Fridge Performance Survey

[Borrego Dave]

Think of the thermistor like the heat/cooling controlling unit you have in your home for the HVAC. If it's in a location that gets the conditioned air temps blown directly on it, it will start & stop well before the areas you really want the set temps to reach. If the location makes the temps work better, yahoo, colder beer .

[Raz]

On the gas refrigerators I've worked on there is a thermocouple that supplies a very small voltage to a safety valve. This cuts off the gas should the flame go out. It's binary in operation. There is no thermostat. Temperature is controlled by adjusting gas flow and is independent from the thermocouple. If the fridge used a thermistor to control temperature the thermistor would be located inside the fridge and would require additional electronics to control gas flow. Does this fridge require DC to run on gas. If not then the temperature control is open loop, no themostat, no thermistor.

[ZachO]

No DC to run on gas. But there is a wire running from the inside fins to the back of the fridge where the electronics are. So possibly it has some effect when running on AC/DC.

[Raz]

Originally Posted by ZachO

No DC to run on gas. But there is a wire running from the inside fins to the back of the fridge where the electronics are. So possibly it has some effect when running on AC/DC.

The fridges I've worked on did have a thermostat for AC operation. That might be the wire you're seeing. No temperature control for DC operation. On gas there is a low medium high control that simply adjusts the gas flow much like a gas stove. When I adjust that I see an increase in the flame. I can also heard a difference. This spring I serviced everything and replaced the regulator. Fridge is working too well. Froze the cucumbers last trip out. I know, you'd like to have my problem. Be persistent you'll figure it out.

[ZachO]

It all depends on the outside temps! Mine alternates between not being able to keep up, and freezing things solid. It's that 80-degree threshold.

Mine doesn't have high/med/low. It has a continuous dial of many settings between low and "MAX". And yes it effects flame height on gas and definitely effects temps on AC.

The idea of just buying a new fridge is fine for those with some disposable income. I've been there before and plan to be there again someday. Not there now. So for now, I'll do whatever I can to get this fridge working.

And as I pointed out early on in the thread, my experience with my last camper is that if it's the installation which is causing the issues, you can spend $600 on a brand new fridge and find you have the exact same issues.

That's a pretty dang expensive lesson. I learned it once. Don't plan to make that mistake again.

If, after I know everything is baffled and set up to spec, it's still not cooling well...then I'll start saving for a new fridge.

But not before then.

[redbarron55]

The temp of the fins change as you go across.
I think they are colder on the right and get "warmer" on the way to the left.
The thermistor clips on one of the fins and the unit gets warmer if you move it to the right and colder if you move it to the left.
If you remove it from the fins the unit should run wide open cooling.
If it is wide open all the time it may be bad.
This is with a control board, but what you have should work in a similar way.
This is a part of fine tuning the Norcold 1200 unit on the 'net
If there is no control the sensor might be bad.
One of the tuning techniques is using a bit of styrofoam cup to insulate the sensor from the fin a little where it has to get a little colder to satisfy the system.

[ZachO]

Here are the best photos I'm going to get of how the wire attaches to the fins.

[rlaggren]

Just thought to mention that cooling unit function doesn't cover all bases in getting and keeping cool. You also got to insulate the box as well as possible to keep the heat out and the cold in. Put cooling fins inside a file cabinet and they won't get it very cold. Now put those same fins inside the same cabinet but with 4" of iso foam insulation on all six sides and all air leaks sealed and you'll have a freezer.

FWIW.

Rufus

[patrick crawford]

i have to agree with rufus. the fridge in my 2012 casita 16'er didn't work well from day one. i spent a great deal of time trying to prevent the flame from being blown out while underway. once i accomplished that task, which i assumed would solve my cooling issues, i realized i was still just wasting propane in an attempt to keep food less than warm. this past summer i gathered all the info i could on other's efforts and basically copied them. this involved insulated baffles to segregate the warm boiler air and the cooling tubes and stuffing as much additional insulation possible into the voids around the fridge's cabinet (that was a lot of insulation). why, i even lined the interior of the fridge's box with reflectix. i'm now 3 weeks into the first trip with these mods. not once has the temp in the fridge box exceeded 40f. the first few days ambient temps were in the mid 70's and the rest have been lower. temps are monitored constantly (ocd?) with wireless remote thermometers. so... the jury will remain out until summer.

another thing with these units...a routine maintenance program is totally required. clean the jet and burner tube, run a brush thru the boiler tube (or blow it out with a compressor) and generally tidy things up. at least that's my theory. i've gotten dometic's "box of promises" to do it's job now it's my job to keep it there?

p@

[ZachO]

Yes, I agree. And I know this is now a huge, unwieldy thread and no ones going to read the whole thing.

So trust me when I say we’ve been through that. Extra insulation, separating the boiler from the fins, cleaning etc. Good ideas and things we’ve been over. All that’s left for me is to check gas pressure, put up a barrier between the boiler and fins, and see about centering my flame.

If those don’t help, my fridge is done I guess.

[patrick crawford]

zach, i'm pretty sure your escape has a dometic fridge alto larger than my mini fridge. my little fridge does not have it's own propane regulator and depends on the pressure from the regulator on the tanks. a while back i became concerned with that pressure thing but could not find a nanometer with someone who knew how to use it. for less than the cost of that meter i just put a new regulator on the tanks. seemed to improve things but, you're right, i still don't know what pressure is reaching the unit. the barrier between the boiler and cooling fins had a dramatic effect toward reducing the temperature of those cooling fins. good luck!

p@

[ZachO]

Thanks Pat. Mine's a Bigfoot. Part of me wishes it was an Escape...but I like my extra space!

That's good to know that separating the boiler can make that big of a difference. I plan to test my pressure with a manometer. At some point...

I replaced my regulator when I bought the camper, but still want to test the actual pressure at the fridge connection. That has been the issue for some people.

[rlaggren]

Looking on Amazon, must be a pretty small market based on the prices asked for a simple piece of plastic w/a rule marked on it and a tube clamped to it! Many people just get a piece of 1/4" wood and clamp some 1/4 vinyl tubing to it in a U shape and staple a tape measure between the vertical legs... Maybe check ebay. Dwyer is the standard in this type of instrument; the U-tube and the the simple "inclined" instruments are bullet proof except for actually breaking the tube - so used ones s/b fine. People of reported that the built-in levels on some of the inclined instruments didn't read right so if using an "inclined" manometer, best to use your own level to set it up.

Here's the most reasonable priced one, a "U-tube". It _measures_ (not reads) up to 9" WC (because when using a "U" instrument you double the reading from one side of the "U"). This particular example will work if your buner has it's own regulator which reduces the 11" WC from the main system regulator down below 9". Or, by using somewhat less fluid which lowers the zero point, there would be enough headroom at the top of the tubes to extrapolate another inch or so; just make sure there is enough fluid to provide 1/4+ of vertical fluid in the "short" leg during the highest pressure reading. Fluid in one side of the "U" gets pushed down while the other side rises so the total fluid movement (which measures the pressure) is the sum of the downward movement and the upward movement. Or double the reading of one side:

https://www.amazon.com/RadonAway-500...tube+manometer

I am probably going to get one of these myself if I don't see any deals on ebay.

The picture shows it "lying down" which is not the position one uses it in. They are gravity instruments and the open ends of the "U" tube s/b up when measuring. In simple pressure tests, one connection is normally left open to atmosphere and the other connected to the test port with a tube of some sort. The auto stores usually have rubber adapters with conical t;ips designed to push into the vacuum ports on an engine for testing. Used with any tube of the correct internal dimension to fit the manometer that makes a fairly simple test set up. Or, ideally, get a male thread x barb adapter that fits the test port on your gas control; probably 1/8" male threads, but take the plug to the supplier or Home Deport and comparison shop. The hardest part usually is deciding and locating the type of test connection you want to use to hook the tube to.

Turn off the gas to the control, connect the instrument and hang it vertically where it's easy to read, turn on the gas, bleed the lines and fire the unit full on. Read the U-tube and double the reading for the actual gas pressure. Some gas controls may have internal regulators which can be adjusted (when you find the installation manual to locate the adjustment...). Otherwise you deal with the system regulator or the burner orifice in the unit you are setting up.

The manual for the unit should spec the proper gas pressure range. The gas control probably also has a manual which would spec the allowable input pressure range and (if it has a built in regulator) the output pressure range.

[rlaggren]

I'm going to pound the soap box once again about simply insulating the box which you hope to get/keep cold.

I have lived on a sail boat for many years and have had occasion to "get into" the best ways to keep a reefer cold using the absolute minimum of energy. The most important factors are universally 1) the door seal; 2) the amount of insulation around the box. I'll leave the door seal to others.

4" of foam insulation is the gold standard; more than that the returns diminish quickly. Because of _serious_ space constraints, 2" insulation is what most of us realistically strive for and most are fairly happy to get 1" around all sides. OEM installations NEVER provide anything close to that. From the two or three RV's I've had apart, it appears that reefer installations are no better than the marine world.

Thus, at least for long term usage, simply insulating the box will probably give as much value as any tweaks to the cooling system. It's a simpler concept, it's cheaper (usually) but it's much harder because the space provided is minimal and the reefer must be removable. But it's _important_.

Closed cell foam makes a much better insulation than any batting material because it will not soak up water and will not pass air. The box stores sell excellent material and you will only need a little. Cut it with a long knife (eg. a ham knife) or (my favorite) a course hack saw blade in a handle. Using a couple thickness (it comes in 1/2" to 2"), will make it easier to apply a fit to all sides. Glue the seams and corners to be air tight - it matters. Use one of the very rough abrading tools found at auto stores to sculpt it.

The "Reflextix" bubble stuff, IMHO from much study, is almost worthless except for a radiant block - which requires 1/2" plus clear space around the shiny side. Better to put foam in the 1/2". It might serve some purpose in situations where there is 1/4" or less space for insulation but I think I would try really hard to get a thin piece of aluminum faced foam in there.

Insulating the box is not a no brainer because of the very minimal space provided in RV's. It will be an exercise in ingenuity, patience and nitty-picky detail work. If you could take a can of spray foam and a 2' straw and hose the interior cavity anybody could do it - but they'd never get that reefer out of there in one piece again!

[DJB]

Originally Posted by ZachO

Yes, I agree. And I know this is now a huge, unwieldy thread and no ones going to read the whole thing.

So trust me when I say we’ve been through that. Extra insulation, separating the boiler from the fins, cleaning etc. Good ideas and things we’ve been over. All that’s left for me is to check gas pressure, put up a barrier between the boiler and fins, and see about centering my flame.

If those don’t help, my fridge is done I guess.

Hey ZachO:

Just wonding here when I read the thread from the start. LP gas has a oil film in it. How much I do not know, I am not the expert on this. I did have a regulator quit on me and out of curiousity I took the old one apart, full of oil frm the gas. I got talkin' to some guys that sugguested I put a drip tube much like you see on natural gas furnances and hotwater heater to collect dirt and debris. So the location of this drip tube is important. My hoses come off of the tanks and godown to the trailer frame to where in put in a t-piece and a two inch piece to collect the oil. From there the hose rise up to the regulator. I undo the cap on the drip tube a couple times a year. I was surprised how much oil was in it.

The reason I mention this that I was having gas problems both at the three burner and the fridge. The manometer showed that there wasn't enough gas flow ( I have forgotten the exact numbers now), so there guys told be to disconnect by appliance and cap all of them except the furthest one. I diconnected the regulator and had that end pointed down towards the ground. With moderate air pressure I shot air into the LP line at the fridge and to my surprise there was a fair bit of oil on the ground. Capped the fridge connection. Then, I did the furnance (next furthest), then the three burner. Put her all back together, did a soup test. Did the mamnometer test with this guy. Bang, on.

Not sure why this is part of LPgas, may be part of the manufacturing. I have read alot of threads on the LP forums. Anywats just my 2 cents here. Usually collects in the bends or dips of the gas line. Also read where the regulators should be as close as to the same as the outlet of the tanks.

Hope this helps

Boler77

[Borrego Dave]

That make a lot of sense David, others have talked of oil in the lines.

[Byron Kinnaman]

Originally Posted by DJB

Hey ZachO:

Just wonding here when I read the thread from the start. LP gas has a oil film in it. How much I do not know, I am not the expert on this. I did have a regulator quit on me and out of curiousity I took the old one apart, full of oil frm the gas. I got talkin' to some guys that sugguested I put a drip tube much like you see on natural gas furnances and hotwater heater to collect dirt and debris. So the location of this drip tube is important. My hoses come off of the tanks and godown to the trailer frame to where in put in a t-piece and a two inch piece to collect the oil. From there the hose rise up to the regulator. I undo the cap on the drip tube a couple times a year. I was surprised how much oil was in it.

The reason I mention this that I was having gas problems both at the three burner and the fridge. The manometer showed that there wasn't enough gas flow ( I have forgotten the exact numbers now), so there guys told be to disconnect by appliance and cap all of them except the furthest one. I diconnected the regulator and had that end pointed down towards the ground. With moderate air pressure I shot air into the LP line at the fridge and to my surprise there was a fair bit of oil on the ground. Capped the fridge connection. Then, I did the furnance (next furthest), then the three burner. Put her all back together, did a soup test. Did the mamnometer test with this guy. Bang, on.

Not sure why this is part of LPgas, may be part of the manufacturing. I have read alot of threads on the LP forums. Anywats just my 2 cents here. Usually collects in the bends or dips of the gas line. Also read where the regulators should be as close as to the same as the outlet of the tanks.

Hope this helps

Boler77

I would like to suggest that you contact the one of Propane companies and as ask them about oil in the propane. I get the impression from a couple propane company web sites that's oil in the propane is a myth.
If you found oil in the regulator how did it get there? Maybe a previous owner got carried away with the oil can an tried to oil the valve parts. Further examination and research needs to be done.

[Raz]

When I replaced my regulator last spring I found a couple of tablespoons of oil in the line. I have no idea how it got there.

[Joe Romas]

Byron

Ain't no myth, seen it first hand.
Especially bad in the water heater line on 17' Casita's.

[rbryan]

Originally Posted by Joe Romas

Byron

Ain't no myth, seen it first hand.
Especially bad in the water heater line on 17' Casita's.

Joe, I found this excerpt on another forum, posted from a fellow who refined petroleum products, including propane, for decades:

I have been involved in the refining process (including the manufacture of propanes, etc.) for over 35yrs. I seriously doubt that the contamination described by the original poster is that of oil. In the refining process, by design there is very nearly no opportunity in which an oil excursion of any kind might occur into the propane fraction, and even if this could happen, realistically this contaminated product would never make it into commercial propane storage facility (e.g. safeguards/quality controls, etc).*

Nor might it be ethyl mercaptian(the agent that produces the odor in propane). Ethyl mercaptian is introduced into commercial propane (e.g. propane destined for use as a fuel) at the extremely low ratio of only (approx) 800cc per 9,500 gallons gross, also not very likely. Ethyl mercaptian (by deliberate selection) is also very friendly to propane handling and storage devices.

Most likely the substance being described here as "oil" is actually a caustic solution which is used during the final finishing phase of the propane stream (lowers sulfur content), but every bit as slippery to the touch as is any oil. Caustic solution is typically misidentified as oil. Unfortunately, no process is foolproof, and while RARE, it is possible via an episode of cascading mishaps (part mechanical), for this caustic solution to become entrained into the final propane product and end up in some unfortunate customers propane tank. This is bad news as caustic solution is extremely corrosive even in small amounts, and can take out LPG regulators. To aid in diagnosis you might try testing this substance with litmus paper (available at pool supply stores) for a high p/h number.