Eleuthera 60: refrigaration enigma

[MIRELOS]

We have an Isotherm 4201&4701 ASU Magnum units serving as refrigerator and a separate freezer unit, it came factory installed with one filter, after arriving in the USA from France the filter was clogged so I cleaned it and thought not much of it......it came clogging so I installed two see through filters...all is well, not, every year there is a problem I have replaced three pumps, two voltage reducers and two electronic units. The mystery is why one of the pumps, brand new does not pump water in but it does from a bucket ( so it works) and it is the lowest of the units so it gets its water supply first.......any ideas.
HELP!
the INdel Webasto guys in Fla are very helpful but they can't figure it out and the folks in the factory think its the double filter system, but this does not effect the other two. ..??????

[Cruisingscotts]

Do the pumps have check valves on the discharge or inlet? If you have two pumps drawing from the same suction point they should have check valves at some point in the circut. Other wise one can pulll air through the other and loose its prime. Most likely it would be a simple flap check on the dishcharge of the pump. It would make sense that at new pump would be intact and the old one have issues. Try plugging the the inlet to the old pump, bleed air from the line and see if it runs. If there are no checks in the system and its only relying on the pump to maintain you may want to add some small inline checks at the discharge of each pump.

We have the same freezer setup, just one unit, with the condensing water drawing from a FW tank and dumping back in. I have found the pump to be fairly sensative to suction head, amount of negative suction line pressure, they do not really tolorate any.

[MIRELOS]

There are check valves for all three pumps and I have tried isolating the pumps all good except the one (bottom). Interesting you have a FW system for yours that seems like a great solution for all the dirty water we are in and could eliminate a filter for sure. How big a tank?
Her's my pump set up (picture). Do you think going into a FW set up would be worth it.
Thanks
Carlos
s/v Mirelos

[MIRELOS]

Originally Posted by MIRELOS

There are check valves for all three pumps and I have tried isolating the pumps all good except the one (bottom). Interesting you have a FW system for yours that seems like a great solution for all the dirty water we are in and could eliminate a filter for sure. How big a tank?
Her's my pump set up (picture). Do you think going into a FW set up would be worth it.
Thanks
Carlos
s/v Mirelos

trying to load up image

[Cruisingscotts]

Originally Posted by MIRELOS

trying to load up image

It's easier to put images in a a online public space like fliker and post a link.

The FW setup all depends on the heat rejection required for the condesening on your system. If you have multiple FW tanks or a RO and keep things pressed all the time then there is good chance you will have the volume of water nessessary to make it work, but you have to account that the tank must have the minumum required FW in or no reefer. Anywhere warm the odds are your FW in the tank will be more or less the same as the seawater it's all about how many BTU's you need to reject. If you talk to the manufacture they can run the math for you based on the compressor and evaporator specs and your ambiant conditions. The isotherm rep in Florida was the one who told me to try it as alot of people had good luck.