Question about AC soft start

[RobertE]

After reading Neal’s post I thought they were only if you were using a generator. If they will prolong the life I’m all for that.

I’m not super good at these things so how hard are they to install? I have a Dometic.

 

[Neal]

I will always have soft starts on my RV A/C's - I think the consensus is the A/C's do last longer with them. Yes, it reduces the startup shock for generator but also could allow you to run two units on 30A supply where you couldn't without the soft start. I had someone install my first one, mistake, they didn't do as well as @Chuggs guidance helping me install the second one. It's not hard, but I don't remember the details. I'm sure Micro-Air has instructions, probably plenty of YouTube about it now too to help.

 

[Kevin D Pem]

There is a falicy concerning what a soft start can do.

It is true that start current is drastically reduced. It is also true that start torque reduces when a soft start is employed. In turn if there are any loose windings less movement will lengthen winding life. Less start shock will lower stress fatigue on the components in the unit and associated mounting.

That is where advantages stop. Running current does not change. There is no co efficiency increase in any other way. Therefore, you may well start two AC units on a 30 amp system, but, your service will suffer. This is what Google AI has to say about power consumption of RV AC units.

A standard 120V RV air conditioner typically draws 12 to 16 amps during continuous running operation, but requires a massive 25 to 50+ amps during the initial startup surge. [1]

Running vs. Startup Amperage​

• Running Amps: Most standard rooftop units (ranging from 13,500 to 15,000 BTU) consume about 12–15 amps (roughly 1,500 watts) once the compressor is fully engaged. [1, 2]
• Startup Surge: The initial millisecond power spike when the compressor kicks on can easily reach 40 to 50+ amps. This brief spike is why standard 15-amp household outlets often trip when trying to start an AC unit without a soft-starter. [2, 3]

Variations by Unit Type​

• 12V DC Air Conditioners: Newer off-grid 12-volt units draw significantly different current, running around 18–35 amps on eco/low modes and climbing to 50–62 amps at maximum turbo capacity. [4]
• Units with Soft-Start Devices: Installing a soft-starter can reduce the heavy 45+ amp startup surge down to roughly 16–18 amps, allowing the AC to run safely on smaller 20-amp household circuits or portable generators. [2, 5]

If you are planning your power setup, let me know:

• What size generator or hookup service (30-amp or 50-amp) you are using
• If you plan to run other appliances at the same time

I can help you figure out if your power source can handle the load.

[1] https://www.microair.net
[2] https://www.facebook.com
[3] https://www.rvacunit.com
[4] https://outequippro.com
[5] https://www.youtube.com