Thanks Mr. Squirrel for the report --- I wasn't all that unhappy with the
Dometic and now I'll stick with it ;-)

Cheers,
Doug

On 6/22/06, Michael Elliott <j.michael.elliott@gmail.com> wrote:
>
> I installed a Norcold DC0040 into Mellow Yellow and during this week's
> shakedown trip, I monitored its performance.
> First, generalities: it kicks butt on the Dometic 182R. Despite all the
> tweaks and modifications I made to the Dometic, it never held cold below
> 50F when the outside temperature climbed past 80F. This reefer, on the
> other hand, is rock-steady at all times, even at 90F outside.
>
> The one issue that concerned me is battery draw. Before putting Mellow
> Yellow to bed at the end of camping season last year, I finished
> installing the solar setup. I now have two BP Solar 45W panels that I
> can haul anywhere within 40 feet of the van where there's sun, and a
> Blue Sky Company Solar 2000E controller to stuff the electricity
> generated by the panels into the Optima aux battery. Even so, if the the
> consumption of the reefer (along with this little notebook that we use
> to watch movies on, and the stereo system I installed . . . oh yeah, the
> fluorescent lamps I installed, too) . . . well, if running all these
> things depletes the battery quicker than I can charge it back up, then I
> will need to re-configure my setup.
>
> I had read that the Norcold draws 2.5 amperes when it is running, and,
> according to . . . someone, I don't recall if it was the mfgr's website,
> or some other Vanagon list member who said this, but anyway . . . I have
> read that the reefer runs about 5 to 10 minutes per hour. At 10 minutes
> per hour it comes to 0.4 ampere-hours (2.5/6) so I reckoned my Optima
> would do nicely.
>
> Theory. Reality turned out to be somewhat different. I noticed during
> the afternoon that the reefer ran a lot. I was busy setting up camp so I
> didn't make an effort to log its on and off times, but I estimate it ran
> 50% of the time. I didn't really use much in the way of other
> power-consuming accessories. A blip of the coffee bean grinder to make
> myself a cup of drip Ethiopian Fair-Trade organic coffee, a minute @
> 250w with the mini food-processor to make my lunch. It's a couple days
> away from the longest day of the year, so besides one LED reading lamp,
> and the car stereo (with subwoofer amp off it draws about 0.3A), the
> only appliance I ran after dinner was the reefer.
>
> The Norcold was still cycling on and off when I went to bed. If you put
> things just so on the stove top they won't rattle too much, which leaves
> only the mild brrrrrr sound of the compressor. At 3am I was awakened by
> the squeal of the low-battery alarm. I peered at the voltmeter . . .
> don't remember what it said, exactly, being farsighted and groggy, so I
> just turned off the reefer and hit the aux battery main shutoff. Figured
> I'd sort this out in the morning. I adjusted the alarm to go off if the
> battery hits 10.7 volts; according to Optima's tech support, their
> yellow top batteries don't want to get discharged below 10.5V.
>
> Of course I tossed and turned for a while, questioning my assumptions,
> wondering if I had a defective refrigerator, whether the solar charging
> system will be able keep up with this energy-consuming monster, and
> wondering whether the food in the reefer would be lukewarm in the morning.
>
> I noted a few things this morning. First, I had left the inverter on
> when I went to bed. It doesn't draw much when idling, but it has its own
> low-battery alarm, and it triggers at a higher voltage than the one I
> installed. So I might have been hearing that one. Second, the battery
> voltage was sitting at 11.7V, when I got up, which is normal bounceback
> unloaded bounceback voltage. Third, it was 38F inside the reefer. Didn't
> lose any appreciable heat.
>
> So I made some coffee (had enough juice to grind another batch of beans,
> left the reefer off, then went outside to place the panels in a spot
> where I could see I would have sun a bit later in the morning. As the
> sun started to hit the panels, I watched the ammeter in Mellow Yellow go
> from zero to over 6 amps of charging current.
>
> The Norcold does draw, as claimed, 2.5A. But it runs a lot more than the
> five to ten minutes per hour claim I had heard. Another interesting
> quality is that it does not seem to be thermostatically controlled,
> i.e., the knob on the front does not set the internal temperature.
> Rather, the knob seems to determine how long the compressor runs. I
> recorded the start/stop times of the compressor during two hours of
> operation. The first run was between 10am and 11am. The the outside
> temperature was 85F. I set the knob to the minimum "1" position. The
> compressor started every 10 minutes, exactly, and ran for 3 minutes,
> then shut off for seven minutes. The internal temperature ranged between
> 40 to 41F. The second run was between 12 noon and 1pm. By this time, the
> outside temperature had climbed to 88F and the temp inside the Norcold
> had gone up some, so for this run, the knob was set to "3," the
> manufacturer's recommended normal position. As before, the compressor
> started every 10 minutes, exactly, then ran for 6 minutes before
> shutting off.
>
> This behavior contributed to the middle-of-the-night discharge of my
> house battery: whether it needs to or not, this reefer turns on every 10
> minutes.
>
> FOLLOWUP: I am mistaken: the Norcold does demonstrate thermostatic
> control. I put a warm liter bottle of water into it and the internal
> temp climbed to 48F,  then I turned it to "3" and it ran for 30 minutes
> to bring it down to 40F then shut off. I guess the thing likes to keep
> to a 10-minute cycle when doing maintenance cooling.
>
> How many ampere-hours are needed to run this thing? Certainly more than
> 0.4Ah, which is based on 10 minutes of operation every hour, or a duty
> cycle of 17%. When set to "1' the duty cycle is 30%, when set to "3" the
> duty cycle is 60%. 30% of 2.5A is 0.75Ah, and 60% is twice that. So a
> reefer set to "3" will, over the course of a 24-hour day, require 36
> ampere-hours. But as last night suggested, it does not need to be on all
> night long to keep things cold. Tonight I will shut it off at bed time
> and see how cold things are in the morning.
>
> So, if you want to take advantage of the superior cooling ability of the
> Norcold, you should consider mounting a thermal sensor in the reefer so
> you can monitor its interior temperature and adjust by hand, as needed,
> to conserve power. Plan on either plenty of battery capacity to run it
> for more than a day or so, unless you can stuff power back into the
> battery, either with an external generator, by driving for a while, or
> other means, such as a solar rig, like I have.
>
> Another consideration I had about this reefer was its noise level. The
> Dometic was, near as I could tell, dead-quiet. It possesses no moving
> parts, unless you count liquid and gas. Once in a while the rear fan
> would kick in during a hot afternoon, but at night, it made less noise
> than Mrs Squirrel's breathing, and she's pretty quiet. The Norcold, on
> the other hand, has a compressor, with oscillating bits of metal hurling
> about.
>
> This thing is quite audible. It makes a "brrrrrrrrr" noise like a Magic
> Fingers bed. Is it intrusive? That depends on who's doing the listening,
> how light a sleeper they are. That unexpected evening solicitor's knock
> on the front door might be a disturbance to me, but for another person
> it might be a welcome opportunity to spend a few minutes with a stranger
> who is selling something which might be of possible interest. I can hear
> this reefer, but by pushing around on the front, sides, and top of the
> sink cabinet, I can tell that it could be made to run a lot quieter if I
> can figure out what bits are vibrating in sympathy and anchor them.
>
> Summary: I'm a little disappointed by how power-hungry the Norcold
> DC0040 is. But Mrs Squirrel and I only camp when it is sunny and nice,
> so I expect to count on plenty of Mr Sun's rays to keep the Optima full.
>
> Next morning follow-up: the battery barely made it through the evening,
> even under minimal usage. I think the cheap Harbor Freight trickle
> charger that I had hooked to the battery while Mellow Yellow sat under
> its cover during off-season may have damaged it. I shut the reefer off
> at bedtime, and the internal temp was 52F this morning.
>
> --
> Mike Elliott
>