Heater / AC unit not putting out heat

markasaurus

New Member
Jun 27, 2020
7
Boat Info
2014 Sea Ray 310 Sundancer
Engines
Mercruiser 450 Bravo III
We have a Heater /AC unit that is supposed to cool or heat both the cockpit and /or the cabin, they both have their own thermostat. During summer, we ran the AC a few times but never needed the heat. When we ran the AC, water would trickle into the bay from an outlet on the side, seemed to work fine.

Now that it is winter, we would like to stay overnight at the marina a few times (with new upgraded v-berth mattress) but when I turn on the unit and put the thermostat to heat, air comes out but it doesn’t feel hot or even warm. Even after an hour, no real heat just air. No water trickles out the side as it does with AC running.

Is there something simple to check? I assume this should work off of shore power and not require the engines or generator to run to heat...?
 
Water should be pumping out the side just like when the Ac is on.
I would check that first.
The unit will not make heat if the water temp is below 45 degrees also.
 
the units has a reverser valve, one side ac the other heat. it could be stuck it u don't exercise it
from time to time. u might try pecking on it once u have good water flow.
 
If water was only trickling this summer you were already having an issue. You should have a pretty solid stream of water from your AC outlet. The amount of water that should be coming out is no different between heat/AC.

Check your sea strainers first. Are you not getting an error on your thermostat display? Generally a "trickle" of water from the pump would show as an error on your display.
 
You need to open up your entire system one piece at a time starting at the A/C strainer and all the way through the complete system to the through-hull exit fitting on the side of your boat to check for proper pump operation, any blockages, kinks, etc. After that, you should use Frank's highly recommended procedure shown below for safely flushing out your complete system. You do not have a good water flow througout your system for proper operation and you really need to find out why.

"I have a 5 gal bucket with a hose fitting in the bottom. I put 1 gal of the 20% phosphoric acid in the bucket then add about 1/2 of water so I end up with approx a 10-15% acid solution. I connect the hose from the bucket to the A/C flush fitting in the bilge at the A/C strainer and start the a/c and a/c water pump and let it run on the acid solution until the bucket is empty. Then shut off the A/C and let it sit with the acid in the cooling lines for about 15 minutes. Then connect the a/c flush fitting to shore water and let the system run for about 45 minutes or an hour on city water to flush it.

My boat has 2 a/c units.....a 16Kbtu in the salon and a 12K but in the forward compartment and I have added a flush fitting to the line between the strainer and the pump. You may need to adjust quantities for the differences between a 290DA and a 450DA."
 
  • Like
Reactions: QT1
You need to open up your entire system one piece at a time starting at the A/C strainer and all the way through the complete system to the through-hull exit fitting on the side of your boat to check for proper pump operation, any blockages, kinks, etc. After that, you should use Frank's highly recommended procedure shown below for safely flushing out your complete system. You do not have a good water flow througout your system for proper operation and you really need to find out why.

"I have a 5 gal bucket with a hose fitting in the bottom. I put 1 gal of the 20% phosphoric acid in the bucket then add about 1/2 of water so I end up with approx a 10-15% acid solution. I connect the hose from the bucket to the A/C flush fitting in the bilge at the A/C strainer and start the a/c and a/c water pump and let it run on the acid solution until the bucket is empty. Then shut off the A/C and let it sit with the acid in the cooling lines for about 15 minutes. Then connect the a/c flush fitting to shore water and let the system run for about 45 minutes or an hour on city water to flush it.

My boat has 2 a/c units.....a 16Kbtu in the salon and a 12K but in the forward compartment and I have added a flush fitting to the line between the strainer and the pump. You may need to adjust quantities for the differences between a 290DA and a 450DA."
 
It is possible to set the operating mode to cool only through the programing mode. If yours is set to cool only you will not get heat until you enter the programing mode and set the operating mode to automatic
or heat. Your manual will tell you how to do it.
 
Ok, rookie mistake!

When I run either salon or cockpit heat/ac, I apparently need the ac relay water pump on, an obvious switch above the switches for either unit on the panel.

I turned that switch on and now have a nicely heated space within 10 minutes in either location. We have had a great few sleepovers, ironically not really needing the heat with body heat below deck. :)

Thanks to everyone who gave me information to debug this!
 
Water should be pumping out the side just like when the Ac is on.
I would check that first.
The unit will not make heat if the water temp is below 45 degrees also.
All replies are things to check. But bottom line, is as CFD said, these are better at cool than heat. They work on sucking heat or cold out of water and below 45 you ain’t gettin much heat out of the water.
 

Forum statistics

Threads
112,950
Messages
1,422,862
Members
60,932
Latest member
juliediane
Back
Top