MANOMETER? - Page 2 - Fiberglass RV


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Old 02-23-2019, 10:18 AM   #21
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That pressure is a bit high, but before you can determine if the operating pressures are too high or too low, you need to measure them under various conditions.

With nothing on, the pressure can be measured anywhere in the line, so checking it at the regulator, as you did, is perfect.

You can also check it there with ONLY to fridge running because it uses so little that the line losses won't cause a false reading.

At that point you have data that shows the static head and the operating head that your regulator is operating at. If it has an internal leak, or a bad seal, the pressure will creep up when everything is off.

When the heater and the stove are on, there is a large draw of gas. The regulator must keep up with this and the piping must be large enough to minimize the pressure drop at the fridge. All piping restricts flow. The farther the appliance is from the regulator the lower the pressure will be at the appliance when it is running. That is why the pressure is measured at the fridge under both conditions, appliances on and appliances off. If the pressure is too low, the fridge may go out or not produce enough heat to cool.

Once you have these readings you can research if the pressures are within specs for the appliance.

The reasons why the pressure may be too low when the other appliances are running are: Undersized or failing regulator, undersized gas piping, a clog in the piping from too much pipe sealant being used or debris left in there, outside temperature too low, propane tank low on gas which means it cannot boil off fast enough.

Remember, in theory, the liquid level in the propane tank has nothing to do with it's pressure. It always boils and feeds vapor to the regulator when in use. But, the boiling process causes it to cool down, which reduces it's boiling temperature. This will make it deliver less vapor as the temp falls. If the tank is low, there is not much liquid and the pressure can drop faster than if the tank is full. Low outside air temp also causes it to boil slower. The operating pressure of the appliances is much lower than the tank pressure, so most of the time it feeds enough gas to work properly, but not always. The output pressure of the regulator is affected by the tank pressure.

The bottom line here is that the fridge should be allowed to operate first, with no other appliances on, to make sure it works correctly at normal room temperatures. Then it can be tested to see if it's flame still operates correctly with the other appliances running. Make sure the propane tank has an adequate amount amount of gas, and is warm enough that it won't affect the outcome. This can be done with the manometer installed at the regulator. Then the fridge can be tested to see if it blows out while driving.

If you are thorough enough with your testing, you can finally get to the bottom of any flame problems, or eliminate that as the reason the fridge doesn't cool.

Too much gas pressure will make the flame more blue and noisier. It may push the base of the flame away from the pilot assembly. Too low pressure will make flame lazier and more yellow. It will produce more carbon. If the venturi or mixing tube area is dirty or has a spider web in it, the flame will be weaker and may fire back in the tube. Make sure all of that area is clean. Make sure, if you have one, that the thermocouple is not burned at it's tip. If it is all electronic and uses flame sensors, make sure they are clean too.
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Old 02-27-2019, 05:59 AM   #22
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thanks for your responses...after checking the pressure with manometer i removed it, replugged the hole it was hooked to and tried the fridge again. more bad news...it will light but when i release the "lighting button" after waiting for the thing to warm enough the flame goes out. this is a new problem and i doubt it's related to my other problems with dometic's box of promises. i'm now shopping for a 2 way replacement unit. i've had it with all the frustration this fridge and propane produces. i've got plenty of 12v power with 2 6v golf cart batteries (225 amp hrs) with 2 100w solar panels and there's always the honda generator permanently mounded on the tongue and wired directly to the converter. i'll post my results with this conversion when it's finished.

thanks again.

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Old 02-27-2019, 09:46 AM   #23
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How long have you had your camper? How much experience do you have with propane fridges? I only ask because they are temperamental, and we never asked the history of your fridge (did it ever work well?) or your history with them.

Mine will often take a long time to light, especially if I've been messing with gas and need to clear air out of the line. If the fridge has been off for a while or I've opened a gas line, I'll run a stove burner while I light the fridge. Sometimes it still takes a while to light. I've sat in my camper holding that gas valve open for 20 minutes, checking "will it stay lit now?"...nope. Eventually it does. Keeping everything clean at the burner helps, but this is just part of the joy of owning a propane fridge.

Anyway, do what you need to do, but these are expensive units so I'd hate to see you waste that much money when you've got a perfectly good fridge.
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Old 02-27-2019, 10:00 AM   #24
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...

Anyway, do what you need to do, but these are expensive units so I'd hate to see you waste that much money when you've got a perfectly good fridge.
On the one hand, it might be just the thermocouple. An easy and cheap fix.

On the other hand, I understand your frustration. With that much 12 volt capacity a 12 volt Danfoss type compressor fridge makes sense also and is not at all temperamental.
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Old 02-27-2019, 11:56 AM   #25
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With all the trouble my fridge has given me, I've been considering just pulling it out and putting a Yeti cooler on slide tracks in its place. But...I'm not there yet.
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Old 02-27-2019, 11:59 AM   #26
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It can be hard to get gas to the fridge. The orifice is small and the fridge might be off for a long time, so it can take a while to purge the line and get gas to the burner. Lighting a stove burner is a good way to partially purge air from the gas line. Once the stove burner lights, it can be turned off and the fridge lit. It still might take a minute or so, but it will eventually light.

The reason the flame will light, but not stay lit after releasing the button, is most likely related to the thermocouple.

The reasons are: Flame too small to adequately heat the thermocouple (low gas pressure or clogged orifice). Flame not properly aligned to surround the thermocouple (thermocouple hot hot enough to work). The thermocouple burned out or faulty (no current from the thermocouple to hold the gas valve open). The thermocouple connection at the gas valve loose, dirty or not making a proper connection (no current to the gas valve).

These things are easily checked and corrected if needed. There are universal thermocouple kits available at hardware stores for about $10. Yours might be non standard, but it is probably a common design.

Typically, the thermostat glows red hot when operating. It should stay clean and without heavy carbon buildup. It should take no longer than about 15 seconds to reach a sufficient temperature to work. The end of it should be a smooth round surface and not a rough, broken or burned surface. Rain and splash can get to the gas valve. This can deteriorate the thermocouple connection. You can remove the nut that secures the end at the valve and spray WD-40 into the hole, then clean the end where the electrical connection is made. Then screw the nut back in and tighten it.
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Old 02-27-2019, 12:50 PM   #27
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P@,

When these propane refrigerators work as designed, they work quite well. They are quiet and run a long time on a bottle of gas, with no, or very little power.

I know it's tempting to simply replace them with compressor fridges, but those bring the need for constant electrical power. This may seem like no big deal, but the power draw is relentless. Mine ran about 30% of the time. Night and day, good weather or bad, trailer plugged in or not, etc. You may have the power, with careful management, but at the very least, it will take away from other draws you may have. I can't remember the exact power draw, but approximately 5 amps at 12volts while running and 13 amps surge to start. it will start about 20 times per hour and run about 20 minutes per hour This adds up and must be accounted for. If warm food items are added to the fridge, it will run more.

When adding this up, remember that batteries should never be run down below 50% charge and the faster the power is drawn out, the less that is available overall.

Full rated power available from solar panels won't be realized if there is any shading or if the panels are not pointed directly at the sun. Real world power from them can be significantly lower than their rating.

Electric fridges may be a perfect answer, just go into it with eyes wide open. It may be more practical to troubleshoot the propane fridge.
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Old 02-27-2019, 01:45 PM   #28
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... I can't remember the exact power draw, but approximately 5 amps at 12volts while running and 13 amps surge to start....
My one cubic foot Indel B with Secop (former known as Danfoss) DC compressor draws less than that. (Same exact fridge as Truckfridge and other brands). Figure 200-750 watthours in 24 hours. Yes, thats a big range.. it depends on many factors and how you use it. Mine is AC/DC so I can move it about and plug it into 120 VAC in the house also.

Indel B brochure: http://www.indelb.com/media/files/57...e-Brochure.pdf
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Old 02-27-2019, 01:53 PM   #29
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I too am using my domestic fridge as a bread box. What are the cons of installing a dorm fridge. I rarely boondock, but could use my cooler when I do?? I have a '94 SD
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Old 02-27-2019, 04:08 PM   #30
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If you're almost always plugged in and can manage temperatures while you're traveling, there really aren't any cons. I guess the con is less flexibility. But otherwise there's nothing wrong with installing a dorm fridge if it won't be powered off your battery.
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Old 02-27-2019, 04:32 PM   #31
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What fits in a one cubic foot fridge?
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Old 02-27-2019, 04:36 PM   #32
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Something with the approximate dimension of 12" x 12" x 12"

But I agree with what you're getting at. Seems like it would fit lunch for the drive to wherever you're going; not much else.
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Old 02-27-2019, 04:57 PM   #33
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gordon,

A one cu. ft. fridge is very small. Handy for a car or a short period, but not a direct replacement after taking out a built in trailer fridge. At least not one I've seen, or one that will hold enough food for a week or so.

Mine was about 6 cu ft and it used about 500 watt hours/day. It was extremely well insulated and a top loader. A good quality group 27 deep cycle battery would run that for about 24 hours max before reaching the 50% discharge level, or below. Then, if more warm food is added, it will run more and might only go for 1/2 day.

The point is that one must keep up with the power draw by keeping the batteries charged. This can become a problem with poor weather, other power draws, poor orientation of the collectors, etc. Running a generator to indirectly run the fridge gets old. I lived on batteries for years and it was always a management issue.

At least with propane, it just goes along silently for a long period on a single tank. The compressor fridges work well and seem to be reliable, as long as they get reliable power. They do make a little bit of noise, but that is a minor issue.
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Old 02-27-2019, 05:03 PM   #34
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I too am using my domestic fridge as a bread box. What are the cons of installing a dorm fridge. I rarely boondock, but could use my cooler when I do?? I have a '94 SD
Dorm fridges are not real efficient. At least the one I have, it seems to run all the time and has thin insulation. Mine is not very quiet either and I can hear it in the other rooms of the house, so in a trailer it would be annoying. The door has no door latch that would be acceptable in a trailer. They are 120 volt only.
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Old 02-27-2019, 05:53 PM   #35
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gordon,

A one cu. ft. fridge is very small. Handy for a car or a short period, but not a direct replacement after taking out a built in trailer fridge. At least not one I've seen, or one that will hold enough food for a week or so.
I didn't mean to imply it was a replacement for a full size unit, I was just giving the OP an idea of power consumption. I believe the same compressor is used in a range of storage sizes so the power draw tends to be similar, until you get to the bigger units.

The major factors in the amount of power used are ambient temp, frequency of opening, temp of items put in the fridge (should be pre-chilled if you want to save power), insulation (built in or added on), etc... and one you mentioned... top load (keeps the cold in better).

I still have my propane fridge and I have no plans to give it up. It can run for a month on a single tank, and NO sun at all.

And you might be surprised how much you can put in one cubic foot. Last time we lost power here, I put almost all of my frozen food from the house in it and set it to zero degrees. Since everything started frozen the power draw was not that much and when the power came back on after 24 hours all the food was still frozen solid (90 AH battery). So its handy that its portable, but frankly.. anything larger would be too hard for me to carry around, esp if full of food.
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Old 02-28-2019, 02:06 AM   #36
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I too am using my domestic fridge as a bread box. What are the cons of installing a dorm fridge. I rarely boondock, but could use my cooler when I do?? I have a '94 SD
Welcome to the forum Beth. The cooler for boondocking, perfect. I've seen many post on dorm fridges and I've always wondered why folks say they don't get "cold". I got two 4cf Sanyo mini fridges in the garage and even when the outside desert temps are 115+* and 95* in the garage, my beer & soda is very cold. I see no reason that it wouldn't work for you. The only issues I've read about from members that have gone to dorm fridges is side clearances and possibly cutting vents in the shell for exhausting the heat. When I defrost my Sanyo's, it takes 24 hours to bring the temp back down to 40* or so but that isn't any different than the time it takes to bring my LP fridge to temp so that's kind of a moot point. BTW, why aren't you using your fridge?
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Old 02-28-2019, 06:53 AM   #37
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thanks for all your comments. my trailer is a 2012 and the fridge has been problematic from the beginning and gradually gotten worse. i'm pretty well versed in all those maintenance measures that have been mentioned. i feel as if i could disassemble the burner section with my eyes closed. and yes, i hate to be throwing the money at a new fridge and have repeatedly tried to make the old one work. even when it does work it's marginal ability to keep things cold is frustrating. i'm convinced that a lot of the issues stem from the way casita installs these units. the install instructions from dometic clearly state that venting the burner assembly thru the roof is necessary. casita (and others) ignore this and attempt to let it vent thru the upper portion of the enclosure which is exactly where the cooling tubes are located. i've done extensive baffle mods to compensate for this situation and have had positive results but, still it remains unreliable. the only thing that has kept me trying as long as i have is the fact that the unit works like a charm on 110v power so i know it's capable of doing it's job. i'm planning a trip to alaska this coming summer and do not want this condition to dog me for a trip that long. i'll keep trying until that departure date nears and i still have time to find a replacement. as far as depending on a 12v/110v i do have twin 6v agm golf cart batteries (225 amp hours), a 100w solar panel mounted on the trailer's roof that remains active while in motion and another mounted on the roof of the truck that can be employed while stationary. then there's the honda generator permanently mounted on the trailer's tongue over the propane tanks that's hardwired to the converter that can be operated going down the road if need be. so i feel pretty confident that i can power an efficient 2 way fridge. so, i'll not give up quite yet however i am stashing some $'s away just in case.

i'll keep you posted on the results.

p@
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Old 02-28-2019, 09:06 AM   #38
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Gotcha, thanks. Yep, been there, done that. I hear you. A fridge like yours and mine can ruin a trip if you let it get to you.

I've considered cutting a hole in my counter and roof, and putting a pvc chimney from the top of the fridge compartment out the roof. But so far haven't taken such an extreme measure...
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Old 02-28-2019, 04:02 PM   #39
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thanks Borrego Dave, I don't have confidence that the fridge will cool consistently. I've been using my cooler, but that gets old. I have not tried it with propane, I'm a little afraid of it
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Old 02-28-2019, 04:27 PM   #40
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I've been using my cooler, but that gets old. I have not tried it with propane, I'm a little afraid of it
Nothing to be afraid of there Beth. I, like many, only use LP. Fire the thing up and see how it works for you. Lite one of the stove burner first to get the air out of the line before lighting the fridge.
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