Posted 2012-08-15 7:57 PM (#146377) Subject: fridge not working on propane-incorrect venting??
Member
Posts: 14
Location: Canton, MI
I recently bought a used Merhow trailer with Harmar conversion. When I went to use it for our first trip the fridge got nice and cold when plugged into AC, but when I switched to propane it never stayed very cold. I took it in to camping world the other day to ask them about it and deal with the recall (it's one of the recalled Dometic fridges) and they said that the venting was put in incorrectly. They said that it needed to go through the roof and so when I try to run it on propane it's getting too hot because it can't get enough air. They can't do the repair because it will entail new vents and new siding etc. so I'll have to take it to a horse trailer or conversion place. My question- I've seen other trailers with vents that look like they are in the same place (looks exactly like the trailer in this ad: http://www.horsetrailerworld.com/home/trailerdetail.asp?ID=393083 ) so it seems hard to imagine that they are all wrong. Does anyone have any thoughts? I have to go pick the trailer up tomorrow and I'm going to call Harmar, but this trailer is 10 years old so I feel like I'm stuck. My first LQ so any other experience or knowledge is welcome!
Posted 2012-08-15 9:28 PM (#146380 - in reply to #146377) Subject: RE: fridge not working on propane-incorrect venting??
Veteran
Posts: 155 Location: North Salem, IN
By the picture you posted, it has both the side vents and the roof vent. I do understand waht you are saying though. I just installed a 6.0 Cu. ft. refrigerator in my trailer and installed 2 side vents. I wasn't about to cut a hole in the roof of my trailer. With that being said, I put the side vents in and was told by a local place that repairs RV refrigerators that it would be fine like that, and at the worst, may have to add an auxillary fan to move air over the condesor on the back of the refrigerator. My unit cools fine, both on gas and electic without the added fan. That is the case even in the extreme heat we have had this summer.
I would look more toward an obstruction of flow in the burner on the back of the unit. That is typically the cause of such a problem.
Pic attached is where i mounted my vents, and they work just fine.
Posted 2012-08-16 9:16 AM (#146386 - in reply to #146377) Subject: RE: fridge not working on propane-incorrect venting??
Elite Veteran
Posts: 804 Location: Tenn/Ala.
You need to find a qualified service tech. If venting was the primary issue- it wouldn't work on AC or LP. The venting involves getting cold air in the bottom, and warm air cleanly out the top. If it is "broken", it affects everything. If it is working on AC, then the venting has been vindicated.
Yes- side in, and top output is preferred. But many units use side:side to good results. You appear to have a LP issue that has not been properly diagnosed yet.
Posted 2012-08-16 9:19 AM (#146387 - in reply to #146377) Subject: RE: fridge not working on propane-incorrect venting??
Extreme Veteran
Posts: 379 Location: Missouri
In my previous trailer the fridge was not vented through the roof since it was mounted under the cabinet. I too had the same symptoms you're describing, works great on electric but not on propane. As you were told it's because the waste heat of the propane is causing the fridge cooling compartment to be too hot. My solution was the same as you were told. I fabricated some sheet metal to close off the upper side vent. Then I cut two holes and attached 6" 12v muffin fans to the sheet metal. Using a bi-metal thermostat, the fans would turn on when the compartment got above 90 degrees. After that, no difference in cooling with electric verses propane. Through the roof venting is optimal. It creates a natural chimney effect to draw the heat out.
Posted 2012-08-16 9:27 AM (#146388 - in reply to #146377) Subject: RE: fridge not working on propane-incorrect venting??
Expert
Posts: 5870 Location: western PA
Harmer builds a quality conversion, and I'm sure that an incorrect installation would have shown a venting deficiency, long before your acquisition of the trailer.
I would suggest openeing the bottom vent, where you will see the gas and electric supplies for your fridge. A common screw driver turning the fasteners 90 degrees, will open the top of the panel. If you follow the gas supply line to the bottom right of the unit, you will find a metal plate with a couple of screws. When they are removed, you will be looking at the burner section.
Any dirt, bugs or sagging insulation in this area will restrict a proper flame. A vacuum cleaner with a soft bristle brush will clean things ups a bit. Do not touch the very end of the burner where the flame is produced, with the brush. Blowing any residue off the orrifice is the best way to clean it.
While you are observing the area of the flame, have someone ignite the burner by turning on the fridge with the gas function. You should have a clean, regular blue flame, about an inch or inch and a half long. Within the flame, you will have a little probe that is constantly heated. If the flame is irregular and yellowish, or it keeps shutting off because the probe is not being heated, things can be adjusted to promote a good flame propagation.
The burner tip can be cleaned and the air flow regulated. The TC probe can be adjusted. These are simple fixes that only take a few minutes to diagnose and effect.
The amount of air being burnt during normal opperation is quite small. The surface area of the two vents of your installation, would only be necessary to vent the gas fumes you might experience, in the event of a gas line failure where large amounts of vapours would be quickly produced.
You can easily trouble shoot this yourself, and anyone with any furnace experience, can make the adjustments you need if you can't do it yourself. A few minutes on the internet will show you how.
I don't think Camping World gave you the correct answer.
Posted 2012-08-16 9:36 AM (#146389 - in reply to #146377) Subject: RE: fridge not working on propane-incorrect venting??
Member
Posts: 14
Location: Canton, MI
Thanks everyone. We are going to open it up and take a look inside tonight. I agree that I don't think they diagnosed this correctly, but being a relative newbie to LQ-land I wasn't quite sure how to proceed. Going to call Harmar in a little bit and see if they have any thoughts as well.
fridge not working on propane-incorrect venting??
