Improved refigerator performance

rwidman said:

The other upgrade to the typical marine refrigerator is the cold plate design where the system freezes a plate when there is excess energy available (engine running or shore power available) and then uses the stored cold (technically incorrect language, but easier to understand) to reduce compressor run time when on battery power.

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The upgrade is expensive with 2 separate compressors plus the cold plates take a lot room the box (s). Caulder does a good discussion of refrigeration in his book "Boatowner's Mechanical and Electrical Manual: How to Maintain, Repair, and Improve Your Boat's Essential Systems. He basically says that the DC evaporative plate systems are hard to beat with the small size, efficacy and reliability.

Larry M said:

. Caulder does a good discussion of refrigeration in his book "Boatowner's Mechanical and Electrical Manual: How to Maintain, Repair, and Improve Your Boat's Essential Systems. He basically says that the DC evaporative plate systems are hard to beat with the small size, efficacy and reliability.

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Nigel Calder has another small book devoted entirely to refrigeration, even including building one! I got my copy from Amazon, can`t give more details of it, I lent it to a friend and....
Eutectic systems work for me, anything to get that big draw off the batteries. BruceK

FF, Is that 60-100 Amp Hours per day?

Yes, this is the most common power burn.

A 300A bat set would be required for just the reefer , for each day of quiet ship.

Eutetic plates work best with a huge energy source. On out 90/90 the engine runs a cast iron auto Air Cond compressor with dual belts.

This will freeze the plates (roughly 10,000BTU cap) in 2 hours and thats good for 4 days , tho we try a 3 day off between re cool.

Great insulation , so tiny loads , is the BEST !!! way to have no problems but as noted at this time it requires a special build and is not inexpen$ive.

Compressor speed test

I have completed data collection on my frig at the four selectable compressor speeds. I used a temperature data logger that recorded temps every 5 minutes. I then took that information and integrated the Danfoss tech manual amperage draw at the various temperatures. The Compressor draws lower amps at lower temps. The results indicate that the highest speed comsumes the least amps in a 24 hr period even with the compressor starting twice as much.
Highest speed:3500 RPM = 59.5 amp-hrs. Lowest speed 2000 RPM = 79.7 amp-hrs.
If you are a curious data geek, send me a message and I will send the spreadsheets and graphs!
Dave

Thanks for the update Dave. I haven't had time to make the adjustments to our fridge but look forward to doing it and watching the results.

"The Compressor draws lower amps at lower temps."

This is because the WORK being done drops as the temp differential drops.

The most amps is usually in the cooling a warm box condition , where its doing more air cond than cooling.

I have tried putting the blue cooler "ice packs" in my little Nova Cool freezer when I know I will be motoring all day. (I don't use my freezer anyhow) but they never seemed to freeze for me. Later I drilled holes in them, replaced 1/2 the fluid with water, and taped over the holes. They still didn't freeze in a 6-8 hp run. Did the same thing again (resulting in 25% original strength fluid) still didn't freeze. Only when I did it a 3rd time (12% original strength) did they freeze in a 6 hr run.
What's up with this stuff?
I thought I was making a "poor man's" removable eutetic plate...

Rambler said:

Not a Crown drinker. Knob Creek, Bulleit, and most any single scotch works for me.

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what no JD?.......not my cup of tea either but i can stomach a sip or two of a good scotch once in awhile

I thought I was making a "poor man's" removable eutetic plate...

In order for the eutetic fluid to freeze it must be cooled below its melt temperature.

Your setup is not getting cold enough to freeze the stock solution.

Lowering the box thermostat enough to freeze the eutetic solution may result in frozen milk and lettuce.