HPF Errors - what causes them?

[toocoys]

Yesterday I learned about HPF errors. About an hour after the strainers were cleaned during the boat inspection, the aft A/C went out and flashed HPF. After some quick research I learned what it was, and went to home depot to get a 5/8" barb to connect the garden hose and blow out the lines. It fixed it and we've had A/C since.

Today I woke up around noon to the diver cleaning the bottom of the boat. Everything was fine until around 4pm. I woke up and felt the boat was rather hot. Again HPF error on the aft A/C which is an AIRRRR unit, and the forward A/C which is an FCF unit had an EI error. I flipped the breakers, on both A/C's and they came back on and were running when I left for work.

Using the big crayons, can someone explain to me what happens in the unit when this error occurs?

Also, anytime this happens does this mean that I have to blow the lines out, because that's going to get old really quickly!

And is there any way to get the units to reset themselves when this happens?

 

[psneeld]

No or too little water.... high pressure error.

Do whatever it takes to restore flow.

Cant remember if too little airflow over evap fins gives the same from dirt on fins or blockage of intake air....but that is probably in the heating mode.

 

[toocoys]

So if this happens during cool mode the only way to fix it is to restore flow?

All I did today was flip it on and off. Is there any way to set up the systems to reset themselves? It's going to suck if it does this when we aren't there and our dog bakes.

 

[menzies]

I have four 16K BTU Cruisair units. Each pair is fed by a raw water pump.

The pair cooling the salon and PH are fine, the pair cooling the two cabins get the dreaded HI/PS but only after a choppy run.

There is a valve between the strainer and the RW pump with a clear hos, when we have the issue we open that and wait until the air is blown out, close the valve and everything is fine. If we are staying put for a week or so atanchor or in a marina, no issues. If running in calm waters no issues, but if in a chop then once anchored we have to bleed it again.

I have checked the strainers and the hose to pump and hose to AC units, no issues. All I can think is that the placement of the external clam shell is allowing air in when running in rougher water.

Still trouble shooting.

 

[toocoys]

Just got a text message from home that the aft A/C randomly quit again. Another HPF error. This is so irritating.

 

[Maerin]

High head pressure is the consequence of inadequate removal of heat from the refrigerant after it leaves the compressor and makes its way through the condenser. The condenser, as its name implies, condenses hot refrigerant gas to liquid by removing heat. Anything that limits that transfer of heat will result in higher head pressure on the discharge of the compressor. If the pressure exceeds the safety switch setting, it will trip and shut down the compressor with a high pressure fault. There are a number of things that can cause the high head pressure-

1. Accumulation of sediment/shells on the surface of the exchanger.
2. Low seawater flow due to a restriction in the piping, pump problem, strainer, etc.
3. A pump not running up to speed due to a failing capacitor could be a cause.
4. Overcharge. Unlikely except by screwup.
5. Obstruction in the refrigerant circuit. Unusual, unlikely.

That you're experiencing repeated faults indicates a need for some service. Start by checking the basics: strainer, thru hull inlet blockage. Consider cleaning the exchanger with an acid wash or commercial preparation. A fouled exchanger is a common cause of high pressure problems. There are threads to describe the procedure.
Make sure the pump is OK, if it's a standard centrifugal pump (not a magnetically coupled like a March) check the amp draw against the nameplate rating. If the amp draw is much lower, it's because the pump isn't moving as much water. The amp draw for a centrifugal will be lower if it's obstructed, higher with free flow, so amp draw may add useful information.
Check for temperature rise on inlet/outled of exchanger seawater.

If you've determined that all is functioning normally, and the fault persists, it may be time to call in a service tech. It's entirely possible that the pressure switch is out of range and faulting erroneously. To determine that, you'd need to have gauges on the refrigerant line to determine what the pressure is when it trips, but that work is beyond DIY.

Resist the temptation to bypass the safety. If the system is in fact developing excessive head pressure, the internal bypass on the compressor can usually handle it, but it's very hard on the compressor, in fact can break it. Don't turn a repair into a replacement.

 

[toocoys]

I'm only in about 5 feet of water with a 3'8" draft, and I'm stern in. I wonder if fish kicking up sediment is causing my pump to suck up too much muck.

The trips yesterday happened right after the strainers were cleaned, so I can understand that. And both A/C's tripping today happened right after a diver cleaned the bottom so he may have kicked up too much sediment as well. I know when I hooked up the water hose yesterday the first bit of water that came out the through hull was black.

I'll blow the lines out again tomorrow. I'm also going to drop some bromine tablets in the strainers.

ETA: Prior to yesterday and today, we haven't had these error messages. Its just been when the lines have been messed with.

 

[LarryM]

You mentioned this happened after your diver was cleaning the bottom. If the A/C was on, some of the debris being scraped from the bottom could have been drawn into the strainers. Check them again.

Again, it is most likely a loss of, or restricted seawater flow. If the flow is ok, then you could have dirty seawater condensers where the scale is acting like an insulating blanket and preventing proper heat transfer to the water (like a dirty radiator in your car). BTW, acid flushing the condensing coils is a normal maintenance procedure for marine air conditioners. It should be performed every two to five years depending upon location. The procedure is often covered in the system owner's manual.

Here is the procedure from the Marine Air Systems Operation, Installation & Maintenance manual.

Condenser Coil Cleaning

1. With the system turned off at the circuit breaker on the ship’s panel, disconnect the inlet and outlet connections of the condenser coil.

2. Use chemical resistant hoses (MAS white PVC 5/8%” I.D., etc.) to connect the inlet of the condenser coil to the outlet of a chemical resistant, submersible pump (MAS P-500 pump, etc.) and let the hose connected to the
coil outlet flow freely into the container mentioned below.

3. Place a strainer or piece of screen over the inlet of the pump and submerse the pump into a container filled with a 5% solution of muriatic or hydrocholoric acid and fresh water or use a premixed over-the-counter solution.

Use a large container as possible to hold the solution (5-25 gallons).

CAUTION: avoid spilling or splashing the solution. Follow all warnings and recommendations given by the manufacturer of any acids or premixed solutions.

4. Power the pump and circulate the solution through the condenser coil for 15-45 minutes depending upon the size of the coils and the extent of the contamination. Visual inspection of the solution in the container should
indicate when the contamination removal has stopped.

5. Circulate fresh water through the coil to flush any residual acid from the system.

6. Restart the system and check operational parameters to ensure thorough cleaning has taken place. Additional cleaning may be necessary with extreme contamination.

WARNING: For the purpose of protecting the environment, dispose of any contaminated acid solutions in accordance with federal, state and/or local regulations.

 

[Wxx3]

I think you just have air in the line. All your problems started after cleaning the strainers.
That's exactly what I did and then spent a week chasing the problem. In my case, the strainers were old bronze and the cleaning made it harder to made good air seal. Once that was solved.
the hose had hardened over the nipple and could not make a tight seal anymore.

All your symptoms are the same as mine, AC runs, but as air collects in high point of the system, it gets worse until shutoff.

Air in the system is the most likely and simplest solution. look there first.

 

[DavidM]

The problems noted result from a lack of raw water flow, either due to fouling or some other blockage or air getting in the system and air locking the raw water pump.


The first cause requires cleaning and removal of the blockage. The error will continue until this is done. If it is scale fouling then chemical cleaning will remove it and it won't occur again. If it is sediment or aquatic fouling, then you are just going to have to remove it by blowing it out with dock water or manually cleaning.


Air locking can usually be solved permanently. It is often caused by poorly routed raw water hose. The hose needs to rise vertically continuously from the thruhull, through the strainer and up to the suction of the pump. If it has any kind of dip or low spot it will air lock. Once this routing problem is resolved the system will continue to run without any problems.


Sometimes both problems occur and a partial blockage lets the pump air lock because the pump can't move enough water to clear the air lock. Rerouting the hose or removing the blockage solves the problem, but dealing with both causes is better.



David

 

[Maerin]

I'm only in about 5 feet of water with a 3'8" draft, and I'm stern in. I wonder if fish kicking up sediment is causing my pump to suck up too much muck.

The trips yesterday happened right after the strainers were cleaned, so I can understand that. And both A/C's tripping today happened right after a diver cleaned the bottom so he may have kicked up too much sediment as well. I know when I hooked up the water hose yesterday the first bit of water that came out the through hull was black.

Fish stirring up mud won't cause this. Air will, and fouling of the exchanger surface will. The idea that the pump suction will suck up mud a foot away from the inlet is fallacious. Velocity drops off to nil just a short distance from the inlet of a suction line. Take your shop vac hose and blow a ping pong ball around with the hose connected to the discharge. Then switch to suction and see how much you can control the ball with the suction. Gotta get right on top of it... Same thing with the pump.

 

[OldDan1943]

I had a plastic bag sucked through the hull valve and lodge in the hose between the hull valve and the sea strainer. HOW? Pulled the bag out, end of HPF

 

[bayview]

You can flush from outside by back flushing from the hull side outlet. No need to turn off the pump. Just force water into the outlet. When you stop hose flow normal flow will resume.
I used the inside of a cheap plastic straight hose nozzle that is tapered and fits into the outlet fitting. For hard to reach fittings duct tape the hose fitting to a boat pole.

 

[toocoys]

It’s got to be air. We can almost consistently make the HPF error come on by stepping on the back of the boat and rocking it too hard.

 

[Gmarr]

Bad o ring on the strainer top? I used grease around the perimeter when I reseated mine after opening to clean.

 

[Jetstream]

If you haven't ever done it descale the condensers with Rydlyme or Barnacle Buster. http://www.rydlymemarine.com/assets/1/7/AC_Cleaning_Instructions.pdf

 

[toocoys]

Ok maybe it’s not air. We fought with it tripping all night.

This morning I am replacing the inlet hose because it was a little bent, not kinked but could have been restricting flow. I’m also replacing the gasket on the strainer basket because it’s a little shot. I’m also going to run some barnacle buster through the system.

My other question is regarding the pump. What is a good operating temperature? It’s a blue seas 500gph pimp and when I shot it with the laser it was running around 125 degrees. It’s a new pump but I’m wondering if I need to clean and check the impeller.

ETA... I just checked my forward pump and it’s running around 95 degrees. So I’m hoping it’s a flow problem.

 

[JohnEasley]

I agree with the others... either you have air trapped in the system or there is a blockage.
You mentioned you flushed the system with a garden hose and the water that came out the through hull was black. That's a really good indicator that it probably needs an annual (or more often in warmer waters) cleaning. It's pretty easy to do.

Start by acid-flushing the system to make sure it is free of gunk, critters, and debris. There are a number of quality products for this. We've frequently used Barnacle Buster and it works great.

Once the system has been acid-flushed, consider installing a T fitting in the hose coming from the strainer to the inlet side of the a/c water pump. This is so you can quickly and easily bleed off the air lock in the system. The previous owner of our boat installed a T fitting with a common garden hose bib. HPF error? Cracking open the hose bib for just a few seconds until the air has been bled out and then restarting the a/c system was all it ever took. The parts, including the stainless steel hose clamps, should be around $20.00 at just about any home, farm, or marine supply store.

There's a really good chance, if you flush your system and install a bleed valve, it'll resolve your issues.

 

[toocoys]

Ok I think I’ve figured out the problem.

The intake hose from the seacock was essentially old fuel line hose. It has half bent just after the seacock. That was restricting flow to the pump. The pump has a thermo protection circuit and was getting too hot. That’s why it was running at 125 degrees this morning whereas the forward pump was running about 95.

Now that I’ve changed the hose out to a reinforced piece, and replaced the gasket on the strainer, the aft pump is running the same temperature as the forward pump, about 95 degrees.

The ac is running again with good flow so hopefully this will solve the issue. Will advise.

 

[toocoys]

Ok hose wasn’t the problem. Pump started heating up and shut down even with the the new hose.

So I just took the pump apart cleaned the impeller and blew out the little cooling lines on the pump itself. Like I actually put my mouth on it (after wiping it) and blew. A whole lot of algae came out and I looked like an infants hind end had exploaded in me. I put it back together and we are cooling again.

We’ll see for how long. If this doesn’t work my next trick is to disconnect the HPF switch from the board and use a jumper to bypass it.

This video is what I’ve been following.

https://youtu.be/uGnHpYDJwrs

 

[JohnEasley]

That you’re still getting algae and stuff out of there, I encourage you to consider acid-flushing the system. No doubt there is more in there.

 

[toocoys]

Well we’ve been gone since 2pm and it’s now 10pm. Ac is still working with no HPF errors.

Bromine tablest are next in the strainers, and a full cycle of barnacle buster through the system.

Kinda proud of myself at this point.

 

[Boatfever]

One thing that I don't think has been mentioned yet is checking your thru hull for barnacles. In our area the inside cross section of the thru hull can become quite reduced by barnacles. Your diver may or may not have cleaned inside of your thru hulls. Pretty easily done with an old screw driver but be careful not to poke to far in if the screw driver is a long shank. It would be a bummer to climb back in the boat to discover you holed the inlet hose.

 

[JohnEasley]

Kinda proud of myself at this point.

As well you should be. Good diagnostic and repair skills.

 

[bnoft]

Mentioned briefly in prior post is possibility of pump failure. We experienced this with 12 year old pump, periodic HPF stoppage of 2 A/C units fed by same pump, had already cleaned system. It would work for awhile then stop, no pattern. Finally called tech as I suspected pump failure when it refused to function at all. Replaced pump, tech took old pump and tried to get it running with no success. I am not well versed on this but the old pump could maybe be rebuilt and then used as a spare but we did't go that route.

 

[MOJO]

So I just took the pump apart cleaned the impeller and blew out the little cooling lines on the pump itself. Like I actually put my mouth on it (after wiping it) and blew. A whole lot of algae came out and I looked like an infants hind end had exploaded in me. I put it back together and we are cooling again.

Based on your comment about "the little cooling lines", it sounds like you have a March pump. If so, they're notorious for having the small diameter lines that cool the motor clog up and cause an overheat. Here's a possible scenario: The pump has a thermal breaker so once it overheats from clogged cooling lines it shuts down. That cuts off your cooling water to the condenser giving you the high pressure error. By the time you notice it, the pump has cooled, the thermal breaker has reset, and once you reset the a/c error, you're back cooling again - until the pump overheats again. Vicious cycle! Your Barnacle Buster flush must include flushing the pump, and plan on it being routine maintenance...

I'd also suggest installing a way to bleed the air out of the pump intake line. A tee and a valve like JohnEasley suggested will work by letting you "burp" the pump when it air locks. But, if you want an automatic solution, install a tee and valve and put a hose on it that leads up and is secured well above the heeled waterline. Leave the valve open so the everything is open to the atmosphere. Any air that enters the line will automatically migrate through the tee and valve and up this hose and out into the boat. No more air locks, no burping the pump when it air locks, cause it won't. (Since the hose is well above the waterline, you really don't need the valve unless it makes you feel better knowing you can shut it off and completely close the system.) This setup also gives you a way to flush the system by using the hose to introduce acid, cleaners, etc.

 

[JohnEasley]

But, if you want an automatic solution, install a tee and valve and put a hose on it that leads up and is secured well above the heeled waterline. Leave the valve open so the everything is open to the atmosphere. Any air that enters the line will automatically migrate through the tee and valve and up this hose and out into the boat. No more air locks, no burping the pump when it air locks, cause it won't. (Since the hose is well above the waterline, you really don't need the valve unless it makes you feel better knowing you can shut it off and completely close the system.) This setup also gives you a way to flush the system by using the hose to introduce acid, cleaners, etc.

Oh, that IS a good idea!