OB~

HPF is a High Pressure Fault…If you have a low refrigerant you should not see HPF…Low refrigerant would be Low Pressure.

You don't give me location or climate like I ask on the first page so I can't really answer much more unless I know if you may have been running in the Heat mode or Cool….Knowing that can be two differing causes for the HPF fault…

• HPF in Cool usually means a Water flow problem…Not removing enough heat…
• HPF in Heat usually means a Air flow problem…Still not removing enough heat, but since it is a "Reverse Cycle" unit the heat is now removed with the air coil in the cabin.
• Overcharge of refrigerant can also cause HPF faults.

It is possible the last guy overcharged the unit causing the HPF…

Do not let anyone put Stop Leak into the system…There are differing kinds…The automotive type is for systems with rubber hoses & compressor shaft seals (which you have none of) There is another type I have tried for residential, and it completely plugged up one system I tried it in….Yes the unit should be leak tested, and any leaks should be repaired with a torch & solder…Not Stop Leak  

One word of advise…Resetting will fix nothing…Do not keep resetting the HPF fault if it goes off more than twice…Doing so can cause the High Pressure Switch (that measures pressure & protects the system) to fail in the off or open position…Then you will be replacing the switch as well…It's best to find the reason rather than just resetting the fault…

As far as references to understand your system/s…It's part of why I started this site/forum    There is a ton of info here to read up on along with others experiences…

Let me know if I can help further…

Steve~ 

Post edited 7:52 am – July 5, 2011 by Steve Pooler

obenton3 said:

I am so sorry about the lack of info. The boat is in Chattanooga Tn. We have had some cold winters but I use the system almost exclusively in the hotter weather. Right now it is in the mid-90's every day with lows in the high 70's...Ok so you are not in a climate that you may be using heat at night…Thanks… My water stream has not changed from March of 2010, when I brought the boat from Florida. It was not well cared for. Had prop spray for months down there...Prop Spray ?…Not sure I have heard that term before…What does it mean ? The strainer is new. I did not put it in but I doubt the tech flushed anything. Last summer we had no problems but I do recall a few HPF codes that always disappeared .  What you said made sense. The aft cabin does put out cold air after being charged with freon but has had the HPF codes . Since I turned off the aft system the others have shown no fault codes. Could that indicate that the system can only  fully supply two?…It shouldn't because the same amount of water will flow thru each unit no matter how many are actually running…Thank you for responding on a weekend.  Thanks.This is an unbelievable service you provide. OB

 

Again, HPF is a protection for both the unit's & you…If the high pressure switch sees pressure above 425 psi it will interrupt the compressor to keep it from pumping even higher pressure & possibly blowing a copper line, or actually burning up the compressor motor…Normal high side pressure should be no more than around 275 psi in the hottest conditions (and I doubt you would ever see it that high in your water temps unless the system is dirty)…

 

Reduced water flow will cause this higher pressure…It also makes the compressors work much harder against that pressure, and thus draw much more amperage that can cause other electrical problems…

 

Things that can affect High side pressure in the cool mode are:

 

• Restricted thru hulls (both intake & discharge)
• Pump size & condition of it's pump head (the part that pumps water) 
• Plumbing…How it's run & type…(Even how the manifold that splits the flow to each unit is made)
• Hard water scale built up in the water coil that prevents heat transfer (like a dirty radiator in your car)
• Marine growth restricting flow (barnacles, mussels, etc.)

How old is the boat ?…Down here in Fl we get a lot of barnacle growth in A/C seawater hoses & your's may still have them…Was the strainer full of them ?…If so, you can bet they are in the hoses too, and a few larger ones may have broken loose & are lodged in an elbow or the like restricting flow to the aft unit…Is it's overboard flow the same as the other two ??…Likely not…

 

What are the sizes of the units & what model pump do you have…We add up total BTU to come up with a pump size…You need 250 GPH per ton (12,000 Btu) of A/C….

 

Everything you are saying is pointing to you don't have enough water flow…And that…The aft unit seems to starve for water first…So either that hose/pluming is the most restricted or it's how Meridian ran the plumbing, thus that unit will always show HPF first because as the system restricts, the flow reduces to all 3, but the aft unit will always suffer the most…

 

I would recommend you get someone to do a complete flush of the system to remove any growth & inspect the pump…Take it apart to check the bronze impeller (I believe that's what Meridian used is bronze head "Scot" brand pumps) those impellers are known to erode away to almost nothing…

 

Once all that is done & you know you have a clean system…See if your flow is not increased considerably…You having bought the boat second hand may have never seen it as it should be, or was as new…If it's not increased after that…Then it's time to look at Meridian's design of the A/C plumbing…

 

Also: Knowing what is normal flow over the side for a clean system…Is the first step to heading off a problem that could ruin a weekend on the water…If it doesn't look right…It's probably not, and is going to cause problems shortly…

 

Lastly…If you have an A/C tech that wants to adjust or add refrigerant for a HPF fault in cool mode…

 

Find another A/C tech     As that one does not have the experience to know what the problem is…

 

Refrigerant leaks are one thing that can stop the unit from cooling…But a unit low on refrigerant will not show HPF with No water flow…Because there is not enough refrigerant there to build that pressure anyway…

 

HPF & Low Refrigerant are not related in any way…They are opposites. 

 

Steve~

Please let us know how it works out  

Steve~