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Old 19-01-2021, 19:16   #1
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120V to 12V Compressor switch

We have a 120VAC U-Line Ice-maker that needs a new compressor. Need the ice-maker for charter business. When it worked, it consumed 25A most of the day, running off a Magnum 3000 Hybrid Inverter.

What chance of leaving the mechanics on the 120VAC supply and replacing the compressor with suitable 12VDC?

I have a 12VDC 900Ah LFP house bank, so if possible to convert compressor to 12V, I figure I should save at least 50% of the present consumption via inverter. I also have 540W solar.

Thanks for any advice.
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Old 19-01-2021, 19:47   #2
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Re: 120V to 12V Compressor switch

Quote:
Originally Posted by prowerg View Post
We have a 120VAC U-Line Ice-maker that needs a new compressor. Need the ice-maker for charter business. When it worked, it consumed 25A most of the day, running off a Magnum 3000 Hybrid Inverter.

What chance of leaving the mechanics on the 120VAC supply and replacing the compressor with suitable 12VDC?

I have a 12VDC 900Ah LFP house bank, so if possible to convert compressor to 12V, I figure I should save at least 50% of the present consumption via inverter. I also have 540W solar.

Thanks for any advice.
I am not sure why you think you can save 50% of the consumption.

Assuming your 25 amps is the 12v x 25 amps you used to run the compressor off the inverter I'd say that is 300 watts. Actually that does not sound like too much, but changing to a native 12 volt system isn't going to be much less. But 300 watts continously, is 600 amp hours per day. Now that is getting up there. Even with a 900 ah LFP you stil have to replace 600 amp hours per day. Yes, I am sure you could find a 12v compressor, (maybe not easily) but where are you going to find 600 amp hours per day?
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Old 19-01-2021, 21:17   #3
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Re: 120V to 12V Compressor switch

i would figure that you would have a 10% efficiency gain by eliminating the inverter- may be able to get a little more with a more modern compressor unit but i really dont know. If it were me i would call Rich Boren at cruise RO andask for his expertise- lots of good info-- might allso PM Tellie also on cruise forum and ask his opinion- these guys are in the business of cooling things off.
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Old 19-01-2021, 22:46   #4
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Re: 120V to 12V Compressor switch

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i would figure that you would have a 10% efficiency gain by eliminating the inverter- may be able to get a little more with a more modern compressor unit but i really dont know. If it were me i would call Rich Boren at cruise RO andask for his expertise- lots of good info-- might allso PM Tellie also on cruise forum and ask his opinion- these guys are in the business of cooling things off.

Hi, I have to agree with this sentiment, you don't say where in the world you are, should you be in Australia or thereabouts I would add Ozefridge to the list.
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Old 20-01-2021, 01:47   #5
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Re: 120V to 12V Compressor switch

Many thanks for responses. We are in Belize.

In addition to the U-Line ice-maker, we also have a built in chest freezer using an Isotherm compressor and evaporator and three Isotherm Cruise Fridges, all on 12V. Collectively, they use an average of 360Ah a day on direct 12V. Hence my hopes that a 12V conversion of the ice-maker would provide some savings.

Where do I find 600Ah. Generator!
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Old 20-01-2021, 06:42   #6
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Re: 120V to 12V Compressor switch

How much ice production do you need in a day? And is the U-Line one of the home freezer types that makes and then stores ice, or is it a commercial type that's constantly making nice into a big bucket and allowing it to melt down?
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Old 20-01-2021, 07:32   #7
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Re: 120V to 12V Compressor switch

The unit is a U-Line SS98 marine unit. 25lbs of ice made per day and stored in integrated ice bucket. Great unit. Works well. The specs claim it uses less power than an old style 75watt light bulb, which of course assumes it is being run off a permanent mains/generator supply without the intervention of an inverter.

The mechanics of the system use very little power and that would have to remain on the inverter source. The compressor is supplied by the same inverter source at present but operates separately, so I see no reason why that could not be 12V.

Looking for informed opinion on that. Thanks
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Old 20-01-2021, 07:42   #8
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Re: 120V to 12V Compressor switch

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Originally Posted by prowerg View Post
The unit is a U-Line SS98 marine unit. 25lbs of ice made per day and stored in integrated ice bucket. Great unit. Works well. The specs claim it uses less power than an old style 75watt light bulb, which of course assumes it is being run off a permanent mains/generator supply without the intervention of an inverter.

The mechanics of the system use very little power and that would have to remain on the inverter source. The compressor is supplied by the same inverter source at present but operates separately, so I see no reason why that could not be 12V.

Looking for informed opinion on that. Thanks

You understand that new or old, 75 watts is 75 watts right? What weighs more; 100lbs of bricks or 100lbs of feathers.



I'm also very skeptical that an ice maker would use less power than a light bulb.
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Old 20-01-2021, 07:49   #9
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Re: 120V to 12V Compressor switch

I found some specs on that unit. Looks like full load amps on the compressor is 2.5 amps at 120v, so about 27.5 amps at 12vdc including inverter losses. If the compressor runs 50% of the time, plus a bit of power for ice harvest, that's something like 350 ah/day. That's shockingly power hungry for the size of the unit. So I'm thinking that either it should run a lot less than 50%, or that thing is just horribly inefficient.
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Old 20-01-2021, 08:02   #10
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Re: 120V to 12V Compressor switch

It gets a lot of use during the day, in a warm climate, and it seems every time I look at the draw it is hanging in there at around 25 amps. But, through the night, I am sure there is some significant idle time with minimum draw, and we switch off the mechanics overnight, so only the compressor required.
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Old 20-01-2021, 08:06   #11
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Re: 120V to 12V Compressor switch

I'd expect a compressor swap could gain some more efficiency, but I'm not sure how much. If it's running most of the time during the day, it sounds to me like it needs more insulation. That's probably going to provide the biggest gain.
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Old 20-01-2021, 11:08   #12
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Re: 120V to 12V Compressor switch

I am in the same "boat" with refrigeration. 700amp/hr Lifepo4 but at 24 volts, therefore 350amp/hr. 900 watts solar with three charge controllers. My compressor runs at 11 amps at 24 volts. This is the amount of current running through to inverter. I am looking at using a 12/24 volt compressor like:

USA STOCK DC12/24V Compressor BD35F Danfoss/Secop R134a Refrigeration for about $120 with free shipping.

But I don't have the skillset to understand the expansion tube or capillary valve. Do I have to change these items if I am not changing gasses?
I have replaced compressors in household units, ie: I can braze with silver, check for leaks, pull vacuum, and add/subtract gases using gauges and temp. probes. But....first time with failure/learning and would like to go in with better knowledge base.
On a side note OP has Lifepo4 and shouldn't take long to charge with genset/propulsion motor with regulation of alternator output. If he needs to add power/maybe a change to better alternator with 80-100 amps but regulated just for his Lifepo4's. Plus add solar. Another thought, I need to run my cold plates/compressor 7 hrs/day to maintain. I run at night in order to have better efficiency. Maybe the OP can run at night and find a better storage system for the ice.

I guess what the OP and I are asking, can we use a BD35 Danfoss 12/24 compressor in our systems?
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Old 20-01-2021, 15:36   #13
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Re: 120V to 12V Compressor switch

To clarify our charging system. We have two 140A Amptech alternators regulated by two Wakespeed WS500's connected for combined charge output via RJ45 network cable. So, when on the move at cruise, we can see 180A + from alternators.
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Old 20-01-2021, 16:34   #14
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Re: 120V to 12V Compressor switch

The swap of the compressor would be a huge roll of the dice.
Capillary tube systems are VERY sensitive to debris and the removal and reinstall requires flooding the circuit with pure inert gas to prevent the brazing byproducts that form from blocking the tiny cap tube passage.
We service literally more than a hundred of these units a year, and every other type of common icemaker as well, Raritan, Vitrofrigio, Uline, Scotsman, all of them.....the funny truth is that they are all the same internals.
In order of occurrence...this is what I have found to kill them.
1-Lack of and/or zero maintenance of a dedicated water filter for the unit itself.
2-Turning unit off and leaving ice mold full of water for months with the door fully shut and not using the built in door latch to keep it open.
3-Not running the unit a few cycles with the feed water turned off to dry the mold out.

--the above are related to the ice mold and it's internals, and the release coating on the mold itself, which is not good to drink with your ice cubes--just saying.

4-Not keeping the condenser clean and working correctly, whether it's the pump, the fan, or the coil itself, the heat needs to move, most are covered in pet hair and lint.
5-Bad gaskets kill refrigerators.
6-Being an impatient dummy and stabbing the dry evaporator plate with a sharp anything because the bad gasket mentioned above is bad and the plate is now covered in 4 inches of ice.
Anyhow...there it is.
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