AC Hard start additions

[popeyemth]

Any new developments (in the last couple years) to the problem of starting/running a Dometic 13500 AC unit with a generator?
Thanks,Mike

[deltabravo]

...the Micro Air Easy Start is a great solution.

Order direct from MicroAir and use discount code of FATE to get 10% off

I have one and have moved it to my 3rd RV.
My EU2200i has ZERO issues starting and running my rooftop A/C

[3_tons]

Mine is a Coleman Mach 1 P.S. 11kbtu with soft-start, and the only problem I’ve had with either the Honda 2000 or 2200i was that they wouldn’t run the air conditioner (once Coleman warmed) while in eco-mode…Turns out (after much hand wringing - lol) that the root cause was due to the ‘pass-thru’ type inverter’s refusal to pass-thru eco-mode…Adding another ATS Switch (and a dedicated power cord) between the air conditioner and inverter was the fix :)…Genny now in eco runs the air conditioner without a hitch…I’ve now happily joined the “I run in eco-mode” crowd…:)

3 tons

[ktmrfs]

2oldman wrote:

ktmrfs wrote:
How other 2000ish generators do, don't know. Some probably would work just fine, others likely are like the old honda 2000 at higher altitude.

My old Honda 2k really struggled running my Briskair 13.5. Two, no problem.

My 2200 runs it ok, but I just don't like working it that hard.

My experience is similar to you. the 2000 motor will give rated output at sea level and 75F or so. But drops off quick with temperature or altitude. End result is overload with what one might think are draws within rated output.

I am impressed with the 2200 by comparison. I think honda made a good choice by increasing engine displacement by about 25% IIRC. Now you can get even max rated output and 7000ft or so.

But without the micro air, the 2200 struggled to get the AC started at low altitude, and not much luck at high altitudes. So without the micro start still needed the 2000 in parallel to reliably run the AC.

[2oldman]

ktmrfs wrote:
How other 2000ish generators do, don't know. Some probably would work just fine, others likely are like the old honda 2000 at higher altitude.

My old Honda 2k really struggled running my Briskair 13.5. Two, no problem.

My 2200 runs it ok, but I just don't like working it that hard.

[ktmrfs]

Gdetrailer wrote:

TurnThePage wrote:
So... Are you saying that soft start devices harm or stress the A/C? Hard start caps also reduce that "thump" that happens at the moment the compressor fires up.

I totally agree that a properly sized generator should be used, but I've never heard from any reputable source that there is any harm in using hard start caps or soft start electronics.

If the gen voltage sags well enough before tripping a breaker or sending gen into overload, absolutely.

Softstart devices which "ramp up" voltage over time in an attempt to break loose the locked rotor are doing the very same thing that everyone on this forum crys foul over with sagging campground voltages by electronically reducing voltage going to the compressor then ramping it up (IE "soft start") over a short period of time.

There is no "free lunch"..

Additionally, the "add ons" may work OK in your driveway in 80F temps but add in elevation at your campsite and more heat and you have a good chance that it isn't going to work reliably or at all.

Why bother messing around with a undersized gen and hoping it will work fine.

For those scared of 50lbs more weight, get creative. You can buy a nice set of light weight aluminum fold up ramps and wheel it right on. You can get portable lift tables with wheels which are nice, a little creativity you can find quite a few ways to safely hoist or lift a 100 lb gen..

Heck for myself, I use my tractor front loader to lift and place my 100 lb 4Kw gen into my truck bed.. I also have used 10ft boards with cheap aluminum ramp ends to ease the gen on to the tailgate..

I do cheat a bit and leave the gen in the truck bed and run it when needed..

my experience with a Coleman Mach III 13.5K BTU AC non "high efficency", honda 2200, micro air easy start, at 7,000 ft altitude, outside temps near 100F. Density altitude near 8500ft.

AC starts smoothly and quickly with generator in eco mode, doesn't ramp up to full rpm. Had the converter off. Next, how much "spare" power could the honda 2200 supply at 7,000ft when outside temp was near 100F and AC running? changed the fridge to AC from propane adds about 300W. Genny still running not in overload. Voltage from the generator still at 122V. turned on the converter with the batteries near full charge, generator still running hours later still at 122 v

measuring generator output voltage during startup with a NIST traceable meter that will catch 10ms windows shows the lowest voltage during startup is 115V RMS, actually higher than some campground voltages!

Measuring running current with a calibrated clamp on meter shows I'm still below the continous current rating on the 2200 on AC only. So, given that I doubt I'm overstressing the generator.

Now a honda 2000 will overload at about 3,000Ft. The 2200 in addition to have 200more VA, has a 25% larger motor so in a sense honda has overcome the altitude derating of most generators.



BTW the micro air easy start has a "overload" sensor that is quicker and more stringent on overload than the honda. It will kick out the AC if it senses an overload instead of waiting for the generator to kick out, then after 10 minutes try a restart. As a test I turned on another 500W load to see what the micro air would do sense that would overload the generator. AC quit, honda dropped down in rpm to supply the other loads. turned off the 500W load, 10 minutes later AC came back on.

next tried the same thing but this time turning on the microwave. Same results, AC quite, generator kept the microwave running.

Conclusion: 1) My honda 2200 will run a coleman MachIII with easy start at 7000ft altitude continously without exceeding continous rating. 2) Micro air does an excellent job of detecting possible overloads and acting as a load shed device shedding the AC under overload.

How other 2000ish generators do, don't know. Some probably would work just fine, others likely are like the old honda 2000 at higher altitude.

[philh]

Gdetrailer wrote:

Heck even just the continuous running current of a 13.5K RV A/C is roughly 13A and in extreme hot weather can rise to nearly 15A.

I measured amp draw of my 15k AC, and running watts was a whopping 1200, aka 10 amps. My 2500 watt generator had no problems once I installed Microaire Easy Start

[Gdetrailer]

TurnThePage wrote:
So... Are you saying that soft start devices harm or stress the A/C? Hard start caps also reduce that "thump" that happens at the moment the compressor fires up.

I totally agree that a properly sized generator should be used, but I've never heard from any reputable source that there is any harm in using hard start caps or soft start electronics.

If the gen voltage sags well enough before tripping a breaker or sending gen into overload, absolutely.

Softstart devices which "ramp up" voltage over time in an attempt to break loose the locked rotor are doing the very same thing that everyone on this forum crys foul over with sagging campground voltages by electronically reducing voltage going to the compressor then ramping it up (IE "soft start") over a short period of time.

There is no "free lunch"..

Additionally, the "add ons" may work OK in your driveway in 80F temps but add in elevation at your campsite and more heat and you have a good chance that it isn't going to work reliably or at all.

Why bother messing around with a undersized gen and hoping it will work fine.

For those scared of 50lbs more weight, get creative. You can buy a nice set of light weight aluminum fold up ramps and wheel it right on. You can get portable lift tables with wheels which are nice, a little creativity you can find quite a few ways to safely hoist or lift a 100 lb gen..

Heck for myself, I use my tractor front loader to lift and place my 100 lb 4Kw gen into my truck bed.. I also have used 10ft boards with cheap aluminum ramp ends to ease the gen on to the tailgate..

I do cheat a bit and leave the gen in the truck bed and run it when needed..

[2oldman]

mr_andyj wrote:
Just getting a bigger gen is not always an option for everyone.

Answers aren't supposed to be applicable to everyone always. We don't even know what kind of generator the OP is talking about, but trying to run air from an undersized generator is not the best idea.

[TurnThePage]

So... Are you saying that soft start devices harm or stress the A/C? Hard start caps also reduce that "thump" that happens at the moment the compressor fires up.

I totally agree that a properly sized generator should be used, but I've never heard from any reputable source that there is any harm in using hard start caps or soft start electronics.

[Gdetrailer]

mr_andyj wrote:


forums are full of
"just take it to the dealer"
"have a mechanic fix it"
"if you have to ask then you are not qualified to work on it"
"spend some of your money you cheapskate"
answers
None are helpful to the OP

Forums are also full of folks attempting the impossible.

As one poster mentioned, typical RV AC can have as much as 50 Locked Rotor Amp draw for a second or two. There is only so much that a piddly 2Kw gen can do. That 50A locked rotor amperage is more than TWICE the surge rating on a Honda 2200i ( specs HERE )

" AC Output 120V 2200W max. (18.3A), 1800W rated (15A) "

Heck even just the continuous running current of a 13.5K RV A/C is roughly 13A and in extreme hot weather can rise to nearly 15A.

Soft starts are not magical creatures that make amperage come out of thin air and folks are being encouraged to not only run on a horribly undersized gen for the job but to sink more money into devices which help you abuse your A/C and your gen..

A $300 add on to a $800 A/C in order to fully abuse your $1200 gen? :E

So, you now have $2300 worth of potential collateral damage all so you don't have to carry an additional 50 lbs worth of gen.. :h

There are easy ways to get around the moving/lifting additional weight of a larger gen and you don't have to sacrifice your A/C or your gen in the process.

[mr_andyj]

Just getting a bigger gen is not always an option for everyone. The small gens have advantages and for some it is a small gen or no gen. Given that, the question is how to run the AC off the small gen, not "just get a bigger gen"

The only thing new is the electronic soft-start that has come on the market instead of just adding a capacitor. Capacitors help, but only give you a boost of power that may or may not be enough to do the job, where the soft-start will make the motor start slower and require less of a power surge. The electronic ones are expensive compared to a $20 capacitor.

forums are full of
"just take it to the dealer"
"have a mechanic fix it"
"if you have to ask then you are not qualified to work on it"
"spend some of your money you cheapskate"
answers
None are helpful to the OP

[ktmrfs]

wing_zealot wrote:
I'd rather put the $300+ it cost for a micro-air easystart into the ability to generate more amps. Much more useful around the house to have the ability to generate more amps than to have a one trick pony. For me, a micro-air may be the cheaper solution but its not the best use of my money. I'd invest my money towards the ability for a wider array of uses; even if at first blush it cost more; YOMV.

for us, since we already had honda 2200 and a honda 2000, the micro air was our choice. Now we seldom need to parallel the genny's saving time during setup, and in about 90% of the times we need are off grid, only need to bring along on 50lb genny. Worth the $ for us.

If it was a case of no genny and deciding what to do it would for us be a decision of how much more weight am I willing to lift to get a bigger genny out of the truck and how much it costs vs. micro air cost and lighter genny.

Ends up being a personal decision on what works best for each individual.

[wing_zealot]

I'd rather put the $300+ it cost for a micro-air easystart into the ability to generate more amps. Much more useful around the house to have the ability to generate more amps than to have a one trick pony. For me, a micro-air may be the cheaper solution but its not the best use of my money. I'd invest my money towards the ability for a wider array of uses; even if at first blush it cost more; YOMV.

[philh]

microaire easy start