My sea water water pumps keep burning out on my Isotherm ASU 5801 marine refrigerator.

I only got 6 mos out of this last pump, which is pathetic. It was a ShurFlo.

The refrigerator doesn't work quickly... it has a holding plate that it cools down pretty slowly using two Danfoss compressors. Because of this, it doesn't deposit much heat in the cooling coil (condenser) where the raw seawater flows through.

I'd like to find a pump that doesn't go full blast spraying a stream of water through the system at something like 6 GPM, as these ShurFlo units do. They seem designed to move large amounts of water, burning up in the process, when this system does not need this much water moved.

Does anyone know of a reliable salt water pump with a similar footprint to every other ShurFlo pump (just like the fresh water pumps)?

I'm getting tired of replacing these all the time. They just aren't built to last. Would an impeller based pump work better than these diaphragm pumps?

I assume the pump is a diaphragm demand pump. If so the pump should have a pressure control switch that allows the pump to run wide open in the absence of back pressure. As the back pressure increases the pump will slow down and or stop. As you, I suspect the problem is the pump is running wide open and wearing out.

I suggest installing a ball valve on the discharge side of the refrigerator so you can pinch down to increase back pressure and allow the pump to run at a moderate speed.

I also suggest you call Shurflo tech before you do anything and see what they suggest. They also may have a pump more suitable for this application.

Looks like your flow rate is way too high. This is from the manual:

Flow rate: 2 l/mm (4 pints/mm).
Maximum suction heigh: 2 m (6.5 ft).
Current consumption: 0.6A
Water connections: 13 mm (Xl’)
Maximum water temp.: 35°C (93OF)

Source: Isotherm Marine Refrigeration

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Regards,

Maren

The sea is always beautiful, sometimes mysterious and, on occasions, frighteningly powerful.

Thanks for the input, everyone.

BA and Maren: Yes, I think the flow rate is too high. It would seem the PO used to use these ShurFlo pumps and probably decided to go through them instead of buying a good pump.

After looking all of this up today, I've got my eye on these:

MARCH - SERIES 893



The March pumps are rated at 55,000 hours continuous use and have brushless DC motors with magnet drive (no seals to wear out). They seem to be the right choice. Also, using 1 amp, (instead of 4-5! of a ShurFlo), my electrical problems are SOLVED!

I guess the pump breaking was a blessing in disguise!

How long you leavin' that pump runnin', man?

__________________
Regards,

Maren

The sea is always beautiful, sometimes mysterious and, on occasions, frighteningly powerful.

The pump takes 4-5 amps and the compressors take 2.5-3 amps.

It runs for 5-6 hours a day sometimes, depending on how hot it is out, then there are other times (like when you buy meats to freeze) that it's on 8-10 hours a day.

As I was mentioning, these 12V systems are slow to move heat, but use much less energy per unit of time than the AC systems do. I used to have a 1/2HP Tecumseh 120VAC compressor that blasted a freezer and refrigerator cold plate down in less than an hour off a genset. I had to run it manually though.

The 12V system operates on a different concept: that of low power impact and longer running times. The pump is actually my main source of power drain when running the refrigerator, it turns out.

Who would have thought??

Sully, Flow rate should not be a factor in pump longevity. The construction makes of breaks it and higher flow is better for the system since it carries the heat away faster. Go with the March pump. The problem is that I don't believe the Shurflo is rated for continuous duty, which is what you need even though the pump is not running all the time. The March pump should resolve your issues. The flow rate for any cooling system is a minimum standard and if exceeded will not affect the system and sometimes makes it work better. The flow rate is also affected by the length of the lines and the height the pump needs to push the water. So you can't calculate based on the manufacturers flow rate. Chuck

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Thanks, Chuck!

Glad to see you got a break from that fantastic refit job you're doing. It's good to hear from you.

I'll go with the March pump for sure.