Improvements in Vanguard's HVAC System: A Closer Look
- Chris Leigh-Jones
- May 24
- 3 min read
Updated: Jun 5
Vanguard's HVAC system has been on my mind for quite some time. Finally, it received the attention it needed. Thanks to support from Marine Tech Services of Hilton Head Island, the HVAC system is now much more reliable. This blog highlights the improvements made and the likely savings that can be achieved with similar systems.
System Configuration on M/Y Vanguard
The installation on M/Y Vanguard includes:
Webasto BlueCool variable-speed chiller: 22kW (77,000 BTU/Hr)
5 Air handlers positioned as follows:
2 units in the main saloon, 5.3kW each
1 unit in each of the three cabins: 2 units at 5.3kW and 1 at 3.5kW
Note: The system rating (kW) reflects the energy transferred, not the energy needed to run the units.
The air ducting system efficiently draws air from the flybridge into the saloon. The air handlers in the saloon condition the space for both temperature and humidity. Air is then drawn from the saloon into the cabins when needed. This method reduces the running time of cabin air handlers by using pre-conditioned air from the saloon.
Air Handler Efficiency
This design leads to better energy efficiency. By minimizing the independent operation of cabin air handlers, the system requires less overall energy. The result is a major cut in power usage without sacrificing comfort.
Energy Consumption Considerations
Startup Current Management
Webasto chillers use soft-start technology. This limits the startup or inrush current. As a result, the system never exceeds the full design load operating current. The Victron Multiplus system can temporarily accept overload. However, it does not favor this.
Effective Cooling Modes
The "F1" cooling function is an example of our initial misunderstandings. I should have done better—Rule 1: Read the Manual! Initially, Naval Yachts in Turkey set the system to "F7." This setting involved dehumidifying by overcooling and reheating the air to reach the set cabin temperature. While this works well for warm, dry cabins, it isn’t efficient for cooling.
By overcooling, we drained our batteries while trying to manage humidity. Now we cool to a few degrees below the set point. As a result, relative humidity drops as the air warms in the cabins. The optimized air distribution from the saloon to the cabins cut cabin HVAC power consumption by over 30%. This also reduced overall system load by 18% when compared to independent systems.
Eco Mode for Greater Savings
In sub-tropical conditions, our system typically operates at 40-60% capacity. Setting to "Eco 2" means the output is capped at about 60% of maximum capacity during chiller cycles. The effect is a peak power consumption of just 2.0kW in Eco 2 settings. This is a significant reduction compared to 4.2kW in standard Eco 0 mode, offering a notable 53% reduction in peak consumption.
Note: This setting is flexible. We can increase the output if conditions require it, avoiding any penalties of overly available power.
Real-World Performance
During a recent cruise along the lower US East Coast of South Carolina, we faced outside temperatures in the high 30s (°C). Over an average of 8.4 hours of daily operation (mainly in the evening and overnight), we consumed just 17 kWh. This is manageable given our hybrid propulsion generators can provide nearly 50kW of charge capacity.
Conclusion
The Webasto BlueCool system, configured for cooling only with optimized zone control and saloon-to-cabin air distribution, delivers remarkable efficiency without sacrificing comfort. The flexibility of the system provides operational advantages for explorer vessels like Vanguard, especially when minimizing generator runtime is essential.
The initial yard-supervised installation faced challenges (to say the least). Fortunately, Webasto-approved technicians improved the system in Palma de Mallorca, correcting circuit plumbing issues. They also optimized the control regime in Hilton Head, SC. Now, we have a system that operates efficiently and within its maximum capacity. We’re utilizing less than 50% of the initial "yard delivered" power requirement while keeping spaces cool and dry.
Enhancing Air Circulation
Each cabin's air vent outlet and exhaust inlet were machined into the ceiling panel. While this created a seamless look, it was also restrictive. The grille holes allowed only about 40% of the flow of the supply pipes, similar to our observations with the bow thruster grills.
To resolve this issue, we replaced these with larger, low-profile commercial grills. This upgrade significantly improves air circulation. It has eliminated stuffiness in the heads and the occasional aromatic toilet we used to endure.
Chris Leigh-Jones
Further Reading
ABYC Standard H-1: "Marine Air Conditioning and Refrigeration"
Calder, N. (2022). Boatowner's Mechanical and Electrical Manual (5th ed.)
ASHRAE Technical Paper 2022-BC-008: "Energy Efficiency in Marine Climate Control Systems"
Marine HVAC Systems Quarterly Journal, Vol. 18 (2023)
Friedman, A. & Martinez, L. (2023). "Integration of HVAC Management with Vessel Monitoring Systems"
Hall, T. (2024). Advanced Marine Air Conditioning: Installation and Troubleshooting Guide
Online Resource: Webasto Blue Cool Advanced Configuration Database
"2kW AC load when running HVAC in all spaces and near 40 deg.C" is an exceptional result, Chris. I will be looking at what you did when we examine our own much more modest air conditioning system on our boat. We are doing a complete revamp of the electrical system and even though this is tiny compared to yours, the 8kVA system that we are installing will be able to handle air conditioning and refrigeration with ease, we believe. We also believe that that African saying, "measure twice and cut once" is always a sound operating principle.