Air Cond Question

[Captain Ralph]

I remember an issue with a small pump getting replaced with a much larger pump. I believe it lost a little bit of efficiencies.
My thought was then, water was moving to fast to transfer the heat.
I can not quote the guideline rite now but there are min & max flows for freon/expansion units.
These guidelines can get weird quickly taking into account any hose head and split systems.

In my notes above in post #3, I still use a 500 Little Giant pump.

 

[riverrandy]

Back in the 80's I remember my father disassembling the ac circulation circuit to unclog them of Jellyfish on the Rappahannock River, they would clog the intakes, and mix with mud and clog the hoses. Down here in Florida it is defiantly the barnacles and etc. that cause the issues. Interestingly, I had to substitute a giant bronze .75 hp pump on one of my units while I waited for a new March pump to come in. It is so robust I rarely have to do anything to that unit. Once a year I clean the strainer and borascope the lines. I guess it is too much flow for barnacles. 3.5 years, fingers crossed.

 

[SeaEric]

I remember an issue with a small pump getting replaced with a much larger pump. I believe it lost a little bit of efficiencies.
My thought was then, water was moving to fast to transfer the heat.
I can not quote the guideline rite now but there are min & max flows for freon/expansion units.
These guidelines can get weird quickly taking into account any hose head and split systems.

In my notes above in post #3, I still use a 500 Little Giant pump.

The spec for the 16k Citimarine Self contained unit calls for 500 GPH. The split system IIRC is 12k btu. I'm going to check with my systems techs before I make the pump change. Logic suggests (the voice in my head) that with separate discharge ports, the 1,000 GPH pump makes some sense. I clearly don't have enough water flow currently based upon the HPF codes that continue to pop.

 

[Captain Ralph]

I clearly don't have enough water flow currently based upon the HPF codes that continue to pop.

Still have HPFs after cleaning?
Are you using an ole bronze pump?

 

[SKYCHENEY]

Water cannot move too fast for basic thermodynamics. The faster the flow, the faster it should cool so, a pump with a higher flow rate can't hurt

 

[Pascal]

Indeed and pumps Never put out the rated flow because of head, restrictions, elbows etc.

 

[SeaEric]

Still have HPFs after cleaning?
Are you using an ole bronze pump?

 

[SeaEric]

Its a March LC-3CP - MD 490 GPH.

 

[Captain Ralph]

Back at my desk and found this;

Rule of thumb: Systems require approximately 1.5 GPM per 12,000 BTU (1 ton) of cooling capacity.
Total head pressure (measured in feet of head) must account for:

• Static lift (vertical distance from water line to pump)
• Friction loss from pipe runs (approximately 1 foot of head per 10 feet of pipe run)
• Fitting losses (each 90° elbow typically equals 2.5 feet of pipe)
• Strainer and seacock resistance (typically 3-5 feet of head)

After backflow rinsing your hoses, did you clear the thru hull and sea-cock?

Per these guide lines, your 500GPH should work fine.

Technical Guide to Marine Air Conditioning Pumps

System Fundamentals and Pump Function Marine air conditioning systems operate under unique conditions that demand specialized equipment. Unlike land-based HVAC systems, marine AC units must withstand constant motion, salt exposure, limited installation space, and fluctuating power supplies. At...

www.marinepumpsolutions.com

 

[carolinacoast]

I have had several problems in this area, and finally resolved with the right size pump for my application. Mine was too big-go figure (had a 2000gph). I spoke to the engineering department at March pump corporate office. Here is the quote that I have in those notes:
1gpm /3000btu for any air conditioning system per March engineering.
There were lots of qualifiers to that formula that did not apply to me. Notes say my system needs 1500gph @17psi to be in the middle of the range with 1 inch out that converts to 1.5 inch for my 61000btu setup (single pump, but I have 2nd plumbed in with extra wet end and 3rd aboard).
Everything has been fine since I upgraded to a smaller pump.