Date:         Sat, 30 Aug 2014 09:09:59 -0700
Reply-To:     Rocket J Squirrel <camping.elliott@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Rocket J Squirrel <camping.elliott@GMAIL.COM>
Subject:      Re: Fridge on 12V
Comments: To: Gilles H Turmel <gilles.turmel@SYMPATICO.CA>
In-Reply-To:  <BLU436-SMTP178CF148740374E74F752CD90D80@phx.gbl>
Content-Type: text/plain; charset=windows-1252; format=flowed

This came up about a week ago. In theory, the 120V and 12V elements
should provide the same heat to the ammonia cycle cooling system. Same
heat = same cooling. This because both elements are rated for the same
wattage.

To assure that the 12V element is getting the current it needs to do the
job, the refrigerator's +12V line and its chassis/ground wire need good
connections from battery and to chassis.

This is theory. There may be some detail in the construction of how the
heating elements are connected to the bit in the refrigerator that needs
the heat to run the cooling cycle where one is more closely-coupled
thermally than the other, I dunno.

IN ALMOST RELATED NEWS, I was camping last week and used a portable
Dometic cooler, the RC2000, for keeping foods frozen (or close to). Like
the RM182, it is a small ammonia cycle machine, and has 12V, 120V, and
propane settings. While driving I had it hooked to the house battery,
and I can tell that it was drawing plenty power because the cigar
lighter plug got real warm -- hot almost. Shouldn't get that hot, I'm
going to look into the thing to see if I can sort it out. The house
battery ammeter showed about 9A of constant current draw, indicating a
solid current path.

While in camp, I had the cooler connected to a 5-gal propane tank. It
was sited in sun, but had a reflective "space blanket" draped around it
to reflect sunlight and radiant heat. I put a remote thermometer inside
and measured temps one day (temps in F):

TIME    OUTSIDE TEMP    COOLER TEMP
0800    50              16
0900    51              17
1000    55              18
1100    65              19
1200    74              21
1300    78              24
1400    78              26
1500    78              35
1600    79              35
1800    77              35
1930    65              35
2100    57              34

That's not to say that these are the same results one would get with the
RM182 -- details of construction including insulation will differ.

--
Jack "Rocket j Squirrel" Elliott
1984 Westfalia, auto trans,
Bend, Ore.

On 08/30/2014 07:13 AM, Gilles H Turmel wrote:
> Question to all:
> What kind of performance are you getting on 12V? Mine sucks.
> Best regards.
>
> Gilles Turmel
>