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post #1 of 12 Old 01-27-2019 Thread Starter
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AC Water pump pressure?

I have a March LCP pump feeding my AC and I'm trying to determine if the output pressure is correct.
When I open the outlet, the resulting water stream drops about 2-3" at 6" out. I expected higher pressure.
I feel a bit of pressure when I momentarily put my finger over the output, but it immediately drops to negligible.

Can anyone offer any comparable experience?

Thanks in advance!
/ed
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post #2 of 12 Old 01-27-2019
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Re: AC Water pump pressure?

Flush the system from the strainer using Barnacle Buster.

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post #3 of 12 Old 01-27-2019 Thread Starter
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Re: AC Water pump pressure?

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Originally Posted by boatpoker View Post
Flush the system from the strainer using Barnacle Buster.
Did that recently (2-3 months ago) with acetic acid; I'll try it again with this product. Today cleaned
filters and made sure water flow was clear.

Thank You!
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post #4 of 12 Old 01-27-2019
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Re: AC Water pump pressure?

March pumps are not positive displacement pressure pumps. They are more like the fresh water centrifugal pump in your engine - they are designed to circulate water, not pump it. Likewise, they are not self-priming, and will not produce much larger pressure than the natural head pressure in the water column they are plumbed in series with - maybe another 5-10' of head. If you plug them with your finger, you won't see more than 20psi or so before they simply stop pumping.

So it sounds to me like yours is working as it should.

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post #5 of 12 Old 01-27-2019 Thread Starter
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Re: AC Water pump pressure?

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Originally Posted by colemj View Post
...
So it sounds to me like yours is working as it should.
Mark
Thank You.
Guess a barnacle cleanse is next!
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post #6 of 12 Old 01-28-2019
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Re: AC Water pump pressure?

Quote:
Originally Posted by edguy3 View Post
Thank You.
Guess a barnacle cleanse is next!
While the subject has often been discussed on this forum (use the search function, above, keyed to "Barnacle Buster" and/or "RydLyme"), it is important to remember to allow sufficient time for the material to work. Recirculating a Barnacle Buster or RydLyme solution from a bucket using a submersible bilge pump through your AC unit for several hours to be fully effective. (In our case I do this treatment annually and find that it generally takes about 3 hours.) As the solution works, more debris will beak free from your system and will accumulate in the recirculation bucket. Placing the bilge pump in a segment of a woman's stocking is effective at preventing this debris being picked up and pushed back through the system.

In the process, do not overlook the raw water supply line. The supply line from your through hull should be disconnected from your raw water strainer to permit you to "back-flow" fresh water through the line for several minutes to blow out any sea grass and/or debris that may have accumulated in the line. Then, close your seacock and before reconnecting the line, tilt it upward and support it and using a syringe, introduce some undiluted Barnacle Buster into the line and allow it to sit for several hours while you recirculate the solution through your AC system. Then, blow fresh water through it again for a few minutes before reconnecting it to your strainer.

We have a similar March Pump pushing 360 gal/hr through our 16K BTU system and when the lines are properly clean, get a very healthy water flow through and out the discharge.

FWIW...

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post #7 of 12 Old 01-28-2019
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Re: AC Water pump pressure?

Before you go and do a flush, why are you asking. Is the outlet flow low or the the system not performing?

Have you tried just pulling a couple of Pan Tablets in the strainer to kill whatever is growing in the lines?

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post #8 of 12 Old 01-28-2019
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Re: AC Water pump pressure?

I'd ask myself Is there a dead mussel shell stuck in the inlet and how much above water line is the outlet (limited head)
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post #9 of 12 Old 01-28-2019
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Re: AC Water pump pressure?

Just had this problem. Condenser was over heating and poor water flow out exhaust. Cleaned out the intake thru hull. Works fine now.
Soft growth and grass get sucked in. The grass doesnít reach the strainer. Need to jump into the water to clean.
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post #10 of 12 Old 02-07-2019
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Re: AC Water pump pressure?

When it comes to water cooled heat exchangers water flow is more important than water pressure. The water flow requirement for the heat exchanger, and the capability of the pump are usually listed in gallons per minute or litres per minute. If you are getting the required flow, the pressure at the outlet doesn't really matter.

Are you having a problem with high head pressure on your A/C?

I would be hesitant to run corrosive or caustic substances through my heat exchanger unnecessarily.

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