a/c winterize problem

[Duetto]

i'm in the process of winterizing out mainship pilot. the task at hand is the a/c. it is a 10K flow (dometic, cruisair, marine air look alike). my thought was to
use a flojet diaphragm pump to supply antfreeze to the system thru the input port on the strainer. so i shut the seacock, vacuum out the seawater in the strainer, connect flojet output to the stainer input, turn on the a/c. when the a/c pump starts turn on the flojet and pump 2 gallons thru. so i turn on a/c, pump starts, turn on flojet but no antfreeze is sucked in. so my thought is the a/c is airbound, so i undo the discharge at the a/c unit. i've had to do this in the past to clear air and get flow going. again same sequence and still no flow. the flojet works because i used it on other systems this week.

so is my logic ok? if so, what could be the problem?

 

[Comodave]

Probably the A/C pump is airlocked. I have a 5 gallon bucket that I installed a hose bib on the side at the bottom. Trac makes an adapter that replaces the top of a Groco strainer. I hook a short garden hose from the bucket to the adapter on the top of the strainer. Set the bucket up high on the deck and turn on the A/C pump. It sucks in the antifreeze all by itself.

 

[Duetto]

thanks for the reply but isn't my flojet doing the same thing?

 

[fgarriso]

Why are you adding a flow jet pump to a system that already has a pump?

 

[Duetto]

not adding it to system. i just use it to provide antifreeze in place of normal water pressure. this is just for winterizing.

 

[fgarriso]

You don't need it the system has it's own pump.

 

[Duetto]

a/c pumps won't suck. they need to be flooded. if there is any air on the intake side of the a/c pump they won't pump.

i thought, perhaps incorrectly , that using a pressure pump would force any air past the a/c pump and then it would pump. that at least was the thought.

 

[fgarriso]

Use the 5 gal bucket that Commodore Dave suggested and hang it above the system pump, and it will clear any air bubbles on it's own.

 

[Bacchus]

a/c pumps won't suck. they need to be flooded. if there is any air on the intake side of the a/c pump they won't pump.

i thought, perhaps incorrectly , that using a pressure pump would force any air past the a/c pump and then it would pump. that at least was the thought.

You are on the right track.
I have used containers on deck to provide enough head pressure to prime the pump.
I am in the process of trying to plumb my raw water pump / system to the A/C strainer for winterizing and spring commissioning.
I dont know why any pump wouldn't provide sufficient prime as simple head pressure of about 2 ft above the waterline seems to work for me.. is the pump you are using a " transfer" pump? If so they won't develop much head pressure as they are meant to discharge to open air as when simply pumpin from one container to another but not against any head or restriction.

 

[Comodave]

I have even use a small hand bilge pump to push the antifreeze through the A/Cs since there isn’t really any restrictions in the hoses. But the easiest is to let gravity feed the strainer and then the A/C pump.

 

[ranger58sb]

Our new-to-us Oberdorfer pump has an air bleed screw (allen head) and won't prime itself without first releasing air from the hose that runs between strainer and pump.

-Chris

 

[FF]

All centrifugal pumps need water in them to function.