I need to replace my original AlderBarbour refrigertion on our 88 Cat 30. I can get a real sweat deal on a entire system that was a demo Isotherm unit. Does anyone have any positive/negative feedback on Isotherm units??? Thanks
Refrigeration
- Thread starter Jeff M10656
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I too have an 88 C-30 with a non functioning Adler Barbour refrigeration system.It was probably installed when the boat was new. I will first determine whether the system can be repaired or needs to be replaced. If it would not be cost effective to repair it, I may have it removed,better insulate the box and use it as an ice box. I have a small refrig. under the nav table that runs off of shore power. I would be interested in hearing about your decision. goldmill@sbcglobal.net
Refrigerator
My wife and I just boght a 77 Cat30. We really like it. The previous owner removed the stove and replaced it with a small Dorm style GE Frige. It currently runs off shore power. However, it draws less than one amp of current. Since we cruise the local Bay and some part of the lake, we usually are not out longer than 4 to 5 hours. I can run the frige off an inverter if I wanted to, and then switch back to shore power later. 5 hours at running the frige at one amp of current per minute when the compressor is running is max of 60 amps per hour if run contineously. Thats 300 amp hours per 5 hrs and the backup battery is rated at 500 amp hours. Coments?
My wife and I just boght a 77 Cat30. We really like it. The previous owner removed the stove and replaced it with a small Dorm style GE Frige. It currently runs off shore power. However, it draws less than one amp of current. Since we cruise the local Bay and some part of the lake, we usually are not out longer than 4 to 5 hours. I can run the frige off an inverter if I wanted to, and then switch back to shore power later. 5 hours at running the frige at one amp of current per minute when the compressor is running is max of 60 amps per hour if run contineously. Thats 300 amp hours per 5 hrs and the backup battery is rated at 500 amp hours. Coments?
Amps is Amps
You have missed the picture here. Amps are a unit of current flow. There's no meaning to amps per minute or amps per hour. (Actually the Amp or Ampere is one coulomb of charge per second.) One Amp for one Hour is one Amp-hour. How do you know that your fridge uses only one amp? Is that the 110 volt AC current draw or the 12 volt DC draw? Usually the steady current draw (1 Amp ?) is one fifth to one tenth of the start up current (locked rotor current). Measuring AC current draw can be tough unless you have one of the nifty clamp on sensors. Measuring DC current is much easier and a standard automotive type ammeter will do it with no trouble (it has a shunt built in). You need to measure the DC current FLOWING INTO YOUR INVERTER with a DC ammeter. Watch the meter as the compressor motor starts up to see the maximum draw. Then figure out the total energy requirement in Amp-hours that you need. Clearly the one amp current is the AC current rating but one amp at 110 Volts AC is going to be around ten amps at 12 volt DC and inverter losses may make it a little more. Ten amps for 5 hours is 50 amp-hours. Since you should never discharge your battery by more than about 40% of its total capacity you will need a 125 amp-hour battery bank (probably two group 27s) just to run the fridge. In addition the starting current could be between 50 and 100 amps at the battery so make sure your inverter can supply 600 to 1200 watts of power (volts times amps) and that your batteries can produce 50 to 100 amps of cold cranking current (CCA). Use big wires to carry this current like the wires on your batteries. PS I am willing to bet that your back up battery is not rated at 500 amp-hours. It is probably 500 CCA. A 500 Amp-hour battery will weigh roughly 500 lbs. (5 group 31s will just do it.) And if you only have one "backup battery" it is probably an 85 to 90 amp-hour group 24 or group 27 battery. Do you have only one battery aboard? Does it have to start your engine too? Time to buy a good book on boat electrics!
You have missed the picture here. Amps are a unit of current flow. There's no meaning to amps per minute or amps per hour. (Actually the Amp or Ampere is one coulomb of charge per second.) One Amp for one Hour is one Amp-hour. How do you know that your fridge uses only one amp? Is that the 110 volt AC current draw or the 12 volt DC draw? Usually the steady current draw (1 Amp ?) is one fifth to one tenth of the start up current (locked rotor current). Measuring AC current draw can be tough unless you have one of the nifty clamp on sensors. Measuring DC current is much easier and a standard automotive type ammeter will do it with no trouble (it has a shunt built in). You need to measure the DC current FLOWING INTO YOUR INVERTER with a DC ammeter. Watch the meter as the compressor motor starts up to see the maximum draw. Then figure out the total energy requirement in Amp-hours that you need. Clearly the one amp current is the AC current rating but one amp at 110 Volts AC is going to be around ten amps at 12 volt DC and inverter losses may make it a little more. Ten amps for 5 hours is 50 amp-hours. Since you should never discharge your battery by more than about 40% of its total capacity you will need a 125 amp-hour battery bank (probably two group 27s) just to run the fridge. In addition the starting current could be between 50 and 100 amps at the battery so make sure your inverter can supply 600 to 1200 watts of power (volts times amps) and that your batteries can produce 50 to 100 amps of cold cranking current (CCA). Use big wires to carry this current like the wires on your batteries. PS I am willing to bet that your back up battery is not rated at 500 amp-hours. It is probably 500 CCA. A 500 Amp-hour battery will weigh roughly 500 lbs. (5 group 31s will just do it.) And if you only have one "backup battery" it is probably an 85 to 90 amp-hour group 24 or group 27 battery. Do you have only one battery aboard? Does it have to start your engine too? Time to buy a good book on boat electrics!
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