MICRO-AIR EasyStart FLEX 398 - Bluetooth Soft Start Kit for Home Air Conditioner, RV & Commercial Use, Works with Generators, Reduces Power Surge, Efficient Start-Up - Up to 6 Tons

Bought this several years ago cause wanted to put a soft start on ac for a generator use. Saw this on a YouTube video had good reviews and install was easy. So for the last couple years I had it on my ac. No issues so far and the ac start up is a lot quieter and hopefully less wear on compressor. It’s Bluetooth so I get feed back on my ac unit and if I ever need help can call the company and see what the issue is. But so far it’s been good.

Very pleased! I do suggest changing your capacitor when you add anything like this to your HVAC system. They do go bad just like light bulbs or batteries as an example. Also make sure all connections are secure as this will cause failure on many components. Installation ease will vary on units. Following the instructions is a must. If you’re not sure have a licensed electrician/HVAC technician do this for you. My 4 ton unit had a 98 amp inrush, now after it’s 26 amp after EasyStart learning curve (chose to do the 7 starts). This is an efficient energy savings. Had no problems with my Heat pump prior to installation of the EasyStart except with my 13000 watt generator. The generator will now start my system from eco mode. Size of the EasyStart forced me to mount externally. If you mount it with screws, exercise caution so you don’t drill or run a screw into any components behind it. Please don’t add this to your unit if you have a problem as this is a start assist device. It will probably help to some degree but can’t fix preexisting problems and will have the potential to damage your EasyStart. When the unit starts now on commercial power, I have no flickering lights in my house (been that way since it was installed). Slightly lowered my running amps. So, between inrush and running amps I believe it’s a good value for the money. Take amperage readings before and after to see for yourself. Downloaded the app and compared its readings to Fluke meter. Pretty much spot on. Time will tell the rest. Hope this helps with your decision to purchase.

Bought this soft-start until to allow us to run our AC off our portable generator (8.5Kw running watts on propane). Haven't test that yet, but will soon. So far, running normally off line voltage, I'm impressed. I went from 167 start up amps to 32 start up amps. That is an 80% decrease! Within 7 learning cycles, this unit decreased startup amps from 54, to 44 to 38 and finally settling at 32-33 amps. I mean, wow! I did replace my start/run cap with this one, which is an OEM-spec replacement: https://www.amazon.com/dp/B00S033F9C?ref=ppx_yo2ov_dt_b_fed_asin_title I read that it's a best practice (though not mandatory) to replace your start/run cap in conjunction with installing this soft-start. The start/run cap takes a beating during normal operation and if yours is more than a few years old and/or you live in a very hot climate like we do, it's recommended to replace it. I replaced the cap and ensure the AC started normally before installing the soft start. I've only had the product installed for a few days on our Carrier 5-ton heat pump/AC model CH14NB060-A, but so far, so good. I'm comfortable working with high voltage wiring but don't know much about AC/heat pump units. So, I did my homework to ensure I didn't make any very stupid and very expensive mistakes. I have to say that Micro-Air's customer service is really great. The wiring diagram they had on their website for my unit was confusing to me and I couldn't really understand it. I emailed customer service and within a few hours I had a customized response from a real human being. He sent me the attached wiring diagram and clearly explained in the email that even though this was not my make/model, the wiring was identical and to just follow the diagram. He was right. The install took just a few hours, taking my time. I had to mount the unit outside of my AC compressor unit as there wasn't enough room inside the control box for the soft start unit. Even if you have to pay an AC technician or electrician to install this for you, it's totally worth it. The fact that we can now run our AC on our generator is a game changer for us.

I started the microcar journey 18 months ago and it’s been disappointing. I purchased a soft start for my 5 ton unit in summer of 2025. It work maybe six times and then just slowed inrush current down to only allow condenser fan to kick on. Compressor would only give a fault code and never come on. Micro air was no help. I wired things back up as normal and the unit worked fine. Six months later I noticed the newer Flex version. It shows it’s rated for 7 ton units. I bought two: one for my 3 Timon upstairs unit and another for the five tone downstairs unit. Upstairs unit has worked fine since it was installed in September of 2026. Now that we are in 100+ temps, the 5 ton downstairs unit is failing again. Same over current fault. Reads an inrush of 89amps and won’t allow the compressor to come on. Last I checked, it had over 700 failed attempts. That means for the entire duration of it trying to come on, the compressor fan and the blower unit far the house just run. Probably hasn’t helped my electric bill. I disconnected the soft start and reconnected it, and it worked for a day. Then, started with the faulty codes again. The failed attempts have caused the insulation on my wires at my contact relay discolor and melt. Very concerning because this could lead to even bigger issues My ac unit has a LRA of around 110a. This soft start should be able to handle close to 160 amps with it being rated for 7 tons. From someone who’s purchased 3 of these units, I’d say they still have work to do for the larger units.

Great product. Inrush amps on my Trane 2 ton went from 88amps to 33 after the fifth restart. The compressor no longer slams into drive but comes on smoothly after the initial fan start. Super easy to install and it fit nicely under the access panel.