A soft start ramps the air conditioner's compressor up instead of hitting it with full line voltage, so the brief surge at startup is much lower. Makers put that reduction at up to 70 to 75 percent. It does not change what the AC draws once it is running.
Soft Starts for RV Air Conditioners: What They Change and What They Do Not
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At a glance
- What it cuts: the starting surge only, by up to 75 percent per Micro-Air and Coleman-Mach, up to 70 percent per SoftStartRV.
- What it does not cut: the running draw. Micro-Air puts a 15,000 BTU rooftop unit at about 1,800 to 1,900 watts while it runs.
- Who fits it: Dometic highly recommends a certified electrician; Micro-Air and SoftStartRV allow owner installation.
On this page (7)
What does a soft start do?
It eases the compressor into starting, so your supply sees a smaller jolt. Micro-Air describes gradually increasing the voltage and current to air conditioner compressors, which significantly reduces the initial power surge; a factory start capacitor gives full voltage and current at once.
Dometic's SmartStart manual says the lower starting current reduces or eliminates flickering lights, brown-outs and nuisance breaker trips. Both makers remove or disable the factory start capacitor, PTCR or start relay when the soft start goes in.
Tip: The soft start learns the compressor, not the other way round. Micro-Air says EasyStart learns over the first five starts, ideally on a 20 amp or larger supply with other RV loads off, and needs a relearn only rarely, such as after the run capacitor is replaced or a move to another AC. Dometic's unit needs no user input.
What it cuts, and what it does not
It cuts the starting surge, not the running load. Micro-Air and Coleman-Mach give up to 75 percent, SoftStartRV up to 70 percent, and Dometic publishes no figure.
No maker gives a running-watts saving; only Coleman-Mach's Soft Start Series page claims lower power use while the AC runs, with no figure. So the running load still has to fit your supply, which is a generator sizing question.
Small generator or 30 amp shore power
It helps the AC start on a weaker supply, as the makers claim it. Micro-Air says the EasyStart lets you run the AC on limited utility power or medium-sized portable generators. SoftStartRV claims you can start one AC on a small generator or a 15 amp house circuit, and start and run two ACs on one 30 amp hookup with one unit per air conditioner. That two-AC claim is SoftStartRV's alone.
A weak pedestal can still beat it: Micro-Air says a compressor may refuse to start if line voltage sags below 108 VAC.
The three units owners ask about
| Unit | Fits | Setup | Installed by |
|---|---|---|---|
| Micro-Air EasyStart | Claims every RV air conditioner; wiring diagrams published by brand and model | Learns the compressor over the first five starts | Yourself or a dealer |
| Dometic SmartStart | Most 120 VAC RV AC units; manual covers Blizzard NXT, Brisk II, FreshJet 3 mechanical, FreshJet 5, Penguin II | No setup step printed; operates without user input | Qualified personnel; certified electrician highly recommended |
| SoftStartRV SSRV3T3 | Marketed as fitting any rooftop AC; one wiring diagram per model | No learning cycle described; a 30 minute run-in check after wiring | Marketed as DIY; otherwise a dealer, AC tech or RV electrician |
From each maker's documents. SoftStartRV's figures, as in its SSRV3T3 sell sheet, are its own marketing claims; Micro-Air's and Dometic's documents are firmer.
Fitting one
Fitting one means working in the AC's electrical box on the roof. On Dometic's Blizzard NXT that means removing the shroud, disconnecting the compressor wires and starter capacitor, and clamping the device to the fan motor. Micro-Air's method feeds only the compressor's R wire through the soft start.
Makers differ on who should do it. Dometic highly recommends a certified electrician. Micro-Air allows owners but warns of fatal shock and points the uncomfortable to a dealer, electrician or HVAC installer. SoftStartRV markets its unit as DIY.
We would put it plainly: this is 120 V work on a roof, with capacitors that hold a charge after shutdown, so it is a job for a qualified technician unless you are confident with mains wiring. Dometic's own step is to kill power, wait five minutes, then confirm with a multimeter that the capacitor is discharged.
Tip: Check for a hard start kit first. Micro-Air notes previous owners sometimes fit one, and it has to come out with the factory start components. Refrigerant tubes puncture easily, so take care with screws and drilling.
The trade-offs
- Restart delay. Switch the compressor off and straight back on and it waits a few minutes: Micro-Air gives both three and five; SoftStartRV gives 3 to 5, to let the compressor equalize.
- Duty cycle. Dometic rates the SmartStart for up to 15 starts an hour at rated ambient temperature.
- Warranty. Dometic's AC warranty excludes damage caused by accessories not made and marketed by Dometic, and Airxcel's excludes damage caused by non-Airxcel parts. Neither says a soft start voids coverage outright.
Common questions
Is a soft start worth it on an RV air conditioner?
Yes, if your problem is the moment of startup: tripped breakers, dimming lights, a generator that stalls as the compressor kicks in. No, if the AC starts fine but your supply cannot carry the steady running load.
Does a soft start void the air conditioner warranty?
Not outright. SoftStartRV's FAQ says its unit should not void coverage but suggests removing it before a service-contract claim. Micro-Air offers its own two-year compressor warranty, for failures its soft start causes, on ACs less than six years old, registered within 30 days, labor not included.
Are there downsides to a soft start?
Day to day, only the pause before a quick restart. Also, a handheld clamp meter often cannot capture the starting peak, so Micro-Air suggests judging the install by simply running the AC on your generator.
Does a soft start help on 30 amp shore power?
It helps with the surge that trips the pedestal breaker as the compressor kicks in. Everything else on a 30 amp hookup still counts against the same supply, because the running amps do not change.