Adding a timer or switch to my refrigerator?

[TMG51]

I'd like to add a timer or manual switch to my DC compressor refrigerator. I shut it off at night to save battery power, but the controls are inside, so it irks me to have to open it and sometimes I forget.

Couple thoughts come to mind:
1) Do appliance timers for 12vdc systems exist? I'm not aware of any.... and if so do they have a phantom draw?
2) Can I even cut the power to the refrigerator in this way or might that damage the compressor?

Input appreciated.

 

[SternWake]

The thing with turning it off at night, is when you turn it back on the duty cycle is much much higher for a period of hours until it can get all food within back to sub40f, and overall uses more electricity than it would had it just kep the food sub 40 in the first place.

Now if one is driving in the morning that alternator can both power the newly powered up fridge and restore the battery bank to some degree this can make more sense.

But if relying only on Solar, the newly turned on fridge will be eating a significant percentage of the solar juice and make it harder for the solar to get the batteries to 14.8v for long enough and the batteries will just lose capacity faster and become progressively harder to recharge fully.

I think removing power to the fridge while the compressor is actually running is Cumulatively stressful to the compressor controller. but switching it off while the compressor is Not running should pose no issues.

If your T-105s are showing their age and their capacity is not enough to meet your needs anymore, that you have to turn off the fridge, well it could be time for new batteries, and or more solar, or less electrical consumption from other loads.

Do ensure the fridge's condenser fan and condenser are not caked with dust/lint. This will greatly increase electrical consumption and wear out the compressor faster. Aslo if it is a truck fridge, the provided fan is only 92MM while the condenser is larger. A 120MM fan would better extract heat from condenser, reducing compressor run times and reduce battery draw.

But I'd not turn the fridge off overnight. Overall, doing so does not save any energy, it likely uses 10 to 15% more over a full 24 hours, but it does obviously change the time at which the electricity is consumed.

I am not aware of any 12vDC timers but have never looked for them either.

Safe storage is below 40F too. Make sure turning it off overnight does not allow it to go much above this.

You can certainly put a 20 amp or higher rated switch on the power feed from fuse block/battery to fridge as listed here in the danfoss/secop compressor controller instructions:

http://files.danfoss.com/TechnicalInfo/Dila/06/bd35-50f_electronic_unit_ac-dc_04-2009_ei100g402.pdf

Could be time to try for a battery equalization to restore some lost capacity to the batteries, but it could be in vain too.

 

[TMG51]

Yes, it's the time of day power is consumed, more than the precise amount consumed, that interests me. I always drive to a job site in the morning. I also don't keep many perishable things like milk in the fridge, but I do require my beer to be cold when I'm off work.

Maybe I'll add a manual switch and shut it off only when the compressor is not running...

 

[SternWake]

The only thing i liked about my old Norcold fridge over my new Vitrifrigo is that the thermostat control/off switch was exterior to the Norcold.

15 amp switches are common but 20 amp less so. Even though the fridge consumes no more than 5amps, they want the 20 amp switch for the bigger contacts and lesser voltage drop they cause.

On that Danfoss data sheet note how thick of wire they recommend for various lengths of wire, also much thicker than 5 amps require.

There are all sorts of little ways to increase efficiency of the fridge over how it was delivered, if you have interest in pursuing those.

 

[royboyprods]

You can use a low amperage switch and a 30A relay to switch your fridge off and on, but all that SternWake is true about overall power usage.

Cold beer is better, good luck!

 

[MrNoodly]

What is your voltage dropping to overnight with the fridge on?

 

[eDJ_]

I'd like to point something out.

Why do we have refrigeration ?   To keep our food safely stored so we don't get sick on it.   Holding it at a constant 40 degrees Fahrenheit should be your first criteria.  I understand wanting to conserve electric but
if you really get sick from cooked foods you've put back in the fridge  and wind up in the hospital....is it worth it?

I would bid anyone to consider building their electrical reserves up to support a fridge that serves you safely so
you can enjoy life on the road and not suffer in a Hospital. 

Young Children,  Old People,  and those known to have weak immune systems are "most" at risk. (and least able to recover from a food born illness brought on by improper refrigeration).

In the cold weather I could see doing this and getting by with it,  but in the summer months when it is hot at night I wouldn't do it.

Please consider yours and your loved ones safety.