Refrigeration – With vehicle feature – Ship
Reexamination Certificate
1999-10-01
2001-07-24
McDermott, Corrine (Department: 3744)
Refrigeration
With vehicle feature
Ship
C062S435000
Reexamination Certificate
active
06263689
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a system and method to provide air conditioning in marine environments. While chilled water systems have been used in large commercial buildings and as the standard on very large yachts (over 80 feet), up until now central systems have been the only cost effective solution for cooling of yachts/marine vessels in the range of 45-75 feet, since the cost of chilled water systems has been prohibitive in this size boat. According to the invention it is possible to use modular units to provide chilled water for marine air conditioning, each unit having a cooling capacity of between 16,000-24,000 BTU's so that one unit may be used, or two through four units may be connected together, to effectively (both from the functional standpoint and cost effectively) cool boats in the range of 45-75 feet. The invention is particularly useful for vessels (such as 45 foot boats) which require a 36,000 BTU or greater capacity, with multiple condensing units and air handlers. The chilled water air conditioning system according to the present invention has reduced BTU requirements for the condensing units, no refrigerant line sets, enhanced balanced temperature control throughout the vessel, system energy management, and compressor redundancy to eliminate down time, as well as ease of serviceability.
As with all types of air conditioning systems, BTU load calculations must first be done on any vessel to be air-conditioned to ensure that the equipment selected can provide adequate heating or cooling for all applicable areas. With split central equipment there must be a one for one match of evaporator air handlers to condensing units. In other words, if a vessel requires 62,000 BTU's of air conditioning one must specify 62,000 BTU's of evaporator air handlers and 62,000 BTU's of central condensing. Normally one will have one condensing unit for each evaporator, in some cases one can have smaller evaporators matched to one condensing unit (i.e. one 24,000 BTU condenser can run 2×12,000 BTU evaporators).
Chilled water equipment, as according to the invention, has a significant advantage over split central systems in that only the air handlers must equal the calculated BTU heat load for the vessel, whereas the chilled water power plant only needs to accommodate 75-90% of the calculated BTU heat load. In the above example, 62,000 BTU of air handlers only requires 46,500-55,800 BTU's of chiller capacity. The size of the vessel, number of air handlers, and equipment selected determines the percentage of capacity required. Experience indicates that under nominal conditions a chiller plant operates at
50
% or less of its capacity because of its automatic energy management feature.
With split central systems one may have only one thermostat control per central condensing unit to control both the condensing unit and the evaporator. Thus, if one has multiple evaporators on one condensing unit, a slave fan speed only control can be used on the slave evaporators, which may not coincide with the end user's preferences. The fan on the second evaporator must always run otherwise, icing can occur resulting in liquid return to the compressor potentially damaging the condensing unit.
With a chilled water system all air handler controls are totally independent from the chiller controls. The chiller has its own energy management system which automatically stages compressors on and off to control water temperature. Each air handler may have individual controls or up to four air handlers can be driven from a single control typically in a large common area. That is, temperature control is totally flexible throughout the vessel.
Installation of split central air conditioning systems requires that an EPA certified technician handle the refrigerant line sets. This is a government regulation imposed to ensure that the R-22 refrigerant used in the system does not escape into the atmosphere. This is a problem for most boat builders as it limits the number of people qualified to install split central equipment in manufacturing. Many boat builders have chosen to contract this work out and as a result can be a logistics problem in manufacturing. Done correctly, the process of attaching refrigerant line sets, evacuating the system, charging the system, finding and repairing leaks in flair fittings and finally balancing the system to ensure the proper refrigerant charge exists for optimum performance is very time consuming and costly for any production boat builder. In reality, due to customer delivery pressures much of this process is rushed, resulting in poor performance of the system in the field often creating warranty and long term reliability problems. Also, because boats, unlike fixed building structures, flex while underway, mechanical refrigerant line set fittings are constantly under stress often resulting in intermittent refrigerant leaks.
Since a chilled water system has a self-contained factory sealed refrigerant system, there are no refrigerant line sets to be installed in the vessel. Therefore, there is no need for an EPA certified technician to perform any installation or system balancing upon startup. The self-contained chiller condensing unit is plumbed to the air handlers via insulated water lines, which is something boat builders are most familiar with. Installing chilled waterlines is as simple as linking a pump, and expansion tank with fill valve, to a closed plumbing loop. Pipe and insulation sizing can be read off of a simple chart and installed by anyone with basic plumbing skills, simplifying the manufacturing process. When the installation is complete, the installer fills the system with fresh water and uses built in air bleeders to purge air from the lines. Then one merely turns on the chiller and sets the air handler thermostats.
Split central systems operate completely independent of one another. This concept has worked well in many applications and gives the end user desired individual climate control, however, there are some drawbacks.
1. Because the thermostats are independent they can easily oppose each other because of air spill over from one area to another. Since each thermostat controls a condensing unit this causes short cycling of compressors leading to premature failure.
2. If a condensing unit fails, there is no redundancy, and the section of the boat which relies on that unit for cooling will not have cooling until the unit is repaired.
3. There is no energy management between the condensing units. They turn on and off independently, and therefore they can be on or off at any given point in time regardless of the total overall heat load on the boat. Only the independent thermostats control the individual compressors.
Although chilled water system air handlers operate independently, they are all tied to the same parallel chilled water loop which is fed back to the chilled water condensing units allowing the compressors to cycle on and off based upon the heat load on the total water loop. Because each air handler is tied into one chilled water loop the total heat load is integrated into one system which is the basis for energy management of the condensing units. The fact that the air handlers are independent allows for desired independent thermostatic control without creating compressor short cycling conditions because the chilled water condensers react to the total balanced load of the chilled water loop.
Each air handler removes heat from the cabin space and transfers the heat into the cold chilled water loop. As air handlers turn on and off, the average temperature returning in the closed loop to the chiller condensers rises or falls. The chiller condensing system senses the temperature of the water and turns compressors on and off based upon the overall total heat load of the boat. The change in temperature of the water is very gradual since the volume of water contains stored energy, which acts as an energy buffer. This gradual change eliminates short cycling of the compressors therefore i
Dodge David A.
Harper James C.
Heydt Mason C.
Marciano, Jr. Frank A.
Ali Mohammad M.
McDermott Corrine
Nixon & Vanderhye P.C.
Taylor Made Environmental, Inc.
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