Generator vs air conditioning

alaska_av8r · May 14, 2008

I have a 10,000 btu heat/air unit. Looks like I will end up having to get a portable generator to power the boat. What minimum KW generator do I need to be able to power the 10,000 btu air conditioning?

DRIFTER_016 · May 14, 2008

Re: Generator vs air conditioning

A 2000 Watt generator should work with some power to spare. It should run somewhere about 50 to 60 percent load.

tashasdaddy · May 15, 2008

Re: Generator vs air conditioning

the coast guard has several rules on generators, check them out.

SS MAYFLOAT · May 15, 2008

Re: Generator vs air conditioning

I don't have the formulas in front of me, but search some of the manufacture websites. Usually they will give either the formula or a chart in which generators will operate what. I tried a 4KW generator on my AC and it made toast,,,,,,,not the kind you can eat either. It was the initial surge demand that cooked it.

Like TD said, check with the CG. I had a Porter Cable that had the spark arrestor on the exhaust and guards over the wiring.

I finally gave up on the idea and got a dock with shore power. Besides, it got annoying hearing the generator run all the time. Good Luck and be careful with the exhaust fumes,,,,,they are deadly and can cause some mean headaches too...........SS

External Combustion · May 15, 2008

Re: Generator vs air conditioning

Check on the manufacturers plate for the full load runing amps. Add at least fifty per cent more for the starting load and multiply this by the working voltage. Make sure there is a good breaker or double fuse to protect the generator and only use the continuous rating on the generator. I have found most of the Chineese rigs are overated.

SS MAYFLOAT · May 15, 2008

Re: Generator vs air conditioning

Side note to EC's response, make sure that you run a ground to the engine/outdrive or electrolisis will eat your outdrive alive. Its easy to tell if you see hydrogen bubbles rising from the outdrive. Not a pretty sight to watch, cause it can damge things in a short time. Again good luck.......SS

JCF350 · May 15, 2008

Re: Generator vs air conditioning

4 times the running current.

Example:
unit requires 5 amps to run (10,000 btu will require more)
5 amps times 120volts = 600 watts to run
need 4 times that for start up
4 times 600= 2800 watts minimum

alaska_av8r · May 15, 2008

Re: Generator vs air conditioning

thanks for the information, that answers my question.

DRIFTER_016 · May 15, 2008

Re: Generator vs air conditioning

You guys are right, I forgot to allow for start up. :redface:

jeffnick · May 15, 2008

Re: Generator vs air conditioning

The EU2000 easily does our 9200BTU

The Great Escape II · May 15, 2008

Re: Generator vs air conditioning

If it's a typical Marine Air unit start-up watts will be around 5800 to 6000 watts on a 10k BTU unit. Do you know your model #? If so, call the manufacturer and they will tell you start-up and run wattage.

I have a 5k BTU Marine Air unit on my boat (2005 Chaparral Signature 240) and I use the Honda EU2000i. It's running at it's limits when the A/C kicks on.

Hitech · May 15, 2008

Re: Generator vs air conditioning

As you have read, just about any one will run it, starting it is a whole different story. Regardless of what anyone claims, there are NO formulas that you can use. Some A/C units require less amps to start than others, even when rated the same when running. I can start my 13500 BTU A/C on my MH with my 2800 watt generator no problem. I know of others that couldn't. There have been others that have started one that size with a Honda 2000. The biggest problem is that you won't know until you try. That said, I'd be very confident that yours will start with the Yamaha 2400. If you want, I can provide a link to a detailed test of that generator and a 13500 BTU A/C unit (these are common in Rvs).

Jerico · May 15, 2008

Re: Generator vs air conditioning

I managed to find the docs on my A/C online. It had the generator requirements in it. Don't remember what it said, but remember it being in there. You can also check with an RV company and see what their suggestions are.

Hitech · May 15, 2008

Re: Generator vs air conditioning

Also note that all generators do not handle current "surge" the same. The inverter models (the hondas and yamahas) run much quiter but do not handle surge demands as well as the older types that run at a constant RPM.

JCF350 · May 15, 2008

Re: Generator vs air conditioning

Hitech said:
Regardless of what anyone claims, there are NO formulas that you can use.

4 times is "rule of thumb" (opined to be a good number to use by many people) to insure adequate power for capacitor start motors, so you don't have to play around guessing. Plus you won't be running your genset as hard after start up.

Hitech · May 15, 2008

Re: Generator vs air conditioning

JCF350 said:
4 times is "rule of thumb" (opined to be a good number to use by many people) to insure adequate power for capacitor start motors, so you don't have to play around guessing. Plus you won't be running your genset as hard after start up.

I'm aware of that "rule of thumb". However, it just doesn't work. In the test I referred to, the running amps were 8.5. 4 times that is 34 amps, and that wasn't even close to what was required. If you use the 4 times rule you can probably almost guarantee what it will work. However, you can almost guarantee that you bought more generator that you need. Some people are fine with that, others are not.

For anyone that is interested, here is a link to the test:

http://www.2manytoyz.com/yamaha2400.html

JCF350 · May 15, 2008

Re: Generator vs air conditioning

Hitech said:
I'm aware of that "rule of thumb". However, it just doesn't work. In the test I referred to, the running amps were 8.5. 4 times that is 34 amps, and that wasn't even close to what was required. If you use the 4 times rule you can probably almost guarantee what it will work. However, you can almost guarantee that you bought more generator that you need. Some people are fine with that, others are not.

For anyone that is interested, here is a link to the test:

http://www.2manytoyz.com/yamaha2400.html

AH yes!, air compressors. Wasn't even thinking about them. Whole nother ball of wax. Lots of weight to get moving from a stop. I always use a gas powered compressor for portable air (or a little 12v for small inflatable stuff).

SS MAYFLOAT · May 15, 2008

Re: Generator vs air conditioning

Keep in mind also that a lot depends on the character of the compressor. Hermetic vs Schroll. The hermetic's usually will draw more power than what a schroll does. Also you should figure in other appliances as well such as hot water heater, stove top, and lighting.

Generator vs air conditioning

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