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08-23-2016, 08:11 AM
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#1
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Rivet Master
1994 30' Excella
alexandria
, Kentucky
Join Date: Aug 2004
Posts: 2,310
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Manometer guru's
This project started out with a family members trailer who had an issue with their dometic refrigerator flame going out down the road.
I went ahead and cleaned the gas orifice and the flame did get stronger but does not sound nearly as strong as the flame on our trailers Norcold refrigerator.
I thought I would troubleshoot a little deeper so I searched and found an article on testing an LP gas regulator with a DIY manometer.
LP Regulator testing.pdf
The lowest pencil mark is 0" WC
I chose to tap into the gas line upstream of the refrigerator gas valve.
The static reading was 11" WC and dynamic was 8" WC. I dialed the regulator adjustment a bit (adjustment bottomed out) and was able to get the static to 13" WC and the dynamic to 9.5" WC.
As far as I know this regulator is original equipment on the 2007 Safari 25' trailer. (I tried this same test on my 94 AS with the original regulator and got similar results).
Does it matter how deep the dip is in the manometer tube? When I first tried the test it just blew all the water from the tube. I lowered the tube a few inches and it seemed to be have properly. The lowest pencil mark is 0" WC
Does this sound like a bad regulator? From my reading I understand that the dynamic pressure should be 11" WC and static can be anything under 14" WC.
__________________
Steve, Christy, Anna and Phoebe (Border Collie)
1994 Classic 30'11" Excella - rear twin
2009 Dodge 2500, 6 Speed Auto, CTD, Quad Cab, Short Bed
Hensley Arrow hitch with adjustable stinger
WBCCI # 3072
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08-23-2016, 08:19 AM
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#2
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Rivet Master
2008 25' Classic
Full Time
, Texas
Join Date: Nov 2012
Posts: 4,309
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I have a 2008 Classic 25fb. I had a problem with the flame going out during travel. There was not enough shielding around the flame orifice. There was a Dometic recall that included adding more shielding around the lower part of the chimney that I had done in 2013. Luckily this fixed my problem and the flame hasn't gone out during towing. My trailer is now 9 years old from date of manufacture so I'm thinking I should replace the regulator and the feed hoses.
Kelvin
__________________
2008 Classic 25fb "Silver Mistress"
2015 Ram 2500 6.7L Cummins. Crew Cab, 4x4, Silver
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08-23-2016, 08:21 AM
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#3
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Rivet Master
Currently Looking...
Mantua
, Ohio
Join Date: Jul 2005
Posts: 7,062
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Yes, there was a a recall, don't remember the years.
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08-23-2016, 09:10 AM
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#4
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Rivet Master
1991 34' Excella
Princeton
, New Jersey
Join Date: Aug 2003
Posts: 7,070
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The recall was not for operational issues but for fire issues if the heat exchange sprung a leak. That said it is far more effective at flame retention then it will ever be at fire suppression. It is an easy install so get one.
__________________
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles
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08-23-2016, 09:21 AM
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#5
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Rivet Master
1994 30' Excella
alexandria
, Kentucky
Join Date: Aug 2004
Posts: 2,310
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The refrigerator has the extra shielding in place.
With the shielding in place I am still able to blow the flame out.......one click from igniter and it immediately relights itself.
__________________
Steve, Christy, Anna and Phoebe (Border Collie)
1994 Classic 30'11" Excella - rear twin
2009 Dodge 2500, 6 Speed Auto, CTD, Quad Cab, Short Bed
Hensley Arrow hitch with adjustable stinger
WBCCI # 3072
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08-23-2016, 09:28 AM
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#6
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Rivet Master
1991 34' Excella
Princeton
, New Jersey
Join Date: Aug 2003
Posts: 7,070
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The next thing to look at is the thermocouple. Check to see if it is well positioned in the flame to detect the flame. If it is loosen the nut on the thermocouple line at the gas valve and retighten to insure a good connection.
If the thermocouple does not detect a flame or the signal is week the gas valve will shut down.
__________________
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles
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08-23-2016, 02:10 PM
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#7
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Wise Elder
2010 30' Classic
Vintage Kin Owner
South of the river
, Minnesota
Join Date: Dec 2009
Posts: 4,169
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Quote:
Originally Posted by crispyboy
I chose to tap into the gas line upstream of the refrigerator gas valve.
The static reading was 11" WC and dynamic was 8" WC. I dialed the regulator adjustment a bit (adjustment bottomed out) and was able to get the static to 13" WC and the dynamic to 9.5" WC.
As far as I know this regulator is original equipment on the 2007 Safari 25' trailer. (I tried this same test on my 94 AS with the original regulator and got similar results).
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What flow rate did you use for the dynamic reading? Just the fridge? That would be a fairly low reading then. If you're dumping gas at 40,000 btu/h, 9.5" is probably reasonable.
Quote:
Does it matter how deep the dip is in the manometer tube? When I first tried the test it just blew all the water from the tube. I lowered the tube a few inches and it seemed to be have properly. The lowest pencil mark is 0" WC
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Doesn't matter as long as there's enough water that the gas doesn't blow it out.
__________________
To learn to see below the surface, you must adjust your altitude
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08-23-2016, 02:40 PM
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#8
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Rivet Master
2007 30' Classic
Oswego
, Illinois
Join Date: Jul 2010
Posts: 13,655
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My understanding is to adjust to 11" dynamic with ALL appliances operating, save the stove. I think most techs use the stove line upstream from the stove's secondary regulator for their gauge tap.
__________________
-Rich-
"If the women don't find you handsome, they should at least find you handy." - Red Green
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08-23-2016, 02:45 PM
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#9
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Rivet Master
2002 30' Classic S/O
Fleming Island
, Florida
Join Date: Nov 2013
Posts: 4,667
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When I did this test, my regulator did like yours and blew the water out when I tried to adjust it. To answer your question, no, the depth of the U doesn't matter as long as you can get the required 11" difference in without blowing the the water out. I took that as a sign of a bad regulator and replaced it. All my propane problems went away.
Al
__________________
“You cannot reason someone out of a position they have not been reasoned into"
Al, K5TAN and Missy, N4RGO WBCCI 1322
2002 Classic 30 Slideout -S/OS #004
2013 Dodge 2500 Laramie 4x4 Megacab Cummins
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08-23-2016, 10:17 PM
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#10
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Rivet Master
1994 30' Excella
alexandria
, Kentucky
Join Date: Aug 2004
Posts: 2,310
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I was thinking about this again today, maybe overthinking.....As you can tell I am weak in the physics and science end of things.
Would it make a difference in the i.d. of the vinyl (manometer) hose? Should it be about the same as the copper pipe? The vinyl hose i.d. is 1/2" I think. I am guessing the i.d. of the copper pipe may be closer to 1/4" or 5/16". The reason I bring this up is consideration of the weight of the water in a 1/2" hose verses a smaller diameter hose. Wouldn't this make a difference in the readings?
To me there seems like there should be a correlation in the depth of the "U" in the manometer to the amount of pressure (water column) that your trying to read....
I think I am going to go back and hook the manometer up right at the regulator and perform the test with the appliances running versus using the orifice load test on the test rig I made up.
__________________
Steve, Christy, Anna and Phoebe (Border Collie)
1994 Classic 30'11" Excella - rear twin
2009 Dodge 2500, 6 Speed Auto, CTD, Quad Cab, Short Bed
Hensley Arrow hitch with adjustable stinger
WBCCI # 3072
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08-24-2016, 12:05 AM
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#11
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Rivet Master
1995 25' Excella
xxxxx
, xxxxxx
Join Date: Apr 2015
Posts: 2,349
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My 1995 has a gauge in line right before the gas line enters the fridge. It makes regular adjustments a breeze.
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08-24-2016, 05:04 AM
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#12
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4 Rivet Member
1986 34.5' Airstream 345
Alliance
, Ohio
Join Date: Apr 2007
Posts: 262
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Crispyboy the diameter of the vinyl tubing is unimportant. You are trying to measure the 'difference' in the height of water in each leg of the 'U'. I can't tell from your picture posted in Post #1 if your graduations are 1/2" or 1" apart. Looking where your '0' mark is and how high the '11' vs the belly of the 'U' I think you could run the lower portion of your manometer a bit lower. you don't want the water to go into the bend of the 'U' section as it will give you invalid readings. Also do you fill the tube with water to the '0' mark before making any measurements? You could add a drop of food coloring to the water to make it easier to see.
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08-24-2016, 05:55 AM
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#13
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Rivet Master
1994 30' Excella
alexandria
, Kentucky
Join Date: Aug 2004
Posts: 2,310
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Quote:
Originally Posted by mehes
I can't tell from your picture posted in Post #1 if your graduations are 1/2" or 1" apart.
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The graduations are every 1/2" apart but numbered sequentially ie: 0, 1, 2, 3, 4....
__________________
Steve, Christy, Anna and Phoebe (Border Collie)
1994 Classic 30'11" Excella - rear twin
2009 Dodge 2500, 6 Speed Auto, CTD, Quad Cab, Short Bed
Hensley Arrow hitch with adjustable stinger
WBCCI # 3072
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08-24-2016, 07:49 AM
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#14
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Rivet Master
2002 30' Classic S/O
Fleming Island
, Florida
Join Date: Nov 2013
Posts: 4,667
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mehes has it right. I didn't notice your design before. Your 0" WC mark (where you fill to) needs to be in the middle of the straight vertical part, and the tube needs to be at least 5.5 inches tall above the mark but I'd make it substantially taller. The food coloring is a good idea as well.
The diameter of the tube doesn't matter. At equilibrium the atmosphere is pushing down with 14.7 psi on both sides. So what creates the difference in height is the increased pressure (not weight or volume) from the propane.
In my opinion, if you got a sudden increase in pressure when you tried to adjust the regulator, that is indicative of a bad regulator, probably something sticking. The risk is that when your appliances demand more pressure it could do the same thing, going to well over 11" WC and blow out the flame in one or more appliances.
Al
__________________
“You cannot reason someone out of a position they have not been reasoned into"
Al, K5TAN and Missy, N4RGO WBCCI 1322
2002 Classic 30 Slideout -S/OS #004
2013 Dodge 2500 Laramie 4x4 Megacab Cummins
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08-25-2016, 08:51 PM
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#15
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Rivet Master
1994 30' Excella
alexandria
, Kentucky
Join Date: Aug 2004
Posts: 2,310
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Ok I went back and retested both trailers again using the same 1/2" vinyl hose. Before starting I made sure the dip in the manometer hose was at 7" below the 0" WC mark. This time instead of using the bleed off valve on the test device I had several appliances running.
On both trailers I had the refrigerator, water heater, 3 burners and the oven operating. It was 90 degrees outside so there was no way to make the furnace operate.
The Marshall regulator on the 2008 Safari had 12" static and 11" dynamic at the final adjustment.
The Fischer regulator on the 1994 Classic had 13" static and 11" dynamic at the final adjustment. Before testing the Fischer I flushed the main trunk of the propane line with acetone and compressed air.
I feel much more confident in the results of the test and I believe both regulators seem to be working properly.
Thanks all for responding to this thread.
__________________
Steve, Christy, Anna and Phoebe (Border Collie)
1994 Classic 30'11" Excella - rear twin
2009 Dodge 2500, 6 Speed Auto, CTD, Quad Cab, Short Bed
Hensley Arrow hitch with adjustable stinger
WBCCI # 3072
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