Update ... so i backwashed the seawater intake from outside, installed a 8.5 GPM saltwater pump and got flow up to 3.5GPM. I had the A/C serviced ... turns out the unit should have had 1 lb of R22 but in fact had 2.1lb of R22 ...(!). I had it evacuated and replaced with 15 oz of R22B. Output cold is 15oF cooler than before, and pressure and super hot and supercold measurements are now apparently in line with specs. so barring an issue with mollusks clogging up the condenser coils and other hoses down the road all good for now ... THANK YOU for your input!
Seawater pump for A/C
- Thread starter 4Winds
- Start date
Do take some pictures! something about these pumps that everybody is calling pumps... they are actually circulators they do not "draw" seawater from outside the boat they use the water that's there by static pressure IE the water that's being forced into the boat through the intake.
you can have flow and it may seem good but it may still be restricted by eel grass other kinds of marine nasties so you want to make absolutely sure your intake from the outside in is completely clear it may mean diving on the boat if you can't take the elbows out from above and run a brush or something down through the valve and strainer,
secondly about magnetic Drive pumps if there is high head in other words the pump is trying to push the water through the condenser harder than it's ratings it will start to get warm, even though they can get quite warm and are rated to do so.
You can should could do the barnacle buster/ muriatic acid reverse flow through the air conditioner heat exchanger two or three times also, check the discharge where the water comes out of the boat sometimes they get clogged
Just the strainer in the hose may be restrictive I had to change mine to a 50 count mesh for it run near continuous the 100 mesh strainer was just too restrictive.
you can have flow and it may seem good but it may still be restricted by eel grass other kinds of marine nasties so you want to make absolutely sure your intake from the outside in is completely clear it may mean diving on the boat if you can't take the elbows out from above and run a brush or something down through the valve and strainer,
secondly about magnetic Drive pumps if there is high head in other words the pump is trying to push the water through the condenser harder than it's ratings it will start to get warm, even though they can get quite warm and are rated to do so.
You can should could do the barnacle buster/ muriatic acid reverse flow through the air conditioner heat exchanger two or three times also, check the discharge where the water comes out of the boat sometimes they get clogged
Just the strainer in the hose may be restrictive I had to change mine to a 50 count mesh for it run near continuous the 100 mesh strainer was just too restrictive.
Congratulations !! That's good your technician caught the overcharge which is common when do-it-yourselfers are involved because everybody believes refrigerant needs to be replaced and on a sealed system that rarely happens
I could be wrong but I thought the minimum recommended flow rate for a 16k BTU unit was 4 GPM. From 8.5 capable to 3.5 actual seems like a significant drop.
I am not sure yet but I could (probably) still have blockage do to mollusk infestation ... also I am told that the piping size (1/2") and right angle bends put a maximum on the speed of water that can flow through the system ... ie 4GPM. If it falls to 3 and I cannot fix it with backwashing I will need to try to have the system descaled ...a for the 8.5GPM, the idea was to have a stronger pump with a slightly stronger head than I needed. But yeah, I'd really like to see 4.0 or 4.5 or so. The boat was in brackish water no friendly to mollusks until 2 mos ago, now it is in very mollusk-friendly water .... I think I will have my answer in a couple months ...
If anyone needs a 30lb can of R14a
I did put barnacle buster down one of my other throughhulls by connecting a long wide diameter hose to the barb, raising it above the water line and pouring barnacle buster down it. seemed to work.
I made a set up with a bucket, a small bilge pump and some hose to pipe couplers and pump full strength barnacle buster into the system. As soon as it starts exiting the throughhulls I stop the pump and let it sit in there for a few hours. Then pump it out with fresh, then reconnect the a/c pump which will blow more debris out as its more powerful.I am not sure yet but I could (probably) still have blockage do to mollusk infestation ... also I am told that the piping size (1/2") and right angle bends put a maximum on the speed of water that can flow through the system ... ie 4GPM. If it falls to 3 and I cannot fix it with backwashing I will need to try to have the system descaled ...a for the 8.5GPM, the idea was to have a stronger pump with a slightly stronger head than I needed. But yeah, I'd really like to see 4.0 or 4.5 or so. The boat was in brackish water no friendly to mollusks until 2 mos ago, now it is in very mollusk-friendly water .... I think I will have my answer in a couple months ...
I did put barnacle buster down one of my other throughhulls by connecting a long wide diameter hose to the barb, raising it above the water line and pouring barnacle buster down it. seemed to work.
Barnacle Buster | Descalers | Drew Marine Trac Ecological
Barnacle Buster® is a safe, non-toxic and biodegradable marine growth remover formulated to meet an industry need for cleaning seawater cooled equipment.
I think its basically phosphoric acid.
That does not mean you achieve that flow. That normally is the pumps rating.
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At standard small centrifugal water pump pressures.
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That depends on 2 temperatures.
1) Surrounding Water Temps
2) Inside the cabin air temps.
That changes, if you have a reverse cycle AC unit.
Jim...
I am going to post soon about Boat Air Conditioning Units.
Simple view is you are trying to exchange Heat. There is no such thing as a HEAT rate meter.
An analogy using Electricity.
1) Heat flow rate = Amp flow rate
2) Pump Pressure = Volts or Pushing power
3) Pipe Friction Loss = Electrical Resistance.
Boat AC units have Specification for ranges of operation.
Most are designed for mid Latitudes like North Carolina.
@4Winds it your boat's AC was installed by Hunter, then your water piping is size ok.
So you are fighting
1) Flow rate resistance
2) Large temperature differences.
Two sides of the Heat Exchange must be clean and maintained.
1) Water side
2) AC side.
Jim...
Simple view is you are trying to exchange Heat. There is no such thing as a HEAT rate meter.
An analogy using Electricity.
1) Heat flow rate = Amp flow rate
2) Pump Pressure = Volts or Pushing power
3) Pipe Friction Loss = Electrical Resistance.
Boat AC units have Specification for ranges of operation.
Most are designed for mid Latitudes like North Carolina.
@4Winds it your boat's AC was installed by Hunter, then your water piping is size ok.
So you are fighting
1) Flow rate resistance
2) Large temperature differences.
Two sides of the Heat Exchange must be clean and maintained.
1) Water side
2) AC side.
Jim...
This means:
Two sides of the Heat Exchange must be clean and maintained.
1) Water side : seawater hoses
2) AC side : condenser coils
..right?
I can run barnacle cleanng solution through hoses and let it soak.
I need to figure out how to clean condense coils. No idea at this point.
It is a dometic marine airsystems vcd 16k/2, 16000 BTU, R22B, Fan 3.3, FLA cool 11.1, FLA heat 14.1
I assume it was installed 2005 new with the boat.
Ok R22B is now called this
Freon™ NU-22B™
And yes folks, Freon® is back. [reason is the Ozone models of the 80's were not proven true]
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Back to your AC issues. Check you private message is 5 minutes @4Winds.
Jim...
Freon™ NU-22B™
And yes folks, Freon® is back. [reason is the Ozone models of the 80's were not proven true]
____
Back to your AC issues. Check you private message is 5 minutes @4Winds.
Jim...
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I gave you my home phone number , private messages is the little Envelope Icon , upper right of your browser.
Jim...
Please explain "Freon is back." Last time I ask I was told that a bottle of R22 was $900, doesn't seem like it's back. I'm not an HVAC guy and this is the first I've heard of this.
EDIT! I wasn't planning on going back to refrigerant School on the eve of selling my boat but I don't want to be verbally crucified here either
"NU-22B can be used to COMPLETELY replace R-22 refrigerant in new or existing R-22 residential and commercial air conditioning systems as well as non-flooded evaporator chillers. Cannot be added to R-22 unless fully evacuated and recharged with NU-22B.
NU-22B® Replaces R-22, R-407C, R-422D and R-417A."
Disreqard this:
R22, there are
Replacements available but they are not drop in Replacement the one I'm familiar with is 407c depending on the location and the manufacturer, it may be a different number, it cannot be used to mix with existing R22 or mineral oil compressors that's why it is generally not mentioned to do-it-yourself people.
"NU-22B can be used to COMPLETELY replace R-22 refrigerant in new or existing R-22 residential and commercial air conditioning systems as well as non-flooded evaporator chillers. Cannot be added to R-22 unless fully evacuated and recharged with NU-22B.
NU-22B® Replaces R-22, R-407C, R-422D and R-417A."
Disreqard this:
R22, there are
Replacements available but they are not drop in Replacement the one I'm familiar with is 407c depending on the location and the manufacturer, it may be a different number, it cannot be used to mix with existing R22 or mineral oil compressors that's why it is generally not mentioned to do-it-yourself people.
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That is a DuPont trade name.
It got a bad reputation, in the 80's, for suspected Ozone Layer reactions or exposing Earth to Solar radiation directly.
A law banned R22 USA Production, since 2020. Thus the higher cost from recovered R22.
It still remains a Trade name and now a almost direct replacement can be used in most of the AC compressors throughout USA.
"Stupid is as Stupid does" quote Forest Gump.
Jim...
PS: So like the Competent AC Tech, like @4Winds used, he put in the new R22B without a need to change his Boat's AC compressors.