The Marine HVAC Evolution
With the continuous development of marine Heating Ventilation and Air Conditioning (HVAC) equipment leading to increased sophistication of the systems available, Dometic Marine’s Ed Todd outlines the key drivers of technological advancement and evolution in the last fifty years.
Today’s vessel operators are able to take advantage of modern heating and cooling capabilities to support crew well-being as well as provide ideal temperatures for sensitive electronics and other systems on-board. With HVAC manufacturers responding to on-going pressure from vessel builders to provide durable and robust solutions that are also smaller, lighter and quieter, the market is increasingly seeing the introduction of advanced systems that provide higher capacity and efficiency.
Specialist HVAC supplier to the commercial, workboat and military markets, Dometic Marine has been manufacturing marine air conditioning for over fifty years. Ed Todd, Director of National OEM Sales explains: “Through our brand Cruisair®, founded by marine HVAC pioneer Jere Cruise in 1959, we have been manufacturing and supplying marine air conditioning to a variety of vessels including superyachts, recreational boats and commercial vessels for over fifty years. Today, we also own the Marine Air brand, founded in 1977, enabling us to draw experience from a wide-ranging customer base.”
“Our supply of air conditioning to the commercial sector dates back to the early days of marine air conditioning. As soon as it became available, the commercial sector was almost immediately recognized as a customer. In the leisure and recreational marine markets, air conditioning is seen as more of a luxury that enhances the experience for an owner and his guests, but on a workboat or tug where crew are working, it’s widely accepted as a necessity. Today, vessel operators are obligated to keep their crew comfortable, not only from a legal and ethical perspective but also to ensure maximum performance.”
System development
In technology terms, fifty years is a significant length of time when considering the rapid technological advances on land. Due to its nature, the marine industry is typically a little slower off the mark, and according to Dometic Marine, it has been developments in electronics and refrigerants which have led to the core changes in HVAC equipment.
“In the early stages of marine air conditioning development, systems were cobbled together using equipment that was available on land. They weren’t as hard-wearing and reliable because manufacturers didn’t really know what to expect after the system had been in operation for three to five years. With very little service and maintenance experience, no one knew what could go wrong and how to fix systems,” Todd continues.
“However, this soon changed as manufacturers began to gain specialist experience and knowledge. Although fundamentally, the actual HVAC machinery hasn’t changed that much, most of the system evolution has occurred through experience and customer feedback. In terms of maximizing the life and durability of our products, we recently introduced corrosion-resistant coatings for external components of our equipment. By providing exceptional protection against the salt-air environment, our corrosion-resistant coatings are proving effective in ensuring longevity of our products and systems.”
One of the most significant introductions to impact the development of HVAC systems in recent years has been the availability of R410A environmentally safe refrigerant. This high-efficiency gas has enabled engineers to redesign and further streamline systems, providing vessel builders and operators with a range of benefits.
Todd explains: “The introduction of R410A enabled us to evaluate some of our designs and review our efficiencies and capacities. The thermodynamic properties of R410A enabled our engineers to increase efficiency of our systems by taking advantage of the superior performance of the refrigerant matched with optimized components.”
In addition to the refrigerant changeover, advances in electronics have driven the availability of smart, electronic controls that monitor and protect the system while providing an easy-to-use digital control to set the temperature. HVAC systems can even be monitored and controlled remotely via the internet.
Modern electronics are also used to minimize power spikes when the air conditioning system’s compressor starts. On direct-expansion systems a soft starter is recommended, such as Dometic’s SmartStart, which can lower the start-up power demand by up to 65%.
On chilled water systems, variable frequency drives (VFDs) are often used to smoothly and gently start the compressor to eliminate large current surges that would otherwise interrupt the vessel’s AC power supply. VFDs, however have inherent side effects of creating signal noise, harmonic distortion, and radio frequency interference (RFI) that require line filters and tedious troubleshooting to overcome. Testament to its position at the forefront of innovation and technological development, Dometic Marine was the first supplier to introduce a Bypassable VFD for marine application, launched in October 2011, which completely eliminates signal noise, harmonic distortion and RFI by taking itself off line once the compressor is operational and coming back online just prior to system shutdown in order to bring the compressor to a gentle stop.
“Out of all the systems installed on a vessel, HVAC is one of the most power hungry, with start-up affecting the boat’s power supply the most. By integrating VFDs, we are able to smooth out and reduce starting current by gradually ramping up the compressor on start-up and slowly stopping it to shut down.
“Our Bypassable VFD takes this process one step further. It not only eliminates start-up surge, but after the start-up is completed it seamlessly disconnects itself, eliminating all harmonic distortion and RFI so installation of line filters and conditioners are not required. In addition, a single Bypassable VFD can manage up to three compressors, saving significant time, space and money.”
Supporting commercial applications
For Dometic Marine, the last five years have seen the launch of a range of products specifically designed for the commercial environment. According to the company, this includes the development of a range of air-cooled systems which, unlike the traditional and older equipment of the past, are robust and durable even in harsh marine conditions.
Moose Boats patrol boat, a Dometic customer
Todd explains: “We’ve always sold our products to the commercial sector, including workboats, patrol boats and other vessels up to 200ft, but these products were also supplied and developed to meet demands in the superyacht and recreational sectors. Due to a growth in demand for our systems in the commercial sector around five years ago, we invested dedicated time and resources into the development of systems that are designed for specific commercial application.
“Today, we are able to offer an extensive range of systems, including both water-cooled and air-cooled systems, which offer different benefits depending on the vessel operator’s requirements for cooling. We are also able to custom-build solutions to meet virtually any customer requirement for size, shape, function and power. If involved early enough in a vessel’s build or refit, we are able to review and interpret layout drawings to ensure sufficient space is allocated for the HVAC system, while also designing a system that fits the engine room and allotted on-board areas.”
As for future developments, with continuous advancements in technology it can be difficult to comprehend what’s next, which is why it’s important for HVAC manufacturers such as Dometic Marine to always look ahead.
“While our customers in the pleasure boat market are generally focused on systems becoming smaller and quieter, our customers in the commercial sector typically require increased efficiency and reliability. We are in a strong position of combining our knowledge with our experience to ensure our systems continually evolve,” Todd concludes.