Running Your Marine AC while on a Trailer

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Running Your Marine AC while on a Trailer

Back in 94, when I used to pull my 2556 Bayliner around the country quite a bit visiting different areas, I got tired of pulling in RV parks and sweating bullets all night, when my boat already had a marine A/C unit sitting there which was un-useable. Finally after a bit of thought, I figured out a way to use the marine air while the boat was on a trailer.

I accomplished this by installing a “T” on the sea-water intake that runs to the A/C water pump. When I pulled into my RV spot, and hooked up for the night, I would hook up the water hose to the “T” and crack the water facet open a bit and “Presto” the A/C kicked on and I was just as cool as the rest of the RV’s except I was in my boat. On the hull outlet where the A/C discharges the water, I had a of garden hose the I cut the end off that wedged right into the outlet, which I ran to either the ground or into the sewer.

I just recently acquired a new Ranger 25 and plan on doing some traveling as well. When I installed my winterizing modification on the A/C unit, http://www.c-brats.com/viewtopic.php?t=10278 I designed the system so I could use the A/C in RV Parks as well. On this system, I simply used a “T” with a shut off valve and hose which normally goes to the RV Solution bottle - which now also doubles as the water tap to use the A/C while on the trailer.


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This is the standard water hose fitting, which I simply slide into the pickup tube which supplies the tap water to the A/C pump.


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This is the components for both winterizing or using tap water for your AC unit


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Here the same tube that doubles for winterizing the AC system, is also used for supplying tap water to cool the condenser unit.
 
Captains Cat":ot3hcite said:
I'm sure it'll work fine but isn't it going to use a lot of water?? :shock: A campground might not like that much...

Charlie
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Since the unit only uses water when the pump is running and it's night - I would be surprised if it used the water it would take to shower.

Besides, that's why we pay $30-$70 a night in RV sites to use them!
 
I don't know which particular water pump you are using, but if it's the standard Cal brand, or anything similar, the trailer setup is probably working a little different than thought.

These pumps are centrigual, rather than fixed or positive displacement. Both types have an inlet, chamber, and outlet. With a centrifugal, the impeller rotates in the chamber, but the outflow results from the impeller acting like a paddle, and increasing the velocity of the water as it flows along the wall of the chamber, to the outlet. A fixed or positive displacement pump actually picks up a fixed volume between the impeller blades, and forces it out under pressure through the discharge. Bottom line is that the Cal and similar A/C pumps allow water under pressure to flow from the inlet to the outlet, without the impeller moving. If they didn't, they'd be fixed or positive displacement.

There's an easy test to see if this is the setup you have: disconnect the inlet and outlet lines, blow in the inlet, and see if air comes out the outlet. It does on the Cal's, and I expect it does on yours, too.

If that's the case, what's happening is that you are always circulating water through the A/C unit. That's probably why you've had to only crack the water supply valve a little: if you open it up more, water gushes out the drain, even when the pump is not running.

When the A/C engages, the pump shoots a small amount of water out, and then cavitates as it's supply is restricted by the mostly closed valve at the RV park's faucet. I don't know if this cavitation is sufficient to damage the pump, but apparently not, since the setup has been working for you.

At any rate, once the pump cavitates, the water continues to flow through the system at the same rate it was doing before the pump engaged, and you get cool air inside, until the unit shuts down. At that point, the trickle water flow refills the pump's chamber, and adjoining lines, and then continues to flow out, down the drain or onto the ground, until the unit goes into it's next cooling cycle.

I don't own any RV parks, and am not on a water conservation jag. But, if this is working the way I think it is, you're using water 24/7, and a lot more than it takes for a shower.

A fun test would be to disconnect the power to the pump, and see if the system still works. If it does, that means the pump isn't really pumping anything, and the cooling is coming from the continuous flow through the hose.
 
I was at a boat show last year and they had two 5,000 Marine A'C units running off one 20 gallon tank. They were pumping the water from the tank and discharging it back into the tank. My first thought was to use the onboard water supply you already have to avoid the problems associated with thru hulls. Don't think I'd want to drink this water after it cycled thru the units but perhaps you could carry some sort of tank and avoid excess water use by recycling it. The dealer claimed they would cool all day long running like this. Just food for thought.
 
Almas Only":224vtifx said:
I don't know which particular water pump you are using, but if it's the standard Cal brand, or anything similar, the trailer setup is probably working a little different than thought.

These pumps are centrigual, rather than fixed or positive displacement. Both types have an inlet, chamber, and outlet. With a centrifugal, the impeller rotates in the chamber, but the outflow results from the impeller acting like a paddle, and increasing the velocity of the water as it flows along the wall of the chamber, to the outlet. A fixed or positive displacement pump actually picks up a fixed volume between the impeller blades, and forces it out under pressure through the discharge. Bottom line is that the Cal and similar A/C pumps allow water under pressure to flow from the inlet to the outlet, without the impeller moving. If they didn't, they'd be fixed or positive displacement.

There's an easy test to see if this is the setup you have: disconnect the inlet and outlet lines, blow in the inlet, and see if air comes out the outlet. It does on the Cal's, and I expect it does on yours, too.

If that's the case, what's happening is that you are always circulating water through the A/C unit. That's probably why you've had to only crack the water supply valve a little: if you open it up more, water gushes out the drain, even when the pump is not running.

When the A/C engages, the pump shoots a small amount of water out, and then cavitates as it's supply is restricted by the mostly closed valve at the RV park's faucet. I don't know if this cavitation is sufficient to damage the pump, but apparently not, since the setup has been working for you.

At any rate, once the pump cavitates, the water continues to flow through the system at the same rate it was doing before the pump engaged, and you get cool air inside, until the unit shuts down. At that point, the trickle water flow refills the pump's chamber, and adjoining lines, and then continues to flow out, down the drain or onto the ground, until the unit goes into it's next cooling cycle.

I don't own any RV parks, and am not on a water conservation jag. But, if this is working the way I think it is, you're using water 24/7, and a lot more than it takes for a shower.

A fun test would be to disconnect the power to the pump, and see if the system still works. If it does, that means the pump isn't really pumping anything, and the cooling is coming from the continuous flow through the hose.
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As I mentioned - I used this system for years on my other boat with no problems. The only difference regarding the pump is it no longer has to draw the water to the impellers, it's doing the same job of displacing water as it did before.

As Marvin mentioned, it takes very little water to cool the condenser perhaps only 25% of what you see come out the discharge. As long as you're moving water out of the heat exchanger the A/C will work to capacity. When I used to hook up, I would adjust the water tap so there was just a small stream discharging. Of course after 30 minutes or so when you move the heat from the cabin, there is very little transfer of heat.
 
Interesting thoughts--and one of the reasons I elect to use RV airconditioners on my boats (I leave the AC on low during the heat of the summer day at my home on the lift to prevent both heat damage, and mildew). (One of the other reasons, is that sea grass, mud, marine growth, jelly fish, fish, and plastic bags have all been culprits in sutting down and damaging my AC systems at one time or another)

I probably would prefer a closed loop--with the tub of water type of concept--but not sure that the pumps are self priming--I belive that most of the AC pumps are installed below the water line--at least the pumps which I have had on the several larger boat which were air conditioned were below the water line, and were not self priming.

My guess is that If the camp ground owner found out about this, he might not be happy--but that depends on the camp ground. We do a lot of RVing, and have been taken to task if our hose was dripping....But we do pay a bunch for a piece of dirt!--and a little water/power...
 
There's little doubt the campground owners are not going to like it - that's the reason I run the discharge hose in the sewer (if available) or somewhere it can perk into the ground.

I think for the most part the A/C intake pump has limited ability to draw water - but they will draw to an extent, the reason is when I winterize my AC the pump does draw it in from the bottle which is about the same hight as the pump.

As I mentioned, campground rates are outrageous now so it don't bother me to use a little water since my boat is maybe using 25% or less electric than what other campers use. What's not fair is for the guy next to me to run 2 or 3 AC units to cool his 45 ft Prevost while I sit there sweating!
 
Of course the other option is to tow the Ranger with your 45' Provost...if you can find a campground which has enough room for you. We had a problem with a 30 foot RV and the C Dory25!
 
thataway":ldfdzefg said:
Of course the other option is to tow the Ranger with your 45' Provost...if you can find a campground which has enough room for you. We had a problem with a 30 foot RV and the C Dory25!
Click to expand...

I'll have to get another side job to get the 45' Prevost! Better yet, I'll get the one that you drive on water! :smilep
 
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