AC problems

[Phasma2128]

Scratching my head….
about 3 weeks ago my salon Cruisaire stopped working on my 1993 48 cpmy. The two dometics for the cabins are still working. The salon AC kicks on but doesn’t cool. It runs for about 30 seconds and kicks off. It then kicks on again for 30 seconds and gives me the Hi PS error on the SMX ir. Reading all that I could find I understood that the water flow through the system was probably blocked. It is a single pump for all 3 units. As I said the two dometics work fine. Comparing the discharge from the side of the boat to my neighbors Bertrand it is about 50% what his discharge is. This all happened about the same time I upgraded my sound system at the helm. The cooling part of the system is under the helm and the compressors are in the engine room.

I disconnected supply and drain hoses, connected a garden hose and back flushed the system. A large amount of black gunk came out of all 3 units. I reassembled everything and tested the system. The same exact error code…. Air flow through the salon seems adequate. I pulled the salon return air filter and cleaned it. I also pulled a large amount of sea weed from the sea strainer and flushed the thru-hull. I connected the pump directly to the discharge line and the discharge did not increase. Pulling the pump apart it doesn’t look like the impeller is bad. The motor was a little hot to the touch.

My thinking….: if. It were the high preassure switch that is bad, wouldn’t it still cool until the pressure built to the shutoff level? Should I jumper across the hi-pressure switch and test? Would loss of R44 cause this to suddenly happen? Replace the pump and motor?

Any ideas? Any help would be greatly appreciated….
Martin

 

[Pascal]

I wouldn’t bypass the HP switch. High pressure is almost always a water flow problem which while it seems like a simple fix, it can actually be tricky

First are we talking self contained or remote condensers?

Back flushing helps but only if you disconnect the other end and collect the water and junk in a bucket. What you don’t want to do is back flush and send the crap into the manifold where it may move to another unit.

Check the manifold carefully. I ve had issues where stuff gets stuck at a manifold outlet. Then make sure the hose from the manifold to that unit is clear. Move on to the coil itself and finally to th discharge hose. Blowing thru the hoses and coils will tell the story.

What I often do is pull the discharge hose, put it in a bucket or gallon jug to see how much flow it has. One trick is to add shut off valves between the manifold and each unit so you can turn off that line, put the discharge into a jug and turn the valve on. This whlay you can work on that unit without having to shut down the other ones

Final thing is descaling. Here in sofl we have to do it every year, 18 months at the most. I use a barnacle buster and circular the mix from a bucket with a bilge pump.

 

[Phasma2128]

I wouldn’t bypass the HP switch. High pressure is almost always a water flow problem which while it seems like a simple fix, it can actually be tricky

First are we talking self contained or remote condensers?

Back flushing helps but only if you disconnect the other end and collect the water and junk in a bucket. What you don’t want to do is back flush and send the crap into the manifold where it may move to another unit.

Check the manifold carefully. I ve had issues where stuff gets stuck at a manifold outlet. Then make sure the hose from the manifold to that unit is clear. Move on to the coil itself and finally to th discharge hose. Blowing thru the hoses and coils will tell the story.

What I often do is pull the discharge hose, put it in a bucket or gallon jug to see how much flow it has. One trick is to add shut off valves between the manifold and each unit so you can turn off that line, put the discharge into a jug and turn the valve on. This whlay you can work on that unit without having to shut down the other ones

Final thing is descaling. Here in sofl we have to do it every year, 18 months at the most. I use a barnacle buster and circular the mix from a bucket with a bilge pump.

remote condenser is under the helm on the bridge. The compressors are in the engine room

 

[Pascal]

It s the evaporator that’s under the helm. The condenser is the unit in the ER which includes the compressor. Not that it matters much

So start by disconnecting the discharge hose, ideally at the sea chest assuming that’s how they re hooked up on your boat. If too hard to reach disconnect at the coil outlet and run a piece of hose into a gallon jug. See how much flow you get.

If flow is good, the jug should get half full in like 10/15 seconds then you probably will need to descale the unit itself.

Again adding quarter turn valves at the manifold helps when working on the raw water side

 

[racclarkson@gmail.com]

Check/clean evaporator coils; clean the filter; run blower motor on high and see if that works.

 

[Phasma2128]

Closed loop, muratic acid wash down. Pull drain line and source line. Connect source line to small bilge pump. Use 5 gallon bucket and partially fill with muratic acid and water. Letting it run for a bit

 

[Pascal]

Dirty coils or filter can cause a low pressure shut down, not high pressure

Muriatic acid is really nasty stuff. Barnacle buster is much safer and as effective

 

[Play'N Hooky Too]

On my units there is a high pressure switch on the refrigerant discharge ("high") side of the compressor. Mine has two purple wires going to it. I've had to replace this switch on both of my units. I can't remember if it is a NC or NO switch. I think it NC so you might have damaged one of the wires or knocked it loose and the circuit is now open. Check the wires and if they look good try running a jumper across the switch and see if it will run for more than 30 seconds that way. If it is the switch, you can order them online. They can be changed out without loosing any refrigerant.

 

[Phasma2128]

The system is now fully flushed. I made a 50/50 solution of water and muratic. I ran it through the system for 30 minutes closed loop. Lots of nasty crap came out. I reconnected all hoses and put the system back together. The problem remains….It runs for about 30-45 seconds, shuts off, restarts for another 30-45 seconds and throws the Hi Ps error on the smx control….I’m stumped

I still question the amount of water being discharged. Would an inadequate amount of water through the system due to an under performing pump cause the Hi Ps error?

I jumpered across the high pressure switch and the problem remained

 

[Pascal]

What kind of pump Do you have? If you an oberdorfer or Scot with bronze impellers and heads, they erode with time and loose their pumping capacity

I had this just happen on the 116 I run. Breaker started to trip as one of the chiller was using more power. Still not bad enough to trigger a high pressure but enough to use more amps and trip it’s breaker.

Checked everything...it had just been descaled a month ago... I pulled the pump and sure enough the impeller was eroded as well as the interior of the head. It was fine up to July but not with water in the high 80s it wasn’t enough flow

Replaced the pump with a rebuilt spare and it’s all good. All three chillers run much cooler.

That s why I much prefer march pumps. Impellers are hard plastic and don’t erode. They can break but if they do replacement takes a few minutes without even having to pull the hoses.


Edit. Never mind I see the picture and it s a march. You can just replace the impeller. As mentioned you didn’t have to take it out. You can’t just pull the cover and swap

 

[Briankinley2004]

I would start with the intake into the sea strainer. It could be clogged with sea grass, a plastic bag or barnacles below the water line. Sometimes you can put a water hose in the glass, sealed with a rag, and blow backwards to clear it. Also the hose could be collapsing on the inside. I would make sure the pump has a good supply and if so it would be from the pump to the discharge thru hull. I agree with the comments that it is probably a water flow issue. Second to that maybe the pressure switch is bad but you state the water flow does't seem right. "edit I see you checked the HP switch. If no restriction to the pump them the pump may be bad or have a restriction on hose between pump and heat exchanger"

 

[Phasma2128]

New impeller this morning. The old one was not broke or appear worn but I replaced it anyway. The unit runs a little longer before throwing the error code. I triple checked the sea strainer and all is clear. When sea strainer was open I opened the sea cock and a solid flow of water came through. I am still puzzled by this. I did notice that when cool is selected on the smx, the display says cool but it no longer says cooling.

Still not happy with the amount of water flow. Maybe in the future swap it out for an oberdorfer.

I did a factory reset on the smx. I didn’t actually believe it would do anything but….. grasping at straws

 

[Pascal]

As I said before, disconnect the discharge hose and put it in a jug to check actual flow to that unit.

 

[rob71]

I had low water flow on an AC. It would start out ok then after a few minutes it would slow down.
It turned out to be air lock. First insure good seals between pump and seacock.
Then I backed flushed with garden hose and rerouted the supply side to insure no dips or sags. That fixed it !

 

[bigbill]

do what pascal said. that unit could be clogged or a hose going to it could be partially collapsed

 

[Pascal]

The heat has been brutal down here. A couple of days ago I was no longer able to run both the chillers on my 53 without tripping the shore power inlet. They were using 6 extra amps each which was enough to trip the main breaker (not the high press). Boat was almost uncomfortable inside on just one chiller

Yesterday i circulated a 1:4 barnacle buster solution for 90 minutes. Both chillers are back to normal

 

[Phasma2128]

Tomorrow afternoon I have an expert coming to look at it. I finally said “give”

When I know what caused this I will post

thank,you all for your help

 

[Phasma2128]

As it turns out……there were 4 missing caps on the ports of the system. All 4 were leaking refrigerant. The system leaked enough refrigerant to no longer work. The assumed low water flow is due to a much larger discharge port on my Hatteras compared to my neighbors Bertrand. I am thinking I’m going to design a back flush manifold to keep all 3 units clean by back flushing.

Thank you all for your help. I now have a nice cool boat again.

 

[Pascal]

Something is wrong with your system of low refrigerant gives you the HI PS error you mentioned in your first post

 

[racclarkson@gmail.com]

As it turns out……there were 4 missing caps on the ports of the system. All 4 were leaking refrigerant. The system leaked enough refrigerant to no longer work. The assumed low water flow is due to a much larger discharge port on my Hatteras compared to my neighbors Bertrand. I am thinking I’m going to design a back flush manifold to keep all 3 units clean by back flushing.

Thank you all for your help. I now have a nice cool boat again.

This is the back half of my HVAC cooling circuit if it's any help.

Closing the valve, I can route cleaning solution in or out after removing the plug in the pic. BTW, the brass plug was temporary.

Don't have a pic handy of the other end. But there's a similar threaded plug after the pump. Closing the discharge valve (above) and the seacock creates a closed loop for flushing. With a setup like this, I can use the same hoses as I use for my HE cleaning. Quick connects make it even faster and neater.

Having a non-metallic, magnetic drive pump also makes it safe for the solution to work its way all the way back to the seacock. There's not much circulation back that far, but in the end the shiny metal tells the tale.