Marine Air Reversed Fan Speeds in Heating Mode

[Traveler 45C]

My unit is set up as follows: In Heating Mode, the fan speed increases as the set point is reached instead of slowing down as it does in Cooling Mode. This seems backwards to me. When its really cold, the fan blows so slowly it takes a long time to warm the boat and when finally warm, the fan is blowing so fast it ‘feels’ cold.

I can program the fan to slow down as set point is reached but the owner’s manual cautions against doing this. Is there really anything for me to worry about if I set it up as in Cooling Mode?

 

[spcoolin]

The reason the manual cautions against changing it is...

As a "Reverse Cycle" system the air & water coils Reverse jobs/duties
With any refrigeration system It's all about moving & removing heat.

In the cool mode...You are removing heat from the cabin and dumping it out into the seawater.
In the Heat mode...You are picking up heat from the seawater and dumping it back into the cabin.

In the heat mode the fan is trying to do the job that the water normally does in the cool mode...Air is not as good at removing the heat from the coil as water is...
Therefore the hotter the cabin gets...The better it is to run the fan fast to help that air coil do it's job of removing heat from the refrigerant.

Just as a restricted strainer in cool mode...Low fan in heat can allow/cause the system to run high pressures causing it to work much harder, draw more amperage, etc...

With the digital control there are other things you can experiment with such as programming how low is low & how high is high...Or you can set it for manual fan but just remember that the hotter the cabin...The higher the fan needs to be.

Steve~

 

[spcoolin]

If after the cabin is warm & it feels cold when running fast...The compressor may have cycled off at the selected setpoint...

How warm do you set the setpoint when in heat mode ?

You could also be slightly low on freon, and when the fan is running fast it's removing too much heat from the air coil...Thus lowering the exit temp...

Is this a split or self contained system ?...being you have Marine Air it must have been retrofitted...Hatteras was always a Cruisair account back then (some newer boats below 50' had Luneair which is out of business now)

Steve~

 

[Traveler 45C]

Ok, I get it. You’re saying that as set point is reached, the fan speed needs to increase because warm air from the cabin being pulled across the coils makes it harder for the coils to give up heat. I’ll play with the fan speeds.

I usually set the T-stat at 70-72f.

 

[spcoolin]

Ok, I get it. You’re saying that as set point is reached, the fan speed needs to increase because warm air from the cabin being pulled across the coils makes it harder for the coils to give up heat. I’ll play with the fan speeds.

I usually set the T-stat at 70-72f.

Actually No...It makes it harder for them to "Get Rid" of the heat from the refrigerant (like restricted flow or hotter water does in cooling mode)...and Yes the hotter it is in the cabin the harder it gets to remove that heat which it is dumping into the cabin, but different than the water & cooling mode...It's really hard for your overboard water to recirculate like the air is doing in heat (unless the boat were in a bucket or pool) and therefore it (the water) stays the same temp...

Steve~