Aircon on yachts

[RenoirIII]

Hi All,
I just bought a small air conditioner for our 44' yacht with the following specs:

• Max power input: 808W
• Cooling capacity: 4100W
• Refrigerant/Charge: R410a/400g
• Rated current: 3.8A

We are happy to use this when we have shore power.
Is there any possibility to run this from an inverter / battery / solar setup?
I'm not sure if this is an 800W or 4K system?
Any fridgies out there that can assist?
Thanks in advance.
Renoir

[skipmac]

Short answer, yes you can run an air conditioner from batteries and inverter BUT unless you have an awful lot of batteries you won't run it very long.

If the unit draws 3.8 amps at 120 VAC that will translate to about 50 amps out of a 12VDC battery system. Not huge but would draw down most boat banks in a few hours.

You also have to consider how you're going to get that power back into the batteries. It takes a lot longer to charge than it does to use the power.

[Moody46CC]

AC will have a pump to circulate the coolant (sea water), a motor for the compressor, and a motor for the blower. Lot of juice coming off your batteries as Skipmac noted.

I'm not familiar with cooling capacity rated in watts--usually it is BTUs. a 6000 BTU unit would do one cabin on a 44' boat.

[transmitterdan]

4100W is about 14,000BTU. At 800W mains power that’s a SEER rating of about 15. What make and model A/C is it?

I assume it is not water cooled so no water pump is needed.

You should be able to run it from an inverter. It will drain a 400AH bank from full charge to 20% in about 4 hours. Maybe a little less. The inverter will need to be sized large enough to start the compressor unit which is probably about 4 times the running power. I would guess a 2,500W inverter would do it.

[a64pilot]

Those numbers don’t add up at all. Just to start with 800W is 6.7 amps at 120 V.
Your not running a 14,000 BTU system off of 6.7 amps.
That is more like min 70 amp draw from a battery bank.

Never heard of cooling capacity in watts?

[john61ct]

Is it actually a 14000 btu unit?

100Ah extra bank capacity per hour of running off the bank would IMO be a low estimate.

You have to run ICE charging to refill the bank anyway,

unless you get back to shore power every night,


so really you're just buying a little "time shifting".

If you imagine doing this off mostly-solar or wind energy, forget it.

[valhalla360]

Maybe post the make and model...rating the cooling in watts is not normal. Yes, you can convert BTU rating to watts but it's not done normally.

Also is it 800w or 3.8amp? Is this a european boat...as that would imply 210v (which still doesn't make sense as it should be 220v or 240v nominal).

As others have said, yes it is technically possible but not very practical to run off batteries. By the time you set up a system that can do it it will be far cheaper and take up less space and less weight to just run a smalll generator.

[john61ct]

which is required in any case

batteries are just a time-buffer, not an energy source

[transmitterdan]

Guys, 800W mains input for 4.1kW (14000BTU/hr) of heat removal is a SEER of 17.5 (14000/800). High but well within the performance of modern whole home air conditioners on the market. I have no idea who makes this unit but it’s probably a consumer window unit. I have never heard of a window unit with SEER > 15.

So I am skeptical of the wattage. I assume this unit is running on 220V. Not sure about that. But watts don’t care about the voltage.

Also, remember that the BTUs are rated under certain specific conditions of ambient temperature and may not be applicable to tropical conditions of temp and humidity.

[a64pilot]

Reminds me too much of the 500W car stereos, with a 5 amp fuse.

[skipmac]

Originally Posted by a64pilot

Reminds me too much of the 500W car stereos, with a 5 amp fuse.

Those 500 Watts they used to call "music power" whatever that meant.

[a64pilot]

Originally Posted by skipmac

Those 500 Watts they used to call "music power" whatever that meant.

I’ve heard IPP, or instantaneous peak power.
Assumption is the theory that music is peaks, so as long as you can peak for a millisecond, that is your rated output?

It’s just marketing lies, no basis of fact at all.
What happened to truth in advertising? Isn’t lying like that illegal?
https://www.audioholics.com/audio-am...-power-ratings

[NPCampbell]

We probably need a little more info.

What is the 800W rating? Is that the rated power of the unit for continuous operation? Or is this the max power (including startup)? ACs rountinely draw considerably more amps at startup. It's known under a number of different names like startup, inrush, surge or locked rotor amps.

If your inverter can handle the surge rating of the AC for the entire duration of the startup phase then the AC can be driven off batteries.

[Pizzazz]

Anyway you look at it, you need a generator to run air conditioning on a boat and the generator has to be well insulated so that you do not waste energy to cooling down the heat from the generator. Further, you do not really need an AC while at sea as usually there is enough wind for good ventilation of the cabin.

One consideration could be to get a compressor dehumidifier. These are usually lower power (~300W) and help bear the heat (dry air feels much cooler and more pleasant than damp hot air).

SV Pizzazz

[RenoirIII]

Thank you for all the advice.
If I "need" an air conditioner or not is perhaps somewhat outside the scope of my question.
We run this aircon (link) when we are in a marina. It is 220v (we are in Australia). I have a 2000w inverter which is not installed as yet. We would like to run the aircon off-grid for 10 -15 minutes to take most of the heat out of the cabin. I understand that we can't run this continuously. I understand that the startup of the unit creates a spike in consumption which seems to be the issue. I just do not know the maths behind it.
I hope this helps...
Renoir