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August 18, 2019

TT #112 The Latest Technology for a Vital Coach Component

By: Rob Lowe

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With new Technology making its way into our coaches, there is one component that has not caught up – the Roof Top Air Conditioner. Many coaches are equipped with digital glass dash displays allowing customizable gauge locations and display, the latest in 4K (even 8K) TVs, multiplex lighting in even inexpensive coaches, WiFi Boosters and even the advent of the connected coach is a reality. Roof top air conditioners still have technology out of the 50’s. Of course, many systems have adopted digital thermostats and controllers to control and run the air conditioner however the compressor uses an electrolytic capacitor to start. If the unit is hard to start, often that capacitor is upgraded to a ‘hard start’ version. The rule of thumb in the industry is to have a generator capable of providing about 3,000 watts per air conditioner in the coach. Thus a generator providing 3,300 to 3,500 watts is required for one air conditioner, 5,500 to 6,000 for two and 9,000 to 12,000 watts on larger coaches since those coaches usually have other power consuming components.

 

As lithium batteries and inverters become more common, there are plans to run one air conditioner on an inverter for six (6) to eight (8) hours overnight for a comfortable, quiet safe rest. The challenge has always been to get the air conditioner started since while many air conditioners can run on lower power, getting them started using old technology starting capacitors has been the challenge. Enter Micro-Air, Inc. with their EasyStart™ soft starters, which are an electronic starting system that automatically adjusts to the compressor. It greatly reduces the power required to start and run an air conditioner. A roof top air conditioner equipped with this system can run efficiently on a 2,000-watt generator and two of these modified air conditioners can be operated on a 30 amps RV electric service.

 

How does an EasyStart™ soft starter perform?

Watch this video to learn more: https://www.youtube.com/watch?v=rCjFBhDy9QI

 

Why would I install an EasyStart™ soft starter?

So, you say, I always run our coach on 50 amps, rarely dry camp, and ask ‘Why would I want to change to these air conditioning starting units?’ The simple answers are lower starting noise, much more efficient starting and longer life from the compressor and ultimately saving money. 

 

Without getting into the technical reasons, a motor will resist turning when it is powered on to run. If the motor is driving a compressor that presents a high resistance to turning, there is a large amount of power required to get the compressor moving. A Start Capacitor provides a boost of power to aid in the start. Think of it as a reservoir for electricity which supplements the power supplied by the AC power source. However, as these capacitors age from use, they lose some of their capacity to store energy. This leads to a longer time where the compressor ‘struggles’ to get going, increasing the noise and vibration, often noticeable in the coach. Eventually either the capacitor or the compressor fails.

 

In addition, on some coaches the control system is incompatible with the newer replacement air conditioning units. A simple air conditioner replacement involves not only replacing the one defective rooftop unit but the other one or two, the control system, adding additional thermostats for the furnaces that can no longer be centrally controlled on the new system, together with the labor and parts to support the replacement. Doesn’t it make sense to replace the weak link in the air conditioning system and extend the life of the existing units?  

 

Our ‘Real Life’ Experience: A Case Study:

During the last year I had noticed that our ten (10) year old air conditioners were somewhat harder to start. We often travel to a campground which is serviced with a few 50-amp sites and many sites with 30-amp and at them we always have been able to run both airs and all other systems without any difficulty. Unexpectedly on hot days in the summer of 2018, we were blowing the campground main breaker. This section of the campground is less than ten years old and had been constructed with new wiring, electrical panels and outlets. The only major drawback is that the circuit breaker for each campsite is in a central panel, only accessible by the onsite maintenance personnel. When a breaker trips, it is much more than simply flipping on a breaker at the post. We experienced a couple of failures and concluded that the power was low since prior to that summer, we had always been able to run both air conditioners there. The power measurements indicated we were drawing more than 30 amps and the breaker was doing its job. The fall season did not present any issues and when we went to our winter resort site, we had no issues with the 50-amp power source. I did notice that the AC units were noticeably noisier when starting but not enough to concern me.

 

I had been doing some investigation for another customer about running an air conditioner on a battery bank overnight. In my research, I concluded that the main issue was the starting load on the power source. When interviewing a REV Group electrical engineer for another Technical Tip article, I questioned him about the large size of the lithium-ion battery bank that they were installing in some luxury coaches, I learned that they were sizing them for the ability to run one air conditioner unit for up to eight (8) hours, on an inverter. The limiting factor was the sizable starting current required, which the batteries could sustain, however the run time was less than the eight (8) hours required.

 

My research led me to Micro-Air’s EasyStart™ soft starters that utilize computer logic to gently ramp up a compressor on start up. Each unit must be ‘trained’ with five (5) starts after installation of the unit in the rooftop air conditioner. Once that process is completed the air conditioner starts up with hardly any strain or co-incident noise. As you can see from the video link above there is a demonstratable reduction in the power required to start the air conditioner. After more investigation, I contacted the company and ordered two units to install in each of our coach’s air conditioners.

 

A Simple Installation:

In early May of 2019, I installed an EasyStart™ soft starter unit in each air conditioner. This involved going onto the RV roof, removing the air conditioner’s shroud, accessing and removing the start capacitor and associated relay, then replacing the wiring to those components with that from the EasyStart™ unit. Another part of the task is finding a suitable location for the unit, securing it and the associated wiring in a dry location out of the way of moving fan blades in such a way that the shroud can be reinstalled. The first unit is a learning experience the second is a duplication of the first. Then a critical step is to start each unit five (5) times to program the EasyStart™ soft starter waiting 5 minutes after shutdown to allow the compressor to equalize. Since my storage unit does not have any accessible power, I moved the coach to my home and connected to my 30-Amp RV outlet. After about 30 minutes, both units were programmed. While it was not hot enough to need the air on, I could hear that the compressor was starting without any noticeable strain.

 

I was unable to use our coach for about three more months, so our first RV trip using these modified air conditioners was in August. What we noticed is that both air conditioners performed very well in 33°C (92°F) humid summer conditions. With the fans set on high (continuously) you could not hear the compressor cycle on and off. You did notice the comfortable temperature throughout the coach. I have no reason to believe that we will not get many more years out of these air conditioners. I’m sure that using the rear unit in heat pump mode will also give quieter operation on those cooler fall evenings.

 

With a relatively simple upgrade you can improve the performance, reduce maintenance and increase longevity of a vital component in your RV. It also could add convenience with air conditioning being able to be used overnight in settings where, other than a generator, there is no source of power. Bring this technology to your RV. Contact www.RV-PartsPlus for special pricing and delivery options.


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