Marine Heat pump

[AKA-None]

Just FYI

My ground sourced heat pump is designed to pull heat as low as 23 degrees F

I’m this case via ground loop

Not saying this applies to marine systems but just to note that there’s a lot of heat just sitting there as mentioned above

[SailingHarmonie]

Originally Posted by fourlyons

That's not really true, 40 deg f water has plenty of heat. Land based heat pumps pull plenty of heat from sub 0 deg air while consuming less energy, but it takes technology that hasn't yet come to boats.
But perhaps you can't do that with water rather than air due to the physics? Some have talked about marinizing the modern air exchanger mini splits.

You are missing a rather important difference between an air heat pump and a water sourced one. It is true 40F water “has a lot of heat.” But… f you extract very much heat from it… it freezes and clogs up the system.

To extract heat from water (or anything) you need to have a cold place for the heat to flow toward. Once the water you are using as a heat source gets down to 40F the temperature of the evaporator needs to be at or below 32F to extract heat, and ice formation starts.

[boatpoker]

Originally Posted by Marc S

Thanks, Scubaseas! By “converting” I meant mainly re-using hose fittings and through hulls. The AC is showing signs of approaching death, so not looking to replace pumps, condenser, or solenoids. Mainly concerned about the actual installation which we plan to do ourselves.

In Michigan you may want to consider a Flagship Marine system, no propietery parts and built in the US with terrific customer service. The a/c side works the same as the system you are used to but the heat side is straight electric furnace. The reverse system is not very efficient at cold water temps for heat ... 30 year satisfied customer

[David Mathis]

We still have the original Marineair units on our 1997 43' Wellcraft, a 9000 and a 16,000 unit. A couple years ago we had a problem with one so the tech dept was called. It was amazing, we didn't have to push a series of numbers to select menus, sub menus, etc. then stay on a long hold due to unusually high call volume. An operator answered (a real one, not a recording or a bot) then quickly transferred me to the tech. He described the fix and sent the part. This is commendable customer service.

As to trying to heat when the water is cold, just use a couple of plug-in electric heaters until the water gets to upper 40s or low 50s. We're in northern New York where the water stays hard until about March so the typical April launch will have very cold water.

Hot weather? One day we saw 102 with the interior a chilly 68. That's much cooler than we tend to keep it but we wanted to see how cool we could make it. The water temp was about 76.

[TBW]

Investigate Mabru; Deerfield Beach.
I have 3. Replaced old Webastos and one from Flagship in Stuart.
Webasto have problems with the boards and if you need FedX overnight saturday delivery forget it. Never was able to get anywhere with heat pump. Threw Flagship off the bow in 2000 feet of water; noisy, noisy; no help, no help.
Mabru has a true variable speed compressor (5 amp draw on startup) great help, service and backup. Heat works as well and as easy as cooling.
Check them out.

[Mauruuru]

All of the equipment can be reused except the thermostat will need to be replaced with a dual function heat/cool which should come with the heat pump. The wiring to the controller may need to be replaced if there are no spare wires in the cable for the mode switching

[Ted10028]

Does anyone know how to winterize a heat pump? Mine apparently was placed in the Catalina 320 and then the deck was put on top of it so now it is virtually inaccessible. I'm thinking I have to put a small electric heater next to it so it will survive the winter?

[BlueH2Obound]

Originally Posted by Ted10028

Does anyone know how to winterize a heat pump? Mine apparently was placed in the Catalina 320 and then the deck was put on top of it so now it is virtually inaccessible. I'm thinking I have to put a small electric heater next to it so it will survive the winter?

Identify the inlet raw water source, hook it up to a jug of RV antifreeze (the pink stuff) run it until the outflow is pink. Shut off the heat pump. No special recommissioning to do in the Spring, just turn it on.