BAC Forum
General Boards => Technical Support => Topic started by: Jason Worman on May 15, 2020, 09:21:57 PM
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Hi All,
So our absorption fridge appears to be on the way out. It either freezes up on the "max" setting or is above 40 degrees on anything less than that. It is 7.7 cubic feet so we are considering replacing with residential model. For the foreseeable future we are parked as hosts and plugged into 50 amp power. We have 2000 watt inverter if we decide to travel. I really like ours now that can run on propane. Anybody switched over to residential? How is it when traveling or dry camping?We don't have solar installed. I imagine the install is quite a job and left too
Thank you,
Jason Worman
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I just replaced our Norcold 1210 w/ a 18 cu/ft Fisher Paykel. For your smaller 7.7, you could look at replacing the absorption cooling unit with an 'HVAC' or residential cooling unit retrofit. See https://jc-refrigeration.com/
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Jason
If your unit is capable of freezing up the fridge section it would appear the cooling unit is working and that your problem may be the thermistor or electronic control board which controls the temp in the fridge.
Eric
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Jason
The temp in the fridge is monitored by a thermistor clipped to the cooling fins.
This thermistor is an NTP ( negative temperature coefficient) meaning as the temperature goes down the resistance goes up
When that resistance reaches the neighborhood of 7 to 10 K ohms this resistance signals the control board to shut down the cooling unit.
This 7 to 10 K ohms should occur at or near 34 degrees F.
With your cooling unit freezing when on Max cool it would appear the cooling unit is working .
The unit provides cooling to the freezer first and then on to the fridge compartment second so if the fridge is getting cold enough to frost the fins then the cooling unit is working.
As discribed above the thermistor controls the cooling unit via the control board on Max cooling the thermistor may be bypassed
Allowing the unit to cool but when not on Max cool the control board relies on the thermistor to control the boards decision to shut down the cooling unit.
With that logic the problem could be a bad thermistor, too high resistance could be a bad connection or corrosion on the board connection.
Disconnect and check the resistance of the thermistor at the control board if it is at or above 7000 ohm at room temperature you've found your problem.
Hope some of this helps
Good luck
Eric
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Eric,
How do I test the components that you mentioned?
Jason
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Eric,
Oops! I was to quick responding! Thank you
Jason
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Absorption cooling uses ammonia as refrigerant; If, when working around the back of the refrig (outside) you smell any ammonia, shut off the fridge asap and move your food to an ice chest. Your fridge is almost 30 years old (if original) and way past due for replacement. Leaking ammonia isn't so bad, but there is also some flammable hydrogen gas in the ammonia, and that, when leaking, can start a fire!
You can keep the fridg 'box' and just replace the cooling unit, for safety sake!
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Bill,
I emailed Dutch Air about needing new cooling unit. RV that did initial inspection after purchase said cooling unit had been replaced at some time.
Jason
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Jason
As Bill mentioned a failing or failed cooling unit is usually accompanied by an amonia smell or a yellow stain or powder near the failure( leak) if you have any of these signs the unit is done and shouldn't be operated as it's a fire hazard.
But if the cooling unit will still freeze up that's not likely the case.
Eric
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Eric,
The fridge seems very solid. So is it okay to have the metal fins frozen over?
Jason
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Our control board was out and we replaced it with a board from Dinosaur Boards out of Ore. It was a plug n play and a adjustable thermistor was built right in, seems like the $100 range.
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Jason
Much is said about the absorbtion fridge. You asked about a residential.
Ours came with the residential by Westinghouse (I believe). It is original so you can take from that it has held up well for 125K miles and 3 trips to Ak.
We do have extra batteries but thats about it beyond the 2500 watt inverter.
If you are on shore power ours is no problem. While driving we have the inverter on so again no problem. Dry camping is a small problem in warm weather. We run the generator twice a day. That is with our 2007 fridge. I understand the new fridges draw about half the power we use.
Replacemen cost and the fire danger all considered you couldnt give me an absorbtion unit.
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Jason
Sorry for the delay frozen over fins are a sign of moisture in the fridge usually caused by a leakly door seal letting air into the fridge with the door closed .
This can be checked using a dollar bill, just close the bill in the door and see how much pull it takes to pull it out through the door seal if there's no resistance the seal needs to be tightened up or replaced.
If the cooling unit is making ice on the fridge fins the cooling unit is working ok.
The fridge should be in the 37 degree ball park for proper refrigeration.
A bad door seal allows warmer air into the fridge and makes the fridge work harder to keep cool as the moisture condenses on the cold fins it freezes which creates an ice layer which insulates the fins somewhat from the air flow making it even harder for the fridge to keep cool.
Some people install a fan to move air over the fins to help alleviate the moisture condensing on the fins this also help cool the fridge compartment more evenly.
First check your fridge temp in the fridge
Second check the thermistor resistance readings against temp.( Replace thermistor if necessary)
Check the door seal around the whole door( correct if necessary)
Depending on the climate your in you may want to add a fan in the fridge to move air over those fins in a very humid climate this becomes more necessary.
In very hot areas it is sometimes necessary to add a fan to the rear cooling fins to help with air flow and efficiency .
And of course these fridges must be kept level to work properly if they are far enough off level they will not return the cooling solution to the boiler and the boiler will run dry this causes the anti corrosion chemical ( zinc chromate) in the solution which is a powder to cook and cristalize these crystals can then move around with the solution and plug the refrigeration office rendering the fridge in operative.( Sometimes burping the fridge will cure this problem)
Hope some of this helps
Eric
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Another common issue that has not been talked about is how well are the refer doors sealing. I have seen several times where the freezer is correct temperature but the refer side is 50 degrees. Seems like when folks do there spring cleaning on their RV, they remove all the shelving on the doors When they reassemble the shelves, one of them is coming in contact with the shelving inside the refer, just enough to wedge the door open at the bottom 1/8". To prove the doors are sealing properly, perform the "dollar bill test". Close the doors with a dollar bill held against the opening where it seals and then pull it out. If you feel resistance, it is sealing. If the bill falls down you have a leak. Find out what may be in the way.
Another way to prove Eric's test on the "thermister" is to remove it from the fins. Get an ice cube and drill a 3/16 hole in it and put the thermister in the cube. Remove the thermister wire from the pc control box at the top and measure the ohms reading with a good meter. Should be 9800 to 10,000 ohms. Hope this helps, Fred
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Me and Eric were typing at the same time,
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Fred and Eric,
Thank you for advice. I did the dollar bill test and surprisingly there was decent resistance on all four sides when I pulled on it. Tested the thermistor and got normal reading. I went back through what records I have and contol board was replaced not that long ago. Currently cooling at about 38 degrees with selector nob almost on Max setting. Just can't decide about absorption vs residential. This fridge has stood the test of time, but the threat of fire still hangs in the back of my mind. Wonder how safe the new Dometic models are.
Thank you
Jason
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If your fridge is 38f now, what is the ambient temp where you are (Oregon coast?; 55-65f). If you venture out into warmer weather in the summer, your fridge temps will climb with the ambient. So it won't take much of a heat wave to get your fridge above 40f. Our 4 door Norcold worked just fine, fins did ice up; I would defrost freezer about 1x/month; But, with all the fridge fires, I just thought that our unit, 15 years old then, was running on borrowed time, so we went residential. Replacing your cooling unit with the HVAC (residential) type from JC Refrigeration seems to be the best of both worlds. You get to keep the same fridge cabinet you have (no carpentry or lost drawers), and you get a reliable, fire free cooling system. Seems the JC units get condensation on the fins, too, they include the fans with the cooling unit. We have a Dometic 8 cu/ft in our 2013 travel trailer. Works just fine; I don't know if Dometic or Norcold can tinker much with absorption technology so not sure if new units are any better. Absorption refrigeration is something like a miracle-you use heat to make cold.
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Bill,
Thank you for your input. We live right on the bay in North Bend, Oregon, so ambient temps never get that warm plus it is very humid. I like the idea of HVAC cooling unit, think it will be almost impossible to replace the entire fridge without lots of tinkering with cabinetry.
Jason
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Jason
If you come to the conclusion that you want to replace your fridge, I would strongly suggest that you go the residential route. Over the years I have owned many RVs with the common absorption refrigerator. I have replaced cooling units on two of them and replaced one completely with a new absorption unit (the box had other issues and was not worth keeping). When I purchased my current motorhome it had a failed absorption refrigerator (I negotiated a nice price because of it). I had been wanting to do a residential conversion, so chose to remove the absorption unit and replace with a Samsung 18 CF 120 volt compressor unit. I have been very happy with the Samsung for the last 3 years. I would never willingly go back to an absorption type refrigerator. It runs flawlessly off of shore power or generator power on 120 volts. When traveling or dry-camping with no power source, it runs off the inverter powered by the 12 volt battery bank. I have a 2000 watt inverter and 400 amp hour battery bank. With 3 years of experience and lots of dry-camping, I have learned the Samsung costs me an extra hour per day of generator run time when I am parked. The biggest issue I have seen with people doing this conversion is failing to have an adequate battery charger to recharge the batteries. The battery charger that comes from the factory in many RVs is totally inadequate for this purpose. My sons trailer has a charger rated at 8 amps. That would take DAYS to recharge my battery bank. My charger is rated at 100 amps and will run off of my little red Honda 2000 inverter type generator. I had to run it 1 to 2 hours a day on my previous motorhome to recharge the batteries when dry-camping (depending on TV usage). That has become 2 to 3 hours with the Samsung refrigerator. So, I consider 1 hour per day generator time to support the convenience of the residential refrigerator to be a small price to pay.
Good luck with your decision whichever way you decide to go.
Richard
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Richard,
Thank you for your input, our only concern is finding a residential refrigerator that will fit in the space in the cabinet. Our current fridge is under 8 cubit feet so the residential equivalent is quite small. My wife is leaning towards the residential version since we are parked most of the time. Our charger is 75 amps which seems to do a fairly good job. This forum is so awesome! Especially to such a novice as myself.
Warmly,
Jason
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Jason-
I won’t say much bad stuff about residential units, except that my personal experience with Samsung-built ones and Samsung-made components of other products has put me off the company. Obviously others here have had little such experiences. We have Samsung Android phones and “wireless” chargers, with no issues except one charger that occasionally overheats.
That out of the way, I’ve had few problems with Dometic RV fridges on our motorhomes. And practically all the problems I read about any RV units involve Norcolds. Breakdowns of my Dometics were of my own greenhorn neglectfulness, not quality of product. 35+ years ago the addition of a solar/12v fan to the rear of our old coach’s 8c.ft. made a big difference in its cooling ability in hot weather. Offering afternoon tree or hand-made shade of some sort over the fridge outer wall and door can help.
Our current 14cf Dometic did pretty darned good parked a month in midsummer eastern Nebraska heat in 2012; most days were 90-100 degrees and too many exceeded 112F with humidity this Willamette Valley native wasn’t used to. Yeah, interior fridge temps then pushed 50+ mid-day and I opened the outside door on occasion to help ventilation, or moved some cubes from freezer compartment to fridge. I flirted with installing a rear compartment fan setup at the time, but encountering such ambient conditions is too rare for us. Normal ambient temps/humidity aren’t a challenge for it.
So I guess you can tell I’d have to encounter repeated, confounding breakdowns to entice my changing to residential, and it would take some convincing to make it a Samsung or any brand built by them. That’s my personal opinion based on experience. That doesn’t mean I’m encouraging you to dismiss that of all the others here who like their residential units; you can’t ignore the many good reviews and installer recommendations. I just would hope, for those that elect to switch, that there were other non-Samsung made brands to choose from.
Probably your wife’s biggest concern if you’re full-time is the size of the fridge. Regardless of what you do, that’s going to take enlargement of the compartment area, which is likely where the most engineering and work will be.
Joel
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Our coach has the Norcold LRIM 1200 fridge. In eight years of ownership, I have replaced the brain board with a Dinosaur board, had the recall device changed, had a new ice-making module installed, and put in a Halon Gas fire suppression bottle behind the fridge. The Dinosaur board cost was about $230 but I don't remember exactly; it was several years ago. The recall device change was no charge. The new ice-making module was $125 or thereabouts. The Halon Gas bottle was over $100, I think. We are still in Yuma and the Norcold fridge has been ON for two weeks keeping cool and making ice in this heat. Last week we had two daily highs over 110F. This week we are cooler; perhaps 100F highs. Since we had Zep's disable our house's RO device two weeks ago, the house fridge isn't making ice. So every couple of days I bring the Norcold's ice bucket in and dump it into the house fridge's ice bucket. When the coach's Norcold fridge gives up and if we still have the coach, then we will likely replace it with a residential fridge. But it will require an ice maker!
And now that I have "praised" our Norcold, it will probably be jinxed and give me the finger, eh? I don't know the manufacturer of the fridge in our house in Hermiston, OR. It came with the house when I made the purchase in 1991. Whatever manufacturer made it might be the manufacturer I choose for our coach residential fridge, eh? Almost 30 years and counting! The fridge in our house in Yuma is a Frigidaire with a water and ice dispenser in the door. That would be a good option for a new coach residential fridge.
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Joel,
I hope to meet up one of these days. Appreciate all your insight and sharing of your experience. My wife is leaving for a couple of weeks and said don't switch out fridge until she gets back. I said, why don't we call it my fathers day gift@ ;)
Jason
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If you are window shopping:
https://www.ajmadison.com/b.php/Top+Freezer%3BCounter+Depth%3BRefrigerators/N~26+4294966342+3895
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For those out there still entertaining the idea of a residential refrigerator that will fit right in that opening of that old 2 door Dometic or No-cold, Avanti makes a 7.4 cu that slides right in. Cost between $350.00 and $450.00. The model is RA7316PST and the dimensions are 22 1/2 wide by 22" deep and 55 1/2 inches tall. Hope this helps, Fred
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Don't know if this will fit, bu Dometic has a compressor-based fridge, 10cu ft.
https://www.dometic.com/en-us/us/products/food-and-beverage/rv,-boat-and-truck-refrigerators/rv-refrigerators
I'm sure it would be spendy!
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Bill and Fred,
Thanks for the suggestions. My smarty pants engineer son is home for a visit and told me after I added a small fan today blowing in the fridge by the cooling fins that it would make the fridge heat up. He went onto give Thermodynamics 101 which made my eyes roll back into my head. I said it helps to moves air and actually cools fridge.
Jason
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Ask him how quickly his beer will go flat (Ideal Gas Laws)!
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Jason
You might want to look at the ARP fridge defender of as others have mentioned the JC people make a compressor based cooling unit in both 120 volt and 12 volt.
I've considered both residential or cooling unit replacement but with my coach I have a Domestic 7832 side by side a d like those who have the norcold 1200 series my fridge is too large to get out the door so to remove the old fridge would require a windshield removal and that opens a whole new kettle of worms.
So when the time comes I may look into the 12volt compressor cooling unit replacement route and eliminate inverter loses.
On my unit as the unit is 23 years old I have an ARP fridge defender which also controls a fan unit on the rear cooling fins to keep the efficiency up even in hot ambient temperatures.
The fridge defender is connected to the fridge and monitors the boiler temp and shuts the unit down if the boiler temp gets out of control caused by a blockage or unlevel condition once the unit has returned to normal operating temps the defender then turns unit back on and returns to normal operation.
On there web site they explain how it the fridge defender saves the cooling unit from damage and fires.
Measure your door opening before purchasing your new fridge make sure you can get the old out and the new in I understand you likely have a smaller fridge but better safe than sorry.
Good luck on your decision
Eric
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Not a good idea to remove a windshield unless absolutely necessary. The last 40 refrigerators that I have replaced have gone thru the window above the sofa with no issues. I wish there was a "silver bullet" fix for all of us out there trying to update our coaches and keep our food cold and stay safe. Happy Trails..... Fred
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In the two or three years I spent thinking about replacing our Norcold with a residential fridge, I went thru all the possible scenarios many times in my head. In the end, two guys from the appliance store carried out the 4-door fridge thru the front door; the new fridge came in the same way. I unscrewed the door stay so the door would swing wide, and I removed the co-pilot seat from the mounting bolts so I could move it a bit. I couldn't figure out how to disconnect the wiring connectors at the base of the seat, so I just moved the seat a bit as needed as the fridge passed by. No scratches, no torn upholstery. The appliance guys did a great job. Of course, the doors came off the old and new fridge, but no issue to re-install them on the new fridge. Our coach has the front tv fold up into the ceiling, so no head banger to worry about. The new fridge just purrs, since we're not going anywhere now!
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The fan I installed on the old Pace Arrow was neat. It’s 4”X 6” solar panel screwed to the top of the fridge’s aluminum roof vent, so when the sun was at its worst on the fridge’s side of the rig, the fan got maximum power. It had a 3-way toggle switch I mounted to the cabinet just under the fridge door; I could choose Off in the middle, and 12v Battery power or Solar to either side of Off.
The fan as I recall was plastic wire-tied to the lowest “coil” loop (absorber tube), just above the vented access door, so it drew cooler air in and up over the evaporator loops and condenser fins to the roof vent. It worked great and the difference was noticeable immediately. Some companies offer a two-fan configuration, one at the bottom and an exhaust one at the top vent.
An interesting install video of a solar unit that replaces the roof vent altogether and is considerably larger and more involved than what I did is here (there are plenty of others): https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=2ahUKEwi--MK-gLzpAhVGJTQIHZXxDJ8QwqsBMAF6BAgJEAk&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DAmr9vbe4WNU&usg=AOvVaw1TcZysOEVI9iS8N3kwX3fQ
And check this site out: https://rvcoolingunit.com/-Cooling-Performance-Fans-items-C320215.aspx
Joel