Load Profile
A daily load profile is the hourly representation of cold loads for a period of 24 hours. Most HVAC applications use a daily load profile to determine the amount of storage required. Some HVAC systems apply a weekly load profile. For conventional air conditioning systems, chillers are selected based on their peak cold charge. For ice storage systems, chillers are selected based on the tons and hours of cold required and the defined operational strategy. Thermal storage systems offer great flexibility to various operational strategies as long as the total number of selected ton hours is not exceeded. This is because when designing an ice storage system we must indicate the exact load profile. Load profiles take different forms depending on their application. Figure 1 shows a typical HVAC load profile for an office building with a cold peak of 500 tons and a cold requirement of 12 hours. The shape of the curve is representative of most HVAC applications. For preliminary equipment selections, BAC's ICV CHILLER Thermal Storage Unit Selection Program can generate a similar load profile. The information required is the manufacturing of cold charge tip and duration of the load.
The Institute of Air Conditioning and Refrigeration (ARI) has published Guide T "Thermal Performance Specifications of Cold Storage Equipment". The purpose of Guide T is to establish the minimum specified user data and the performance data specified by the provider. Design data delivered by the engineer includes: System loads, flow rates, and temperatures.
Operating Strategies
The next step in the selection of thermal storage equipment is to define the operating strategy. The selection includes both total and partial storage.
Partial storage operational strategies can be categorized either by demand limits or by load level. They are dependent on the load profile, utility rate structure, energy costs, and the cost of the first equipment (or initial cost).
Total storage systems eliminate the need to operate the chiller during the peak period of use through the storage of the required cold during low periods of use. This strategy avoids high electricity demands and results in lower operational costs. However, the first investment in equipment is considerably higher than partial storage systems due to higher refrigeration and storage requirements. Unlike total storage systems, the chiller can operate during low periods when using an operational partial storage strategy. There are two types of it: the first is demand limitation: non-storage system loads set the high point of demand for the building or facility. The items considered in the loads of non-storage systems are lighting, equipment, appliances, fans, motors, etc. Thermal storage equipment is selected so that the chiller operation does not increase the demand for non-storage facilities. This operational strategy provides lower operational costs for partial storage systems. It also requires smaller storage capacities and smaller chillers than a total storage design.
The disadvantages of a limited demand operational strategy are that both the storage requirements and the capabilities of the chillers are greater than those required for a load-level operational strategy. This means a longer period for the economic return on investment. The second operational strategy of partial storage is by load levels. This, to distribute cold loads evenly over a 24-hour period, reduces the size of thermal storage equipment and chiller compared to those of total storage or with limited demand strategies. This translates into lower initial investment costs and shorter periods of economic return. When the refrigerator operates fully loaded during the period of low demand, the operating costs are higher than those that arise by applying strategies of limited demand or full storage.
Modes of Operation
The modular ICE CHILLER Thermal Storage Unit can operate with any of the five operating modes. These provide the flexibility required by building operators to meet their daily cold HVAC requirements.
Ice Build
In this mode of operation the ice is manufactured by circulating a 25% solution (by weight) of inhibited ethylene glycol through the coils (coils) existing in the ICE CHILLER Thermal Storage Unit. Figure 2 shows the temperatures of a chiller in manufacturing cycles of 8, 10 and 12 hours. For a typical 10-hour manufacturing time cycle, the temperature is never less than 22oF. As the graph shows, in times exceeding 10 hours the minimum temperature is greater than 22oF. And in times less than 10 hours the temperature will be less than 22oF at the end of the manufacturing cycle. This performance is based on a chiller with a flow rate associated with a range of 5oF. When the selection of a chiller is based on higher temperature ranges, this may be lower than those shown in Figure 2.
Ice Build With Cooling (Ice Generation and Simultaneous Cold Requirement to Replenish Ice)
When there is cold charge during the ice making period part of the cold ethylene glycol used for the latter is redervated to the cold charge to generate ice production. The amount of glycol derived is determined by the temperature of the manufacturing cycle. BAC recommends that this mode of operation be applied in systems that use primary/secondary pumping. This reduces the possibility of damage to cooling coils or cold glycol pumped heat exchangers, less than 32oF, for these equipment.
Cooling – Ice Only
In this mode of operation the Chiller is disconnected. The warm return of the decooled ethylene glycol solution to the desired temperature by mixing ice stored in the modular ICE CHILLER Thermal Storage Unit
Cooling – Chiller Only (Generación de Frío por Chiller sin Banco de Hielo)
In this mode of operation the Chiller provides all the requirements of cold manufacturing. The glycol flow is directed through the thermal storage equipment to allow the cold glycol supply to flow directly to the cold load. The temperature is maintained by the Chiller.
Cooling – Ice With Chiller
In this mode of operation the cold is provided by the combined operation of the chiller and the thermal storage equipment. Glycol refrigerant preheats the return of warm glycol. The partially cold solutions then pass through the ICE CHILLER Thermal Storage Unit where they are cooled by the ice to the specified temperature.
Schematic Systems
Two basic schematic flows are applied to select the BAC'S ICE CHILLER Thermal Storage Units. Figure 3 illustrates a pipe cycle with the chiller installed behind the thermal storage equipment.
This design allows this equipment to operate in four of the five modes of operation. These are Ice Making, Only Cold - Ice, Only Cold - Chiller and Cold - Ice with Chiller. The following logical controls apply to this schema:
The V-1 valve modulates in response to the temperature sensor, TS-1. The V-2 valve can be placed either to maintain a constant flow, less than P-1 or modulated in response to the temperature return of the glycol from the cold charge. When the manufacturing cycle contains chilled water, a heat exchanger can be installed to separate the glycol cycle from the cooled water manufacturing cycle. In applications where water cooling is available, it can be installed in the cooled water cycle to reduce the load on the thermal storage system. This design should not be used when ice making exists and cold is provided, which would require a cold return of glycol from the thermal storage equipment to be pumped into the cold load or heat exchanger. When the glycol temperature is below 32oF, cooling coils or heat exchangers can freeze. The flow scheme shown in Figure 4 details a primary/secondary pumping cycle with a chiller located behind the thermal storage equipment.
This design allows you to work with all five modes of operation. For this scheme the following logical controls are applied:The V-1 valve and the modulated V-2 valve, depend on the mode of operation, in response to the TS-1 temperature sensor. The benefit provided by the primary/secondary pumping cycle is that the system can manufacture ice and provide cooling without the risk of freezing a cooling coil or heat exchanger. This system design also allows different flows in each pumping cycle. When this happens, the flow rate of glycol in the primary cycle should be greater than or equal to the flow rate in the secondary cycle. As in a simple cycle scheme, a heat exchanger and a water-based coolant can be added to a system scheme.
These schemes are the most common for thermal storage systems, although some modifications are possible. A common modification is to place the refrigerator under (down stream) the thermal storage equipment. This design is used when with the glycol temperatures off , the ice cannot be maintained for the full cooling period. By placing the chiller behind the ice, it can be used to maintain the required temperature supplies. In figures 3 and 4 the chiller is installed behind the ice. This offers two comparative advantages to systems designed by locating the chiller under the ice: first, the refrigerator operates at higher glycol temperatures to pre-cool the returning glycol. This allows the chiller to operate at a higher capacity which reduces the amount of ice required; second, when the chiller operates at higher evaporation temperatures, the chiller's efficiency (Kw/TR) is improved.
Chiller performance
Most chillers can provide a wide range of glycol discharge temperatures and are suitable for thermal storage applications. They include reciprocating, rotary screw and centrifugal. The type of chiller depends on the capacity, the glycol discharge temperature, efficiency, type of condenser and refrigerants. Glycol discharge capacity and temperature should be evaluated when designing a thermal storage system. For various modes of operation different glycol discharge temperatures are required that affect the capacity of the chiller. The one provided at 22oF is considerably lower than the capacity of the chiller with a glycol discharge temperature of 44oF.
Chillers selected for use with the BAC'S ICE CHILLER Thermal Storage Unit should provide glycol at 22oF when a 10-hour manufacturing cycle is applied. Longer cycles produce higher temperatures at the end of the period when shorter manufacturing times require the chiller to keep the glycol cooler at 22oF.La required capacity of the chiller could limit the use of a specific type of chiller in small applications. The nominal capacity range of each type is shown in the following table:
Centrifugal and rotary screw chillers have the highest efficiency, ranging from 0.6 to 0.75 kW/ton at 44oF chiller temperature and 0.87 to 1.1 kW/ton when producing glycol at 22oF. Reciprocated chillers are less efficient with ranges from 0.85 to 1.1 when producing glycol at 44oF and 1.1 to 1.3 kW/ton when making ice at 22oF.La heat rejection function of an ice storage system can be handled with any of the three types of refrigerant condensers: air cooling, water cooling or evaporation. An air cooling condenser removes heat from the refrigerant and condenses it by forcing the air through a coil through which the refrigerant vapor circulates. The latent heat of the refrigerant is removed by a sensitive heating of the air. The capacity of the condenser is determined by the temperature of the dry environment bulb.
A condenser based on water cooling with a cooling tower rejects heat from a cooling system in two steps: first the coolant is condensed by the flow of water in the condenser; second, the heat is rejected into the atmosphere as condensed water, cooled by a cooling tower. The evaporative condenser combines a water cooling condenser and a cooling tower in one piece in the equipment, which eliminates the sensitive heat transfer passage of condensed water. This allows for a condensation temperature close to the designed wet bulb temperature. When evaluating chiller performance, variations in condensation temperatures should be considered. Reduced nighttime ambient dry bulb and wet bulb temperatures offer lower condensation temperatures that help compensate for the reduced capacity and efficiency of the chiller. Below are percentages of nominal capacity of chillers at different glycol discharge temperatures, based on water cooling at 44oF.
Nominal capacity ranges are based on:
Water condenser at 85oF or condensed temperature at 115oF
80oF water condenser or 105oF condensed temperature for ice making operation.
The types of refrigerants for chillers vary. Centrifuges can be used with R134a, R-123 and R-22. Reciprocals and those with rotary screw with R134a, R-22 and R-717 (ammonia).
Installation
ICE CHILLER Thermal Storage Units must be installed on a flat surface. The pitch of the slab should not exceed 1/8" over 10-foot span. Figure 5 provides the location guides of the ICE CHILLER Thermal Storage Unit. Units should be placed where there is sufficient space between the unit and adjacent walls to allow easy access. When installing multiple drives, a minimum of 18" between each and 3"-0" end-to-end is recommended to access the operation controls.
There may be times when the thermal storage unit needs to be installed outside and the visibility of the equipment is reduced. If a fenced enclosure or garden does not provide a suitable environment for the cement surface where the unit is installed, it could be partially buried. PRECAUTION: When burying the equipment, special care must be taken in the excavation, drains, design of the concrete support, location of the unit and filling to prevent damage to the bituminous protective coatings of the unit. The concrete surface must be designed by a qualified engineer.
When installed indoors, the access and support surface requirements described above apply. Units should be installed near a drain. The minimum height required above the tank, to install the appropriate pipe is 3 feet.
Figure 6 shows the free spaces required for ICE CHILLER Thermal Storage Units
BAC'S ICE CHILLER Thermal Storage Units are available unassembled when they must be installed indoors and access is limited. The assembly of the units will need personnel to support this process. Contact local BAC representatives for additional details. For high-demand applications (ton-hour), BAC will provide ICE CHILLER thermal storage coils for installation in on-site manufactured tanks. This product offers the design and flexibility of renowned BACs. When coils are required, BAC's production capabilities allow them to be produced with the size and configuration needed for specific locations and performance requirements. The design of the concrete tank must be carried out by a qualified structural engineer.
Figure 7 illustrates the installation guide for an ICE CHILLER thermal storage coil. The forces of buoyancy due to the difference in density between ice and water require the installation of fastening angles at the ends of the coils. This will not allow the coils to float under overload conditions. For larger projects you should contact local BAC representatives for selection and dimensional information.
Pipes
The ICE CHILLER Thermal Storage Unit must follow established guidelines. The unit connections are galvanized steel and ribbed to allow mechanical coupling.
For single-tank applications each pair of coil connections must include a shut-off valve so that the unit can be isolated from the system.
Figure 8 shows the valve arrangement for a single unit. It is recommended that the pipeline include a bypass circuit to allow the operation of the system without the ICE CHILLER Thermal Storage Unit in the pipe cycle.
This bypass can be incorporated into the pipe design to install a valve of three options or modes. This valve can also be used to control the loss of glycol temperature from the thermal storage unit.
Temperature and pressure indicators must be installed in such a way as to facilitate flow balancing and fault detection. At a maximum of 150-psi a relief valve should be installed between the disconnect valve and the connections to the coils, to protect the coils from excessive pressures from hydraulic expansion. The replacement valve must be applied to a portion of the system that can accommodate the extension.
CAUTION: The system must include an expansion tank to accommodate changes in fluid volume. Air vents of an appropriate size can be installed at the high points in the pipe cycle to remove trapped air from the system.
Figure 9 shows the return pipes for multiple units installed in parallel. The use of them is recommended to ensure a balanced flow in each unit. The shut-off valves of each unit can be used as balancing valves.
When installing large quantities of ICE CHILLER Thermal Storage Units, the system must be subdivided into groups of units. Thus, the balance of each unit can be eliminated, installing a common balance valve for each group of units. Shut-off valves can be installed to isolate individual units, but should not be used to balance the glycol flow in the unit.
Controls
To ensure an efficient operation of the ICE CHILLER Thermal Storage Units, each system is delivered with the Operation Controls option installed, which is described below. Once the ice manufacturing cycle has begun, the glycol chiller should operate at full capacity without cycles or discharge until the ICE CHILLER Thermal Storage Unit is fully charged. Once this happens, the chiller can be turned off, not allowing it to restart until cooling is required. The ice making cycle is finished by the Operations Control device. This includes a low water cut-out, a cut-off switch and a safety switch. The low water cut-out prevents the ice-making mode from starting if there is not enough water in the pond. The kill switch will end the manufacturing cycle when the units are fully charged and will take care that the next mode of ice making does not start until 15% of the ice has melted. The safety switch is arranged to end the manufacturing cycle when operation controls indicate function failures.
Stock checks that deliver either at 4 – 20 mA or 1_ 5 Vdc are still available. These controls should be used to determine the amount of ice accumulated but not to stop the ice-making cycle. Further details of the operation controls are provided in the Installation, Operation and Maintenance Manual.
Glycol
ICE CHILLER Thermal Storage Units use 25% (by weight) of an industrially inhibited ethylene glycol solution for both corrosion protection and freeze protection. The industrial grade of inhibited ethylene glycol is specifically designed to prevent corrosion in HVAC and heat transfer equipment. Inhibitors are used to prevent ethylene glycol from acidifying and to protect metal components in the thermal storage system. The lowest operating temperature of the system should be 5oF to 7oF above the freezing point of the glycol. This, in a system with 25% ethylene glycol, is 14oF. Two acceptable grades of inhibited ethylene glycol solutions are Dow's DOWTHERM SR-1 and Union Carbide's UCARTHERM. The use of other products of this type in BAC'S ICE CHILLER thermal storage products must be approved by BAC.
Caution: Uninhibited Ethylene Glycol and automotive antifreeze solutions are not for use in thermal storage applications.
DOWTHERM and UCARTHERM are registered trademarks of The Dow Chemical Company and Union Carbide Corporation, USA, respectively.
Water treatment
At temperatures close to freezing in the ICE CHILLER Thermal Storage Unit, scale and corrosion are naturally minimized. Therefore, water treatment for these two conditions may not be required or require minimal attention unless the water is corrosive in nature. Biological growth control may require a bioacid that prevents the spread of iron bacteria or other organisms. For more specific recommendations you should consult your local water treatment company and follow the guidelines.
Note: If a water treatment is implemented for the system, it must not alter the freezing point of the water, in order to ensure full capacity of the ICE CHILLER Thermal Storage Unit.
WinteringPREVENTION: Precautions should be taken to protect the unit and pipes associated with freezing conditions. Heat tracing and insulation must be installed in all pipes connected to the unit. If units are installed outdoors and exposed to environmental conditions from subfreezing, the sight tube, operation controls and optional inventory sensors must be protected.
For this, BAC can provide an optional, complete heat aggregate with 100 W of heat. On the other hand, the sight tube, operation controls and optional inventory sensors must be isolated. There is no need to drain the unit during cold weather. Freezing the water contained in the unit during the winter will not damage the coil or unit.
Drop Pressure
The ICE CHILLER Thermal Storage Unit is designed for low drop pressure. Figure 10 shows the drop pressure associated with each unit for 25% of industrially inhibited ethylene glycol solution. Unindicated flow rate data should not be extrapolated from the performance curve. Drop pressures for flow rates not presented in this table or for alternative fluids are available by contacting your local BAC representative.
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Product Specification
The ICE CHILLER Thermal Storage Unit(s) will be Baltimore Aircoil Model TSU-________. Each unit has a storage capacity of ____________________________________GPM________________ The minimum temperature required during the icemaking mode should be ________oF. System performance rates must be delivered in the format recommended by the Air Conditioning and Refrigeration Institute (ARI) Guide T. Thermal storage units should be modular in design and available in 237, 476, 594 or 761 latent ton-hour increments. Designs should allow for units of different sizes to be installed in order to optimize selection and minimize space requirements. Pond sizes can be combined due to internal pipe arrangements that create given bale flows for uniform drop pressure through winding circuits.
The tank should be constructed of galvanized steel panels and include double flanges for structural strength. Tank walls must have a minimum of 4-1/2" insulation that delivers an insulation range of R-18. The tank design can use multiple liners. The first, which forms the interior of the unit must be a single piece and capable of low temperature applications. The secondary liner/vapor barrier must be separated from the first by 1-1/2" of extruded polystyrene insulation. The bottom of the tank must be insulated with 2" expanded polystyrene and 1" extruded polystyrene.
The ICE CHILLER Thermal Storage Unit(s) must be provided with water-tight, section covers constructed of hot-dip galvanized steel. Covers must be insulated with a minimum of 2" expanded polystyrene.
Contained in the tank should be of a heat transmitting steel that is constructed of 1.05" O.D., all prime surface serpentine steel tubin encased in a steel frame. The coil, which is hot-dip galvanized after manufacturing, must be tested at 190 psig underwater air pressure and priced for an operating pressure of 150 psig. The coil circuits are configured to deliver maximum storage capacity. The coil connections in the unit are galvanized steel and ribbed for mechanical coupling. Each ICE CHILLER Thermal Storage Unit must be delivered with a sight tube mounted at the end of each unit. This, which must be manufactured from a clean plastic pipe, indicates the water levels in the tank and the corresponding existence of ice. The operation controls, consisting of two floating switches are mounted outside the tank. The high-level floating switch finishes the manufacturing cycle when the water level of the tank reaches 100% of the level of manufactured ice. It also prevents the restart of the manufacturing cycle until approximately 15% of the ice has been discharged. The second switch is a low water cutout. This requires the water level in the unit to be equal to or above 0% of the ice level before starting the manufacturing cycle. A safety switch that ends the ice-making cycle must also be delivered if any of the operation controls indicate failures (the number of operation controls varies based on project requirements). An optional differential pressure transmitter is available to deliver electrical signals indicating the amount of ice in existence.
The heat transfer fluid must be an industrially inhibited ethylene glycol solution, at 25% by weight, specially designed for HVAC applications. The 25% solution is designed to provide freezing/burst and corrosion protection as efficient as water-based closed-loop systems. Corrosion inhibitors must be delivered to keep pipes corrosion-free without fouling. DOWTHERM SR-1 and UCARTHERM are accepted fluids. All dimensions of the unit do not exceed approximately ______ feet per ______ feet with a total height not exceeding ____ feet. The operating weight does not exceed _____libras.
Why use ice bank?
Lower initial design cost
A BAC-engineered ice storage system, which has the advantage of using a low-temperature fluid results in a lower initial design cost. The savings obtained from the use of chiller and reduced cooling towers, decreases the sizes of pumps, pipes and connections to power sources compensating the cost of thermal storage equipment. Below is a summary of the potential component savings in a cooling load with a peak of 1000 tons.
Smaller Chillers and Cooling Towers
For the design of a 24-hour/day system of operation of a chiller, the size of these and the cooling towers required for an ice system is significantly reduced when compared to conventional chillers and towers designed for instant peak load. A partial ice storage design includes chillers that provide approximately 60% of the peak cooling load. The balance of the cold requirement is given by the thermal storage system. For the 1000 ton example, the nominal capacity of a chiller and cooling tower is reduced to 580 tons and an associated total savings of $126,000.
Reduced Size of Pumps and Pipes
The size of pumps and pipes is also reduced in a proper design of an ice storage system. When the system design integrates lower fluid rates by using a greater temperature range in the water loop, substantial savings are resulting in these devices. Using a temperature range of 18oF instead of the conventional 10oF results in a reduction in pipe size from 12" to 10". This decrease in pipe size corresponds to a saving of US$100 per linear foot installed. Condensed water pipe sizes are reduced due to the lower flow requirements of a small chiller. By using 3GPM7ton, the condensed water pipe can be reduced from 14" for conventional systems to 10" for the ice storage system. This gives an installation savings of US$175 per linear foot. Reducing the flow rates of chiller water and condensation water also results in savings in pumps. In the example below, the savings of the pumps are US$15,000.
Lower Power Source / Lower Power Requirement
By reducing most of the elements of the mechanical system, the energy needs associated with these elements are also reduced. The 395 HP power reduction saves transformers, switches and wiring by approximately $50,000.
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Ice storage
The savings associated with a proper design of an ice storage system are substantial. The savings described are partially offset by the cost of ice storage equipment. The ice storage system includes: The ethylene glycol ice bank, heat exchanger and concrete pads for the thermal storage unit. For an example of a peak of 1000 tons, the ton per hour requirements are 3281. The associated additional cost for this equipment is US$196,000.
Lower operating costs
With less need for energy, ice storage can require over 50% less electricity demand. The annual total of kilowatts/hour used is many times lower than with a conventional instantaneous cooling system. As utilities are imposing recharges in peak demand times, ice storage can lead to greater savings in operating costs.
Improved system efficiency
The ice CHILLER ® modular thermal storage unit is specifically designed for partial storage with internal melting applications. With this operation strategy the glycol that returns warm is pre-cooled by the chiller before it passes through the steel heat exchanger and cooled indirectly by the melted ice. The ability to locate the upstream chiller of the BAC ICE CHILLER ® product generates two benefits: first, when operating at higher glycol supply temperatures to precool the glycol, the capacity of the chiller increases. Second, the efficiency (kW/TR) of the chiller is also improved. Finally, the pressurized loop reduces the energy needs for pumping. The need for a heat exchanger between the thermal storage unit and the cooling system can be eliminated when glycol is circulated through the air conditioning system.
Improved system reliability
The ice storage system provides the reliability needed to secure air conditioning. In conventional systems, the installation of multiple chillers causes redundancy. In the event of a mechanical failure of one chiller, the second chiller provides limited cooling capacity. The maximum cooling available by a conventional system could be only 50%. Most ice storage systems use two chillers in addition to ice storage equipment. The two chillers are designed to provide approximately 60% of the cold needed while ice storage delivers the remaining 40% of the cooling capacity. In the event that only one chiller is running in the day, the cooling capacity will be about 70%. This is because the chiller in operation provides 30% of the requirements while the ice provides about 40% more. Based on typical HVAC load profiles and ASHRAE time data, 70% of cooling capacity could cover daily cold requirements 85% of the time.
Modular construction
The rectangular design of the ice CHILLER ® modular thermal storage unit maximizes ton-hours per square foot. The product is designed for small facilities where access is limited. The 7'-10" units are designed so that they can be installed by double door openings. The units are designed to be installed indoors or outdoors.
1) Storage ice quantity sensor enclosureTo protect this sensor BAC offers a heater to keep it at 40oF even if the outside temperature is 0oF.
2) Differential Pressure SensorA differential pressure transmitter is included to provide an electrical signal of 4-20 ma, which is proportional to the amount of ice existing. The 4-20 ma signal is used by the building's energy management system to determine the amount of ice available during the day.
3) Visor TubeEach ICE CHILLER ® Thermal Storage Unit has an indicator tube. This allows the equipment operator to visually determine, by the water column of the indicator tube, the amount of ice in the unit.
4) Ice Bank Cover or LidHermetic sectional covers are constructed of hot-dip galvanized steel and are insulated with 2" expanded polystyrene.
5) Glycol ConnectionsThe ice CHILLER ® modular thermal storage unit has victaulic connections to simplify the area of the pipes.
6) Side panelsThe outer panels that form the wall of the chiller are constructed of heavy gauge galvanized steel with double-break flanges for structural strength. The wall panels include 3" of expanded polystyrene, which helps to obtain a total insulation value of R-18.
7) Primary SheetA one-piece sheet, suitable for low temperature applications forms the inside of the tank. Before shipment, each unit is filled with water for 48 hours to check the tightness of this sheet.
8) Extruded Polystyrene Insulation11/2" extruded polystyrene is installed between the primary sheet and the secondary sheet. The insulation barrier contributes to a total insulation value of R-18.
9) Secondary Foil/Vapor BarrierLocated to prevent moisture transfer through thermal insulation.
10) Galvanized Steel CoilsThe steel heat exchanger is constructed of a single main surface serpentine steel tube and located in a steel frame. The entire piece is made of hot-dip galvanized steel after manufacture. Each serpentin piece is tested at 190 psig of underwater air pressure and rated for an operating pressure of 150 psig. Only an industrially inhibited ethylene glycol solution, specially designed for HVAC applications, should circulate through the ice bank serpentin. A 25% by weight solution of ethylene glycol is considered to adjust the operation to cold weather and give corrosion protection. Corrosion inhibitors are to reduce corrosion of the system without embedding it. Accepted fluids would be Dowtherm SR-1 and UCARTHERM.
11) Coil SupportSteel heat exchangers are attached to supporting beams to prevent contact between the tubes and the primary sheet.
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