Reverse Cycle difficulties

[Scott T-Bird]

A "reversing valve" is part of the refrigerant system, not the water system. Think of it this way, Scotty: take a window air conditioner - it blows cools air in and hot air out. Then, during the winter, you simply take the window air conditioner and reverse it, so the hot air blows in and the cold air blows out. That is all a reversing valve does, but it does it all inside the unit. So you don't have to open the window when you turn it around, and drop the unit down on your mailman.

Right, I understand. What I don't understand is why the pump circulates sea water no problem when running AC but it has failed to circulate water when in heat mode. It's not random, there has to be a reason. I'm thinking that the valve must cause a block in the circulation of the sea water somehow. If it's NOT related to the reversing valve, then there must be some reason why the pump fails to circulate sea water only when in heat mode.

 

[Terry Cox]

Both our 1991 MarineAir reverse cycle systems are original as well as the :Little Giant sea water pump. Never had to prime the system, but I always check to make sure that sea water flows through the discharge through hulls once I turn the system on. Both sides work, but only use the heat side during the winter while on the boat at the slip. Once had to recharge the aft cabin system as it was not pumping heat, otherwise, a good system.

 

[Stu Jackson]

Right, I understand. What I don't understand is why the pump circulates sea water no problem when running AC but it has failed to circulate water when in heat mode. It's not random, there has to be a reason. I'm thinking that the valve must cause a block in the circulation of the sea water somehow. If it's NOT related to the reversing valve, then there must be some reason why the pump fails to circulate sea water only when in heat mode.

Ask yourself what is the only thing connecting them. Should be either electrical or a logic board in the controls.

 

[JamesG161]

If it's NOT related to the reversing valve, then there must be some reason why the pump fails to circulate sea water only when in heat mode.

I am not sure about the Cat 320, but boats of that size normally has provisions for 2 AC units.

If there are provision for 2 in their design...
You may have a ...

AC Water Pump Relay Panel

My old Marine Airee had this.

That Control board would be located in a small White box near the AC unit.

Check for that box, since that controls the Sea Water Pump.

Jim...

 

[JamesG161]

a logic board in the controls.

If no Pump Relay Panel, then Stu has the key.

A single Circuit Board [CB] and the respective Thermostat control panel may need replacement.

That CB is found inside the Electrical Box on your unit.
I replaced mine and have a SBO thread on that replacement procedure.
Jim...

 

[Scott T-Bird]

If it was electrical or in the control panel, I would guess that some disruption would cause the pump NOT to run. But that is not the case. I have experienced on at least 2 occasions (once last fall and again this spring), that in heat mode only, the pump runs but is not circulating water. I think that since the pump is running but not circulating water, that would be a symptom of something other than an electrical or control panel issue. But what do I know?

Last weekend, the pump became very heated and I was afraid it was damaged. Now I have found that it does run and it circulates sea water when I put it in AC mode. Next time I'm at the boat, it should be in the low 70's. I think I will turn on AC and let it run, then turn it on heat and see if everything works in heat mode.

I've just watched a few vids about reversing valves, and I can see why it would be unrelated.

 

[Scott T-Bird]

If no Pump Relay Panel, then Stu has the key.

A single Circuit Board [CB] and the respective Thermostat control panel may need replacement.

That CB is found inside the Electrical Box on your unit.
I replaced mine and have a SBO thread on that replacement procedure.
Jim...

I'll look into it, but if the pump is running, then why would it only not circulate water while in heat mode?

 

[JamesG161]

if the pump is running, then why would it only not circulate water while in heat mode?

The CB controls the Refrigerant reversing valve too.

We are having terminology issues in this thread. Note: Engineering terms to proceed.

Sea Water side...
1) 120 VAC water pump which is activated by CB. On and Off.
2) Outlet water flow should be visible flowing overboard, if pumping. Verify this please HEAT or COOL.
3) Water Flow direction does not change. There is no internal water circulation.
4) There is a heat exchange between Sea Water and Refrigerant.

AC Refrigerant side...
1) 120 VAC Refrigerant Compressor [RC]. Starts and Stops by thermostat control panel.
2) Dual mode or HEAT or COOL
3) Thermostat Control panel setting decides HEAT or COOL Cycle.
4) The RC compresses Refrigerant in one flow direction.
5) There is a Solenoid Control valve that Reverses Refrigerant Flow in the Heat Exchanger only. No Water flow direction change.

Once you separate these issues. The Calvary will arrive.
Jim...

 

[Scott T-Bird]

The CB controls the Refrigerant reversing valve too.

We are having terminology issues in this thread. Note: Engineering terms to proceed.

Sea Water side...
1) 120 VAC water pump which is activated by CB. On and Off.
2) Outlet water flow should be visible flowing overboard, if pumping. Verify this please HEAT or COOL.
3) Water Flow direction does not change. There is no internal water circulation.
4) There is a heat exchange between Sea Water and Refrigerant.

AC Refrigerant side...
1) 120 VAC Refrigerant Compressor [RC]. Starts and Stops by thermostat control panel.
2) Dual mode or HEAT or COOL
3) Thermostat Control panel setting decides HEAT or COOL Cycle.
4) The RC compresses Refrigerant in one flow direction.
5) There is a Solenoid Control valve that Reverses Refrigerant Flow in the Heat Exchanger only. No Water flow direction change.

Once you separate these issues. The Calvary will arrive.
Jim...

Thanks for the summary! It does help clarify the issues. When I wrote "seawater circulation" I meant that the seawater is picked up by the seawater pump and returns to the sea. I wasn't knowledgeable about what takes place in the RC until I watched a few vids that describe the reversible flow of refrigerant within its own separate circulation. So now I understand that the reversing valve would have nothing to do with the seawater pump performance.

I am aware of 2 occasions when the seawater pump was running but not pumping water. Perhaps it is just coincidental but both occasions occurred when the control was set to heat. The first time was last fall and it was the first time setting it on heat after using it all summer for air conditioning without any hick-ups. I noted fairly quickly that there was no heat being generated and no discharge from the thru hull, so I shut it down. The next weekend, I gave it another try on heat and it ran beautifully then and for several more occasions until I stopped going to the boat when December rolled around. The first time when it failed, I suppose it could have been a priming issue but that doesn't make sense to me because it was certainly primed when I ran air conditioning all summer.

The second time the seawater failed to pump water was the past weekend, which happened to be soon after putting the boat in the water. The pump actually became very heated because I left it on much longer. Before shutting it down, I noted that there was no water flowing at the discharge thru hull and going below, I could feel that there was no water in the hoses on either side of the pump. It was running dry. This was also in heat mode on a cold day.

Then, last Friday, with temps in the 90's, I ran it in AC mode and I could immediately feel water coursing thru the hoses, and water was discharging at the thru hull. Cold air was being distributed, so it appeared that all was normal and running fine.

Why the seawater pump was running dry on 2 occasions in heat mode is what I am trying to determine. It could have been a priming issue and it could have been a coincidence that it happened only in heat mode. But my gut is telling me that is not the case. It hasn't taken any special procedure to prime the pump. There doesn't seem to be any problem with air conditioning, which has been used far more often than heat.

 

[Rich Stidger]

Scott,

Here is what I think: Since the pump is running but not moving water, there is nothing wrong with the A/C controls.
After first launching, the pump did not fill with water, probably due to an air lock. So no water flow immediately after launch. Later, the air lock worked it's way out and the pump self-primed. Now you have flow.

The fact that the first time you were asking for heat and the second time you asked for cooling is completely coincidental.

I have had times when I needed to prime the pump after launch too. Even though the pump is below the waterline, the long runs through the condensor and to the thru-hull can slow the air movement and cause the temporary air lock.

 

[Davidasailor26]

Since you felt the pump getting hot you know it was trying to run, so I think that eliminates any electrical or control issue. On the seawater side the only things the pump needs to cycle water are electricity and water. You know you had electricity to heat the pump, so lack of water (due to clog or airlock) is the only other possibility.

 

[Scott T-Bird]

Two things I think are wrong and should be corrected:
1. I don't have a strainer between the pick-up and the pump. It is a very short run and perhaps with the pick-up strainer, the installer didn't feel a need for an in-line strainer.
2. The hoses on the pick-up side, to the condenser, and to the discharge (all hoses) are garden hose that are cut off and clamped to the hose barbs. Perhaps they are collapsing too easily.

I think I will add a strainer and replace with higher quality hoses. I just read thru an on-line manual for Marine Air and picked up a few tips for required maintenance. This equipment is new to me and I think I'll have to pay more attention to the maintenance.

 

[Davidasailor26]

The hoses on the pick-up side, to the condenser, and to the discharge (all hoses) are garden hose that are cut off and clamped to the hose barbs. Perhaps they are collapsing too easily.

The suction side of the circuit (between thru hull and pump) could collapse. Everything past the pump should be the pressure side, so those shouldn’t collapse inward. In any case since many of those hoses are underwater I would be more comfortable with below waterline rated hose and double hose clamps than garden hose.

 

[JamesG161]

The Calvary will arrive.

The Calvary has arrived!
_____
Sounds like you should start the AC in COLD first, to verify sea water flow.

After 15+ minutes, switch to HEAT mode. Observe and note down any Error Codes on Thermostat panel display.

If the sea water flows STOPS, then you have a Control Board [CB] problem and replacements are available.
Jim...

PS: A stainer pick can come later. There is a type that lets you blow clean the sea water lines.

 

[Stu Jackson]

The Calvary has arrived!
_____
Sounds like you should start the AC in COLD first, to verify sea water flow.

After 15+ minutes, switch to HEAT mode. Observe and note down any Error Codes on Thermostat panel display.

If the sea water flows STOPS, then you have a Control Board [CB] problem and replacements are available.
Jim...

PS: A stainer pick can come later. There is a type that lets you blow clean the sea water lines.

A very cogent diagnostic approach.