Air Conditioning On the Hook?


"The dream" was originally defined as being able to head off into the sunset, exploring deserted beaches and uninhabited islands.  Whether gunk-holing or exploring the ICW, at some point spending the night on the hook will be necessary, whether due to the distance between locations, to save $$ (transient slips are expensive!), or just for the hell of it.


In Texas (and many other places in the summer), spending the night on the hook requires air conditioning.  For trawlers, running the air conditioner traditionally meant running the generator.  But the generator is LOUD, vibrates the whole boat, and gives off exhaust.  On Sunset Dream, the generator has not worked since well before I bought the boat.  It will start.  It will even generate electricity - as long as you hold the "stop solenoid" to prevent the generator from shutting itself down.   The previous owners had at least 3 separate visits from technicians to repair the generator.  The typical sensors (over temp, low oil) were replaced.  The fuel solenoid was replaced.  The main control board was replaced.  (And, the wiring harness between the generator and the main breaker panel was removed...)  No luck.   I spent time with a different technician checking the sensors, checking the control board.  No luck.  I even sent the control board back to the manufacturer for testing - they reported that the control board passed all tests.

Now, even if I do explore further and find the answer to getting the generator to run (and keep running) - then there is more.  The water pump is leaking, and will need to be replaced (not a deal breaker, but more...).  There is a water leak somewhere else in the system that needs to be tracked down and fixed.  And then, once the generator works - it must be maintained.  The generator needs to be started and run on a weekly or at least bi-weekly basis to ensure it keeps working.  The sea strainer needs to be periodically cleaned.  The oil needs to be changed.  The impeller needs to be replaced.    All this upkeep for the occasional overnight on the hook.

This section will explore possible experiments and research data to determine whether there is a way to sleep comfortably on the boat without needing to run the generator.

What are the electrical requirements?

I mentioned above the need for air conditioning.  Personally, I won't sleep well if the inside boat temp is 80F at night...  The other primary AC load is the refridgerator (there is actually a primary and a small secondary refridgerator on Sunset Dream).  I currently use an APAP machine at night.  That could be run on a separate battery/inverter if needed.   And there there are small loads like the Internet device (Tmobile Home Internet, or StarLink).

There are options for air conditioning:

How much power are we talking about?

The marine air conditioners can be expected to draw 9-15A at 120V.  In the heat of summery, these can be expected to run nearly constantly.   This needs to be measured.  Assuming 10A at 120V, that's 1200W

The refers typically draw about 1A at 120V, so assume about 100W each.  This assumption needs to be checked, and needs to be monitored over a couple of days to get an average power usage number.   NOTE that the refers run 24/7 - Not just at night!  They can be unplugged for several hours at a time and stay cool enough - but for planning purposes, we will assume they stay plugged in.

The APAP machine probably draws 100W or less when running.  (This needs to be monitored for several nights to validate.)

A 5000 BTU window unit draws about 600W.   If this is sufficient to cool just the aft cabin (with the cabin door closed) for moderate portions of the summer / fall, that would save a tremendous amount of power.


For an 10 hour period at night, assume:

Water Heater:

1300W, 11.5A peak Need to collect data on the percentage that the water heater runs...  And experiment with what we can get away with, and see how long it takes to heat up from cold, and how long to heat up from being off overnight...

WINTER:

For mild winter temperatures, the boat can be heated with two oil filled space heaters, running at 700W each.

One could consider a single heater in the aft cabin, or setting the heaters to run on low (300-400W range) with a 100W electric blanket.


COOKING - All of the above ignores cooking requirements.   Sunset Dream has a fully electric galley.  There is the original stove with oven burners (that do not work well), a 700W microwave, and a 1500W induction stove top.


Lithium Battery House Bank and electrical system upgrade

One of the previous projects on the boat was to update the electrical system.  When I bought the boat, there were two batteries - each a single 8D. The batteries ended were connected in parallel using the battery selector switch.  Both batteries in parallel were used to power both main diesel engines, as well as the house needs (lights, pumps, etc).

The following steps were taken:

Solar?

From research, I'm making the following assumptions:

As a simple example, consider BougeRV 200W flexible solar panels

Conclusion:   This is busted.  There is no way to put enough solar panels on the boat to charge the batteries to run overnight.


Generator:

Charging:


Splitting banks...

If we isolate the AC - then it's 600W @ 8 hours >> 4800WH >>  Almost in the range of a 400AH battery.  Within the range of 2x300AH battery bank.  This could be charged in 5 hours with a 1000W source.


Links to look at:

Sunrgy Solar Distribution; 832-768-5050 https://g.co/kgs/BRtNJYS

Signaturesolar.com

Conclusion:

Solar power alone is not sufficient to run AC and other power needs overnight.

Solar supplemented with at least a 2000W portable generator could charge the batteries enough to run overnight.

A 3500W or more generator could charge a LARGE battery bank sufficiently to run overnight (assuming large enough chargers could be found...).


AC Data

For more details, see Sunset Dream log, 5/2/24

AFT Marine AC unit - Dometic 10,000BTU, with 1000GPH water pump running:

Approximately 900W at inverter (including inverter load)

Honeywell Room AC - 8000BTU Model HF8CESVWK5

Max observed approximately 890W (7A @ 115V) on power meter (without inverter load)

Also observed 600-650W nominal at low compressor / fan load.

Walmart Midea 5000BTU window unit 

Approximately 600W