Running an A/C unit on an inverter

[Foghorn]

I have a 29' Back Cove with no generator. On rare occasions I need to run the A/C (for the Admiral) when away from the dock and shore power. Looking at the $12K + cost to install a generator, I'm looking for a cheaper alternative. Does anyone have experience with running an A/C system on an inverter? Or it that just a a bad idea? The A/C system is a Marine Air Systems 9K BTU.

 

[DavidM]

It can be done for overnight use with a big Li battery bank and a 2000 watt minimum inverter. If you want to run it for a second night, the problem will be recharging the battery.

To run ten hours overnight requires 500-750 amp hours of Li battery capacity depending on local climate.

With Li battery prices dropping you should be able to do it for roughly $2,000 in parts cost, ignoring recharging.

You could recharge while moving five hours to a new anchorage but that will require upgrading to a high output Balmar alternator for roughly another grand.

How about a no name inverter based portable generator to run the A/C overnight for $500 or $1000 for a Honda.

David

 

[Graeme Walker]

We have run our 6k unit for a few hours to cool down. We have 960ah Lithium and 990watts solar, neither is quite enough, should have ~2x solar for each ah Lithium if you want to use solar to recharge. Our twin dc-dc chargers are not enough over the roughly 3-4hrs of travel each day.

 

[more]

9K BTU super easy this is 500-600W but non inverter 12 000 btu mobile AC is under 1000W around 700w you need minimum 2000w or best victron inverter 3000

I testing soon my AC 48000 btu, but I must try on inverter I have 20 kw generator

 

[READY]

It is the start current that might be the biggest obstacle. It could be 30-70 amps. Recently installed Velair ACs in my 48LRC. Variable speed compressor so the start up has no spike. Have not pulled the actuals yet but amazingly efficient and quiet. I think they probably pull less than 10amps start up for 16k BTU.

 

[Turtle Blues]

DavidM gave you good numbers in post #2.
The addition of a Soft Start module (assuming it does not have one) will make it much easier to get it past the initial voltage surge and running on it's operating amperage. Especially if you go the small genset route.
I am referring to a real soft start module with a programmed ramp up, Dometic's for example. Not a cheap HVAC hard start capicator.

 

[mvweebles]

If you only need base cooling for occasional use, you might consider an Ecoflow portable for around $1100 on sale now. Would only run one night but you could recharge via your car or engine while running, or take it home and charge there. A bit pricey I suppose, but cheap compared to the alternatives. Reportedly delivers 8-hours of cooking, though if coupled with the Costco solar generator (below), would double the capacity for an extra $800 and provide two 110w solar panels (these would take a couple days to recharge a 100ah battery)

Note - I do not have personal experience with this product but reviews seem favorable (second link). Also note that the ecoflow description is confusing to me - you need a battery and not all of them come with one so definitely call before you order.

By the way, Costco carries the ecoflow solar generator for $800 and includes two 110w solar panels. Temu has off brand solar generators that have 2x the capacity at a bit less, but buying an unknown brand.

Costco solar generator

https://www.costco.com/EcoFlow-DELTA-2-Portable-Power-Station-with-2-piece-110W-Solar-Panel.product.1836563.html?sh=true&nf=true

Ecoflow AC

EcoFlow WAVE 2 Portable Air Conditioner with Heater | EcoFlow

WAVE 2 • 5-minute warmth in any compact space. • Fastest Cooling and Heating • Installation-free! Fits Anywhere • 8 Long Hours of Comfort (With Add-on Battery) • 44dB: Perfect For Quiet Sleep • Using R290: A Greener Way to Beat the Heat • 4 Ways to Charge

us.ecoflow.com

Review of ecoflow AC

EcoFlow’s Portable AC Can Keep You Cool (or Warm) Anywhere

This portable air conditioner doubles as a heater, but it doesn’t come cheap.

www.wired.com

Peter

 

[High Wire]

Before you buy an inverter type portable generator, RENT a similar one for a day to see if it can handle the start. My 2000 watt Honda EU could not handle a 9000 BTU A/C. It could barely handle a Freezer box that drew 4.5 amps running and that was only if the ECO switch was off.

 

[Barking Sands]

I have a Victron Multiplus II 3000 watt inverter and 2 Epoch 460AH batteries that will run the Marinaire 16k btu AC unit for around 6-8 hours depending on settings, OAT and cycling.

Also for reference I have the new Honda 3200 fuel injected inverter gen that will run and start the same AC unit with no issues.

 

[mvweebles]

Before you buy an inverter type portable generator, RENT a similar one for a day to see if it can handle the start. My 2000 watt Honda EU could not handle a 9000 BTU A/C. It could barely handle a Freezer box that drew 4.5 amps running and that was only if the ECO switch was off.

Good advice. I was surprised when my 2400 watt inverter generator (knock off of Honda) wouldn't run my Keurig coffee maker during Irma in 2017. I love my other half dearly, but when she doesn't have coffee in the morning the going gets rough. As in hide the sharp objects .......

Peter

 

[READY]

A true soft start as mentioned will help reduce the start up surge but not total demand. I have no vested interest in the Velair but if the existing AC is getting old I would at least consider changing it out. The Velair should consume 30-40% less power all the time. This would probably be 2x more expensive than some of the other options mentioned but provide some great long term benefits.

If you are thinking about a portable genset on deck be very careful and evaluate safety risks. Also please don't ever be near me in an Anchorage! Those drive me crazy. Especially if the intent is to run it all night.

 

[READY]

Also look at the Anker Solix solar generators. I have the 2kw unit to use with my Airstream and very pleased. They come in even larger sizes or you can add extra batteries. Would solve the problem if you only need for 1 night and they can recharge off 12v or your inverter/alternator if running your engine. I think we are just about at the point that many might not need a generator. Most boats cannot accommodate massive solar but high output Balmar alternators really can provide significant charging. Even at close to idle my 170 amp 12V puts out 40+ amps. At 1500 RPM I can easily get 125 amps. No generator to maintain and even if not transiting you can just run your main engine to charge if needed. Some would have concerns about light loading and carbon build up so I wouldn't run it for 8 hours at high idle but still there is a significant load from the alternator so I personally wouldn't be overly concerned if this was not a regular/all the time occurence.

 

[Barking Sands]

One other thing to add. If you get a quality inverter/ charger like the Victron multiplus II 3000kva and also use a small Honda inverter generator hooked up to shore power inlet that runs through the multiplus II....the MP2 is a "pass through" inverter.
So if you have even a moderate sized lithium bank, when the Honda 1800 watt or equivalent knock off inverter gen is running power through the MP2 it will be charging batteries and powering other items. And then if you turn on a sizable ac unit, larger than what the Honda 1800 gen can handle, the MP2 will "assist" starting by using battery power and inverting via the MP2 and add to the starting power of the Honda 1800 (i believe up to 5000 watts?) This combo works very well in tandem for very little money.

I did this by accident the other day when I limited the shore power inlet amps via Multiplus to 15 amps and then ran the 16k btu AC and the microwave simultaneously for a total of 2900 watts. The multiplus seamlessly went into assist mode....and unless you looked you'd never even know it.

 

[mvweebles]

To answer the OPs question, yes you can run the AC off an appropriately sized inverter system......but whether your system will deliver the desired result requires some missing information on your current system and intended use.

What does "occasional use" mean? Does it mean once a year for several consecutive nights for sleeping comfort, or does "occasional" mean the handful of hot days you're using the boat for summer day trips? What is your current battery/inverter/charger setup? Any idea what size alternator on your engine?

Peter

 

[Chuck34]

Before you buy an inverter type portable generator, RENT a similar one for a day to see if it can handle the start. My 2000 watt Honda EU could not handle a 9000 BTU A/C. It could barely handle a Freezer box that drew 4.5 amps running and that was only if the ECO switch was off.

Agree, you should give one a try before buying, but you must have an older, inefficient AC unit if a Honda 2000 couldn’t run it. I’ve got a buddy who runs his 16000 BTU unit on a Honda 2000. I was floored when he told me he did this, so I asked if I could try his 2000 on my 16k BTU unit. Ran like a champ…no issues.

 

[SteveK]

post 2 has the answer.

Any inverter that can carry the continuous load will work, a large battery bank will support that inverter until depleted.

Now, how to recharge that battery bank quickly to be able to do it all over becomes the problem to solve.

 

[Kaniksu]

My 44 year old diesel Onan grew weary this summer and I grabbed a Honda EU2200 during one of the infrequent sales for $999 at Home Depot. I believe it will happily power your AC. You can also find on another recent thread a "silent box" made by Honda to shush the noise. I believe it was $699.

 

[O C Diver]

Just as a point of reference, I had a 16,000 BTU air conditioner on my charter boat. Didn't have room for a generator. With a 3,000 watt inverter, a soft start capacitor, and a 2nd 150 amp Delco alternator, i was able to provide air conditioning for my charter on the way out and back. The Delco wasn't really up to the challenge on a continuous basis for hours on end. When it died, I replaced it with a commercial grade 220 amp Leece Neville fire truck / ambulance alternator. The air conditioner drew about 110 amps at 12 VDC. Part of what made it work was the 8D battery to start the Cummins 6CT engine.

Often thought about a smaller trawler without a generator. The plan was to use the same alternator, inverter, and a 12,000 BTU air conditioner. On the rare occasion when AC was required on the hook, I'd run the engine at about 1,200 RPM.

Ted

 

[Bud]

I realize i am late to this thread but I have done some research on this and the main issue I ran into with running A/C on inverter/batteries was cycle times. All A/C's have run time amps and watts so we can do the math to figure amp hours needed, the issue is how long will it cycle for? For example the Ecoflo in eco mode spreads out the cycle so it takes longer to come down to set temp. It runs for 20 minutes then shuts comp off and just fan for ten minutes. Other A/C's Marineaire, dometic, ect I have not found that they have the ability to control the cycle. You set it for a temp and comp stays on until temp is reached. That burns up amp hours fast.

 

[READY]

I know I sound like a salesrep for Velair (I have no vested interest, only a new customer). They have a night mode that limits the power consumption (airflow) and then turns up set temp by 1 degree after 1 hour and another degree after another hour. That is in Cool mode. In heat mode it decreases the temp. I have not tested it but should help to reduce the power consumption.

 

[Barking Sands]

My Marinaire cycles. As a matter of fact when it gets to with a degree or two of setting point the fan reduces...and runs for a while and later it shuts off completely. How long it stays off is mainly due to the subsequent rise in temp in the area of the thermostat. That time period is affected my all manner of things, OAT, insulation of the space, water temp, air leaks etc.

But yes it's super hard to calculate because of those variables. And it changes of course with the seasons.

Are there units with variable speed compressors?

 

[Bud]

The Velair A/C is interesting. It uses R32 refrigerant and it uses a DC brushless motor to drive the compresor. That means the compresor is variable speed which will help especially with starting current. My Isotherm frig and freezer units I put in last year, have the DC compresor motors and they work great. Low power draw if you desire. I can set comp speed basically three settings slow med and fast. I have never seen the frig or freezer draw more than 4 amps at 12v.