Visit our Popular Forums

Cowboy Sailer · 17-08-2013, 16:25

I recently bought a Webasto FCF 16000 BTU/hr. air conditioner. Unlike my old air conditioner it would not start if powered by my Honda EU 2000i generator. I added a Supco SPP6E hard start capacitor to the air conditioner. This allowed it to start and run when powered by the Honda generator. The generator has an eco-throttle position that allows the Honda engine to slow down to an economy idle speed when it is not producing a lot of current. The generator has to be running at a faster speed when the air conditioner compressor kicks on. This means that the eco throttle must be off and the Honda engine is spinning much faster when the air conditioner compressor kicks on.
The new air conditioner, the Webasco FCF 16000 BTU unit has a logic board that first turns on the blower motor then after a three minute delay it turns on the salt water circulating pump. After a delay of 5 seconds it then turns on the compressor. When the thermostat calls for the compressor to turn off the salt water pump continues for about five seconds and then it shuts down.
I got to wondering what percentage of time the compressor actually stays on when I need air conditioning. I added a “wall wart” power supply to the terminals that power the 120VAC salt water pump. It was one of those my brother-in-law had lying around from some forgotten 12 Volt battery powered toy. It put out 12VDC at a rated current of 200 ma. I mounted a green LED below the thermostat. The green LED stays on WITH THE SALT WATER PUMP which is about 75 % of the time during the day and about 30% of the time at night. I chose a dropping resistor of about 940 k-ohms to give about 15 ma to the LED. The LED was rated at 30 ma max, but that was too bright.
Next I added a 12V relay in parallel with the eco on/off switch. So 5 seconds before the compressor kicks on the Honda ramps up from ECO to normal speed and then the air conditioner pours out cold air. Next I added an outside electrical outlet box and a normally closed relay to turn off the electricity that comes out of that outlet. It is also has a 12VDC coil so it also is controlled by the air conditioner’s 12 Volt signal.
Then I rewired the boats electrical panel so that the battery charger circuit breaker gets its power from the shore power connection even if the rest of the boat is getting its power from the inverter. So when the air conditioner compressor is off the 40 amp battery charger is on and charging the house batteries. It turns out that the charging current when averaged over a night is way more than the inverter draw when averaged over the night. We wake up in the morning with fully charged batteries after having slept cool all night long!
I had earlier added a connection to allow me to use my 3 gallon outboard gas tank to supply fuel to the Honda. The longest that I have run it is 15 hours. That used about 2 gallons from the outboard motor tank and about a gallon from the Honda. The lowest that the batteries fell to was 12.4 Volts during noon day sun.