Fridge Performance

[pdemarest]

Questions:

In terms of getting the best cooling in very hot weather (90 degrees plus) which power source works best for a 3-way fridge - LP or 110volt?

I'm aware that when in 12 volt DC mode these fridges can eat up the batteries in a hurry but while in transit will the engine's alternator make up for the power drain? I know you need to remember to turn the unit off or switch to LP when stopped for any length of time but wondered if there's a disadvantage to running in the DC mode while driving. Is the DC mode less effective in cooling the fridge than using LP?

Paul

[pdemarest]

Well, I think I answered my own question on this topic. Yesterday I drove my rig about 150 miles and then stopped and tried to turn on my fridge. Battery condition was great per the the solar charger panel and the range hood monitor. The fridge wouldn't start on LP (probably needs burner cleaned) so I switched over to DC and drove back home. After about 100 miles the low battery alarm went off which I guess means that the alternator does not charge the batteries enough to deal with the fridge.

Paul

[Blue~Go]

When you look at the specs, it's really quite astonishing just HOW MUCH power an absorption (i.e. propane) refrigerator uses while running on electricity. They are just SUPER inefficient that way. And it gobbles the power just as badly on 110volt/AC as it does on 12volt/DC -- but just you don't "notice" it on AC as you generally have an "unlimited" power source (shorepower, etc.).

I can't remember the exact specs, but I think an absorption refrigerator the size of the ones in the Chinook takes something like 30 amps to run on DC (whereas a similar compressor refrigerator would be using maybe 5 amps DC). It's formidable.

You might have more success running it on DC (alternator power) when driving if you had a larger wire than a stock one running from the start battery (alternator) to the house bank, plus a separator that doesn't impose a voltage drop like the Surepower type does (such as the Blue Sea 7622), but it's still a power hog no matter how you slice it.

PS: I have a friend (other brand RV) who has had both a Dometic (then) and a Norcold (now) of the same size as ours. He's heard people say that they don't cool as well on DC, but "technically" it should be the same on AC vs. propane, because all the AC power is doing is mimicking a little flame with electricity; the cooling process is the same, just flame (propane) vs. little element (electricity). The same fluids go through the same tubes, etc. to do the actual cooling. Maybe the "DC cools less" just has to do with how the DC takes so much power that it's always struggling with not enough battery power (I don't know; just thinking out loud).

[pdemarest]

Hey Blue - yep, the low battery alarm came on after about 2.5 hrs of running on DC power. When I got back I called the rv place that had checked the appliances when I bought the rig to find out why it wouldn't run on LP. Turned out to be air in the lines and once that was cleared it started right up. Left it running on LP for about 4 hours and the freezer got down to 0 degrees and the fridge was at 40. Woke up this morning and went out to check on it and the thing was in "check" mode and the fridge had warmed up to room temperatures. So, I know it works but can't figure out why it would have stopped. I was able to restart it and will check it later. Any ideas on what would make it shut off like that?

[Manitou]

mine would go to "check" randomly (seemed to be random.. It got to the point where it would t stay on for more than an hour or 3). Dinosaur replacement board fixed it and has been stable since.

[pdemarest]

Well, I dropped my Chinook off at the repair shop. The burner looked clean so they suspect it could be that my batteries are not charging properly from the engine and if so they think low batteries could be what's causing it to turn off while running on LP. Will provide an update when I get the diagnosis.

[Blue~Go]

Well, I dropped my Chinook off at the repair shop. The burner looked clean so they suspect it could be that my batteries are not charging properly from the engine and if so they think low batteries could be what's causing it to turn off while running on LP. Will provide an update when I get the diagnosis.

I may not be remembering everything that goes into your mystery, but this sounds slightly odd. For sure, the refrigerator DOES require some DC power when running on propane, but as far as I know it is a very small amount. Just enough to power the control board, I think. So if your batteries were too low to power the refrigerator on propane, I should think everything else in the "house" part of your rig would also be not working (water pump, lights, etc.). Is this the case?

Note that I can't immediately find the DC draw in amps when running on propane, so I can't put a number on it.

[Manitou]

The low voltage disconnect will alarm and shut down DC before the batteries are too week to manage the fridge in LP mode. (At least on my rig)

[SMan]

I also believe that the fridge requires very little power and that the draw is in micro voltage. After buying our Chinook the fridge would work for a day sometimes, then maybe only an hour or so before getting the dreaded check light. It was very random and intermittent. The burner was clean and the propane was full. (I've had a Dometic fridge fail before for the burner having soot and rust built up) I haven't had a problem since replacing the control board with the Dinosaur board. (Which only took a few minutes.) Had to replace the control board in my previous motorhome as well for the same reason.

Good luck and look forward to your update.

[Blue~Go]

I found the Dinosaur replacement board page on Amazon while I was looking for the spec on the amp draw of the control board. It seems reasonably priced and the reviews contained a number of tips for DIY installation. To each their own, but if it were me, I'd buy one of those and put it in ASAP. Sounds like a better design and like the originals are prone to "flaky" problems. Even if that didn't turn out to be the problem you'd have a better fridge for it (but it sounds like it very well could be the problem).

Double check if you are going to purchase it, but this is the one I was looking at:

http://www.amazon.com/Dinosaur-Electron ... tic+rm3663