Air Conditioning Pump Lost prime

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V1rowT8

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Well, as careful as I was during A/C system winterization, I still seem to have managed to get some air in my circulating pump water lines, and the system is air locked. Being that the pump is not self priming, what is the proper procedure to re-prime the system. It's a 18K BTU Marine Air Systems unit, and of course the pump is not self-priming. There's no kinks in the associated lines, and cycling the bleed valve just downstream of the pump did no good. Advice would be appreciated.

Thanks in advance.

V1
 
Not an uncommon occurance. I used to have the same issue with our older Carver. I finally rectified it and made my winterization easier by getting one of those radiator flush kits with a hose hook-up and installed it in the RW line ahead of the pump. Whenever the pump lost prime I just hooked a garden hose up, turned the hose on and then the AC and primed the system. I used the same process to winterize the AC system, just substituting AF for water.
 
Thanks Mike.

I only have about 3.5 inches of hose between my strainer output and my pump input, and this doesn't include the 4 stainless clamps. That said, it may not work there. I wonder if one could be inserted prior to the strainer without issue.

Also, did you find a kit suitable for marine applications? Some of the ones I have seen could degrade to the point of cracking/failure, and obviously, we wouldn't want that.

Thanks again.

GW
 
With the seacock closed, break the pump outlet connection, open the seacock until water flows, close the seacock, reconnect the outlet, done.
 
if the hose run from the strainer to the water pump inlet is upward with no high/low points, it will self prime. unfortunaytely, some builders cant' read simple instructions and deliver boats with hoses on the intake side, going up over stringers and back down.

if that's the case, you may indeed have to stick a hose in the discharger TH, or open the outlet side of the pump...
 
Pascal,

There's only about 3 1/2 inches between my strainer outlet and the pump's inlet, and the hose connecting the two runs slightly uphill. Still, I was unable to successfully re-prime. I cracked the bleed valve on the discharge side of the pump, and it had a steady stream of water coming through it, which led me to believe there was no air in the system between the through-hull, and the discharge side of the pump. From there, all lines run slightly uphill to the A/C unit, with no kinks, loops, elbows, ect.... In other words, the system is properly installed on this vessel. That said, one of the "downstream" lines must be air locked. I moved them around while running the A/C unit in an effort to migrate any air out of the system, to no avail.

In the interim, due to plumbing constraints on the supply side of the pump, I'm going to try what Harlan suggested above, and connect a hose to the discharge side of the system to back flush water through the entire loop to get the air out. It appears that the A/C discharge hose dumps right into my shower sump, which is easily accessible on this vessel. That said, if this method works easily, I'm going to connect a permanent hose fitting to the end of that hose, so as to easily have a connection there for future use.

Prior to doing this, I am assuming there is no problem for the pump to receive a backwards flow of water. (I'm thinking about the pump's impeller vanes in particular.) I'll check with the vendor, or seek advice here from others who may have utilized such a method.

Thanks to all for the guidance so far. Any comments or further suggestions/advice?
 
The line to the shower sump is probably your AC condensate line, not the cooling water line. Normally AC cooling water, supplied by the pump, goes from the AC heat exchanger overboard via a through hull. On my boat that through hull line has a ball valve in it.

If the pump has water coming out the discharge, then prime is not the problem. Air in the lines from the pump through to the discharge shouldn't be a problem either. You must have either a pretty good physical blockage between the pump and the discharge or there is a valve that should be open but is closed. Check the line from the AC unit to the discharge through-hull for a valve.
 
there is no way that your water discharge goes to the shower sump.... that would be the surest way to sink the boat when the sump floatsiwtch fails!! condensate goes to the sump, not cooling water, it has to go overboard.

i've never seen an issue with air locking on the pressure side of the pump. there has to be enough flow to push the air out. it's impossible not to have air trapped high on that side, look at the coils on the AC, they are often the highest point.

take a look under the boat, this sounds like the typical plastic bag stuck in the scoop. Usually happens to me on a hot summer sunday morning at 6am when the display by my bed flashes HHH... :-0

with the pump off, the bag is loose and lets some water in. when the pump kicks in, it sucks the bag tight killing water flow. the bag usually gets trapped in the scoop or barnacles and doesn't dislodge. if you dont' want to go for a quick swim, take the boat out, a high speed run may clear it
 
quote:
Originally posted by divedaddy

With the seacock closed, break the pump outlet connection, open the seacock until water flows, close the seacock, reconnect the outlet, done.

Click to expand...


My mechanic has installed a ball valve in the line for just this purpose. I do not have to disconnect anything, I just have to open the valve.

I am going to have to do this re-prime myself because I forgot to close the seacock on my recent haul.

G
 
I could have sworn the line going to my sump was the main discharge line, but I'm probably wrong. In retrospect, it's more likely it's merely the condensate drain line I saw going to the sump. As Pascal says, this would be an easy way to swamp the boat if the sump's float switch or pump failed. I'll look again closer to check things over.

In the meantime, if you just stick a water hose in the overboard outlet and turn it on, will this provide enough volume of water to get the job done, or is it necessary to seal around the outlet somehow, to make sure all the water goes through the plumbing. On a related note, do you feed water through the hose at a slower pace, wide open, or something in between? I just don't want to burst anything inside.

Thanks guys. This is my first boat with A/C, and I'm still learning about that system......learning lots I might add, thanks to each of you.
 
Just stick a hose in there. You can hold it against the hull hard enough to cause the necessary pressure. You will see a bunch of bubbles than nothing. You are all primed and ready to go.

Edit:

Forgot to mention. If you keep the boat out of the water when not in use (lift, trailer...), this is going to happen each time the boat is lifted. You can close the seacock before lifting to avoid the occurance.

If you remain in the water and this is a constant every time you go to start the A/C after an extended period of it being off, the problem may be that the pump is not below the water line. If it is factory air, I doubt that will happen. Formula makes a fine product with a lot of attention to detail.

HTH
 
quote:
Originally posted by KiDa

Forgot to mention. If you keep the boat out of the water when not in use (lift, trailer...), this is going to happen each time the boat is lifted. You can close the seacock before lifting to avoid the occurance.
Click to expand...


How do you explain that I did a year of dry-stack boating in Tampa, probably 50 in-and-outs, and only lost prime once? (never closed the seacock).

Even last year after winterizing in FL, I left the seacock open. Then after sitting all winter and bein transported accross the country, we splashed it and the air started right up.
 
quote:
Originally posted by Ernesto

quote:
Originally posted by KiDa

Forgot to mention. If you keep the boat out of the water when not in use (lift, trailer...), this is going to happen each time the boat is lifted. You can close the seacock before lifting to avoid the occurance.
Click to expand...


How do you explain that I did a year of dry-stack boating in Tampa, probably 50 in-and-outs, and only lost prime once? (never closed the seacock).

Even last year after winterizing in FL, I left the seacock open. Then after sitting all winter and bein transported accross the country, we splashed it and the air started right up.

Click to expand...


Positive displacement diaphragm pump - self priming.
 
Eric, i have never found a self priming air con pump... if you have, i'm curious to know the brand and model.

this is why with the proper hose routing, you dont' have this problem. If he has water coming out of the outlet, i doubt it's a priming issue.
 
Pascal,

My answer on self priming pump was directed at Ernesto's question. Crusair reportedly (from them) offers self priming pumps for above waterline installations as an option.

I agree with you - from what has been described this isn't a priming issue.
 
"...I cracked the bleed valve on the discharge side of the pump, and it had a steady stream of water coming through it, which led me to believe there was no air in the system between the through-hull, and the discharge side of the pump...."

I missed the part about a bleeder valve. Never seen one. However, I have cracked the hose on the discharge side and still had to hold a garden hose to the TH. What was being pulled up and squirting out was not enough to prime the unit.

Out of curiosity, did you tape over the outlet at the end of last season?

Crack the bleeder valve and run a garden hose in back through the thru hull. If you get nothing out of the bleeder valve then you may have mud dobbers or the like in the outlet hose.
 
David,

A 330 DA question -- my discharge line has a small ball valve at the through hull under the forward berth. Does yours, or do I have a custom mod of some kind ?
 
Yikes; sorry for a newbie question here and don't mean to hijack the thread but we just bought a new Glastron GS-259 with AC/reverse cycle heat.. The dealer told me to always leave the seacock open even though we will be trailering all the time.. Is this bad advice?
 
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