Effects of Soft Start on an AC Unit

You enjoy going away in your RV during the warmer summer months – but how to deal with the dreaded RV AC unit? 

It’s noisy, guzzles away at energy, and requires a massive surge of power to start up, despite the running torque then dropping significantly. 

The answer to all your issues is to use a soft start. 

The main purpose of a soft start is to reduce the strain put on the motor during the typical power-up phase. To do this, a soft start will slowly and gradually begin applying increasing voltages to the motor, which provides a smooth acceleration of power rather than a sudden burst of power that risks damaging the motor and machine as a whole.

Because a soft start offers a smooth and steady linear slope of power, it reduces the overall wear and tear on the motor’s circuits, which prolongs the machine’s overall lifespan. 

In this article, we’re going to be covering the positive and negative impacts of using a soft start on an AC unit, and we’ll also be discussing the SoftStartRV and how this helps RV AC units perform better. 

Advantages of a soft start on an AC unit 

Reduced Energy Use

With a conventional start, the motor immediately starts running on the maximum amount of energy and does so for the entire duration that it’s running.

Because a soft start gradually builds up the voltage, overall, less energy is used. 

Lower Risk of Power Surge

Without a soft start, there’s always a risk that you’ll trigger a power surge when the maximum voltage immediately rushes into your motor when it starts running. 

Because of the rush of power, there’s always a chance that the circuits will become overloaded and your motor will experience a power surge. A soft start avoids this risk by building up the voltage gradually, rather than all at once. 

Adjustable Acceleration Time

This isn’t a feature found in every soft start, however, it’s a great feature to look out for and can be a significant advantage. With this option, you have greater control over your motor and the duration it takes to power up to its full voltage. 

This works well if you know your motor or machine is prone to power surges or is old and worn out, as you can set your soft start to a longer time setting so it builds up power gradually.

Alternatively, if you’re lucky enough to have a reliable and well-maintained AC unit, you may be able to opt for a shorter power-up duration. Either way, this flexibility and added control is a major plus. 

Potential Increase of Possible Starts Per Hour

Conventionally, a motor has to expend a lot of energy simply to power up, which means some machines will struggle to start up multiple times within an hour.

With a soft start, the motor uses less energy to start up, meaning it has more energy to expend on powering up multiple times, should it need to. 

Reduced Risk of Overheating

Due to the large surge of energy used by a conventional start-up, it’s possible that the motor can overheat, which could potentially cause the motor to shut down or could even cause long-term damage to the motor. 

A soft start provides a gradual, linear stream of energy rather than one big surge, which significantly reduces the chance of the motor overheating.

Improved Operating Efficiency

While conventional startups may work fine, there’s always a greater risk that problems will arise: there may be a power surge, the motor might overheat, or the machine could malfunction.

A soft start is generally a more reliable and less risky way to start up your machine, as it doesn’t rely on that initial blast of power which can lead to the above issues. 

Extended Lifespan

While it’s always possible that problems can arise and lead to a machine breaking down, it’s still important to maximize your machine’s lifespan in whatever way possible. 

One way of doing this is by using a soft start, as this provides less strain on the motor and reduces the risk of overheating the motor, which can lead to long-term damage and increased wear and tear. 

Disadvantages of soft start on AC unit 

Less energy-efficient than VFDs 

Variable frequency drives (VFDs) are a motor control device that protects and controls the speed of an AC induction motor. Unlike soft starts, a VFD can also control the speed of the motor during the start and stop cycle, as well as throughout the run cycle.

This enables you to save more energy, as the VFD isn’t just limiting the speed of the motor during the power-up phase, but during the running cycle, too. This enables you to reduce power when it isn’t needed, resulting in a more efficient use of energy. 

How the SoftStartRV helps RV AC units perform much better

RV air conditioner units hog energy like no other and that energy surge is worst during the initial power-up, which can cause all sorts of issues.  

When you start your AC compressor or induction motor, these are accompanied by in-rush currents that can be up to 7-8 times higher than the running current, as well as a starting torque up to 3 times higher than running torque.

Once it starts running, the power needs of your AC unit usually decrease significantly to around 13 or 14 amps.

This increased unnecessary torque results in sudden mechanical stress on the machine which of course can lead to greater wear and tear and higher service costs, needless to mention an overall reduced lifespan. 

So how to deal with that initial power blast? 

The answer of course is a soft start, and the best one for your RV AC unit is the SoftStartRV, which is designed to effectively reduce the start-up current, typically up to 70%, while still providing full startup torque for compressors and motors. 

SoftStartRV regulates the start-up voltage of the compressor/motor so that you can effectively reduce the in-rush and surge current when you start up your unit, which allows you to reduce your power consumption from your on-site AC power supply system.

By reducing the in-rush current, SoftStartRV improves the stability of the power supply and reduces transient voltage drops that may cause issues or break down other loads. 

This increases overall efficiency, as it eliminates the need for excessive power supply and, as a result, reduces equipment costs and extends the service life of the motor and compressor.

As well as reducing the strain on the power source, SoftStartRV is also less stressful for the compressor itself as it allows it to start more gently. It also provides valuable protection by shutting down the compressor if the power source or the connection to the compressor is suddenly interrupted. For maximum safety, it then delays start-up for three-minutes before re-attempting it. 

The SoftStartRV is designed to be lightweight and compact in size and is encased with fireproof housing and sealed with resin, making it capable of resisting extreme weather even when exposed to harsh environments such as an air-conditioner outdoor rooftop unit.  

If you run your AC unit off a generator, you’ll know that these can be extremely noisy and disruptive, not at all ideal for a peaceful weekend away.

On the other hand, if you use the SoftStartRV along with a lithium-battery-powered inverter (which is much quieter), you could run a 16,000 BTU RV for up to several hours, depending on how hot and humid it is. 

Specifications of the SoftStartRV 

  • Nominal Working  Voltage:  110Vac  (90~135Vac)  /  220Vac  (187~266Vac),  single
  • Maximum continuous  working  voltage:  135VAC  /
  • Maximum continuous  working  current:  18A
  • Over Current limit:  30A/1  minute.
  • Maximum non-repetitive inrush current: 170A  (<20  ms).
  • Maximum surge current:  120A  (<350  ms).
  • Soft start-up time:  1±0.5s.
  • Current consumption: 48mA (Capacitive 110VAC,  220VAC)
  • Power consumption:  less  than 3W 
  • Operation hours: better than 45,000  hours  (rated working temperature).
  • Effective soft start on/off service:  >100,000  times  (soft-start interval not less than 3  minutes).

Benefits of the SoftStartRV

  • Limits inrush current which eliminates current surges and voltage drops
  • Built-in  electronic overload  protective relay extends motor/compressor  service life  
  • Integral bypass contactor  reduces  heat  generation
  • Provides greater control of torque, which produces smoother  starts  and  stops  
  • Reduces vibration  and  mechanical  damage
  • Relieves shock and drivetrain stress on startup
  • No need for additional start capacitor  and  AC  contactor 
  • Easy to wire and install
  • Decreases equipment downtime
  • High reliability and long lifespan 
  • Fireproof and waterproof housing and sealed with resin to increase weather resistance
  • Compact size and lightweight design

Final Verdict

So there you have it, a soft start can offer a myriad of benefits: it lowers power consumption, reduces the risk of the motor overheating or power surging, and prolongs your machine’s overall performance and lifespan. 

A soft start such as SoftStartRV can transform how you use your AC unit in your RV. It will increase overall efficiency, reduce noise levels, and allows you to keep your RV cool while minimizing the wear and tear on your unit’s motor.