Fridge Flue Temperature

[Travelin2]

We recently bought a 2003 Pleasure-Way van. It has a Dometic RM 2353 fridge with two side-wall vents for draft. It is the manual model with a Piezo igniter. It is a 3-way. To check the fridge operation, with a thermometer in the refer' area reading 70*, I turned it on 120 AC operation mode overnite with the rotary temperature control on "MAX" and the next morning the main food storage area was at 32 degrees so I figured it was going to be fine. I turned it off and let things warm back up to ambient. To check the 12V operation I didn't let it run long enough to cool the fridge because I didn't want to kill the battery but I connected a volt meter to the battery and when I switched on the 12V mode the battery voltage immediately started steadily dropping, indicating an amperage draw. I also touched the heating element and it was hotter than H&ll! That element lays right beside the 120AC element so I figured that system would work but would confirm on a trip while running the alternator.

So, now it was time to check it on gas. I started again with the refer' area at 70*. I turned the rotary control to gas, held in the "gas-on" button and pushed the Piezo sparker. I had lit the cook top burners previously to purge the gas line but I was still pleasantly surprised when the little flame indicator jumped up after only the second click. I had the "temp" setting at "MAX" and after about two hours the thermometer in the fridge was only down to 54*. I could feel considerable heat coming out of the upper sidewall vent. I checked some temps with an IR gun and I found a whopping 400 degrees when checking on the little deflector plate right over the top of the flue tube. Down by the burner I found 160* or so on the base of the stack. Up the stack on the outside of the insulation it was only around 120*. I had heard in the past that over heating the cooling unit can wreck it and that 400* reading surprised me that it was that high so I shut it down. I could find nothing anywhere about what temperature to expect.

This fridge is fairly old but has been used little. Mostly sitting idle not being in service. I'm in Florida and I had noticed immediately that there were no bug screens on the vents so to make sure the mud dobbers hadn't plugged things up, I removed the top deflector, pulled out the spiral baffle hanging on a wire in the flue and used a mirror and flashlight to look down the "barrel". I was pleased to see that it was clean as a whistle with no rust and appeared to be lightly galvanized or something similar. The bottom of the baffle was discolored due to heat. I removed the burner shroud to have a look at the flame and it looked fine. Nice consistent blue, well defined flame.(I will try to attach a picture)

Opinions and thoughts on the operation of this would be welcome. I'm wondering...
1. Do I dare run it for a long time with that 400* flue temp?
2. What is the expected flue temp?
3. How long should it take for the gas system to bring the refer
section down to 38* or so?
4. If it is cooling on 120AC does that mean I don't have the
dreaded "crystal build-up/blockage?
5. If there is some crystal buildup inside the cooling unit
will running it for long periods on 120AC dissolve them back into
solution and improve performance?

[Gjac]

You need more than 2 hrs to bring the refer temps down lower than 54 degrees. I let mine run over night to get to 38 degrees. If it works on electric your cooling unit should be fine. Where exactly are you measuring 400 degrees? Is it on the flue itself with the sht metal and insulation around the flue remove or on the outside of the sht metal surrounding the flue. I would take a reading about 4 ins above the above the flame on the flue itself and post that reading. Some of the members on here have the ARP system and they monitor that temp continually with their system. I forget at what temp the system shuts the refer down but I sure someone will post that temp.

[wasatchmtnatvr]

1 Ignore your temp gun reading as you are not measuring boiler temp but chimney cap deflector temp. 2 Don't know , its irrelevant. 3. Usually similar time as 120 operation. 4. Cools under demand you should be fine. 5 If crystal build up operating on 120 long term will do nothing for dissolving of crystals into functioning solution.