Running a 5000 BTU airconditioner w/inverter
 

I have a 33' Donzi with NO air/NO generator and live in TX. BAD!
I would like to add a Optima D31T deep cycle battery,
a 3000W inverter, and a 5000 BTU airconditioner. Has
anyone had experience in try to do something like this?
Anyone near Dallas you'd recommend? The airconditioner
draws 3.9 amp. The optima battery has a 75 amphour
rating with tells you how long you could sustain over a
20 hr period.....75amphour/20hrs=3.75;
http://www.1st-optima-batteries.com/amp_hours.asp
Technically, it looks as though I could have this set-up
and make it through an 8hr night of sleep while
still being able to have airconditioning in the cabin
@ 70 mph......not being limited like generator boats
not being able to run a generator above 35 mph. Any ideas?
I'm hot and sweaty right now unable to think because
I'm burning up in this un-airconditioned cabin!!!

Re: Running a 5000 BTU airconditioner w/inverter
 

Hi MJB

Assuming your airconditioner and inverter works at 110v the unit will draw 3.9amp at 110v which is 429 watt to get 429 watt at 12 volt will use about 36 amps which will give you less than 2 hrs on battery.
3000w inverter should work fine

regards

Rick

Re: Running a 5000 BTU airconditioner w/inverter
 

don't forget losses on the inverter 10% or more
and do you really have room for 4 batts thats what is going to take to get you through 7hrs of air, most inverters will shut down when the voltage goes below 11,
if you try some type of timer you could run it 15 minutes on 15 off and get by with 2 optima's

Re: Running a 5000 BTU airconditioner w/inverter
 

Brian and Rick covered it.

I've got some more.
First off, I've seen a lot of low consumption marine air conditioners, but I've never heard of one that only pulls 3.9 amps at 120volts. Mermaid Marine Air makes one of the Least hungry power consumers and their 5200 btu unit takes 4.4 amps PLUS another amp for the required seawater pump... This is for a total of 5.4 amps. Multiply that by 120 volts and you have 648 watts of power consumption.

To provide 648 watts, as Brian said, you gotta divide by 90% and get the consumption of the inverter itself. This would be 648/.90 = 720 watts.

At a fully charged state of 13.2 volts the beginning current draw would be 720/13.2 = 54.5 amps. At the cutoff point of 11 volts, the current draw will have increased to 720/11 = 65.5 amps. If you plot that on a usage curve, you'll end up seeing a continuous runtime of around 1 hr 15 minutes, and 36 seconds.

I figure you knew this in the back of your head cause if it was as easy as you were calculating it, everybody would have battery powered AC.

You could run your (engine driven) alternator to power the cool down period (probably only 30 minutes) and then if you keep the doors closed, I would guess that the AC would only need to cycle for appx 20 minutes per hour, for a duty cycle of 30%. This would extend your 1.26 hour runtime to 4.2 hours. Dual batteries would give you the 8 hours you desire. That's not too bad...

My family just slept a night on the cruiser with no AC. Cabin temps rose to 84 degrees at night. While that is not a "deadly" temperature by any means, it sure is more comfortable and pleasant at 68 degrees all rolled up in blankys...

Re: Running a 5000 BTU airconditioner w/inverter
 

Thanks for the info.....I also saw some guys this weekend running a
2000W Honda generator that they ran to their shorepower input on
the boat. I have heard bad stories of people on lakes like Havasu that
have done this with houseboats and the consequence is deadly.....CO2.
Molecule half-lives occur alot faster w/water cooled exhaust on a
generator thus reducing/eliminating the CO2 exhaust problems.

Re: Running a 5000 BTU airconditioner w/inverter
 

I know a few people who have done that. The new inverters are much better. Most upgrade their alternator and have two or more batteries to run the inverter. You shouln't have a problem.

Re: Running a 5000 BTU airconditioner w/inverter
 

Don't fool yourself about water cooled exhausts on generators. CO is present in all internal combustion exhaust emissions. A water cooled exhaust stream is just that, a cooled exhaust stream. While there may be some percentage of the CO molecules that are recompounded due to contact with water, it is certainly not a significant enough difference to brand a WC exhaust as being "clean" of CO. Not hardly enough to brand it "cleanER" at all.

Complete combustion in an engine results in nothing but CO2 and H2O coming out of the tailpipe. The more efficient an engine is, the less other combustion byproducts are present.

Marine gas powered gensets are relatively large, low output, lightly stressed motors. They typically provide moderate combustion efficiency. Compare this to a Honda EU series generator. A small, highly efficient motor running at high rpm. Miserly fuel usage. I would expect a small Honda genset to compare very favorably to the marine genset when comparing undesired exhaust emissions.

Water COOLED exhaust? Not a significant reduction in CO emissions.
Water IMMERSED exhaust (like the waterlock mufflers used on most marine gensets) still doesn't scrub out CO.

A CO detector is a MUST.
Nighttime use of a gas generator dictates a breeze. Still air is not a good place to run your generator.

just gotta use sense.

Re: Running a 5000 BTU airconditioner w/inverter
 

Third battery, inverter works real good. Most of the Midnights have them. I offer that or shorepower, or off the motor but only operates when the engine is running. Over night inverter is the set up it should go 7 hours.

Re: Running a 5000 BTU airconditioner w/inverter
 

Don't to forget about the water pick up location on the ac unit. I have a 38 ZX and the manufacture does not recommend running over 3000 rpm. ZX's have the steps that tend to put much air under the hull decreasing the water available to the ac unit.. You better check that out first.

Re: Running a 5000 BTU airconditioner w/inverter
 

Thanks for all the good info.