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Old 11-09-2012, 01:53   #1
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High Fridge Amps

I'm just wondering what is normal amps for a fridge to use. My new boat is using 13 amps to run the fridge. I haven't checked cycling frequency as the finishing touches are still being made to the boat and I haven't taken delivery yet. It's a 120 litre top loading Ozefridge / Eutectic ER480 system with air and water cooling. It runs a pump (manuf. claims only .25 amp) to circulate cooling water into one of our water tanks and it has two electric fans that come on with the fridge to circulate air around the refrigeration unit. Am I using too many amps and does anyone have any idea what % of time the motor should be cycling for?
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Old 11-09-2012, 06:02   #2
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Re: High fridge amps

Try: http://www.ozefridge.com.au/
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Old 11-09-2012, 09:41   #3
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Re: High fridge amps

The important number is how many amps per hour and day it uses. Not so much how much it draws. I have a 120V fridge that pulls 15 amps, but runs 2.5 minuted in 12 minutes or about 10 minutes per hour. So it only uses 2.5 amp/hr. Which is right around the good 12V systems.

Sounds like yours is a multi-speed unit that uses more power when the power is available to cool the box down faster. Need to measure the run time and cycle time after the box has been loaded and cooled down.
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Old 11-09-2012, 10:11   #4
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Re: High fridge amps

Ozefridge is an excellent unit. We've had ours for six years. It is a BD80 compressor with earlier controls. The newer ones have a bigger compressor to take advantage of the ample power while motoring to bring the temps down. Then the control should automatically sense when the engine is off and back off on the speed of the compressor to save energy and be more efficient. Of course this control system depends on what is ordered and installed.

We found the water cooling pump circ with domestic H20 effective when temps get higher say 90-95f.

Ours is very efficient and runs off 150amphour batteries and daily engine running time. First startup takes amps and engine running time to get fridge cool, then it usually draws 17-20 ah/day. This year after 6 years it started drawing more once fridge was initially cooled down, about 24-30 ah, because I need to add more refrigerant, (perhaps some very small leak at the valve).

I am sure Ozefridge will provide good quidence. It is an excellent unit.
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Old 11-09-2012, 10:21   #5
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Re: High fridge amps

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Originally Posted by Sabbatical II View Post
I'm just wondering what is normal amps for a fridge to use. My new boat is using 13 amps to run the fridge. ..... Am I using too many amps and does anyone have any idea what % of time the motor should be cycling for?
Wow, that's way more than I am used to seeing, but I don't know your system. Amps in AC or DC?

I currently run Danfoss BD25 and BD50 based systems which draw dramatically less.

I've often heard 25% as a reasonable cycle on time and that is about what I experience. The more insulation the better.
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Old 11-09-2012, 10:51   #6
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Re: High fridge amps

The most ours draws is 7.5amps/hour, that is when the engine is on, controls are overridden so it keeps getting colder over setpoint, and 40% mode is off (higher compressor loads and operation speed) and the small water pump is on. In energy saving mode when the engine is off, water pump off and 40% mode is on to save energy (slower compressor operation) it draws 5.5amps/hour, all at 12VDC

Initially it will run for 3-4 hours and we try to run the engine for part of that time because of our smaller 150 ah batteries, and we can put it on full power. (This is a balance because the engine compartment also gets hot, so we have a fan too.) Need to add some more insulation in engine compartment adjacent to ref box.

Box is 6.1 cuft. 2.5"-3" insulation (this is not super insulated which I would have preferred, but not possible). We cut up 1/2" foam sleeping mat to fit inside of box. Sometimes we bring milk frozen to help the startup.

A lot depends on climate, we're in Rhode Island. Sun on a black hull where ref is located can be really bad.
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Old 11-09-2012, 14:06   #7
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Re: High fridge amps

Ok, thanks everyone for the info. At the moment I'm only measuring it with nothing in it. Maybe 13 amps is OK when the unit is first switched on and it is trying to cool the box down. I'l wait until it's in service and check again.
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Old 11-09-2012, 15:20   #8
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Re: High fridge amps

Run some tests.

Put a couple of gal bottles of water in it and bring it down to temp while measuring the AH used and amount of time running. (need a Link or something similar) without running engine if possible.

Then measure how long until it starts up again, and then measure the AH used and time run.

At some point you'll need to start the engines or charge the batteries with a charger preferably while you are not measuring ref run time and ah.

Read about the limit settings needed for the unit
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Old 11-09-2012, 15:30   #9
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Re: High fridge amps

Can't speak to your specific brand, but my Nova Kool 12V Danfoss based system draws about 2.5A and has about a 25-35% duty cycle in temperate climate in summer. That works out to about 25 Ah per day. This is on a typical top loading fridge with mediocre insulation.
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Old 11-09-2012, 16:19   #10
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Re: High fridge amps

Air has piss all thermal mass, as said put ten liters o water in it or something then test it out.
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Old 11-09-2012, 18:30   #11
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Re: High fridge amps

After putting some thermal mass inside (for example, water bottles) give the system several hours to cool the mass to box temp before starting the measurements.
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Old 11-09-2012, 19:37   #12
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Re: High fridge amps

Hi Sabbatical, your Ozefridge ER480 system should not be drawing such high amps. The ER480 has a six stage soft start and although draw will be higher in the initial part of the cooling cycle, while running it should settle to consume between 7 and 8 amps on 12VDC and less than half of an amp on 240VAC or less than one amp on 110VAC.
The common causes of high power consumption are (A) air in the system, (B) Inadequate condenser or condensers ability to dispose of heat, (C) Overcharged with refrigerant gas. With both A & B unlikely in this case, I suspect that the system is overcharged as would be indicated by frosting/ icy cold sweating of the suction pipe coupling on the side of the ER480 unit.
Please contact us at Ozefridge so we can sort this for you. (Contact details are in your operators manual)
Cheers!
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Old 12-09-2012, 01:14   #13
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Re: High fridge amps

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Originally Posted by Ozefridge Pete View Post
Hi Sabbatical, your Ozefridge ER480 system should not be drawing such high amps. The ER480 has a six stage soft start and although draw will be higher in the initial part of the cooling cycle, while running it should settle to consume between 7 and 8 amps on 12VDC and less than half of an amp on 240VAC or less than one amp on 110VAC.
The common causes of high power consumption are (A) air in the system, (B) Inadequate condenser or condensers ability to dispose of heat, (C) Overcharged with refrigerant gas. With both A & B unlikely in this case, I suspect that the system is overcharged as would be indicated by frosting/ icy cold sweating of the suction pipe coupling on the side of the ER480 unit.
Please contact us at Ozefridge so we can sort this for you. (Contact details are in your operators manual)
Cheers!
Thank You Ozefridge Pete. Since the builder is still trying to commision the vessel I will make him aware of your post and get him to sort it out with you. They have reduced the amount of gas in the system and I suspect problem "B" may be the winner. Thanks again for your reply.
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