Aircon on yachts

[StuM]

Originally Posted by 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?

In most of the world, BTUs are an archaic unit. Most of us have been metric for quite some time and most of us run on 220-240V, not 120.



Air Conditioners | Energy Rating


Single phase non-ducted air conditioners for household use are regulated for energy labelling in Australia and New Zealand. All three phase and single phase ducted air conditioners up to 65kW cooling capacity are regulated for Minimum Energy Performance Standards (MEPS).


...
Domestic single phase, non-ducted air conditioners must carry an Energy Rating Label.


The demonstration label on that page is a very close match to the OP's figures (just a bit more efficient)

[StuM]

Originally Posted by 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.

Another one who thinks "my world" is "the world"

[Reefmagnet]

Originally Posted by 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

Starting an electrical motor under load usually takes about 3x (minimum) the nameplate power specification to start. I suspect an inverter will "soft start". I noticed my inverter air conditioner at home starts at 35Hz and ramps up to a maximum of 120Hz over the course of a few minutes. Because inverters can turn off like a conventional air con, if they can't ramp down enough to maintain set temperature, this would occurred during this cycle too, I would guess.

I suspect 2000 watt may be marginal, but a lot of inverters specify a peak output of about 1.5 times the rated output.

Anyway, this is academic, imo. Those portable air conditioners are as useless as ashtrays on a motorbike because they pump out as much air as they cool, making them much more inefficient than the brochure would suggest. I think you'd need to bite the bullet and install a water cooled unit to achieve your objectives.

[a64pilot]

Stu, I stated amps and volts
I still don’t think your running a 14,000 BTU ac with 800W.
I guess then you can run two after starting, off of a Honda 2000 then?

[OzePete]

Originally Posted by StuM

In most of the world, BTUs are an archaic unit. Most of us have been metric for quite some time and most of us run on 220-240V, not 120.

And thank God for the metric systems.
The only three countries in the world still using Imperial weights and measures methods are Liberia, Myanmare and the USA!
Must be costing their industries a fortune.

Before Oz converted to metric decades ago, engineering refrigeration heat loads and appropriate systems was a nightmare and although like many, I initially bucked at the idea of change, we soon came to value the benefits.

Cheers OzePete

[john61ct]

There are some "portable" units that are somewhat effective

but not "pull out most of the heat in the cabin in under 30min" effective

and only ones with two hoses, running to different spots to the outside.

For off-grid use, a quality inverter plus a separate soft start unit is likely required. They can each cost more than a better aircon unit.

If you only use it in a marina then run it off mains. Otherwise use the genset if you're being practical.

A window unit stuck in a hatch is the usual redneck way of doing it.

[mickt243]

We have a small air conditioning unit for our boat - at full power it draws 760 watts, claims to have a cooling capacity of 12000btu. On a hot day (with either no/unfavourable wind) it is barely adequate. Our victron 1200 watt inverter has no trouble starting it, and transmitterdan’s estimate of 4 hours from 400ah batteries is spot on.

If we need to in it, it runs pretty much flat out when we are in the cabin - there is no “run it for a few minutes then shut it off”......

[skipmac]

Originally Posted by a64pilot

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

Very amusing article and regrettably very accurate. I thought that sort of thing had sort of died out but according to the author has seen a resurgence in the car audio and low end market. Seems like a good marketing idea never dies.

[Adelie]

Originally Posted by 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.

It would draw 42amps assuming 90% inverter efficiency. Lower but not enough to make it viable for long.

[valhalla360]

Originally Posted by StuM

Another one who thinks "my world" is "the world"

Haven't been to austrailia but picked up a portable in spain and it still listed the BTU. We had been eyeing them and saw similar in multiple EU countries. In Thailand right now and guess what...the box lists BTU.

So there may be places that list watts but it's not common.

[valhalla360]

Originally Posted by 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

I doubt 10-15 min would do anything noticeable. Most boats are horribly insulated, so any cooling would quickly be lost.

Probably better to just open all the hatches for 10-15 min to flush out the hot air.

[Marc1]

Mate, you can run an aircon whilst underway. Motorhome do it, cars do it, busses do it, you can do it.
All you need is a source of power. Batteries store power do not generate power, despite what the premier of SA wants you to believe, so ... if you are running on puff power, all you need is a small generator to power your aircon. No big deal, Honda makes some very small and very quiet generators. And you don't need an inverter, just plug and play in a 240v generator. As long as you have petrol, you can stay cool.

[NPCampbell]

Originally Posted by OzePete

And thank God for the metric systems.
The only three countries in the world still using Imperial weights and measures methods are Liberia, Myanmare and the USA!
Must be costing their industries a fortune.

Before Oz converted to metric decades ago, engineering refrigeration heat loads and appropriate systems was a nightmare and although like many, I initially bucked at the idea of change, we soon came to value the benefits.

Cheers OzePete

Not so fast there fellow aussie ... last time I checked, "knot" wasn't an SI measurement

[Reefmagnet]

Originally Posted by NPCampbell

Not so fast there fellow aussie ... last time I checked, "knot" wasn't an SI measurement

Ahhh, but the nautical mile shares more similarities with the metric system then it does with the imperial system. For example, the length of both a nautical mile and metre are ultimately derived from the circumference of the earth.

[StuM]

Originally Posted by Reefmagnet

Ahhh, but the nautical mile shares more similarities with the metric system then it does with the imperial system. For example, the length of both a nautical mile and metre are ultimately derived from the circumference of the earth.

Maybe once upon a time, in a land far, far away


The metre is defined as the length of the path travelled by light in vacuum in 1/299 792 458 of a second."


The international nautical mile and the knot while not part of the SI are 'non-SI units accepted for use with the SI" and the nautical mile is defined as exactly 1852 m. (But the poms, define a nautical mile as 1853 m )