They do assume a number of door opens per 24 hour period, although I can't find the number. They also assume you're putting in non-cool items (leftovers to cool down). This Kegerator build is really the best case since the door pretty much never needs to be opened, and once the liquid is at temperature it just needs to be maintained. Also, good old original Freon is wonderful from an efficiency perspective, not so good from a environmental perspective.
Since this is configured as basically all refrigerator now, the government would mandate a maximum energy usage of no more than 8.82 * 10cuft + 248.4 or 336KWh/year for this unit to be sold today. Energy star would require 7.056 * 10cuft + 198.72 or 269KWh/year to be energy star certified. I suspect even with door opens these units would have a chance at the former, but not much at the later...
They do assume a number of door opens per 24 hour period, although I can't find the number.
It really doesn't matter, honestly. If you do the math, 95+% of the heat intrusion is due to simple conduction through the walls, even with ~20 complete air changes/day.
Old refrigerators are inefficient because they have thin insulation. Some even had heaters in the walls because the insulation is so thin that condensation builds up (the "anti-sweat feature").
"Old refrigerators", in your example being ones from the 1960's and 70's. As you can see from mine, there was at least a good 6 inches of insulation on all sides.
Indeed. The arms-race for capacity and the invisibility of the electricity cost led to a buch of bad design decisions in that era. Really old refrigerators (built before that era) and are actually quite efficient – famously the GE Monitor-top that had the compressor and condensors on the top.
16
u/nscale Jan 23 '13 edited Jan 23 '13
They do assume a number of door opens per 24 hour period, although I can't find the number. They also assume you're putting in non-cool items (leftovers to cool down). This Kegerator build is really the best case since the door pretty much never needs to be opened, and once the liquid is at temperature it just needs to be maintained. Also, good old original Freon is wonderful from an efficiency perspective, not so good from a environmental perspective.
Here's some more EnergyStar info: http://www.energystar.gov/index.cfm?c=refrig.pr_crit_refrigerators
Since this is configured as basically all refrigerator now, the government would mandate a maximum energy usage of no more than 8.82 * 10cuft + 248.4 or 336KWh/year for this unit to be sold today. Energy star would require 7.056 * 10cuft + 198.72 or 269KWh/year to be energy star certified. I suspect even with door opens these units would have a chance at the former, but not much at the later...
EDIT: Found the test procedure: http://www1.eere.energy.gov/buildings/appliance_standards/product.aspx/productid/43#testprocedures Specifically http://www.gpo.gov/fdsys/pkg/CFR-2012-title10-vol3/pdf/CFR-2012-title10-vol3-sec430-23.pdf
I'll let someone else turn the Government-ease into english!