How Effective Is An Air Conditioner Soft Start

A soft start air conditioner is a must-have in an RV, allowing you to run two AC units in your RV rather than one. The initial surge of power is often too much for the second AC unit to take, preventing it from turning on and leaving you with one cool end of the RV while the other is stiflingly hot.

If only one of your air conditioners is working inside your RV, the one running will have to work twice as hard to keep you cool. The air-conditioned air will mix with the hot air and leave you with only slightly cooler air inside the motorhome.

This has the potential to ruin your holiday when you’re staying in an RV for the summer. Today we will be looking at what an AC soft starter is as well as how effective they are for your summer holiday.

What is a soft start air conditioner?

A soft starter is a small device that is fitted into your AC unit to reduce the in-rush of current. Once the battery of an RV powers on and sends an electrical current to the air conditioner, the charge is so high that it can be too much for two units.

To protect the second unit from the in-rush of current, the power will not reach the second unit. This in-rush of current can cause a shorter lifespan of your AC units and even leave you with no AC for the remainder of your vacation. For this reason, soft starters are very important.

A soft starter lowers this in-rush of current by 70%, making it much safer for your AC units to run both of them. What’s more, a soft starter will remove the thumping noise that your air conditioners make throughout the day and night, allowing you to enjoy AC as you sleep with no interruptions.

How does an AC soft start work?

A soft starter works to control how much energy runs throughout the circuits of your AC unit’s motor. On startup, the soft starter will reduce the inrush of current before slowly allowing it to build up until the maximum current has been reached.

The soft starter’s job is to create a smooth progression for this current to increase, rather than allowing it all to rush to the AC unit on startup. It will also work to reduce the torque that occurs on startup as well, creating a much safer usage for your motorhome’s battery and AC system.

Soft starters can come in either three-phase or single-phase types, although an AC soft starter will benefit more from the latter. The single-phase soft starter will reduce both torque and starting current on an AC induction motor.

Modern soft starters use solid-state technology and silicon controlled rectifiers (SCRs) to remain so effective at protecting your AC system. The SCRs prevent the maximum amount of current from reaching the motor at startup, before slowly relaxing to allow more current to pass through.

Once the motor powers up, so will the SCRs. At the initial startup, they will restrict the amount of voltage passing through tightly. Once the motor begins to accelerate and needs more power, the SCRs will begin to open more so that the necessary amount of power is allowed through.

Soft starters can be used to ensure that your motor doesn’t become damaged from overheating. It can also help reduce the risk of your air conditioning units becoming damaged due to too much current passing through.

How effective is a soft starter?

There are five different types of soft starters out there, each having different effectiveness ratings. Below we’ve listed these with how effective they are. To find out how effective each type of soft starter is, we took how low they reduce the starting current into consideration.

As soft starters are most important when it comes to reducing the soft starter, we thought that this would be a good way of showing how effective they can be.


As we have already mentioned, solid-state soft starters are the newest and most modern invention, being used in a lot of soft starters nowadays. Instead of using mechanical components, they have been all replaced with electrical counterparts.

The silicon control rectifiers control the current and torque of a motor at startup, relieving a lot of the pressure from the AC units. These are considered one of the most effective types of soft starters, with the starting current being lowered to 30 to 50% of the initial voltage.

Primary resistor

On the other end of the spectrum, primary resistor soft starters are the oldest type on our list, dating as far back as the 1900s. This type is the most simple soft starter, but if it’s not broken then why fix it?

A primary resistor will have three resistors within it to account for each current. Primary resistor soft starters are among the least effective, reducing the starting current to around 70%. While this will still protect your devices and likely be enough to get all of your AC units started, it is not as impressive as solid-state soft starters.

Part winding

A part winding soft starter requires two or more separate sets of motor windings. You can use these to create parallel operations, allowing the initial voltage to only run through one motor winding at startup.

Once the motor begins to accelerate, more part windings can come into play and increase the voltage. Part winding soft starters can reduce the initial current to 65% to 75%, making it as effective as the primary resistor but not as effective as a solid-state soft starter.


An autotransformer soft starter is another effective type, and they are usually reserved for applications that need the starting current to be held at a minimum while the maximum torque per line amp is applied.

There are no resistors within an autotransformer soft starter, but rather transformer winding taps. These control how much power reaches the motor, giving you a lot more control over the starting current. The taps are pre-set, with the most common settings being 80%, 65%, and 50%.

So, the autotransformer soft starters are not as effective as the solid-state soft starters, but it is up there with the more effective soft starters out there.


Wye-delta soft starters are another effective type, although they don’t work for every application out there. This is because the motor will need three connection points to fit the coil windings.

The soft starter will begin in a Y shape, allowing the voltage to be applied to the electrically bigger winding. Once the motor begins to accelerate, the connections will turn to the delta configuration, allowing the full current to move around the system.

Wye-delta soft starters are very effective with the initial voltage being reduced to 58% and the initial torque being reduced to 33%. However, not everyone has a corresponding motor to allow for a wye-delta soft starter to be used.

Why is SoftStartRV the most effective soft starter for air conditioners?

The most important piece of information you need to know about the SoftStartRV is that it can reduce the starting current from 100% to 30%. You’ll be hard-pressed to find another model on the market that will lower the starting current by that much.

With a small size of just 6 x 3 x 3 inches, this soft starter will fit seamlessly into your AC system without any specialist intervention. You can install it by yourself to prevent having to arrange a meeting with a professional.

What’s more, the soft starter weighs less than two pounds. Many of the most effective soft starters weigh more than this, so RV owners decide against them to protect their weight limit. SoftStartRV ensures that you can use the best soft starter out there without this weighing on your mind.

SoftStartRV allows you to run two air conditioners off of a 30-amp hookup, which is the most common hookup that you’d find in a motorhome park. In the past, many RV owners have had difficulty getting more than one AC unit to start with these hookups, but SoftStartRV ensures that this is a problem of the past.
Overall, soft starters can be very effective when you choose the correct type. All of the soft starters available today will successfully reduce the starting current from 100% to at least 70%. However, some are able to get it as low as 30%.

The most effective air conditioner soft starter on the market is the SoftStartRV by NetworkRV. This model reduces the starting current up to 70%, making it a must-have to RV owners everywhere.

Getting more than one AC unit up and running will no longer be an issue with SoftStartRV, as you can run two air conditioners on a 30-amp hookup. You’ll also be able to run one AC unit on a small portable generator or a 20-amp household hookup.

Air conditioning soft starters can be very beneficial, and the SoftStartRV is definitely our first choice when it comes to effectiveness.