"Poor heat transfer causes high operating temp & thus pressures..."
Agreed, I already acknowledged that. Do not want to accidentally mislead anyone....always something more to learn....
When I bought my YF, I flushed the a/c raw water lines...and got almost nothing...barely discolored water for a moment....that's in salt water in the LI sound area and I am POSTIVE the prior owner did nothing for the prior ten years...so I guess crud accumulation varies widely by local water conditions.
After my main engines were overhauled and cleaned at my purchase. I flushed the raw water cooling using the approach favored here...it was after about 7 or 8 years after overhaul, maybe 1,000 operating hours....it was hardly worth it.....saw very little discoloration and operating temps did not change....
So wasting time and effort with alternate year a/c cleaning in my area would be a waste of time...time far better spent with wine,women,and song....
In contrast, however, I had to clean barnacles off intakes and especially toilet discharges annually in those same waters.....they really grow FAST in LI waters....So getting your marina/yard to paint intake hull strainers and up inside discharge thru hulls is a must in our area. For the last several hauls and bottom painting of my Hatt I slept aboard the last day before launch...and inspected every discharge before launch .....and had to repeatedly nag the yard boss to paint up inside....
Here's the Straight Skinny...For your and others benefit, and so that you don't think the service guy is BS'in you..It may take a minute so bear with me.
First...Everyone should know that with refrigerants, Pressure & Temperature Automatically Correspond...Higher temp equals higher pressure...Lower temp equals lower pressure...It's what makes refrigerants work in a system...
You pump the refrigerant with a compressor (think pump) thru an orifice (think hose nozzle) into a larger area called an evaporator (think a larger hose) then return it to the compressor to cycle again.
The pressure drop after the orifice into the larger hose return is what is cold...
That area is also known as the Low, or Suction Side (low pressure = low temp)...
The pressure side before the orifice is known as the High or Discharge Side (high pressure = high temp)
In this process of refrigerant circulation, heat is picked up & then removed, so there are 2 heat exchanges...Heat is picked up (absorbed into the refrigerant) from the cabin in the evaporator by the fan passing that air across the cool coils...
Now think of the refrigerant as the vehicle that carries that heat to the dump to get rid of it...Where does it dump, & how do you unload the truck ?
This is where the heat picked up is exchanged (dumped) into the seawater (with the condenser)
If the condenser is dirty (scaled up) or its designed amount of seawater flow is restricted....The ratio of heat removal, versus the amount of heat being picked up is upset.
The result is kinda like a backed up highway...Traffic jam so to speak...More vehicles on the road than can get off with more entering all the time, but the same lesser amount getting off...Then...
As the seawater warms, and or more growth or scale occurs (less efficient heat transfer) Less & less heat can exit...All this amounts to Higher Heat & Pressure on the High side (that the compressor has to work against) and since the the highway is full (refrigerant flow is impeded) the Low side pressure is also higher, which in turn raises evaporator coil temp (pressure & temp thing) resulting in warmer discharge air output...Less cooling to the cabin, and at the same time drawing more amperage to remove less & less heat...
As you might see...It's not quite the same as a dirty heat exchanger on an engine that might have the extra horsepower to overcome the extra load.
REBueckner...I can understand that you may not have much of a growth or slime problem (not the case down here) but I'm also reasonably sure you still have hard water scale (and you wouldn't necessarily see scale in your bucket once dissolved)...that's a problem everywhere...even in controlled fresh water chiller environments such as their cooling towers on buildings...They D-scale them for all the same reasons...
How often it is done to any system can relate to things such as run time & water quality...But rest assure it is needed procedure...How often can be determined in a few ways...
Once clean, the easiest way for a DIY guy to check quickly is to feel the bottom coil of each unit aboard while running in cool to get a reference...Then as time goes on...Every time you are down at the units give them a feel in the same place as before (yes warmer water will affect this) compare them to each other...If one is considerably hotter than another (and you are sure both compressors are running) then the hot one may have a restriction.
The most accurate way to check is with a set of refrigerant gauges...
Down here in Florida we get seawater temps of 90-94 degrees in some basins during the summer and I see high side pressures on a clean unit as high as 250-260 psi...If it's much higher than that we start to look for a problem...
Depending on water temp & cabin heat load...High side pressure on a R-22 system should run between 200 to 250 psi....Both amperage draw & performance suffer greatly if the system is running higher than that.
Hope this helps all...
Steve~
