disc and shuts off all power to the refer. BUT, the damage to the cooling unit has already happened. If I had a rental or was dumb enough to let friends and family use my RV, I would install the ARP device . This keeps anybody from operating the refer when it starts to overheat. Doug


I guess a high temp thermostat would solve the problem of overheating and destroying the cooling unit, even for those dumb enough to rent out their RV or let friends and family use their RV.

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