leaving fridge on

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snipped-for-privacy@ece.villanova.edu wrote:

It might, that is, if you could insulate the coil from the ambient environment during the off cycle. It's doable, but it would be an engineering nightmare on a stock domestic refrigerator. Refrigerators take awhile to stabilize running pressures, so starting with a subfreezing condenser coil might mean that the cycle finishes before the head control even has a chance to takes control. Head Masters, or equivalent devices, are installed on commercial refrigeration systems in order to simulate higher ambients. Without head pressure control, when the condenser gets too cold the head pressure will drop to such a level that the evaporator will be starved of refrigerant, even with a TXV in place, and as a result and superheat will escalate. The evaporator and compressor are starved of refrigerant. Turtle had it exactly wrong; flooding back is assured not to happen.
hvacrmedic

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With little mass and no fan, it might heat up fast when the compressor starts.

Seems easy enough to put a thermostat near the hot coil that turns on the fan when the air temp rises to 70 F. Or another Thermocube and bulb or heat tape near the hot coil.

Is that bad, or just a transient self-correcting condition?

Good.
Nick
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snipped-for-privacy@ece.villanova.edu wrote:

You have to count the compressor mass, and take into account that the cycle will be extremely short given the low load condition due to subfreezing ambient around the box.
Here's my suggestion: turn it off, take the food with you :) Somebody is likely to break in and eat it anyway while the cabin is unoccupied for long periods.
hvacrmedic

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At 100 W, 10 Btu/F would warm 35 F in 1 hour, so maybe we need insulation and/or heat...

Less energy use sounds good to me :-)

My poor friend just wants to keep ice cream in her full-time 50 F house, not to become homeless :-) When I kept my old stone kitchen at 36 F, the fridge seldom ran but the frozen food tended to thaw. OTOH, leaving the carton of milk out on the counter overnight wasn't a problem.

Nick
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snipped-for-privacy@ece.villanova.edu wrote:

This is Turtle.
Let me pass this this one by you.
take this refrigerator and have it running in zero f temp and the refrigerator or coil is at 35 degree f inside and out side is zero degree f then then the refrigerator does not cycle back on for all nite and part of the next day and for some reason the refrigerator temp gets up to set point and turns on with it being at this condition for 24 hours.
All the feon will go to the coldest point of the system and all the freon will be in the compressor for refrigerators don't have compressor heaters at all. alleon will be in the compressor mixesd with the oil when it comes on.
Try this thought out on a refrigerator only and no high fangle refrigeration system. What would happen.
TURTLE
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RP wrote:

this is Turtle.
Richard your walking on thin ice here with refrigetator not coming on in sub freezing ambiants. Before you step too much farther off in to it , there is a good number of dual thermostat controlled thermostats in refrigertators and they will be coming on and off all the way down to ambiants of zero F or below.
now here is another lesson for you and CB to know and not try to guess at the answers when whirlpool does have a opinion which i would take before your words. You say a refrigerator can't have flood back when and if you would read the installation instruction for the refrigerators today. they will state that you should not run a refrigerator in below 40 degree F ambiants for the fear of liquid freon from forming in the compressor and when it turns on it will flood the cyclinders with liquid and wash the oil out of the compressor. i know this does not call it flood bad of the compressor but i would call it that it was pretty damn close to the same thing.
Now that you and Cb got burned on this one , i would like you to try to keep to answering the questions of the posters and not try to degrade one of the member for personal pleasure. also i know you two don't work on these frigerators for you would not have walked off into this one so easy. OH , Richard i have work on these things for a living for years with a BIG S .
TURTLE
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TURTLE wrote:

RP: "How many US Presidents have there been?" TURTLE: "4" RP "Wrong there have been 43." TURTLE: "No it isn't wrong, there have been 4 US presidents killed in office." RP: But that wasn't what I asked! TURTLE: Doesn't matter, I gave the right answer to my new version of the question so I'm right about everything, and you stepped in doggy doo.
RP: Sigh.....
hvacrmedic
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This is Turtle.
i do accept the wrongly judging you as wrong here and should have called you wrong about 7 threads above here when you was dead wrong. when your wrong from now on , i will put the exact wrorng words exactly at the wrong point. now when you said there was going to be NO flood back on a refrigerator, you was wrong because Whirlpool does state that you can flood the compressor with freon if it is run in below 40 degree f condition or ambiant. I will take the words of Whirlpool before Richard any day !
TURTLE
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It turns out my 50 F friend has a Gibson model RT215BCW fridge/freezer, and Gibson/Electrolux/Frigidaire (800) 599-7569 make a $15 "garage heater kit," part number 5303918301 that screws in near the defrost timer in all their top-freezer products and keeps the fridge working right down to a 20 F room temp. It uses 120 V. I think it just provides enough constant heat for the fridge to make sure the compressor runs and the freezer stays frozen. Less energy-efficient than a freezer thermostat, but simpler.
Some alt.home.repair threads are like ancient Greek "scientists" deciding how nature works by discussion vs observation. They would sit at a table and ask "How do porcupines defend themselves?" After enough discussion, they concluded that porcupines must pull out their quills and throw them at enemies :-)
Nick
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This is Tuirtle.
Yes , I think the porcupine won this thread !
TURTLE
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snipped-for-privacy@ece.villanova.edu wrote:

That's interesting info Nick. Thanx. The porcupine thing is pretty neat too :) Any idea of its origin? It reminds me of the one where they are amputating frog legs one by one, measuring how far they hop, and concluding finally that a frog with no legs is hard of hearing.
hvacrmedic
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Ill throw my hat into the ring. There is no headmaster on home refirgerators, no fan cycling switches, or for self contained commercial units for that matter. "at least in the units I have serviced" Yes refrigerant does migrate to the coldest area which I belive would be the condenser/ not the compressor. The tstat would occasionally call because the evaporator fan motor is running and does produce heat, "up to 90 f if tstat is bad, It is amazing how much heat a 3000 r.p.m fan can put out" I would be more concerned with decreased compressor life do to thick oil and not getting proper lubrication, If you notice on remote units they have heaters either wrapped around the compressor or heaters that slide into the compressor.
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unattended cabin food can spoil with a simple power failure. the duration of the power failure and the unknown refrigerated product temperature create the hazard. "In the event of a power failure, frozen or refrigerated foods warmed to above 40 F for two to three hours may not be safe to eat." please see full information at: http://www.cdc.gov/nasd/docs/d001201-d001300/d001288/d001288.html
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Just to add some new data to this debate, I just bought a new Frigidare Frost Free Freezer. The manual specifies it should not be used above 110F and also says there is no problem or special precautions required at low temps.
So, I guess the answer is the lower safe operating temp depends on the unit.
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Right, it depends on the unit, as my 3 yr old stated not below 50f, but I know of people using them in unheated areas for years with no problems. Here it goes to - 15f.
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