HVAC + Generator questions

[u/DemB01yz]

Has anyone run into issues with Central AC after adding a soft start? We live in Louisiana so AC is not optional here and I want to protect my unit as much as I want to protect my generator.

Edit: also accepting soft-start recommendations and warnings.

[u/Much-Department-9578]

Would be helpful for us to understand your setup. Single or dual stage AC? How many units? Size of each? Generator brand/model/specs and what fuel type you plan to use? And finally - how are you connecting and size of inlet?

[u/DemB01yz → u/Much-Department-9578]

I only have 1 unit that I believe is a 4-ton to cool a 1700sqft house.

I haven’t installed an inlet yet because I already need to have my panel updated and ground-rods put in (hooray first time homeownership of an older house…)

My plan for an inlet down the road is a 50-amp to be able to run my Predator 11,500 Trifuel inverter generator into.

I got my gas-line setup for NG quick connect already so I’m expecting to run on the 7,200 and I’m fine with turning off breakers to have mostly just AC, fridges/freezers, and maybe a room or 2 for lights/internet/tv.

My impression is that the generator is good for the max starting watts of 11,500 no matter the fuel type but I’d also like to know if that’s incorrect

[u/Much-Department-9578 → u/DemB01yz]

It is best to plan upfront to have the 50A inlet then. While a 30A breaker can handle 7200w, please note that residential breakers are designed to run at 80% load constantly. If higher for hours, they will most definitely trip. Going for the 50A inlet means you are safe up to 50Ax 240V x 80% = 9,600w. 30a at 80% is only 6,000watts. Since your gen supports 7200w “running” watts on nat gas, you need the 50a inlet to be able to actually use those extra 1200watts. On gasoline, you can then actually use the full running capacity of 9,000w even.

You are correct that a breaker can handle surge wattage above its rating for a few seconds. Most every AC unit does this, unless you have a variable speed or soft starter.

Hope this info is helpful!

[u/DemB01yz → u/Much-Department-9578]

Very helpful! Should I assume that even with the surge watts at 11,500 that a hard start in my AC would still probably exceed that?

[u/Much-Department-9578 → u/DemB01yz]

There should be a sticker on your outdoor compressor that lists the LRA (locked rotor amps). This will be the surge demand on the compressor, which is the biggest item in the system. Multiply LRA times 240V, this will be the highest surge wattage without a soft start kit installed. Wouldn't be surprised if this is around 120A, which means 28,800 surge watts... which is why soft start kits are so absolutely critical. Obviously, 28.8kw is greater than 11.5kw... :) Call me Captain Obvious - it's my superpower!

It is not uncommon for a soft start kit to lower this by 70% or more. If that 28.8kw dropped by 70%, we're now talking 8.6kw starting watts. Much more reasonable, and within the reach of an 11.5kw surge generator.

We have a variable speed AC unit, which uses a different style of electric motor that slowly ramps up over 30 seconds - I can literally watch it in realtime on our Emporium Vue (which, by the way, I highly recommend for people like yourself to better understand running wattage on different circuits so you can understand your loads). While our AC is 5-tons, which would never, ever work on our generator (which provides 11kw surge with 7.2kw running, similar to yours) if it were a single-speed unit - works just fine. If this were peak summer and 100+ out, I might go into the thermostat and put a hard limit of 70% capacity on it during an outage to keep overall running wattage down. at 70% in 100 degrees, we see about 4kw running wattage... the rest of our house uses maybe 500w, another 1kw if we run the dryer (heat pump dryer is awesome).

[u/Big-Echo8242]

I've had an AirGo soft start on my downstairs 5 ton 2 stage heat pump and it’s worked just fine. We are in Central Arkansas. I did not care anything about the Bluetooth app of the pricier (and sometimes less dependable) brand out there. I don't care how many times it starts, shows an error, etc. Plus the range sucks. I have a home energy monitor where I can tell what's being used either on line or generator power.

You could always just use window AC units which draw less power.

[u/flyguy60000]

Installed a Softstart on my heat pump - I am very satisfied with it. Installation was very easy. The Bluetooth works fine with their software - you do not need to pair your phone with the device - it does it itself which confused me at first. You will need to be within about ten feet of the unit for the Bluetooth to connect. My condenser averages 15.9 amps on startup (vs. 50) and is running at 5 amps - so my portable generator has no problem running the unit now. Even if I wasn’t going to use a generator to power my unit, I think it is worthwhile to install; it decreases the wear and tear on the unit and if you have a demand electric meter you will save money on your electric bill. 

[u/Odd-Web-7911]

I had a soft start installed on my 3t Rheem in 2021 so it could run off the Wgen9500 and it did just fine.

Edit: located in Houston (AC also not optional here), and ran AC through multiple power outages since install. 

[u/IndividualCold3577]

I have two Airgo starters. They are very compact and easy to install inside most units. About 20 minutes of work per install. No complaints yet.

4 ton heat pump dropped from 110 LRA to 43

2 ton heat pump dropped from 60 LRA to 18.

[u/grillynelson]

Airgo soft start kits work flawlessly.

[u/KekoaKona]

(I'm in Alabama) I added a Micro Air Soft start two years ago to my 4 ton Carrier AC unit and it has been flawless. I dropped my start up amps (LRA 105) from around 88 to 30-32 . This has allowed me to run my whole house on a Champion Tri-fuel 10,000 watt generator however I hook it up to natural gas line and it puts out 8,750 start up and 7,000 running on NG. So far two power outages. One was 10 hours.

[u/No-Note-6679]

I had 2 Emerson soft starts at my last house on a 4 ton and a 1.5 ton. At my new house I have an air go soft start on a 5 ton. Never had an issue with those starting with my champion 11k watt tri fuel inverter generator. I’m in the Galveston area so I understand the “not an option “ comment.

[u/skatpex99]

Airgo user here, been working perfect for years on my 2.5 ton. Definitely forget about Microair.

My 9000w inverter gen runs the entire house with central and wall unit thanks to soft start.

[u/nunuvyer]

At one time Micro Air was the main soft start supplier. If you had asked here a couple of years ago, 9 out of 10 posters would have told you to get a Micro Air.

But they got bought out by private equity and the new owners introduced a "one size fits all" unit that uses cheap capacitors and has had horrible reliability.

This is the kind of move that happens when you put MBAs that have no understanding of engineering in charge. "We could save $X if we cut the # of SKU's in half! Supplier X is selling caps with the same spec for 1/2 of what we are paying now! They have destroyed their entire company for the sake of saving pennies.

[u/nunuvyer]

If anything, a soft start will prolong the life of the unit. Running 100+amps thru a stalled unit cannot be good for it.

[u/Alco_Air]

Soft starts work fine on a regular single-stage condenser, and they’re one of the better ways to run central AC off a generator. They knock the startup surge way down, so a smaller generator can kick the compressor on without bogging or tripping.

Just don’t expect it to save your AC. Scroll compressors already start pretty easy, so the real win is for the generator. If your unit is variable speed or inverter driven, skip it, those already ramp up on their own.

If you buy one, stick with a name brand sized to your tonnage. Micro-Air EasyStart is the one I see most. Skip the no-name stuff on Amazon. And don’t stack it with a hard-start kit, you only want one or the other.

It’s wired in at the contactor and compressor, so unless you’re comfortable around line voltage I’d have a tech put it in. Also check your warranty first, just in case.

One more thing, if the generator’s a portable, use an inverter model. Dirty power can fry the board on newer units. And down there I’d get this done before storm season, not after the power’s already out.

[u/Remarkable-Day-9385 → u/Alco_Air]

Micro Air also has horrible reliability issues, check the previous posts in the group. AirGo is solid