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Old 17-07-2012, 19:50   #1
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Crunched some Engel refrigerator numbers, I'm impressed.

For those that want independence from running the engine for the old cold plate systems, and don't want to spend the coin and complexity of efficient keel cooled compressor systems, I think Engel might have a good solution. Anyone using the Engel and are your numbers close to what I crunched?

At 25 C ambient (77 F) for their model MT80, dual voltage 84 qt (118) 12 oz cans, 86 lb chest fridge/freezer

Box temp 3 C (37 F)
Running time 18% @ 0.6 A = 31 w/hr/day

Box temp -13 C (8 F)
Running time 45% @ 1.6 A = 208 w/hr/day

Box temp -22 C (-8 F) @ 2.5 A = 518 w/hr/day

Rather efficient for an all in one portable fridge/freezer of this size. If the above pans out, then the output of a single 120 watt solar panel for (2) hours could power (2) of these large units, one set as a freezer and the other as a fridge for 24 hours.
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Old 17-07-2012, 20:14   #2
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

I have an Engel 45 and i run it as a freezer . it burns 2.5 amps when it runs and runs about 95 % of the time and burns about 60 amp hrs / day. i cruise in the caribbean area and the ambient temp is 80 plus and the box temp is about -8 F. but it makes great ice cubes and i love it.
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Old 17-07-2012, 20:21   #3
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

G'Day Bob,

Those are indeed impressive numbers... so much so that I have a hard time believing them! Are you sure about the 0.6 Amp figure, for instance? Seems very low for what I believe is basically a Danfoss compressor inside.

Wonderful if it is accurate, though!!!

Cheers,

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Old 17-07-2012, 20:22   #4
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

Bob,
Would you please share your math on how you came up with those numbers? And I thought the power consumption was measured in amp-hours per day, not watt-hours per day--or maybe I'm confused. Please elaborate.
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Old 17-07-2012, 20:28   #5
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

Quote:
Originally Posted by deckofficer View Post
For those that want independence from running the engine for the old cold plate systems, and don't want to spend the coin and complexity of efficient keel cooled compressor systems, I think Engel might have a good solution. Anyone using the Engel and are your numbers close to what I crunched?

At 25 C ambient (77 F) for their model MT80, dual voltage 84 qt (118) 12 oz cans, 86 lb chest fridge/freezer

Box temp 3 C (37 F)
Running time 18% @ 0.6 A = 31 w/hr/day

Box temp -13 C (8 F)
Running time 45% @ 1.6 A = 208 w/hr/day

Box temp -22 C (-8 F) @ 2.5 A = 518 w/hr/day

Rather efficient for an all in one portable fridge/freezer of this size.
I've never crunched the numbers like you did but, you've got me curious. I had my smaller MT 25 Engel on board for over ten years:
THE BIANKA LOG BLOG: WHAT WORKS! WHAT'S COOL!
I do know draws a little under 3 amps when operating. It just works great with two 75 solar panels keeping things topped up with it in freezer. I operate it in full freezer mode during the day and cut back on the thermostat at night. I really should put a thermometer inside and see what the actual temps are. I just know it works for my needs very well. Looking at your numbers I might be able to cut back on the thermostat and still keep things frozen.
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Old 17-07-2012, 20:31   #6
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

I used this......


And crunched numbers like this, Box -13 C chart says 1.6 a/hr @ 45% duty cycle. 1.6A X 12 Volts = 19.2 watts X 24 hours = 460.8 w/hr/day * .45 (duty cycle) = 207 w/hr/day. Did I muck up my math???
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Old 17-07-2012, 20:38   #7
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

Quote:
Originally Posted by deckofficer View Post
For those that want independence from running the engine for the old cold plate systems, and don't want to spend the coin and complexity of efficient keel cooled compressor systems, I think Engel might have a good solution. Anyone using the Engel and are your numbers close to what I crunched?

At 25 C ambient (77 F) for their model MT80, dual voltage 84 qt (118) 12 oz cans, 86 lb chest fridge/freezer

Box temp 3 C (37 F)
Running time 18% @ 0.6 A = 31 w/hr/day

Box temp -13 C (8 F)
Running time 45% @ 1.6 A = 208 w/hr/day

Box temp -22 C (-8 F) @ 2.5 A = 518 w/hr/day

Rather efficient for an all in one portable fridge/freezer of this size. If the above pans out, then the output of a single 120 watt solar panel for (2) hours could power (2) of these large units, one set as a freezer and the other as a fridge for 24 hours.

I think youmay be misinterpreting the graph I read it as at 3 C it runs 18% of the time and consumes .6ah/h at 12.8 volts.

The wattage calculation is then 12.8Vx.6ax24H = 186 Watt/hrs/day for the fridge and 12.8vx1.6x24= 491.5 Watt/hrs/day for the -13C freezer.

This is still pretty good but not as good as your interpretation.
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Old 17-07-2012, 20:48   #8
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

I get the same results, just approached it a little different.

1.6a x 24 hrs = 38.4 ah/day. Cut that down to 45%; 38.4 x 0.45 = 17.28 ah/day.

Then multiply by 12v to get 207 watt-hours.
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Old 17-07-2012, 20:52   #9
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

Quote:
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I think youmay be misinterpreting the graph I read it as at 3 C it runs 18% of the time and consumes .6ah/h at 12.8 volts.

The wattage calculation is then 12.8Vx.6ax24H = 186 Watt/hrs/day for the fridge and 12.8vx1.6x24= 491.5 Watt/hrs/day for the -13C freezer.

This is still pretty good but not as good as your interpretation.
So, if I understand correctly, when it runs, it always pulls 3.3 amps and then they apply the duty cycle. At -22C (-8F) 2.5 a/hr = 32 watts (2.5 X 12.8) X 24 = 768 w/hr/day. OK, that makes better sense, holding that much mass that cold, would take the full day's output of a single 120 watt panel in summer conditions.
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Old 17-07-2012, 23:06   #10
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

Ahoy Bob, I have run the engel, until it died last year and a danfoss BD50.
Engel was set up as a single evaporator plate in a top loading fridge. It did not work well and would not freeze and ran the batteries flat if the day was cloudy. Had 170 watts of panels and an aerogen wind genny.

Now, with the danfoss and the single freezer style , open top evaporator in the converted ice box, wonderful, makes ice quickly at 4 on the thermostat and will freeze the whole box at 7. Now have 450 watts solar panels and the batteries are full by midday, unless raining all day. In full sun with 75% batteries will put in 19 amps!!

Very disappointed with the engel, they use a swing motor, not a compressor like the danfoss. Could not recharge it without breaking the line. Their stand alone units are impressive?

No way you could run 2 of them on 140 watts solar panel for a day!!

Cheers from Keith.
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Old 18-07-2012, 04:52   #11
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

there's no free lunches just like there isn't really any free refrigeration, you can not change the physics of the things and the energy is the energy

in today's modern systems the only real factor is insulation and a potable unit isn't going to have what a "real" system has, so I'm never going to believe a potable unit uses less energy for a given size than a well constructed permanent one
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Old 18-07-2012, 06:13   #12
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

The ICEER system in my boat amazingly robust and efficient. Its made locally in Brisbane (Australia - Not san Fran) I have 2 125 watt panels, everything on the boat runs off them, never been plugged into shore power and batteries never seem to get below 80% and fridge and freezer have never been turned off.
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Old 18-07-2012, 19:03   #13
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

I have an Engel 35 and it makes 4 regular trays of ice per day. Link meter says the draw is 2.5 amps and it runs about 95% of the time. That is about 70amps per 24 hours so one needs lots of solar/wind and big battery bank. The first unit ran for 8 years and failed. I replaced with same model
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Old 19-07-2012, 18:15   #14
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

Just FYI, with the typical 0.15 duty cycle I get, my 3.5 CF 120V magic chef pulls 2.5 amps per hour and 230 watts of rated solar panel keep it and everything else topped up day to day on the hook. I figure I get 65-70 amps a day from my two panels total a day.

Really a BTU is a BTU. My guess is for the Cubic feet cooled overall the engel sling compressor uses about the same power as a danfoss 12V or 120V compressor. BTW the 120V compressor runs about 10 minutes per hour in 2.5 minute chunks, in the CA Delta with 80-90 degree boat temp (81 at the moment ).
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Old 19-07-2012, 18:47   #15
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Re: Crunched some Engel refrigerator numbers, I'm impressed.

I have the Engel MB40 drop-in, with an extra couple inches of foam insulation around it - I think 3 on one side, 1.5 on the bottom, sort of, 2 on 2 sides, and an inch on the remaining side. Love the thing, it's just small - which is OK for me. I've only operated it in northern CA, so have nothing like tropical numbers available. It doesn't seem to do anything a lot differently when (very occasionally!) it gets into the 80s (F).

what I believe is basically a Danfoss compressor inside.

This is incorrect. It has a (proprietary?) "swing compressor," which means it can draw anything from close to nothing up to something like 3 amps. Mine almost always runs around 2a.

when it runs, it always pulls 3.3 amps

See above - it draws what it needs.

would not freeze

I suspect something's wrong with your unit. My dial goes from 0 to 5. 1 is about refrigerator temperature. 2 is ice, eventually. 2.5 is frozen orange juice and eggs overnight. I've never had it above that.

Their stand alone units are impressive?

As far as I know, it's the same box and mechanical as the portables, minus the "shell." The compressor sort of hangs off the bottom of my box, and it a little wonky/fragile looking, but no problems with it so far.

No way you could run 2 of them on 140 watts solar panel for a day!!

I'm not so sure about that. I've never sat and watched mine or anything, but I'd guess it runs maybe 10m/hour, max. 2amps x .16hours/hour x 2units x 24hours = 15 ah/d. Who knows how that might scale to somewhere more tropical, or what the thing would do in freezer mode though.

there's no free lunches just like there isn't really any free refrigeration, you can not change the physics of the things and the energy is the energy

Exactly. All you can do is try to control how much electrical energy gets turned into heat, and how much of what gets turned into cold leaks out and needs replaced. I think the Engel compressor is remarkably efficient on the former, and the boxes are pretty good on the latter - adding up to a fairly efficient system.
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