Post edited 4:32 pm – September 1, 2010 by Steve Pooler

CarverBill said:

Hi Steve, maybe you can help me. Have a 82' Carver 3607 with 3 a/c on board. The salon a/c being the biggest has it own sea strainer and pump, the forward berth and aft berth share a ARG 750-S sea strainer with individual pumps for each unit...Two pumps on one strainer is a No No and it may be the root of most of your problems…I'll explain in a minute…The salon and forward berths are original A/c units that came with the boat The aft unit was replace prior to me buying the boat 3 years ago with the above unit in topic which I'm not sure of the BTU of unit because it is shoved into a cabinet. I did get model number of the compressor for that unit and it's made by Tecumseh RGA5467EXA which is a 1/2 Ton rotary AC/HP Compressor if that helps any. The problem is I can turn the units fan on and it works but as soon as i hit the cool button the volt meter on the electric panel drops a couple volts and than rises until it trips the breaker for that a/c...I'm not sure I understand that statement that the voltage rises until the breaker trips…Do you have an ampmeter & mean amperage ?… Prior to this happening I noticed that the forward A/c unit discharge was get sporatic and I shut it down along with the aft a/c...This can happen with two pumps on one strainer…It turn out that I suck up a settee in the strainer and cleaned it out and turned both a/c's back on and they worked fine. It was about 6-7 hours later when the breaker for the rear a/c tripped. After that the problem existed. My first thought was that it was probably the pump which I changed out because I keep a spare rebuilt one on board and the problem still existed I also changed the 30 amp receptical because I noticed that one of the post was burnt alittle bit at the dock figuring maybe it's not getting enough volts because it was a ground in the 30 amp that was melted.…Ground was melted ?…If so, somewhere ground & neutral must have been reversed as you should have NO current flowing back thru ground unless you have a short or leak…Ground is for protection, not current flow…The forward a/c works fine and has strong discharge and the rear I cannot check because it will not run long enough to see if the new pump is working. I'm Stump right about now. I look through about 8 pages of troubleshooting and the only thing that resembles my problem would be the hi-pres. switch kicking it out and it never resetted. I don't think I ever got a code for it because I didn't check because all I have is the general installation booklet (DX Remote & Self-Contained installation) So is there anyway of recalling the trouble codes...Codes are not recallable with SMXII…But if you had had one, the system would have shut down, and the code would have been flashing on the display…The only way to operate the system after that is to clear the flashing code by pressing the off button, and then selecting what you want to do (Cool, Heat, Fan, etc) Until you clear the code, all buttons, but the off button, are inactive…Thank you for your time and hopefully you and the forum can help me.

Two pumps on one strainer…

First…The 3/4 inch ARG-750 Groco strainer & thru-hull would only be large enough for one pump's suction…They would be marginal at best even when squeaky clean.

Second…All it would take is the slightest amount of junk in the strainer or thru hull to cause the two pumps on that smaller plumbing to starve for water…

Third…Since these pumps cycle with the compressors of each unit…When one unit cycles off…The other will try to get all the water it can, and in the process it will suck the water out of the unit/pump/plumbing not running, until it is sucking air thru that pump & plumbing…

Sucking air can cause both pumps to get air bound…Do you occasionally see the water overboard discharge from these units looking white & milky ?…That's an indication that a pump is sucking air… Aerated water is also not as good at removing heat as solid water, therefore the unit that is running is likely running higher than normal head pressure & drawing extra amperage too…

Anyway…The pump that has shut off with it's compressor then has to try to re-prime itself when it's compressor calls for it, because the other has sucked the water out of it…This (re-prime) may, or may not happen, and if it does it won't be reliable.

My guess is this boat originally only had 2 systems…Along the line, an owner wanted more cooling, so they installed the third system…

When installing an extra system in any boat that was not setup for it originally…There are things that need to be considered, but sometimes are neglected or not addressed…Things like:

• Is there enough power aboard (Generator & Shore Power) and which shore line do you tap into to get the power for the third system without overloading that cord and causing overheated connections.
• What about pumps, thru hulls & strainers ?…Do they add another pump, thru hull, & strainer for the third system, or add a single larger pump to the existing plumbing, split it's discharge to two units, then install a pump relay to tell the pump when to start (probably your best option unless you want to install another thru hull) 

With a large thru hull & strainer, and even with one way check valves…Two pumps on one strainer is never going to be as reliable as one…Every installation I have ever seen like that has been trouble….And it causes added stress on the a/c units that are supplied by that system from multiple shutdowns on high pressure from the lack of water flow

Shutdowns…SMX II will make 4 attempts to run a compressor (initial start + 3 restarts) before it will shutdown the system & show the fault code of HI/PS…This is done so as to avoid nuisance shutdowns from long pump runs & can also allow a bag to float away when suction is stopped…If you can imagine in your setup with two pumps sucking air…That could amount to a multitude of shutdowns and much stress from the compressors pumping up to 425 psi (where the switch cuts out at)

This also adds stress to the electrical system & connections with those compressors pumping that high pressure (normal is around 250 psi) as they will draw much more amperage than normal in doing so….

To sum this up…I can't really say with the info I have (and not seeing your unit) what the reason is the aft unit won't start..But you have given me enough info to see why you are having trouble… 

Since you say access is limited to the aft unit…It may need to come out to be bench tested & find why it won't start it's compressor, but one thing to check while still installed is voltage while attempting to start…If it drops below 100 on shore…I would then try to start it on generator…If it does the same on genny…Pull the unit out…If it starts on genny…Look at the shore power as the problem…Try starting it with nothing else on…

Steve~  

Steve, I found a picture of my distribution center on my PC. How can you post a picture? Anyway I explain it to you. It has the main Breaker at the top(30amp). With a reverse polarity light next ot it. Below that are the breaker for the pumps (5amp) which is disconnected inside. Next Breaker Aft AC (10amp),then the Salon Breaker (20amp), then the Forward AC Breaker (10amp) thats all the breakers. There are (2) meters for that panel also;one for the power coming into the boat when you first turn on the main which is 115 – 125 volts on my boat,the second meter is AC Amperes which according to the photo is between 18-20 with the salon running at time of photo. When this happened my Salon and forward berth ac's were running so I was at approximately 25-28 when it went down then rose until it tripped. Again this happened real fast and I caught it out of the corner of my eye. That's all that I can think of until I go down to the boat I'm located in Phialdelphia so I'll beheading there tomorrow night in time for the hurricane passing on Friday. Thanks again Bill