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Old 07-04-2015, 06:56 AM   #1
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Chilling discovery

About 2 years ago I replaced my MEC auto change over regulator with a newer 2 stage model.... I was smelling propane and determined it was from the old regulator.
Since that change, I have had a steady decline in the cooling performance of my fridge only on lpg. Recently the temp spiked. I removed the whole thing, cleaned the flue, checked the thermistor, cleaned the seals, everything was perfect, including the flame.... Or so I thought!
On a whim I hooked up my manometer, and to my shock, I measured only 6" watercolum pressure! Not having an rv dealer handy, I removed the adjustment cap to find the adjustment totally maxed out! I removed the spring, stretched it out which applied more pressure against the diaphragm. I re assembled the whole deal and pow up to the 11" my appliances need. Since then the fridge is back to normal. Even in 90 degree heat the fridge is keeping cold. I reinspected the flame, and sure enough it is still clear blue like it had been, but the shape and height is now different!

I might suggest if you are experiencing warm temps on lp, get a gauge and check out your pressure, this was absolutely my problem! I naturally assumed that since I replaced the regulator it would be perfect set to 11"..... Not the case!

Years ago, I installed a computer fan inside the fridge, and on the coils on the back. Combined with a cleaning, I'm happy with my old Dometic again!
Hope my little discovery keeps your libations cold!
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Old 07-04-2015, 08:01 AM   #2
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A redneck check is to, on a quiet day, open the fridge access door, and stand close with it on LP. You should be able to hear a light "roaring" sound from the burner. I've been "burned" before by flames that looked good, but really weren't.
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Old 07-04-2015, 08:06 AM   #3
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A new part is identical to an old part until it proves itself. Thanks for the post.
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Old 07-05-2015, 06:15 AM   #4
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Ironically I could hear the flame with the bad regulator setting, it always made a slight roaring sound!
Looking at the flame before it was a clear blue, wide on the burner, now it is still clear blue, however much narrower an taller in the flue.
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Old 07-05-2015, 06:50 AM   #5
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Originally Posted by AtomicNo13 View Post
Ironically I could hear the flame with the bad regulator setting, it always made a slight roaring sound!
Looking at the flame before it was a clear blue, wide on the burner, now it is still clear blue, however much narrower an taller in the flue.
That is interesting. I'll pass this along to the guys in the shop as a reminder. Checking pressure is one of the things done before recommending a replacement cooling unit or fridge, but I know sometimes somebody gets in a hurry, and skips it.
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Old 07-05-2015, 07:40 AM   #6
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Mine wasn't cooling well on gas. Fortunately, my fridge had a gauge. I noticed the pressure wasn't high enough. I adjusted the regulator and she cools great now.
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Old 07-05-2015, 07:51 AM   #7
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Thanks for the post, good reminder to check the pressure.
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Old 07-05-2015, 07:55 AM   #8
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I suspect this is fairly common and most folks aren't aware of it. We took our Airstream to Jackson Center Service just before the two year warranty expired to have a multi-point inspection done. They found slightly low gas pressure and adjusted the regulator. After that she noticed our range burners and oven were easier to light.
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Old 07-05-2015, 08:11 AM   #9
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Mine was only at 9" static when I checked it last year. Spec is 11" with all gas appliances on.
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Old 07-05-2015, 09:58 AM   #10
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11" WC is the key to cold fridges!
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Old 07-05-2015, 11:15 AM   #11
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Originally Posted by AtomicNo13 View Post
11" WC is the key to cold fridges!
I have suspected that for a long time but fortunately have never had it happen to me.

Mostly I have run into rust from the boiler tube falling down into the burner and clogging it. Judging the heat output of the burner from looking at the flame is difficult. You can tell if it is blue, not yellowed, but as you report, the size and length of the flame can be off and you do not know it is wrong.
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Old 07-06-2015, 08:04 PM   #12
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Actually, the pressure spec. for LP is 11" water gauge (they stopped using water column, or WC as it is too easy to confuse it with the WC marked on LP tanks) with 50% of the appliances on. That was the last RVIA specification that I am aware of.


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Old 07-06-2015, 08:10 PM   #13
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But what many miss is that the 11" spec is not static pressure but dynamic pressure.
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Old 07-06-2015, 11:37 PM   #14
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Quote:
Originally Posted by lewster View Post
Actually, the pressure spec. for LP is 11" water gauge (they stopped using water column, or WC as it is too easy to confuse it with the WC marked on LP tanks) with 50% of the appliances on. That was the last RVIA specification that I am aware of.
Learned something new. Had I not read this I would have set at 11" static. Thanks!

My trailers are 16 and 17 years old. I assume they both have the original regulators, so I should be installing new regulators and flexible hoses soon.

The furnace, water heater, oven/range, and fridge could be on simultaneously in my trailers. One trailer has a quick connect for a grill or portable fire pit, but I hardly every use those. So should I assume the quick connect would account for no additional propane flow for this measurement or should I assume the largest appliance that might be connected?

Am I correct in assuming you are saying 50% of the maximum BTU rate, of all appliances combined, should be operating/burning, with a dynamic pressure adjusted to ~11" on the water gauge? When checking regulator pressure, which combination of appliances would you suggest should be operated during the pressure test, to represent 50% of the appliances.

Should the static pressure with no flow be slightly higher than 11"? (how much is to much)
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