Micro Air

[StirCrazy]

Hi, just looking for input from people that have them on their effectiveness. I am thinking of getting a portable genny for the 5th wheel for those times that I need an AC and don't have power. I have a 15000BTU dometic AC, and I must figure out what size genny I need also.

As some of you know I personally hate the noise they make, so it must be quiet and really won't be used for anything else as my solar can do everything else. the other issue I have is there has only been 4 days in the last 5 years of camping where I needed an AC when I was boondocking, so I am really torn weather I need a genny or just see what it would take to be able to run on solar, but I think it's too tall of an order for solar.

[3_tons]

3 phase motors don’t require capacitors to get the rotor to spin, since multiple alternating phases do the trick - not so with single phase…Voltage sag is the result of the difficulty ‘single phase’ has to motivate the rotor to spin…Adding an autoformer may help to slightly boost the voltage (which may help preserve the windings), but doesn’t alter this hard single phase dynamic…Consider too that a quarter of a second response time still equates to about 15 full AC wave cycles, which is like running molasses compared to a fast acting capacitor or a MicroAir soft start device, which nowadays are a common upgrade in the HVAC industry, even including now capacitor free blower motors - check your blower motor…

Besides high cost, this is why we don’t see sluggish autoformers featured on single phase motors…JMO

3 tons

[pianotuna]

theoldwizard1 wrote:

Here is the short electrical engineering of what is happening.

All electric motors that power heavy loads have a "starting capacitor" (there is a mechanical switch that cuts out the capacitor once the motor is "up to speed").

When a capacitor is fully discharged (before the motor starts), it "looks like" a short circuit when power is first applied. Additional/larger starting capacitors just make this worse. The MicroAir actually "limits" (slows down by a few hundred microseconds) how fast that capacitor charges up eliminating the current spike.

What is in the MicroAir that limits the surge? I do know they had a replacement for the 'hard start' kit on the oem air conditoner.

Thanks for this information--it explains why the autoformer cuts in so fast without MicroAir, and why the autoformer doesn't with the MA in place.

[pianotuna]

3 tons wrote:

... my view is that the Autoformer is no substitute for a Micro-Air, because of it’s slower response time, a characteristic of it’s slower transformer based induction response time versus the MicroAir’s near light-speed response mosfets…

My tests of the autoformer show these results.

The back yard experiment was at my brother's cottage with a 50 amp outlet. It is in a resort area fed by an ancient grid connection. The autoformer would cut in perhaps 1/4 second (or less), before the airconditioner motor even finished getting up to speed.

Once I added the MicroAir, the autoformer did not cut in any more but that meant the air conditioner ran at a barely acceptable 107 volts, rather than the 112 on the autoformer. The motor speed was lower as well.

I did find a work around by fudging the cut in voltage for the autoformer upwards from the factory setting to 113 volts.

The sequence now appears to be fan start, time delay, compressor start, autoformer cut in. Before it was fan & compressor start with almost instant autoformer cut in.



My view is the MicroAir is no substitute for an autoformer. It does NOTHING to raise the voltage.

Running from the generator the microair seems to make no difference. That is with the Magnum generator input throttled to 23 amps (which is the output from the generator).

[3_tons]

theoldwizard1 wrote:

3 tons wrote:

... my view is that the Autoformer is no substitute for a Micro-Air, because of it’s slower response time, a characteristic of it’s slower transformer based induction response time versus the MicroAir’s near light-speed response mosfets…

Here is the short electrical engineering of what is happening.

All electric motors that power heavy loads have a "starting capacitor" (there is a mechanical switch that cuts out the capacitor once the motor is "up to speed").

When a capacitor is fully discharged (before the motor starts), it "looks like" a short circuit when power is first applied. Additional/larger starting capacitors just make this worse. The MicroAir actually "limits" (slows down by a few hundred microseconds) how fast that capacitor charges up eliminating the current spike.

Rather than to modulate the starting capacitor, the MicroAir replaces it…

3 tons

[theoldwizard1]

3 tons wrote:

... my view is that the Autoformer is no substitute for a Micro-Air, because of it’s slower response time, a characteristic of it’s slower transformer based induction response time versus the MicroAir’s near light-speed response mosfets…

Here is the short electrical engineering of what is happening.

All electric motors that power heavy loads have a "starting capacitor" (there is a mechanical switch that cuts out the capacitor once the motor is "up to speed").

When a capacitor is fully discharged (before the motor starts), it "looks like" a short circuit when power is first applied. Additional/larger starting capacitors just make this worse. The MicroAir actually "limits" (slows down by a few hundred microseconds) how fast that capacitor charges up eliminating the current spike.

[theoldwizard1]

3 tons wrote:
“Well you look at them with a proper scope you feel the need to change underwear they are that scary”……

Now that some advice that’s well worth following 😉 !!

Brushless generators are notoriously BAD ! Stay away from them !!

[StirCrazy]

Cptnvideo wrote:
It's 11:45 MST, A/C just kicked on. Solar is putting out 86 amps and batteries are putting out 45 amps. So, 131 amps to run A/C, res fridge, TV, misc. In 2 hours time assuming the A/C runs 50% of the time, I would consume 150 ah. But my solar would put out 172 ah during those 2 hours (mid-day).

StirCrazy, I agree with you - I hate to listen to a generator. Could you add more solar for what you would spend on the soft start? For my system, the only difference between running the unit with soft start vs one of the units without is the Dish receiver re-starting.

I am going to add more solar; do I have enough space to add that much haha... Right now, I have three 160watt panels (480watts total) and a pwm controller. The 5th is getting upgraded to around 800 to 1200 watts depending on how I can fit things and MPPT. My main reason is so that I can run the bar fridge in the outdoor kitchen when camping and keep the beverages out there, can't quite do it right now but I did test it during that heat wave so that couldn't have helped my testing... but I am also going to switch to LFP batteries in the 5th as soon as my battery savings account has enough money in it 😉 I am not sure what level of solar you need to run an AC as I haven't ever thought about that. Remember it's only one weekend since 2016 that I wished I had a genny when boondocking.

[Cptnvideo]

It's 11:45 MST, A/C just kicked on. Solar is putting out 86 amps and batteries are putting out 45 amps. So, 131 amps to run A/C, res fridge, TV, misc. In 2 hours time assuming the A/C runs 50% of the time, I would consume 150 ah. But my solar would put out 172 ah during those 2 hours (mid-day).

StirCrazy, I agree with you - I hate to listen to a generator. Could you add more solar for what you would spend on the soft start? For my system, the only difference between running the unit with soft start vs one of the units without is the Dish receiver re-starting.

[Cptnvideo]

Nice post on 4/15, Itinerant1.

I will post some numbers after my A/C kicks on. But in the meantime.... I have 3 A/Cs with the middle one also being heat pump with "soft start". While unplugged, the soft start unit doesn't disrupt anything at start up, but if I try that with one of the other 2, TV and microwave clock stay on but Dish receiver goes to re-start. Obviously, the Dish receiver doesn't like that very brief surge.

[3_tons]

Doug said:

“ The "surge" is a split second. You watch the ampmeter(digital) and it is so quick you have a hard time seeing the upper range. Doug”

*************

Correct, the true surge level (often 4-5 times run watts…) occurs so fast (milliseconds) that a Kiii-a-Watt meter or a VOM is unable to measure it…

In a similar sense, having both a Micro-Start and a Hughs Autoformer, after a bunch of hands-on ‘trail and error’ test (rendering only ‘one off’ success), my view is that the Autoformer is no substitute for a Micro-Air, because of it’s slower response time, a characteristic of it’s slower transformer based induction response time versus the MicroAir’s near light-speed response mosfets…

Thus, while there IS a place for autoformers, their real design utility is to help resolve dreaded summertime voltage sags when in campgrounds…Since I almost never camp in CG’s, if anyone needs one (still as new) just PM me…

3 tons

[dougrainer]

StirCrazy wrote:

dougrainer wrote:

StirCrazy wrote:

dougrainer wrote:
15k AC will pull 1600 to 1800 watts. About 14.0 amps. So, base the size of your Genny on that. Doug

Surge start up, about 1900 watts

thanks Doug. is that with the micro air or with out?

That is standard SPEC. No Micro air or a Hard start kit on the AC. Doug

that seams low for a surge, but it does have capacitors so it's feasible... I might have to measure mine and see what it does go to...

The "surge" is a split second. You watch the ampmeter(digital) and it is so quick you have a hard time seeing the upper range. Doug

[StirCrazy]

dougrainer wrote:

StirCrazy wrote:

dougrainer wrote:
15k AC will pull 1600 to 1800 watts. About 14.0 amps. So, base the size of your Genny on that. Doug

Surge start up, about 1900 watts

thanks Doug. is that with the micro air or with out?

That is standard SPEC. No Micro air or a Hard start kit on the AC. Doug

that seams low for a surge, but it does have capacitors so it's feasible... I might have to measure mine and see what it does go to...

[StirCrazy]

pianotuna wrote:
Hi,

I don't like my Micro-Air Easy Start.

Do you care to elaborate on this to make it useful information to me?

[pianotuna]

Bobbo,

The micro-air makes just enough difference that the autoformer doesn't cut in. That leaves my air conditioner running at a barely safe voltage.

[Bobbo]

pianotuna wrote:
ktmrfs,

I had better results using an autoformer.

There is no reason you can't use your autoformer AND the MicroAir at the same time. I do.