Originally Posted by travellerw
Wait... You used a standard number and not the number posted on Rich's website. His website shows 35Ah/day or 420W per 24 hours (at 12V). That pretty much exactly the same as the fridge I listed.
If he posted those numbers on his site, I trust he actually tested them. I'm pretty sure the standard numbers posted by manufacturers are in the perfect environment at 15 deg C ambient.
The posted numbers on power usage are the average of a 4 days test in a 70-deg climate controlled test room.
(sounds better to say Test Room than a temp controlled office bathroom...
Of course the power usage will increase with ambient temps, and one day when I have time I should break our our data logger and get some test data in 5-deg increments up to 100-degs. Man would that tell all you need to know about the value of insulation! Which, by the way is the weak point of ALL of these drop in dorm type boxes. They all SUCK, ours or anyone elses just have about 1" of Polyisocyanurate insulation
or an approximate R-value of 7...ha ha ha..that's crazy bad!
The industry seems to like 70-degs, so that's what we used to be able to compare to other units. Notice the manufacturers of these don't even talk about insulation or the R-value of their boxes? Why...because other than Government
Regs, these units are not made for efficiency but for convenience and a price
point. Would anyone buy one with 3 or 4" thick walls of insulation? Not a chance. Then again who in their right mind would buy a front opening refrigerator/freezer if Efficiency was one of their big buying
considerations? Answer...no one, which is why front opening boxes are almost all you see on power boats (hint generator
running all the time).
From test we have done, a front opening door can cost you about 30% efficiency on a refrigerator
and up to 40% on a freezer
. I know they are convenient but they SUCK power. The biggest issue is frost insulating the evaporator and killing your Box/evaporator heat transfer.
Life and Boat gear
is a compromise...budget, space, needs, wants.
There is a market for these down and dirty easy/cheap units, which is why I make them. I also don't pretend they are what they are not. Do I push them and hype them to cruisers setting out on a world cruise
...no I don't and I'm not here. But they work great for some folks and in September we shipped 16 of them, which is good because replacing 21 through hulls on my boat is expensive!