Dometic fridge woes.

[btcruzer]

I have a Dometic model RM2453 3-way fridge that works in all 3 modes but the LP mode is a problem. It always ignites and burns clean. However I don't believe that the flame is hot enough. I've always heard that LP mode usually cools better than electric and that has been my experience with several different RVs. But this one is different.
This model does not use a "pilot Light" - instead it has a thermostat controlled gas valve with two passages. One is the bypass that allows a small flow of LP to flow in order to maintain the pilot light. The other is is the full flow passage that should cause a larger flame when the thermostat calls for cooling. The thermostat also controls a simple off/on switch in the electric mode. I have tested the electric side and determined that the thermostat does turn the electric on and off as needed.
I have measured the temp of the boiler tube at the same spot (just above the top of the flue) in both electric and LP mode. Electric is hotter.
The thermostat has 9 settings -
OFF ( not really off but bypass mode)
1 through 7 are temp settings - 1 warmest and 7 coldest
MAX is full time operation not controlled by the thermostat.

I've read that there is a visible difference in the flame height in the bypass and full operation. I have observed the flame while in the OFF position (bypass mode) and then someone switching the thermostat to all the other settings. No difference. I've also heard and observed that you can hear the flame. Not this one.

The burner assembly has been removed and cleaned several times. The jet (#43 per Dometic) has been removed soaked, cleaned and blown dry several times. The flue has been swabbed full length several times.

I have replaced the 2-stage LP regulator. I have measured the LP gas pressure with a manometer. Initial pressure was 13 inches of water. Dometic manual says 11 inches. Adjusted pressure and observed pressure for probably an hour in operation -- never varied.

I replaced the thermostat. No change.

I am out of ideas. The LP pressure is taken within an inch of the jet. Seems to me that the proper pressure through the specified jet should produce the full flame. What am I missing?



I'm convinced that the ther

[ernie1]

btcruzer: thanks again and will followup with the info you've given and hopefully have the same results.

[btcruzer]

Doug - my RV is a 2000. Assume the fridge is the same.

[btcruzer]

earnie1 -- I got the jet from RV Superstore in Vandalia, Il.
phone 618 283 4396
handwritten note on the package says DOM#0169353-002...
I'm going to call anc check if they have others available.
Good luck with yours.

[btcruzer]

UPDATE --- back from trip . new jet was in the mail-- did NOT fit--- not really surprised -- with a selection of brass fittings was able to adapt the fridge to use the new jet. I was replacing a #43 jet with a #48 -- would have preferred maybe a #46 but you take what you can get. THE BEST PART-- fridge is cooling on propane like a champ !!
Been a 3 day test with outside temps in the 90s and temps inside the RV sometimes up to 105 degrees. Parked in the sun with fridge side to the sun. The thermostat has been on " 4" for the entire test. Highest temp measured in the food section has been 37 degrees.

So no other changes except the jet replaced with a larger one.

The #43 was listed in the Dometic manual as the part# for this model. It had been inspected with magnifying glass and endoscope. Cleaned numerous times.

Anyway, the thing is working well and I'm happy.

[ernie1]

btcruzer: Thanks again for your helpful response.

[dougrainer]

what year model is your RV/refer?

[btcruzer]

trailrider...I just sold my complete set of 120 Holly jets. Unlike Holly, Dometic jets are not real common. Some of the jets for dometic are priced at $50 and more. most are listed for a model # or a part # .. the one I ordered is the only one I found that listed a size..not sure it will even fit...
so yes - good idea..execution gets more complicated.

[btcruzer]

ERNIE1 - found the jet on ebay..no guarantee that it will fit
picture looks like it but who knows. $10 and I'll take the chance..no more ideas..
no idea how to find it again..I googled "ebay dometic jet" passed the phone and told wife to order. I'll try to remember to let you know if i can get the sellers info.especially if this fiasco works.

[trailrider]

What did I already suggest on the previous page? Put in a new orifice!

[ernie1]

btcruzer: Where are you able to locate the larger jet? I contacted Dometic about purchasing another jet sometime back and they just blew me off and said it wasn't available. Very anxious to hear about your results with the new larger jet. My Dometic is acting like yours and always has even when new.

[btcruzer]

actually.i have a hopefully bigger jet on order. presently the installed jet is a 43. I have a 48 on order. It will be a while. Jet is supposed to arrive next week but we'll be on a trip..sadly- the manual for this model specifys a 43 jet..you'd think that would indicate that something was amiss with this jet. as we're warned not to poke into it..hard to imagibe one could screw it up cause less flow.
UPDATE..I now have a bbq tank and the original regulator rigged up to now bypass EVERYTHING except the burner assembly with the 43 jet..guess what ! same results.

Thanks for all the input/ideas. I'll post results when 48 gets tested.

[dougrainer]

I think you have narrowed the problem down to a BAD/Wrong orifice. Refers use very little LP in terms of Volume. The only variable now is the orifice. The system is working as designed except the Orifice is NOT large enough for the correct flame. I think you stated you are not the original owner of the RV. Who knows what previous owners did. Doug

[btcruzer]

Doug... we can eliminate the t'stat as a problem. ( As you suggested earlier) I bypassed all the controls on the LP side. Ran a tube from the unit cutoff valve directly to the burner assembly. Now only things involved are the LP tank, regulator, cutoff valve and Orifice. I had a manometer connected at the test port. 11 inch water column. Manually lit the flame. This arrangement should allow the burner to operate at full capacity with out any complications.

refer temp had been maintained at 20* to 22* on electric for at least 12 hours.
When switched to gas the refer temp went from 20* to 35* in 6 hours. Those temps don't sound bad but I know from earlier camping trips that the temp would got to 45 of 50 degrees if continuing on LP.

I increased the LP pressure from 11 to 13 and then to 15 with no change in flame appearance. Nor did the increased pressures raise the boiler temperatures.

Someone earlier had suggested that even though the pressure is correct that the flow might not be sufficient. I don't know how to test the flow but at this point I have to assume that the orifice is not big enough to allow a larger flame but a larger flame is needed to produce more heat.

It is ironic that with all this heat I'm wanting more heat to cool my refer.

[dougrainer]

btcruzer wrote:
I guess so far all I have found is that the thing works well on a/c. The whole idea of buying the Roadtrek was to be able to boondock at race tracks for 3 or 4 days without running a gen. So I am particularly interested in the LP option.

At 5 PM I switched to LP mode. Nothing else was changed. Except the temp inside the rv has dropped from 105 degrees to 94. Within 5 minutes the refer temp increased to 27. The condenser tube I had been monitoring for temp dropped from 114 to 107. I was running a small fan on the condenser fins but turned it off when switching to gas. Without the fan the condenser tube was over 130 degrees at times. Time will tell.

I would state the new tstat is bad. Doug