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Old 07-01-2013, 11:09 PM   #197
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I am trying my hand at getting a "made in '88" RM2821 going, and first thing I checked was the 120V element, and guess what? It was D.O.A.

Anyways, I ordered a replacement online, and $60 including delivery to me here in Canada and I am keeping my fingers crossed that that's the end of the new parts needed!

Buttercup, I want to put ONE thermocouple in to see what is happening in there. My concern is the refer's performance in hot weather. Knowing what you know now, if you were limited to one thermocouple, which one would it be, and where would I find one of those?
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Old 07-02-2013, 02:21 AM   #198
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Quote:
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I am trying my hand at getting a "made in '88" RM2821 going, and first thing I checked was the 120V element, and guess what? It was D.O.A.

Anyways, I ordered a replacement online, and $60 including delivery to me here in Canada and I am keeping my fingers crossed that that's the end of the new parts needed!

Buttercup, I want to put ONE thermocouple in to see what is happening in there. My concern is the refer's performance in hot weather. Knowing what you know now, if you were limited to one thermocouple, which one would it be, and where would I find one of those?
One only would be tough for me! The 6 I have aren't enough!!! I could use 20 more. Hahaha.

That is a rough one because the value of having 6 is that they can be used relative to the others. Looking at one and comparing it to another really shows you so much more than one alone. For example, if you mounted it only at the inlet to the condenser, you could see the temperature coming into the condenser is high enough to still be in a vapor state, but you would really have to see the outlet temp then to get an idea that the condenser is really removing enough heat.

It's really tough to say. One isn't enough, really. I bought a cheap TC reader on eBay for $25 that came with 2 TCs. They were only 3 feet in length so, it's hard to place them where they can be of most use, around the condenser area in my opinion.

However, that being said, based only on what I know, it would help to know more about the hot weather performance issues. What is happening, what temperatures, is the AC running? Etc.... Your problem may just be a simple air flow issue as in not enough.
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Old 07-03-2013, 06:19 AM   #199
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What is your opinion of your new cooling unit performance compared to the one replaced? Does this Amish cooling unit live up to the hype?

We went out this past weekend. Up unit Sunday the temperatures in Dallas were close to 100F. My AS is in a back-in covered storage with electricity and I turned on the fridge a few days before departing. Despite being in the shade the temps inside were 99F, my indoor/outdoor thermostat indoor reading was pegged at 99F and with the fridge on 5 the reading was 44F. We didn't bother transporting food from the ice chest to the fridge until we got to the campsite. The campsite was in full sun but it was early evening and with the AC on and as the interior cooled the fridge started to recover and by the morning it was down to 32F. Being a weekend trip we didn't have much in the Dometic 3762 fridge. I deployed the curb, rear and street side awnings so for the most part the curb side of the trailer where the fridge had awning shade. The fridge was able to maintain about 37F at the hottest part of the day. We kept the ice chest inside the trailer for the beverages.

Keeping the inside of the trailer cool goes a long way to improving the fridge performance.

Kelvin
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Old 07-03-2013, 07:00 PM   #200
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I don't think the Amish units have any greater performance abilities than any other units. They ALL have the same ingredients, water, hydrogen, ammonia and rust inhibitors. Maybe the amount of ammonia is varied in the Amish units or maybe they have a little more hydrogen - I don't know. The only way to really tell would be to test them side by side with identical calibrated test rigs to see if they have differing temperature drops from an identical thermal input.

I suspect the differences would be minimal in a side by side comparison.

Here is what I do know, running a bypass test on your unit on electric will show its capability. I cooled our fridge into the teens easily with both units, the new one was a little faster, but that could be a function of differing ambient conditions. In my opinion, I believe that with these units, with proper heat input and adequate heat removal at the condenser, they should work, even in fairly hot climates. If it can cool to 13 at 70 degrees, it should be able to cool to 43 in a 100 degree day. Of course, that is just my opinion and I will have to test that with my unit on some really hot day.
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Old 07-04-2013, 09:21 PM   #201
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Longevity would concern me more than performance.

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Old 07-05-2013, 12:46 AM   #202
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Longevity would concern me more than performance.

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Longevity from a rebuilt unit?
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Old 07-06-2013, 08:36 AM   #203
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Any unit

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Old 07-06-2013, 11:00 AM   #204
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Well, I have seen several units that have lots of years on then and are still plugging away. The only real problem you can have with these units is getting a hole in the unit and venting the pressure & ammonia off of them. But this is a rare condition actually. These units have no moving parts so the failure mode is fairly low. It is more likely that a circuit board, solenoid, thermostat or some other part before the cooling unit fails.
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Old 07-09-2013, 01:00 AM   #205
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Well, once again I found the temperatures going up while we were on the road. Started measuring temperatures and saw the boiler at 340, boiler outlet at 190, condenser inlet at 130 (too low) and liquid ammonia at ambient, 90 degrees. The High temperature evaporator was at 29 degrees, so I knew 2 things; I was condensing ammonia prior to the condenser and that was cooling boiler outlet temperature and what little ammonia WAS being produced was being evaporated in the freezer section.

So, I added more baffle stuff to the grate, blocking more airflow and voila!! The boiler outlet temp rose 50 degrees, the condenser temp is above 180 and liquid ammonia temp is still ambient - meaning I am now condensing in the condenser rather than the moisture separator piping. Also, the high temperature evaporator is now running at 19 degrees, so cooling is now happening in the fridge like it should.

I am thinking of all sorts of modifications to supercharge my fridge. I am thinking more and mor of wrapping that moisture separator piping with fiberglass wrap all the way to the condenser and better directing air flow straight to the condenser fins so that it can do the job it was created for - condensing vaporous ammonia.

I realize I have a test rig I could experiment on, my old unit. I have not sent it back yet. Time to make me a test rig. What harm could I do?
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Old 07-09-2013, 06:27 AM   #206
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Our '63 Safari Dometic lasted 'til 1991.



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Old 07-09-2013, 09:49 AM   #207
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Our '63 Safari Dometic lasted 'til 1991.

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Looks like the dog is aware of what the refer has in it...
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Old 07-09-2013, 09:53 AM   #208
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So, I added more baffle stuff to the grate, blocking more airflow and voila!! The boiler outlet temp rose 50 degrees, the condenser temp is above 180 and liquid ammonia temp is still ambient - meaning I am now condensing in the condenser rather than the moisture separator piping. Also, the high temperature evaporator is now running at 19 degrees, so cooling is now happening in the fridge like it should.

I am thinking of all sorts of modifications to supercharge my fridge. I am thinking more and mor of wrapping that moisture separator piping with fiberglass wrap all the way to the condenser and better directing air flow straight to the condenser fins so that it can do the job it was created for - condensing vaporous ammonia.

I realize I have a test rig I could experiment on, my old unit. I have not sent it back yet. Time to make me a test rig. What harm could I do?
Wow, and the beat goes on! Any chance you could demonstrate on a drawing or photo what you have done (and are thinking of trying) there?

And I think the 'test bed' of your old unit is an opportunity you will probably never see again. Go for it!
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Old 07-09-2013, 11:27 AM   #209
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I have used a piece of MDF to baffle off the air flow. Thought I posted a picture of it before.

Click image for larger version

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I believe I will incorporate a thing that will deflect all airflow up and allow me to regulate it per my specific needs. That way I can have full flow if I want. Also, I will put an air filter in there as well as the door has a lip around the whole inside that I can pack one in.

Lastly, I think I could install a duct of sorts to port any incoming air right to the condenser where it is needed most.

Lots of things I could do. Question is will I actually do them?
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Old 07-09-2013, 05:46 PM   #210
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What was the ambient temperatures when you experienced these failures. Living in Nevada its so dry. I think these fridges work better in dryer air than the humidity in Texas. Its crazy how you are blocking off your whole vent now while everyone is struggle to find ways to add fans and all sorts of gizmos to move air over the back of their fridges.

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