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Old 08-27-2013, 06:55 PM   #15
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Thanks, guys. All very helpful thinking. Duh--hadn't thought to just check thoroughly the propane system, and I'll have the guys do that when we get back.

To answer Jammer's question, what we're trying to accomplish is:

(a) Better cooling by using AC (from inverter) instead of propane. Our experience has been that shore power has provided much better cooling than propane. If your instinct about the propane system being fouled or the regulator iffy is correct, then that may fix that single important issue. Again, thanks!

(b) Better and foolproof cooling while towing by using AC from inverter. Again, if propane system is the problem, then we can just deal with creating wind baffles, but if the AC/inverter is a good solution, we won't have to deal with that issue.

(c) While doing (b), making sure that we don't damage the alternator with a heavy load of supplying the reefer through the battery bank/inverter. I've read on other strings that there have been alternator problems when towing due to running off batteries and the associated tasking of the alternator.

(d) Saving battery life (four xpensive Lifeline AGM six volt 220 amps units wired to provide 12v 440 amp system) by keeping them off the Airstream- provided single level charge converter. A reputable tech just informed us that although we correctly replaced our converter in our factory solar system from the Airstream supplied single level charger to a three level charger, the primary converter for our coaches are also only single level. If we can run the reefer on inverter supplied AC, we can avoid using shore power, at least during the day, and therefore avoid 24 hour flood charging of the battery bank. We'd simply turn off the shore power in the morning and let the reefer run off the battery bank/solar/inverter all day, and then re-engage the shore power if we want to run the HVAC at night. This instead of replacing another lesser quality Airstream factory part with expensive after-market labor (the primary charge converter.)

We're hoping that a very simple solution for ALL of the above will be to unplug the reefer from its shore power supplied AC socket and plug it in to the inverter supplied AC socket that we installed to power another very small draw appliance that's installed above the reefer, so there's already an inverter supplied AC socket installed in the reefer cabinet with easy access.

Since you guys are confident that the rather weak 600 watt inverter supplied by Airstream with the factory package is adequate to the task, the only remaining problem seems to be possible overload on the alternator when towing.

Any more thoughts?
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Old 08-28-2013, 11:51 AM   #16
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Quote:
Originally Posted by gecko View Post
Thanks, guys. All very helpful thinking. Duh--hadn't thought to just check thoroughly the propane system, and I'll have the guys do that when we get back.

To answer Jammer's question, what we're trying to accomplish is:

(a) Better cooling by using AC (from inverter) instead of propane. Our experience has been that shore power has provided much better cooling than propane. If your instinct about the propane system being fouled or the regulator iffy is correct, then that may fix that single important issue. Again, thanks!

(b) Better and foolproof cooling while towing by using AC from inverter. Again, if propane system is the problem, then we can just deal with creating wind baffles, but if the AC/inverter is a good solution, we won't have to deal with that issue.
Right, we've covered this.

Quote:
(c) While doing (b), making sure that we don't damage the alternator with a heavy load of supplying the reefer through the battery bank/inverter. I've read on other strings that there have been alternator problems when towing due to running off batteries and the associated tasking of the alternator.
You're not going to damage the alternator in the tow vehicle by virtue of the presence of a heavy load in the trailer, unless the alternator is marginal due to dirt, age, or small size. If any of that applies, you should replace it anyway. The charge circuit from the tow vehicle to the trailer just won't deliver the kind of current that would pose a problem for the alternator, and on most vehicles, it's fused at 30a or less.


Quote:
(d) Saving battery life (four xpensive Lifeline AGM six volt 220 amps units wired to provide 12v 440 amp system) by keeping them off the Airstream- provided single level charge converter. A reputable tech just informed us that although we correctly replaced our converter in our factory solar system from the Airstream supplied single level charger to a three level charger, the primary converter for our coaches are also only single level. If we can run the reefer on inverter supplied AC, we can avoid using shore power, at least during the day, and therefore avoid 24 hour flood charging of the battery bank. We'd simply turn off the shore power in the morning and let the reefer run off the battery bank/solar/inverter all day, and then re-engage the shore power if we want to run the HVAC at night. This instead of replacing another lesser quality Airstream factory part with expensive after-market labor (the primary charge converter.)
Sorry, but this is inside-out thinking. Batteries deteriorate with use. If you're constantly charging and discharging the batteries, they'll deteriorate faster. Also, the stock converter will probably not fully charge your batteries overnight, at least not in cool weather. If you are going to run AGMs you need a new converter.

New converters are way cheaper than 4 new lifeline AGMs, which is what you'll need to buy in a couple years if you don't replace the converter.

I run flooded batteries in my rig. They're cheaper and they're less prone to damage from overcharging. AGMs have their advantages but if you're going to play the AGM game you've got to have a converter that can handle them. I would suggest the Xantrex TrueCharge with the temperature compensation probe, but there are other good ones out there.

Quote:
We're hoping that a very simple solution for ALL of the above will be to unplug the reefer from its shore power supplied AC socket and plug it in to the inverter supplied AC socket that we installed to power another very small draw appliance that's installed above the reefer, so there's already an inverter supplied AC socket installed in the reefer cabinet with easy access.

Since you guys are confident that the rather weak 600 watt inverter supplied by Airstream with the factory package is adequate to the task, the only remaining problem seems to be possible overload on the alternator when towing.

Any more thoughts?
Sure, one more piece of math. Your refrigerator draws maybe 200 watts. The inverter will draw around 18 amps when the fridge is on. So after less than 24 hours of fridge on-time you'll have a dead battery bank. Maybe less since your converter doesn't charge them fully.
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Old 08-28-2013, 12:34 PM   #17
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An excellent 3-stage converter (Iota or Progressive Dynamics 80-amp, e.g.) costs about half of what *ONE* of those big Lifeline AGMs cost. Thinking of a quality converter as "too expensive" when you're managing $1600 worth of batteries is a good definition of false economy.
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Old 08-28-2013, 03:52 PM   #18
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If it works on either electric or gas, it WILL work on the other. Really, what everybody is saying - to check the propane system - should be your first step. You should check the pressure leaving the regulator to be about 11" of water column pressure and you should have about 7" at the burner. You should check and possibly clean your burner nozzle because it can become gummed up. Soaking it in some alcohol for a day then blowing it out should clear out any obstructions or gook. NEVER stick anything into the nozzle and that is sure to enlarge the hole and will cause excessive heat input to result which could destroy your cooling unit.

The burner itself should be blown out also. If a spider builds a little web inside, that is enough to impact gas flow to the boiler (happened to my water heater). Just a puff or two of compressed air is all you need.

You should also vacuum out/blow out the boiler tube - where the flame goes. If it becomes obstructed with anything like rust particles it could alter how heat flows through the tube.

All of these steps are simple things you should do every year anyway (except cleaning the burner nozzle) to ensure that all the heat gets to the place where it belongs.
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Old 08-29-2013, 12:22 AM   #19
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I upgraded my rig with 4 AGM's and getting a quality 3 stage charger is a must. Not that expensive to upgrade your existing Airstream charger. I also added a solar panel for a total of 300W of solar. You will need at least that much with 4 AGM's. Not a good idea to use solar only for charging when shore power is available. Batteries only have so many cycles in them. Use the solars when boon docking.
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Old 08-29-2013, 12:47 AM   #20
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Thanks everybody for your input. to answer the three inputs:

We have 260 watts of solar. At that time, we were stuck with our limited roof real estate already having the low output 56 watt Airstream supplied panels, and the large output panels that we could find 4 years ago (tons more available now) were 80's. Coupled with a BlueSky converter, however, this system has proved to be quite good for our dry camping uses, which are typically not longer than two weeks--even with some cloudy days and fog limiting input. If we have trouble with the existing panels, we'll definitely swap all four out for 100's or 120's, and have an even more powerful system.

As far as a good converter, it's definitely on our list. But because I'm not comfortable with doing electric myself, it's not only the cost of the converter but the high cost of local labor ($100/hr plus) to install, combined with making it a bigger job than just swapping out because the local tech feels that the Airstream provided wires are too light, too. I will get a second quote once we return to home base, and it is on the list. It just never would have occurred to me that Airstream would have "cheaped out" on something so important.

The advice about the batteries having only so many cycles so do not rely on solar/batteries when shore power is available is excellent. So the replacement of the Airstream converter has moved up the list.

And Wally 54's amplification of the advice (with much appreciated added detail) to check out the propane system is good, too. This is definitely something we will do soon. Of course, the system does currently operate in both modes--it's just that it's much less powerful in propane mode than in electric. All of the advice and experience from you guys has been very helpful in letting us know that this is not normal, and we will focus on this in five weeks once we reach home port (until then, we're on shore power except for the 1500 mile trip home).

Thanks again!
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