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Generator for 189

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offgrid View Drop Down
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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Topic: Generator for 189
    Posted: 17 Jul 2019 at 5:47am
Originally posted by Babysaph

I can't imagine camping this time of year without being able to use the AC at night

Check your campground rules. Many, probably most, do not allow genset use at night, so planning on using a genny overnight to keep cool wouldn't be an option.


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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2019 at 6:08am
I've run (not started) my ac on my Honda 2K at 3000 feet and was Ok but I doubt it would have handled it much higher (all other ac loads off). A lot depends on how hot it is as the current draw of the compressor increases as the pressure differential between the evaporator and the condenser increases in hot weather. I took a couple measurements and on a 90 degree day with an inside temp of about 78-80 I was seeing 15.3 amps load from the a/c at 115V, or about 1760 VA. The continuous duty rating of the Honda is 1600 VA so I'm over the rating a little but it handled it OK. Here is a graph from Honda about altitude derate, it indicates 70% at 9000 feet, and that assumes rejetting the carburetor. 


So I wouldn't expect to be able to run the a/c at 9000 feet but when would anyone need to?

What really interests me with mcarter's report is starting, not running the a/c. My Honda (and most everyone else's reports I've read) wouldn't come close to starting the a/c without the easy start. So I'm curious what the difference is in mcarter's setup. Maybe his genny has a heavier flywheel that can carry it through the compressor startup surge? Just speculating...

But there is
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Post Options Post Options   Quote Tars Tarkas Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2019 at 7:41am
My generator has peak capacity of 2400 watts and it's never had a problem starting the a/c, without turning off the converter.  It can act a little iffy until it gets the a/c going, but that's it.

As for a/c at night, about the only way to count on that is to camp where there are electric hookups.

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Post Options Post Options   Quote mcarter Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2019 at 8:04am
+1 to Tars, I have started and run my AC with Converter ON, but it can be iffy, found that disabling the charge circuit takes the iffy out of start run.
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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2019 at 9:23am
Originally posted by Tars Tarkas

My generator has peak capacity of 2400 watts and it's never had a problem starting the a/c, without turning off the converter.  It can act a little iffy until it gets the a/c going, but that's it.

As for a/c at night, about the only way to count on that is to camp where there are electric hookups.

TT

Some folks report that 2400 watt gennies start the a/c OK, others don't, but it seems to be fairly unusual for a 2kw to do it reliably without some type of soft start system. On mine I notice that the second or third cycle once the a/c has built up the refrigerant back pressure seems to be quite a bit harder than the first cycle where both sides of the compressor are at the same pressure. 
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Post Options Post Options   Quote marwayne Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2019 at 1:05pm
Here is what did. My RV tec told me you can only run the AC on low, start fan, let run for about 5 min to cool the AC down then start compressor. Never had a problem, once the AC was running watts dropped down to 1480 
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Post Options Post Options   Quote podwerkz Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2019 at 1:25pm
Originally posted by offgrid


So I wouldn't expect to be able to run the a/c at 9000 feet but when would anyone need to?


All summer long in the Southern Rockies the daytime highs can reach 85 to about 100 degrees. Not everyday, but fairly often.

Nighttime lows are USUALLY in the 50s to 70s...but if one goes to bed early, and the camper has been in the sunlight all afternoon, the A/C (and generator) might be needed.

Checking the Cloudcroft weather today,7/17, the highs will be in the mid 80's, and elevation there is around 8600 feet.

Timberon NM will hit about 90 degrees, at about 7000 feet.

Grand Canyon Village in Arizona will hit close to 90 degrees today, at about 7000 feet, but it's normal to be close to 100 degrees on the Kaibab Plateau (7000-9000 feet elevations) where many RVs can be found in parks and campgrounds. 

Southwest of Carlsbad NM, up around 6000 feet at the BASE of the Guadalupes near Pine Springs in West Texas, it is often over 100 degrees all day long in the summer. 

Just a few examples, there are many more locations that are high AND hot.

I realize some of you are at lower elevations and might be un-aware that these higher elevations (especially in southern lattitudes) can be quite warm, so it really depends are where you are camping.

Just FYI, my current home base is about 3500 feet, and if I head west 100-300 miles, I quickly get into 4000-7000 feet elevations without even heading into any mountain ranges...that's just the average terrain elevations...and that open expanse of desert and foothills and rolling terrain (and campgrounds) can get REALLY hot in the afternoons in the summer.


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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2019 at 2:34pm
Originally posted by podwerkz

 
All summer long in the Southern Rockies the daytime highs can reach 85 to about 100 degrees. Not everyday, but fairly often.



Yeah, I know that afternoons highs can get up there even at relatively high elevations, I lived in AZ for many years and camped often on property on Humphrey's peak above Flagstaff at the 8800 ft elevation level. Not once did I feel any need for a/c there. It would get into the 90's on a hot day but very low humidity so quite comfortable. And always cool at night. A far cry from the sticky 80 plus percent humidity at 80 degrees all night long as we get here in the South. For me, as long as its cool at night I don't need the a/c. We're outside all day anyway while camping so its pointless to have it running.
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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2019 at 3:31pm
 
Originally posted by marwayne

Here is what did. My RV tec told me you can only run the AC on low, start fan, let run for about 5 min to cool the AC down then start compressor. Never had a problem, once the AC was running watts dropped down to 1480 

1480 watts or 1480 VA? Note that with an ac motor load you have a power factor less than 1 so watts do not equal volts x amps, it equals V x A x power factor. So the power factor of the a/c unit results in watts load being less than VA. 

And, knowing the inside and outside temperatures when you make the measurements is critical. The compressor load goes up, NOT down, as you run the a/c and these temps stabilize. That is because the pressure differential across the compressor is proportional to the temperature differential. The higher the temp difference the higher the pressure difference and the higher the current load. Those higher currents will translate over to higher startup currents the second and later cycles of the a/c.

I just measured mine again. Fan on low, outside temp 86, humidity 79%, inside temp 78, 114.6V, 15.0A, or 1719VA after it stabilized. Took about an hour.  It was about 12 amps right after startup.  A little less current than I got last year but its a bit cooler today than it was then. I don't have a true power meter available but podwerkz measured his power factor last year at 0.95 so if my unit is the same that would translate to 1633 watts. 

So, those of you who are running your a/cs on a 2kw without a soft start circuit, you  might want to try this to be sure you can stay cool on the genny:  pick a hot day in the 90's or higher, run the a/c with the thermostat set where you normally want it until it cycles off and then let it come back on on its own. See if it will start, stabilize and run on that second cycle. If it does, great. There might be something different about that generator or a/c unit from mine.  Mine wouldn't do it till I put in the easystart. 
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Post Options Post Options   Quote mcarter Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jul 2019 at 5:24pm
Offgrid,

I agree with your actions and assessment 100%. It gets to 90's here, and I have verified your conditions. If and when I can't pass my test I will apply the easy start. Until then I'm fine. AC is a low priority to me. I have other things I want a small genset to do, that's why I stayed small. Appreciate your input.
Mike Carter
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