Heat pumps during the winter

[hillsideshortleg]

We I figure I may as well ask this also. Why wouldnt I want to use my heat pumps during the winter to keep the cabin from freezing? We have a twin Hornet heater in the engine area and a Sensored life Cellular reporting the temps and sending an alarm if the power goes out or the temps drop below 38deg. I am also putting one in the cabin to monitor power, temps and humidity. Thanks for all your advice.

 

[hughespat57]

The question is how cold does your water get?
Marine heat pumps are only effective down to 50-40 degrees depending on your unit.
Below near or below that ceramic or oil filled are more efficient.

 

[Ericinmich]

As stated, a boat heat pump falls off quickly and won't get any energy out of the water when it's 50deg (it actually states that in the manual). People that boat in the colder areas (NW, Seattle, etc) have small diesel heaters to stay warm when it gets that cold.

 

[b_arrington]

As stated, a boat heat pump falls off quickly and won't get any energy out of the water when it's 50deg (it actually states that in the manual). People that boat in the colder areas (NW, Seattle, etc) have small diesel heaters to stay warm when it gets that cold.

This.

Also, if you get really cold the raw water going through the heat pump is going to freeze and then you've got big problems. Salt water has a bit of buffer but your fresh water lake water is going to freeze at 32 degrees.

I recently read about a boat project where the a PNW boater switched from diesel forced air heat to hydronic hot-water heat, with the hot water supplied from a hot water tank. Much more efficient for his application.

 

[Ericinmich]

This.

Also, if you get really cold the raw water going through the heat pump is going to freeze and then you've got big problems. Salt water has a bit of buffer but your fresh water lake water is going to freeze at 32 degrees.

I recently read about a boat project where the a PNW boater switched from diesel forced air heat to hydronic hot-water heat, with the hot water supplied from a hot water tank. Much more efficient for his application.

With hydronic heat (basically hot water heat like on an old baseboard water system) you still need to get the energy to the water. It's likely going to come from a diesel burner system on a boat... but I guess electric would work if you aren't paying for the electricity!

A fiberglass hull doesn't provide much insulation so if the water is 50 and outside air even colder it will take a lot of energy to keep a boat comfotable.