Winter & heat

[River Cruiser]

I was interested in the water temp here in the harbor so I dug out my temp gun & found it to be 38f. Then I decided to check the output of my reverse cycle units because I've read they aren't efficient below about 40f water temp. I thought this was pretty good, better than I expected.

 

[DavidM]

Check your IR gun against a known thermometer at the 38 deg temps. My Fluke IR gun is off about 10 degrees at those temps, but right on at 75 deg F.

And unless the return air was 80 or more, I would suspect the 104 deg reading as well. Heat pumps rarely have more than a 20 deg temperature rise particularly at low outside air temps.

And finally, not to be a smart&*%, it is not the efficiency that drops off. My home heat pump works down to about 15 degrees outside air temperature. But the seawater will freeze in the condenser of a marine unit at much below 40 degrees. That is why Dometic and other marine heat pumps have a sensor that cuts off at that temp.

David

 

[magicbus]

So my heat pumps are gonna shut down when the temps hit under 40°? That happens I'm in big trouble in December when we finally head south. I'm not going to tell my wife...

Dave

 

[boatpoker]

Re-read the manual for your gun. I think you'll find that they warn against aiming it at a reflective surface as that can make it wildly inaccurate.

 

[sunchaser]

My reverse cycle units worked while we were anchored in front of Reid Glacier in Glacier Bay Alaska. Water temp around 39 - 40. With heat strips they work at temps below that I'm told.

 

[River Cruiser]

I know last Saturday it was 12f with a stiff north breeze and it was 67f on the boat & today the temp in the bilge was 41f, water checked at 38f. Last weekend the water temp was 44f at St. Louis so 38f here today isn't that far off seeing as how we're about 70 miles upriver. The air coming out of the grill is nice & warm on my 98.6f hand;-)

 

[FF]

>With heat strips they work at temps below that I'm told.<

Heat strips are what is in a toaster or any portable heater.

As long as the electric doesnt blow a portable heater (or 5 ) works fine, and there are no losses heating ductwork.

Reverse cycle stops working in air source models when the unit ices up.

Water cooled , the same , the heat exchanger ices.

The new Mini splits work down to real cold and are all over northern Europe.

But none are made for boats yet , sad as they are 400% to 500% more efficient than the toaster wire .

 

[River Cruiser]

Had some skim ice in part of the harbor this morning. Back home in Kansas now & the lake behind the house had some ice in the cove.