Running Air Cond off Inverter

[Dockhead]

Originally Posted by wyb2

What's the charging current? You said plug the inverter into the Honda, I assumed that meant the 8 amp DC output. If you're running the Honda 120v to a battery charger that should work better. Depending on the duty cycle the a/c compressor is running, you're probaby looking at at least a 40 amp charger.

He proposed using a charger, not (obviously) the wimpy DC output.

But this would work best of all with an inverter/charger which passes through the AC output of the generator to the loads, without converting back and forth to DC. These devices will also supplement the generator power with inverted power from the batteries to handle the startup loads. So you have full AC output of the generator plus full AC output of the inverter combined. This will deal with quite huge startup loads, and is the elegant solution to the OP's problem.

[galynd]

Originally Posted by wyb2

What's the charging current? You said plug the inverter into the Honda, I assumed that meant the 8 amp DC output. If you're running the Honda 120v to a battery charger that should work better. Depending on the duty cycle the a/c compressor is running, you're probaby looking at at least a 40 amp charger.

Sorry, I didn't mean the DC output. Yes, the charger 120v would charge the batteries which runs the A/C through the inverter.

Question: how do you run the A/C off the inverter (to support surge) and generator simultaneously as mentioned above?

[john61ct]

Victron kombi style inverter/charger, called the "power boost" feature

Magnum, MasterVolt may also do it.

[wyb2]

Originally Posted by Dockhead

He proposed using a charger, not (obviously) the wimpy DC output.

...

Originally Posted by galynd

...and plug the Air Conditioner directly into the inverter then plug the inverter directly into the honda 2000...

I agree, using the DC output on the Honda doesn't make a ton of sense.

Edit: Nevermind, I missed the OP's post that clears this up

[Dockhead]

Originally Posted by galynd

. . . Question: how do you run the A/C off the inverter (to support surge) and generator simultaneously as mentioned above?

It's called "Power Boost", and you get it on Mastervolt, Victron, and some other kinds of charger/inverters.

The generator AC output is connected to the charger/inverter. Then all AC loads are connected to the charger/inverter. In normal condition, generator output is simply passed through to the AC loads. But if the AC loads exceed the generator capacity, then the inverter switches on and supplements the generator power with inverted power from the batteries.

Obviously this doesn't solve the problem if the sustained AC loads are greater than the generator capacity -- you will run the batteries down. But for short term peak loads -- not just electric motor startup loads, but also things like running a kettle or microwave for a couple of minutes -- it's brilliant. It's called "peak shaving" in the power industry, and it allows you to use limited generating capacity more efficiently.

On a bigger boat, it allows you to use a smaller diesel generator and run it more efficiently. For the OP, it would deal perfectly with the problem of starting his A/C.

[Cadence]

Originally Posted by wyb2

Some quick math. What does the A/C draw on 120V - say 12 amps. So the inverter will need at least 120 amps at 12V. Ignoring all the startup issues, are the batteries up to supplying 120+ amps for long periods of time?

You nailed it. I don't understand the connect the Honda to the batteries? As I understand it the DC output of a 2000 is not that great although it is a hell of a little AC source with a good start up surge ability. If one Honda won't carry the load add a second. Long periods of air conditioning from batteries seems foolish.

[yachtgemini]

OK this may sound stupid...

I have tried starting a 10k btu air con off my mastervolt 2.2 kw inverter with 8 T125 batteries and it was not happy. Tried the same thing using a massive 250ah engine starting battery and the A/C started easily.

The moral of the story is that the surge capacity of your batteries may also be very important.

Ross

[Jhowell5558]

I have a 18K BTU Ocean Breeze water cooled a/c.
This year, I installed a Micro-Air Easy Start 364 ($300ish) in front of my A/C
Then hooked up my Honda 2000 to the ships A/C Dock Cord
Works GREAT!

My A/C is 17 years old so I"m sure the compressor is drawing a bit
more than normal at start up - but hey - it still works!

Have fun!

[dakno]

Good thread but missing something. An AC has 2 start loads that are each double the running loads in general. !) fan motor start load is 2x running load, 2) compressor start is 2x running load. If you start your ac in fan only, let the running load settle down and then engage the compressor you can avoid the simultaneous start loads. My small 7k ac would run on a Honda 1000 this way. Your start load on your water pump could complicate things. Avoid everything coming on at once.

[Dockhead]

Originally Posted by yachtgemini

OK this may sound stupid...

I have tried starting a 10k btu air con off my mastervolt 2.2 kw inverter with 8 T125 batteries and it was not happy. Tried the same thing using a massive 250ah engine starting battery and the A/C started easily.

The moral of the story is that the surge capacity of your batteries may also be very important.

Ross

Why stupid?

Did you have AC power supplied to the inverter when you did this? Or, if your Mastervolt is not an inverter/charger, did you have power on the battery charger at least?

[Dockhead]

Originally Posted by Cadence

You nailed it. I don't understand the connect the Honda to the batteries? As I understand it the DC output of a 2000 is not that great although it is a hell of a little AC source with a good start up surge ability. If one Honda won't carry the load add a second. Long periods of air conditioning from batteries seems foolish.

See the post just before yours, which explains where the batteries come into it.

No need to have two Honda generators just to supply a load which lasts less than a second. One of them will easily run the A/C once it's started.

[yachtgemini]

why stupid to try a 250ah battery?

simple... with no generator/dock support it was not going to run for more than a few minutes. It was simply to check that the AC units would start.

I later tried and successfully used the inverter in power support mode with the 6 amp 220-volt dock supply to help the start and run the AC for a while.

My point is that the startup surge is a significant multiple of run current and that by accident I found the starting battery even though significantly smaller than the house bank had the surge (cranking amps) to start the AC.

My situation is probably analogous to using the 2kw Honda (actually 1300w from dock) and illustrates it can be done.

[Cadence]

Originally Posted by Dockhead

See the post just before yours, which explains where the batteries come into it.

No need to have two Honda generators just to supply a load which lasts less than a second. One of them will easily run the A/C once it's started.

I did after the fact. The inverter is only supplying the start up surge in effect.

If I'm reading correctly?

[Mango51]

Yes the smart start works amazing. My 16k btu starts at 11 amps and runs on 11. The aft 8k btu with no smart start starts at 36 and runs at 11. This is what my anolog amp meter reads. My gen is a northern lights 6kw 50 amps.
Hope this helps some

[MCOS]

A capacitor bank wired into the input circuit of the inverter could possibly supply the extra kick needed to start the compressor. If wired in parallel with the input, it will charge to the capacity of the capacitor and add to the current when the draw is more than the genset provides. The capacitors will recharge as current is available for the next call for an extra surge. This will work for DC - check You Tube, some mechanics have used a capacitor bank as a replacement for a conventional lead acid battery.