15000 BTU AC Surge power requirements

Mouse

Member
Model: 2011 3300QS

I am looking for a generator to power the AC should we choose to rough it. How big do I buy? Cost, noise, and weight all factor in. The answer to this question, how big (KW) generator to buy, hinges upon what are the peak amps for the AC compressor?

Conventional wisdom is to buy 4kw min. This sounds like it would be over-kill. 1. The AC is on a 20a breaker (2.k kw at 120vac); 2. Domestic 15k BTU ACs, according to specs found at Domestics website, pull 2.8a for the fan and 13.2a for the compressor, for a total of 16 amps. 3. If AC startup amps exceed 20a, why doesn't the breaker trip?

So, what are the surge amps of the AC?

Thanks,
Mike
 

jimtoo

Moderator
Hi Mike,

I don't think 4k would be overkill at all. You will have a lot of other stuff running also. Your generator will make less noise and burn less fuel if it is operating at 50% than if at 80 to 90% capacity. And if you decide to add the second A/C later you can power it if needed.

I did move the thread out of ATF area so you will get more actual experienced replies here from other owners.

Jim M
 
Hi Mike,
I can't exactly answer your question on how many amps your A/C will pull on start.

First, Circuit Breakers are not instantaneous trip. A 20 amp breaker might take a 40 amp surge for a second or so without tripping. I've seen breakers that are specifically labeled for HACR applications to accommodate the surges of the motor loads. I can also tell you that the start current surge is quite apparent to the generator load when the A/C starts up.

I can tell you from first hand experience, I had a travel trailer with a 15kBTU A/C and a portable (Coleman - read as cheap) 4000 watt generator. It would start and run the A/C, but nothing else of significant load. I'll also tell you that the generator didn't last long. The tech explained to me that the Coleman genset had two 110V windings to generate 220V, and when I was running high 110V loads it created a large imbalance and heat difference that cooked the armature.

I now have a Honda "portable" 5500 watt generator (and a Bighorn!) it handles the main A/C fine and most of the other common loads. I still can't run the bedroom A/C or microwave at the same time without tripping the 240V/30A breaker on the generator. I also don't get too carried away with other electrical loads when running on generator. I switch the fridge and the hot water heater to gas. Remember your converter that charges your 12V batteries can pull about 6.5 amps by itself on demand.

The cost, weight, fuel for the larger generator are concerns obviously but the cost of buying one too small would be way higher to correct later.
 

newbie

Northern Virginia
If you look on the boiler plate for the air conditioner, you'll see a couple of amp ratings. One of them is FLA or Full Load Amps. This is kinda like a worst case scenario for amp draw (at start up, on a very hot day, after a short delay or no delay, after the compressor has been shut off and tries to restart). The hotter it gets, the harder for the compressor to start.

Last weekend we were at a park with 30 amp service. We could not run both a/c's during the heat of the day as the 30 amp pedestal would trip. We could run both at night when the temps had cooled down. Point being, the hotter it gets, the larger the amp draw will be on the generator. When you really need the a/c, you wouldn't want to be faced with the generator tripping out because of too high a current draw on the genny.

John
 

Mouse

Member
Everyone,

Thank you for your input and advice. After a great deal of research, I decided to go with 2xHonda 2000i's with the parallel kit. The most watts, amps, weight, endurance, warranty, with minimum size and noise for the $.

BLUF: I usually don't make out well when I cut corners. I considered buying one of the various chinese made units (Ramsond, ETQ, etc). Half the price of the two Hondas, but not quite the watts, weight, endurance or warranty. But, given my experience with all of my kid's chinese toys and other products we've bought from Walmart, I just couldn't risk the drama a less than adequate chinese unit would induce if it were to fail at critical time and place. Also, if the Chicom's needed service, bon chance. I know I can get the Honda's serviced. Also, a little rationalization here, the Honda's will in all likelyhood have 2x the usefull life of the ChiCom stuff. Amoritizing the price delta over the expected life of the Honda's, the Honda "premium" only works out to $100/yr.

I bought local. They basically matched the best internet price I could find, less the tax.

Of course, as life would have it, after making my purchase I discover the answer to my question, what is the start up watts of a 15,000 BTU RV AC - 3300 watts surge, 2000 steady state.

Thanks again,
Mike

From:
http://www.hondapowerequipment.com/products/generators/content.aspx?asset=gg_wattage
 

Rickhansen

Well-known member
Mike,
You'll proud of the Honda equipment in all respects, I'm sure.

I was surprised seeing the startup load rated in Watts. If you didn't know, 3300 Watts is 30 amps inrush at 110VAC. The breaker is sized at 20 amps.
 

bigdob24

Well-known member
I have 2 Honda 2000s paralleled together and they run the air just fine. They are a bit pricy but easy to handle and not bad on gas.
There are three other friends we travel with and do allot of dry camping and everyone has 2000s . If your not running the air or Microwave then one works for everything else.
 
A 15K BTU RV air conditioner can easily draw up to 52A but very briefly (less than a second) when firing up the compressor. That is why a 30A circuit is required. A 30A circuit breaker usually won't trip for such a brief but intense surge, but a 20A circuit breaker will usually trip. Most people using portable generators that can afford it will use a pair of Honda EU2000i generators tied together with a combiner. These are relatively light weight (easier to haul out and put away two 60# units rather than a single 100# unit of equivalent power output), very quiet, and very reliable. I used these when I had a travel trailer with a 15K BTU air conditioner for years. However, it is possible to run most 15K BTU RV air conditioners on a single Honda EU2000i, or even a 20A household garage circuit if you install a device on the air conditioner called the SoftStartRV. These are about $300- so a whole lot less expensive than a second Honda EU2000i with combiner. It works by modifying the startup current requirement for the compressors, delivering the same amount of power over a longer period of time flattening the current demand curve by 65%. I installed one on my Coleman Mach 10 15K BTH heat pump, and it works as advertised. I can run the AC on a single Honda EU2000, or a standard garage 20A 110v circuit. https://youtu.be/87cQe4-7pf8
 

Hollandt

Well-known member
Model: 2011 3300QS

I am looking for a generator to power the AC should we choose to rough it. How big do I buy? Cost, noise, and weight all factor in. The answer to this question, how big (KW) generator to buy, hinges upon what are the peak amps for the AC compressor?

Conventional wisdom is to buy 4kw min. This sounds like it would be over-kill. 1. The AC is on a 20a breaker (2.k kw at 120vac); 2. Domestic 15k BTU ACs, according to specs found at Domestics website, pull 2.8a for the fan and 13.2a for the compressor, for a total of 16 amps. 3. If AC startup amps exceed 20a, why doesn't the breaker trip?

So, what are the surge amps of the AC?

Thanks,
Mike
I have had two different RVs, both with Dometic 15K AC units. I have used my Champion 3400 Invertor generator with both with no issues. You are limited to about 28 amps but both RVs had no issue with the AC starting while in the eco mode. The generator will run about 6 to 8 hours at night with minimal AC usage on one tank of fuel. (about 1.5 gallons I think).
 
An air conditioner typically uses 1 amp for every 500 BTU. Hence, 5,000 to 15,000 BTU air conditioners normally require 10 to 30 amps. However, several elements, such as voltage and efficiency rating, may have an impact on amperage draw.
 
Last edited:

wdk450

Well-known member
From websearch:

How many amps does A Dometic AC 15000 BTU draw?


13.2

Nominal Capacity, BTU/hr: 15000. Compressor-rated load amps: 13.2. Fan motor-rated load amps: 2.7.
 
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