priming a water cooled fridge and freezer

[JOURNEYMAN]

Hi,

New boat with teething issues. Both fridge and freezer stooped working. traced the problem to a split hose between seawater in seacock and pump. Replaced hose. Now can't get the pumps to suck water up and pump through compressors. The compressors and pumps are sited above the waterline level. Have tried undoing, sucking through water then re-joining - to no avail. Have tried detaching pump, bringing it down to waterline level - it fills with water, but when raised, goes dry again.

I guess gravity is the enemy here?

I guess its unusual to have the pumps above waterline plane so they need to prime. There is no priming pump or screw or anything that I can see on them. The boat was on the hard to 2.5 years before I bought her. I guess it would drain the system. But the freezer id 12 yr old and the fridge 5, so it must have been dried and restarted before. Indeed it must have been primed when installed.

I cant tell the make of the pumps - one is a 3 ventricle 5 volt pulse type, the other looks more conventional 12 v diaphragm. The former is approx. 12 inches above waterline plane, the latter 18 inches. so not a mammoth uphill climb ....

any insight would be welcomed

thanks

J

 

[vyv_cox]

Both types of pump you describe are positive displacement types that should self prime. Mine is a small Par Max1 that is a couple of feet above the waterline. It never fails to prime and runs perfectly. If yours do not there is another fault, either the valves in the pump are not seating because of debris or something similar. In theory pumps of this type will prime up to 10 metres above the water, unlikely in practice but they should do three or four.

 

[TradewindSailor]

First check that water is getting to the pump ..... blocked filters, blocked or broken seacock, blocked hose, or the filter seal broken and sucking in air.

Provide the pump with a local source of water and see if it is able to pump it. If not the pump is faulty. There is nothing special about the pump, and yes it should self prime at least 3' above the waterline. If the pump is bad replace with a simple 2 gph water pressure pump .... perhaps the same as on the fresh water plumbing side so you have interchangeability for tests.