commentary on power consumption of refrigerators/freezers

The household refer/freezer in the house kitchen is on its' last legs. The refrigerator section is at slightly below room temp and the freezer barely makes ice. Chocolate ice cream gets soft when left near the coldest part. Of course, both sections are set to "11". The compressor makes funny noises.

This situation got me wondering about power consumption of refrigerators as opposed to the badged numbers (fire safety electrical ratings). The most convenient way to measure actual consumption of power while you use it is with a $30 meter called "Kill-a-Watt".

Dying bought-new-and-never-moved 2003 Energy Star kitchen full-sized self-defrosting refrigerator with top-freezer: 125W with compressor running (almost all of the time).

GF's boss offered us a 1980's upright refrigerator with self-defrost: 115W for an hour from warm. Next to that was a late-1950's manual defrost rounded-top kitchen refrigerator with built-in ice box: 105W for an hour from warm (hooray, vintage R-12!)

Found on curb across the street: Haier HSB01 cube dorm refer. Cleaned, plugged in, worked great at about 110W. Unbeatable for price, power consumption high for volume cooled, good for temporary use when kitchen refrigerator is too full or too far. FS: http://portland.craigslist.org/mlt/app/2613985118.html

Found on Craigslist by a Columbia river marina: 2003 model Norcold DE-441 medium sized refer pulled from a boat. What's interesting is that it runs on 120/60Hz as well as 12/24DC and uses 45W peak with a duty cycle dependent on ventilation/outside temp/openings. Casual observation suggests that it can run on 300W/H per day if left shut. Retail is about $1250, but used for $100 seemed fair. Web search resulted in mean criticism of "Nevercold" brand refers, but I suspect that the users didn't allow enough ventilation for the coils and pump to remove the interior heat. Norcold specifies them with 100 square inches of overhead and another 100 square inches of below venting for passive or 50 & 50 inches square with a stout 24v fan.

There are refrigerators that have peak power consumption of about 30W and 4" insulation available. Expect to pay over $1000 for a 12/24v DC model, but if you are off-grid, it's worth the money for energy not needed to be generated.

The big surprise was the Dometic ammonia refrigerator in the trailer. Connected to 120v from the house, it's using 195W. From an inverter, this would drain your batteries flat fast. To its' credit, the freezer compartment is +13F with 80 degree ambient. Use propane with ammonia refers for best off-grid results. A 5 gallon tank of propane will last weeks and provide very cold beverages. When there is extra space in the freezer, I put extra blocks of "blue ice" inside to freeze and take up air space. Same strategy in the refrigerator but with jugs of drinkable water.

I'd like to know what kind of power consumption a Peltier device cooler like "Kool-a-tron" has in warm weather. I have read that they have some difficulty cooling more than -40 degrees F below ambient.

It's interesting that much larger capacity household refrigerators have similar power consumption (between 110-150 Watts) to vehicle mounted Dometic when using grid power ("shore power" to boaters). Household models may not hold up to boating or road travel, but they cost so much less that breaking (under warranty?) is okay if you need the refrigerated space.

dangerously cold weather RV heat

http://bdbud.com/stupid-rv-mistakes-1-winter-heating-battery/

Comment Quote: "Given that waking up dead is a real possibility with an external temp of -35C when cabin heat stops, I suppose that idling a gasoline engine is a rational response. In a crisis, we do what we can.

The solution is several things:

More house battery capacity,
isolated generator start battery,
Low-voltage cut-off to protect the battery bank,
non-electrified heat source like catalytic propane cabin heater,
improved insulation and heat-zone control in sleeping compartment to minimize furnace run-time,
CO & smoke detectors in cabin if engines (propulsion or gen-set) run while people are sleeping.

Plug-in to the municipal power grid when it’s so freakin’ cold!

Does your RV have block/oilpan heater to ease very-cold-weather starts, both propulsion and gennie, in case of 120v grid-power loss? Do your batteries have heatpad/insulation?

Upgrade cables to and from battery bank to high-drain items like refrigerator (if DC) or forced-air furnace/Air-Conditioning. Standard cabling in RV is as wimpy as is acceptable for certification. Stranded 8 gauge with heavy crimped ring-connectors tightly installed on clean terminals will reduce voltage drop at the load compared to “standard wiring” 14 or 16 gauge. Copper losses will also be much reduced.

If you have an inverter, thick & short DC cabling is a must. A 3000W 12v inverter needs at least #2/0 stranded copper and it shouldn’t be longer than 20′ long (loop length), IIRC. 24v and 48v inverters can make do with slightly longer runs, but also work best with thick and short copper between inverter and battery bank.

I would also look seriously at a few hundred Watts of roof solar panels/membrane and a good MPPT charger (as little as $199, made in USA) to maintain the expensive batteries in off-season. Betcha US$1000 would do this whole job if you are handy and a good shopper (and buy in the US via mail order).

I, too, have a stupid forced-air propane heater in my 1973 Timberline trailer. If the propane runs dry, the thermostat will run the fan at full-blast and attempt to spark the fuel (no fuel) until the battery is flat. Battery cut-off is set to 12.1v, and furnace is set to OFF each evening, but it *never* gets below about +15F in the Willamette Valley. Our solution is 4-season sleeping bags in the trailer -just in case-. unquote.

Trailer extra-room

The trailer sat in front of the house for MONTHS before the City green-tagged it (72-hour tow) on a friday afternoon. Some angry drunk/meth-head punched his fist into the trailer door the week before the green-tag, putting a dent into the panel deeper than the door itself and nearly allowing an arm to reach in to unlatch the door from the inside. So, I had a couple projects to work on.

Trailer/RV doors are made of almost NOTHING! It is an aluminum extrusion frame pushed together at the corners with thick aluminum foil skin. Insulation is honeycomb cardboard, which was decayed from 35 years and some insect damage. I disassembled the frame to remove the skin panels and couldn't easily get them back together (warped from punch), so I cut plywood panels and assembled only the exterior cosmetic panels (so it would look "stock"). The plywood panels bridged to the strong aluminum frame on the inside (and look scruffy) so I went with the sturdy aesthetic and glued them in with PL poly construction adhesive, attaching the exterior panels and the al frame to the plywood. I just doubled the door weight, but the next person who punches the door will need a hand cast. Camping foam cut and glued with a fabric treatment will look okay, but it's "in progress" for now. After 9 months, I couldn't smell the solvent in the glue any more.

Fortunately, the 1969 Econoline SuperVan and 1988 Subaru DL occupying the back yard were sold a few weeks before, making a good spot for the trailer. A friend and I trimmed the pine tree limb that would be touching the trailer roof and used a come-along to drag the tongue-wheel over plywood to place the trailer in a good spot. It took about 5 hours to move 25 feet over soft lumpy ground and get squared up. Yes, I emptied every possible pound from inside the trailer to the side yard before taking it off of the car hitch.

The 18' trailer (shower, toilet, SS sinks, 4-burner w/oven, forced-air propane heat, vintage interior half-gutted and replaced, many upgrades and repairs along the way) is safely tucked-in to the back yard and is actually useful!

Friend visiting from upstate NY stayed for a few days and found it "compact & cozy" but comfortable and fine for a stay of less than 2 weeks. When comparing to a less-convenient and much less-safe motel room for $59/day, the not-missing $500 was appreciated much during eating out and drinking-in. We have extended the land line telephone to the interior and plugged the trailer in via big black extension cord to the basement power. The built-in absorption Dometic refer runs well on 120v as long as you don't open it too long or too often. It's summer, so heat was not much of an issue. Making a cup of tea on a propane burner warms the cabin from (Brrrrr!) 59F to (brisk morning!) 65F in a few minutes and a wool lap blanket helps. No need to fire up the furnace. Since the house is 4 steps away, water is best handled by a gallon in the refrigerator, outside hose, or coming inside for facilities. Emptying tanks is a thing to avoid, but they are functional.

Functional trailer refrigerator saves us money! Our full-size house refrigerator has partially failed (the freezer section works, but refrigerator is 62F at MAX cooling setting), so we moved the refrigerator contents out to the trailer Dometic. The house 'fridge is going to be replaced, but the panic of no cold for milk and beverages is mitigated until we can get a good deal on a scratch-n-dent or used one. The problem is that the house is small and pre-car/pre-household refrigerator and doesn't have a lot of space to hold a modern mcmansion mega-fridge-freezer-beverage-ice-center. The models that fit perfectly are European$$$, super-low energy consumption DC alt-power $$$, or crappy dorm models (low-efficiency and bad -designed to last 15 months, not exactly cheap).

I suppose that I wasted money putting good matched tires on the trailer just to plop it into the back yard, but who knows what the future may require.