ENVIRO-TEMP™ Commercial Heat Recovery Systems by Turbotec Products, Inc. Installation, Operation & Maintenance Manual Heat Recovery Units from 10 to 200 Tons Contents Function and Design Equipment Mounting Refrigerant Piping Design and Sizing Single Compressor, Non-Unloading Single Compressor, Unloading 1 Multiple Compressor Systems Segregated Refrigerant Systems 5 Multiple Compressor Bypass Type HRU 3 4 5 5 5 6 Bypass/ Isolation Circuits Water Piping Design and Sizing 7 8 Single Tank 9 Multiple Tanks, Series 10 Multiple Tank, parallel 11 Multiple HRUs, Parallel Connection 11 Plumbing with Hot Water Systems 13 Electrical Controls 14 Electrical Connection 14 Thermostats 16 16 Maintenance and Troubleshooting 18 Refrigerant Leak Test 20 Cleaning / Descaling Water Tubes 20 Winterization Procedure 20 Pressure Controls NOTE: Installation of this Heat Recovery Unit (HRU) should be done by licensed professionals and in accordance with state and local standards and codes. The manufacturer accepts no responsibility for failure to follow the applicable standards and codes. 2 FUNCTION AND DESIGN Application: Enviro-Temp Heat Recovery Units are designed to heat water, or other fluids, by recovering a portion of the heat of rejection from refrigerating equipment. By means of conduction and turbulent convection, this heat is transferred from the higher temperature refrigerant vapor into a lower temperature fluid. R-717 systems, steel or stainless steel heat exchangers must be used in place of copper. Enviro-Temp units can be applied to air conditioning, refrigeration, heat pumps, and even air compressors. They may be used with air- or water-cooled equipment. The Enviro-Temp is designed to remove superheat at condenser, which is usually 20-25% of the heat of rejection. It is not intended to replace the condenser, but rather is a pre-cooler, to be connected in series with, and upstream of, the condenser. Heating capacities and temperatures produced by the HRU are dependent upon the proper operation of the refrigerating equipment to which it is applied. Therefore, proper operation of the refrigerating equipment should be verified prior to installing the EnviroTemp unit. The most common application for a heat recovery unit (HRU) is domestic water heating or pre-heating. However, there are other applications that can be very cost-effective. Such uses include hot deck reheat for humidity control, space heating, and swimming pool or spa heating. Fluids other than water can also be heated, providing the refrigerant discharge temperature is greater than the fluid temperature. (Consult factory for heating of other fluids, as special pumps and other considerations may affect application). Since the Enviro-Temp unit becomes an integral part of the refrigerating equipment, proper sizing and design will produce a system that not only saves energy costs from fluid heating, but can also improve efficiency of the refrigerating equipment to which it is applied. A properly engineered and installed system should provide years of trouble-free service and savings for the end-user. Enviro-Temp units can be used with most any refrigerating equipment using reciprocating, rotary, or screw type compressors. They may be used with halocarbon refrigerants (R-22, R-134A, R-404, R-407C, R-410A, R500, R-507 ) or ammonia (R-717). When applying to 1 EQUIPMENT MOUNTING The commercial/industrial Enviro-Temp units have straight tube heat exchangers manifolded in parallel, and are designed to be mounted horizontally. This is to prevent trapping of refrigerant oil. You will see that the refrigerant enters at the top of the HRU and leaves at the bottom, which promotes proper oil drain in the compressor off-cycle. The HRU, where practical, should be mounted above the condenser so that oil and/or liquid refrigerant will drain into the condenser rather than back to an idle compressor. The circulator pumps in active units are gen- erally designed for operation with the motor shaft in a horizontal position. With some circular pumps it may be permissible for the shaft to be in a vertical position. Consult Enviro-Temp or pump manufacturer for mounting positions other than horizontal. The HRU should be mounted so that access is provided for service and repair. “C” model EnviroTemp systems have mechanically cleanable water tubes, so be certain there is adequate space available at the cleanable end for the cleaning brush handles. 2 REFRIGERANT PIPING DESIGN AND SIZING Oversizing hot gas lines will reduce refrigerant velocity, and may promote oil trapping. The HRU is normally designed to accept the full flow of refrigerant vapor discharged from the compressor. As with any component in the refrigerant piping, there is pressure-drop associated with the addition of components. However, the Enviro-Temp unit, when properly sized, will keep pressure-drops well within acceptable limits. It is usual practice not to exceed a pressure-drop in hot gas lines that corresponds to a 2 degree change in saturation temperature (see charts). The pressure-drop through the HRU must be added to the pressure-drop in piping, valves, fittings, and components in the hot gas lines so that total pressure drop does not exceed acceptable limits. When sizing Enviro-Temp units it is imperative to use compressor horsepower, rather than tonnage, due to the difference in horsepower-per-ton requirements of different refrigerants at varying saturated, suction temperatures. The lower the suction temperature, the higher the volume of refrigerant that must be circulated per ton. This requires greater horsepower per ton on mid-temp and low-temp refrigeration than on high-temp air conditioning. Once the HRU has been mounted and the refrigerant piping has been assembled, a nitrogen atmosphere should be present during brazing to prevent oxidation from taking place on the inside of the piping. It is a good idea to replace refrigerant filter driers at this time. All braze joints should be pressure-tested for leaks, and system should be thoroughly evacuated prior to recharging and restoring the system to operation. Another factor that must be considered when sizing hot gas lines is oil transport. Since some oil is discharged with the refrigerant from the compressor, it must be returned at the same rate at which it leaves. For oil to be carried by the refrigerant in hot gas lines, a minimum velocity of 500 fpm in horizontal runs and 1000 to 1500 fpm in vertical upflow lines is required. 3 SINGLE COMPRESSOR, NON-UNLOADING REFRIGERANT SYSTEMS Where possible, the HRU should be mounted above the condenser and as close as practical to the compressor to keep discharge line length and refrigerant pressure-drop to a minimum. This will promote oil drain-down into the condenser inlet during the compressor off-cycle. If the HRU must be mounted below the condenser, vertical upflow lines greater than 8’ should be equipped with a trap at the “refrigerant out” stub of the HRU, and the vertical riser should be sized for a minimum gas velocity of 1000 fpm (see figure R-101). For systems where oil movement may be a problem (long discharge line lengths, low temperature applications, etc.), an oil separator may be required (see figure R-103). The use of oil separators does not, however, negate the need for proper line sizing and design, since they may not be 100% effective. mounted in an occupied area where compressor noise could be a critical factor. Bypass/isolation valves, installed in the discharge lines, may be a desirable feature. These valves allow the HRU to be isolated and bypassed so that the HRU can be cleaned, repaired or replaced (in the event of a failure), without taking the refrigerating equipment off-line (see figure R-105). The bypass/isolation circuit can be factory-installed or field-installed. On field-installed valves, be certain to use refrigerant valves that are designed and rated for this purpose. The total pressure-drop of the HRU, fittings, valves, tubing, and other associated components should be calculated so that pressure drop is kept within maximum allowable limits. Charts and schematics are provided in this manual to aid in the design and sizing of the hot gas circuit. For special systems or applications, consult Enviro-Temp and/or refrigerating equipment manufacturer for recommendations. A vibration isolator mounted in the discharge line will reduce noise and lessen the chance of tubing fractures caused by compressor vibration. Gas pulsation noise can be dampened by the addition of a discharge muffler if the HRU is to be 4 SINGLE COMPRESSOR, UNLOADING TYPE CAPACITY CONTROL REFRIGERATING SYSTEMS The hot gas circuit and HRU should be sized to handle the entire discharge of the compressor at fullyloaded conditions without causing excessive pressuredrop. At the same time, proper velocity of refrigerant should be maintained. If the hot gas line is to have a vertical riser of 8’ or greater, a double riser should be used to assure proper gas velocity during part-load operation. (See figure R-107). The small riser should be sized for a minimum gas velocity of 1000 fpm when the compressor is operating at its minimum load capacity. The large riser should be sized to handle the difference between minimum and maximum compressor capacity so that, during full-load operation, the two risers combined will allow full refrigerant flow within acceptable pressure-drop limits, and with sufficient velocity for proper oil movement. Again, if an oil separator is used, it does not negate the need for the proper piping design and sizing. MULTIPLE COMPRESSOR SYSTEMS Segregated Refrigerant Systems ED and SD series are particularly suited to this application when dual compressors are used. These systems, since they are non-unloading, do not usually pose complications with respect to piping design and sizing. Each circuit, since it is a separate circuit, should be treated as a single compressor, non-unloading system (see Single Compressor, non-unloading refrigerant systems section). Many systems use multi-circuited evaporator and condenser coils, each circuit having its own compressor. This allows for capacity control by offcycling of compressors. This type of system requires a separate heat exchanger/refrigerant circuit for each compressor. The water circuits in these heat exchangers are usually circuited in a parallel configuration so that fluid may be heated whether one or all of the compressors are in operation. The Enviro-Temp Multiple-Compressor On multiple compressor arrangements of this type there may be refrigerant check valves installed on each individual compressor discharge line to prevent refrigerant from active compressors from condensing on the heads of idle compressors. The HRU should be installed downstream of these valves. As always, good refrigeration practice and piping design should be followed to minimize pressure-drop and promote proper oil movement (see figures R-109 and R-110). Common refrigerant circuit systems may use a single HRU sized to accept the full hot gas discharge when all compressors are in operation, or may use multiple HRUs sized for the full load capacity of each individual compressor. These systems are usually manifolded into a discharge header which brings the refrigerant flow of all the operating compressors into a single hot gas line. This hot gas line would then connect to the “refrigerant in” line on the HRU. 5 Bypass Type HRU If partial superheat recovery is desired, a bypass system using a smaller HRU may be used. This type of installation requires that the hot gas line be branched, so that the required tonnage is routed through the HRU with the balance of the system tonnage routed around the HRU to the condenser inlet (see figure R-121). Proper line sizing of the two branches will maintain proper gas velocity and system balance. When this type system is applied to unloading compressors, and the HRU is sized to the capacity at minimum load, a solenoid valve should be installed in the line bypassing the HRU. This will ensure desired gas velocity through the HRU for proper oil movement during part-load compressor operation. This design will keep the HRU active through all stages of compressor loading (see figure R-123). R-121 On compressors with multiple steps of unloading, HRUs sized for each step of unloading may be used. Solenoid valves should be installed on the “refrigerant in” lines of the HRUs to close off those circuits that are not needed as the compressor unloads (see figure R125). The method of controlling this solenoid valve will vary depending upon the type of unloader employed by the compressor. Solenoid valve closes when compressor unloads to HRUs capacity R-123 R-121 6 Bypass/Isolation Circuits three (3) refrigerant valves, one each on the “refrigerant in” and “refrigerant out” lines and a bypass tube between the “refrigerant in” and “refrigerant out” lines (see figure R-105). Be certain to use proper size and type refrigerant valves to keep discharge pressuredrop within acceptable levels. A bypass/isolation circuit offers the advantage of being able to bypass the HRU if service or replacement becomes necessary, without having to take the refrigerating equipment off-line. This can be especially desirable on multiple compressor, common discharge systems. This type of circuit requires 7 WATER PIPING, DESIGN AND CONNECTION Enviro-Temp HRU units are designed for a water flow rate of 0.4 gpm/H.P. This flow rate will produce optimum performance in most cases. The flow rate can be varied to meet differing requirements. With any heat exchanger, as water flow rate is increased, the total BTU heat exchange will increase, but temperature rise of the fluid will decrease. Greater fluid temperature rise can be achieved by reducing flow rate through the HRU. Plumbing and piping connections should be made using approved materials and connections for potable water systems if the HRU is to be used for domestic water heating or pre-heating. This usually means a pressure rating of 150 psi. Another issue is with respect to the solder used in sweat joints. Most code bodies require low-lead or no-lead content solder. Consult the appropriate code enforcement department for approved materials. If the application of the HRU is for spa or pool heating, heat exchangers and piping should be constructed of a material approved for use with chlorinated water. Since the acidity of the water can become quite high, cupro-nickel, stainless steel, titanium, or other suitable material should be specified. These applications usually require negative suction lift pumps. Consult factory or pump supplier. In most applications, HRUs are used as preheaters, or supplementary heaters, and are usually connected to a storage tanks (or tanks). The water in the storage tank is pumped through the heat exchanger in a closed-loop configuration. Each time the water is passed through the HRU, its temperature will be raised. With sufficient passes through the HRU, the water can be heated to within a few degrees of the hot gas temperature. As the water temperature in the storage tank increases, a lower BTUH recovery rate will result. For this reason, a storage capacity of approximately 10 gal/H.P. will usually produce best overall performance of the HRU. If higher water temperature rise, rather than greater total BTUH recovery, is desired, a storage capacity of 5 gal/H.P. is recommended. When making water piping connections between the HRU and the water heater, boiler, or storage tank, there are some considerations that should be made. First consideration should be given to the applicable plumbing codes. A great deal of extra work can be avoided by using approved methods and materials for the plumbing hookup. This information should be obtained from the proper code enforcement body prior to installation. Some other factors to consider are performance of the HRU and serviceability of the system. The best performance of the HRU will result from pulling the coldest water at or near the bottom of the tank. This can be accomplished by installing a tee in the cold water feed to the water heater for the supply line to the HRU. Most tanks use a dip tube for delivering cold supply water to the water heater. The return water line from the HRU can be connected to the tank, by means of a tee, to the bottom drain port of the tank see figure W-101). The serviceability of the system can be improved by using unions on pipe connections and a bypass/isolation circuit on the water lines. This will enable the HRU to be bypassed in the event of a need for service, without interrupting the hot water circuit. There are schematics and instructions for various types of connections within this section of the manual. These examples, by no means, represent all the ways in which a successful installation can be accomplished. For engineering assistance with special applications, consult factory. The water usage should also be considered when sizing storage tanks. If the HRU is to be used for domestic water heating, as the water usage increases, the storage tank temperature will decrease. For applications having short periods of high usage and long periods of low usage, increased storage capacity (thermal storage) may be used to accomplish the desired results. The purpose and design of the heat recovery project should be to replace as many BTUs as possible with the heat from the HRU. This design strategy will usually produce the greatest dollar savings for the enduser. The pumps used in Enviro-Temp HRUs are centrifugal circulators designed for potable water. They create differential pressure through the heat exchanger, causing the water to be circulated between the storage tank and the HRU. The pumps are constructed with either brass, bronze, or stainless steel volutes (impeller housings or heads) and impellers to resist corrosion that could contaminate the water supply. The circulator pumps are available in a wide range of horsepower and performance characteristics to meet the various pumping needs of different applications. It is best to determine the required flow rate and piping losses of the HRU plumbing circuit to assure that the proper pump is supplied. 8 Single Tank There are many different ways in which the HRU can be connected to a storage tank or water heater. As a general rule, the best results will be realized if the coldest water is piped to the HRU. The heated water is normally returned through the drain port of the tank. Since heat rises, the hottest water will go to the top of the tank. Figures W-103 and W-105 illustrate some typical plumbing connections of HRUs to a single stor- age tank. When connecting to an existing tank, a thorough flushing of the tank is recommended to remove sediment that accumulates in the bottom of the tank. When pulling water form the bottom of the tank, caution should be taken so that sediment that accumulates in the tank is not pulled into the pump where it may foul the impeller. This can be accomplished by 9 installing a Y-strainer or fabricating a suction trap (see figure W-104). Water lines between the HRU and the storage tank should be insulated separately with an approved tube insulation. If these lines are to be direct-buried in the ground, use an insulation approved for this application so that water will not penetrate the insulation and reduce the insulating value. Insulating all valves, pipe, and fittings will reduce line losses and improve energy savings. To make the HRU more serviceable, shut-off valves should be installed on both water lines. These valves are usually installed at, or near, the storage tank. When these valves are used, a pressure relief valve, installed on either water line, between the HRU and the shut-off valves must be installed. This is to vent excessive pressure in the event the valves are closed, trapping water in the heat exchanger while the refrigerating equipment continues to operate. By add ing another pair of valves (figure W-103), one valve tee’d into each water line at the lowest point in each line, the HRU can be isolated and drained. This design is particularly useful if the HRU is to be drained for freeze protection during the winter season. Thisalso provides access to the heat exchanger for chemical cleaning and descaling. This arrangement is useful in purging the air from the system and is recommended on all installations. (NOTE: If system is to be drained for freeze protection, circulator pump must be electrically disconnected to prevent damage to the pump from dry-run).Once the plumbing has been completed, any air trapped in the system must be purged. The circulator pump will not pump if air is trapped in the volute. The removal of air is a simple operation when isolation and access valves have been installed. By opening the valve on the “water in” line at the tank and opening the access valve on the “water out” at the HRU, the air can be purged from the suction side of the pump. After the air has been removed, close off the access valve and open the shut-off valve on the “water out” line at the tank. Automatic air vents may also be used to remove and keep air out of the system. Continued operation of any air-locked (dry run) pump can cause premature pump failure. Multiple Tanks, Series When Enviro-Temp units are connected to multiple tanks in series, it is usually done so that the first tank provides storage capacity for the HRU and the last tank in the series is used as a booster or backup heater. This configuration is designed so that water is preheated in the storage tanks, thereby reducing the heating load on the booster heater. With this design, the cold water supply would enter the storage supply would enter the storage tank at the “cold” water port and preheated water would leave at the “hot” port. This preheated water then enters the booster tank at the “cold” port where it can be boosted to the proper temperature. The heated water leaves the booster heater at the “hot” port where it is piped to the desired appliance (see figure W-107). 10 Multiple Tank, parallel In some installations, a parallel piping configuration is desired to increase storage capacity. This is easily accomplished by manifolding the “cold” ports and “hot” ports together into common supply and re turn pipes (figure W-109). This system may be desired if periodic large volumes of hot water are required with extended periods between hot water demands. This is common in wash-down operations. Multiple HRUs, Parallel Connection Many applications will have multiple HRUs, each connected to a separate compressor to reclaim the heat from several condensers. In these cases, it is usually easiest to run one supply and one return line between the storage tank and the HRUs and connect the HRUs, in parallel, with the two water lines. When this design is used with active HRUs (units with pumps) care should be taken to assure that the pumps do not work against each other. This can be accomplished by installing a check valve on the “water out” line of each HRU, upstream of the return line (figure W-110). Be certain, when using spring check valves, to use a valve with light spring pressure so that the pump can overcome the additional head loss. Swing check valves may also be used. The additional head losses associated with these valves should be calculated into the total system head loss when sizing the pump(s). 11 This same design often lends itself to the use of slave HRUs (units without pumps), using a single circulator pump (see figure W-111). If using this type system, be certain to size the pump for the proper flow rate and head loss for all the HRUs and associating piping. If no flow through idle is desired, the installation of a pressure-actuated water flow control valve (Penn V46 series or equivalent) will stop water flow when the compressor is idle (figure W-113). These valves can be set to open at a desired head pressure, thus helping to maintain head pressure of the refrigerating system by modulating water flow. A solenoid valve can also be used to stop flow during the compressor off-cycle. This type of valve is usually fully-open or –closed, and does not modulate flow. If this type of valve is used, be certain that it is rated for the temperature and pressure that will be encountered with heating water. 12 Plumbing Connection with Hot Water Loops or Solar Systems It is also possible to connect HRUs to a solar system. Depending upon the desired use of the HRU, there are several methods of connection. Some hot water systems will use two pipes (supply and return) to circulate hot water continuously. This system is commonly used in hotels, where it is desirable to have hot water instantly available to many rooms. A pump will circulate water from the water heater through the hot water loop and return it to the water heater to be reheated. When installing an HRU to a system of this type, care should be taken in the design of the HRU piping so that the two circulator pumps (HRU pump and Hot Water Loop pump) do not work against each other. It is best, if possible, to keep the plumbing connections of the HRU and hot water loop separate (figure W-111). If the connection must be made together, check valves and proper line sizing will allow the two systems to operate properly (figure W-119). • If the HRU is to be used as a booster for the solar heated water, the HRU should be connected in series. • If the HRU is to act as an alternate heat source when there is little or not sunlight, the HRU should be connected in a parallel configuration at the tank. This arrangement will allow water to be heated by solar or the HRU. Again, care should be taken in the design to prevent two pumps (solar and HRU) from working against each other (see figures W-111 and W-119). 13 ELECTRICAL AND CONTROLS Electrical Connections ible. In some cases, (such as 3 phase or higher voltage systems), 115 VAC pumps may be used, as the available control circuit, be certain the control transformer, if used, has sufficient capacity to operate the pump and controls (figure E-104). If the control transformer is already operating at its rated output, an additional step-down transformer may be wired into the load-side of the compressor contractor to supply proper voltage to the pump (figure E-102). The Enviro-Temp active HRUs are designed so that the circulator pump will operate when the compressor operates. The simplest method is to connect the pump to the load side of the compressor contractor (figure E-101). Each time the contractor closes, the compressor and HRU pump will be started. Since pumps are available in different voltages, be certain the pump voltage and compressor voltage are compat 14 All wiring should be done in accordance with applicable codes. The HRU pump controls should be fused separately (normally factory prewired) since the pump is usually a smaller horsepower motor than the compressor. The HRU should also be properly grounded. relays and pressure or temperature controls, so that the pump can be activated if any or all of the compressor(s) are operating (Consult factory for pump modules). Continuous operation of the pump will use additional energy and increase heat loss through the piping, and is not recommended for systems with long compressor off-cycles. Since there are many different methods of control and connection of the HRU, it is impossible to give examples for every situation in this manual. However, a thorough knowledge of the controls and control strategy will be very helpful in determining the best design. Controlling pump operation may be desirable in some applications, such as multiple slave HRUs connected to a single supply and return water lines. Timed operation can be accomplished using a time clock. Running the pump in conjunction with a compressor(s) requires a pump control module (figure E-107). The pump control module can be designed with control 15 Thermostats There are three thermostats that are commonly used in HRU systems. There are water temperature limit, freeze protection, and refrigerant temperature thermostats. Water Temperature Limit Thermostats domestic water heating, the temperature should be limited to 160 degrees or less for safety purposes. If a tempering valve is used on the plumbing circuit, there will be not need to reduce the temperature setting on the thermostat unless a redundant limit control is desired. These thermostats are designed to open on temperature rise to limit the temperature of the water. The sensor for these thermostats is usually mounted on the “water in” line of the HRU. When the desired temperature is achieved, the thermostat opens and terminates pump operation. When the HRU is used for Freeze Protection Thermostats These thermostats are designed to close on a fall in temperature (nearing the freezing point), so that the pump will be activated, circulating warm water from the storage tank through the heat exchanger. This thermostat must be wired in parallel around the other controls to a constant power source such as the load line side of the compressor contactor (figure E105). Refrigerant Temperature Thermostats be used to provide for electrical isolation in conjunction with freeze protection thermostats (see Figure E-105). These controls are available as options on EnviroTemp commercial / industrial units. These thermostats are designed to close on temperature rise and open on fall. They are used to prevent premature or overcooling of the refrigerant which can reduce refrigerating effect. They may also Pressure Controls ing of the refrigerant may drop head pressure too low, and reduce refrigerating effect. This situation can be corrected by installing a pressure control (fan cycle type) in series with the other controls in the HRUs electrical circuit. It is important to maintain proper operating pressures of the refrigerating equipment to maintain efficiency. In certain situations, such as low ambient conditions or cold water in the storage tank, overcool 16 The pressure control can be adjusted to open on a fall in refrigerant pressure, terminating pump operation. Once the pressure has increased sufficiently, the pressure control will again close and start the pump. Most of these controls offer an adjustable differential which should be set at a range wide enough to prevent short cycling of the pump motor (figure E-103). lowest de sired head pressure setting. As the head pressure increases, the valve will open wider, allowing more water flow, which will serve to maintain proper head pressure. This control is refrigerant-pressure operated, eliminating the need for additional control wiring (see figure W-113). There are numerous controls and control systems that can be used with heat recovery systems. A thorough knowledge of the different controls and desired sequence of operation for the HRU will be very helpful in the design and application of control systems. Consult factory for special applications. Another control that is often used wit the HRU is a pressure actuated water flow control valve (such as the V46 series Penn valve). This valve is installed on the “water out” line of the HRU with the sensor line connected to the refrigerant liquid line (preferably the high pressure line). The valve should be set to open at the 17 MAINTENANCE AND TROUBLESHOOTING Performance Testing After installation of the HRU, a performance test will confirm the proper operation of the system. The performance figures obtained from this test on new equipment can serve as a guideline in the future as to whether the unit is in need of maintenance or servicing. When comparing future test figures with the original test data, be certain that the operating conditions are reasonably similar so that a valid comparison can be made (i.e. entering water temperature, water flow rate, hot gas discharge temperature). If water flow rate and temperature rise of the water through the heat exchanger are known, the BTUH recovery rate can be easily determined. The following formula can be used to calculate the BTUH output of the HRU. By transposing the equation, flow rate or gpm can be found. Q = 500 x GPM x T.D. Q = BTUH 500 = 60 min./hr x 8.33 lbs./gal. GPM = Gal per minute T.D. = Temperature Difference (Leaving water temp – Entering water temp) GPM = Q 500 x T.D. T.D. = Q 500 x GPM By installing a flow-setter/indicator, flow rate can be established at a glance. This is a very useful component for testing and is inexpensive to include during system installation. Testing Controls Since there can be numerous controls that can be installed with the HRU, an explanation of the troubleshooting every possible control is practical. However, a discussion of basic controls is in order. Water Temperature Thermostat temperature (closing the contacts) and checking for electrical continuity. If this procedure is done while a test thermometer is attached near the thermostat sensor, the accuracy of the thermostat can be determined by comparing the thermostat setting with the actual temperature readings. This control is designed to limit water temperature at some desired setting. This control opens the circuit when the set point temperature is reached and terminates the circulator pump operation. The sensor for the thermostat should be mounted on the “water in” line of the HRU. This control should be checked by setting the temperature higher than the water 18 MAINTENANCE AND TROUBLESHOOTING Freeze Control Thermostat This control must be wired in parallel around any other HRU controls and is designed to close on a fall in temperature. (Figure E-105). When the contacts close, (approximately 35° F) power is supplied to the circulator pump so that hot water is circulated from the storage tank through the heat exchanger and water lines to prevent freezing. This thermostat can be used to sense either water or air temperature. If it senses water temperature, it will open when the water line temperature reaches the limit set point (i.e. L45-10 closes on fall at 35°F and opens on rise at 45°F). If the thermostat senses air temperature, it will close on temperature fall and stay closed until the air temperature rises above limit set point. To test this control, the temperature at the sensor must be lowered below the closing temperature (35°F) while checking for electrical continuity. Again, a thermometer should be used to check the accuracy of the control during the test. The temperature of the sensor can be lowered by spraying with liquid refrigerant or immersing the sensor in an ice water bath. Head Pressure Controls set points of the control. This can be accomplished by manipulating the head pressure of the refrigerating equipment during actual operation. For air cooled equipment the head pressure can be raised by blocking air flow through the condenser or cycling off of the condenser fan. Head pressure can be lowered by spraying cool water on the condenser. Check for opening and closing of the control at the desired pressures and adjust or replace the control as required. If the HRU is installed on water cooled equipment, pressures can be manipulated by increasing and decreasing water flow through the condenser. The two common types of head pressure controls are operated by refrigerant pressure or refrigerant temperature. To test the temperature type, check for electrical continuity while heating the sensor to its closing set point temperature. Once the thermostat closes (reads electrical continuity) remove the heat source from the sensor. While testing for continuity allow the sensor to cool, measuring the temperature at the opening point. Compare the actual operation temperature with the desired operating temperatures and adjust or replace the control as necessary. To test the pressure operated control (fan cycle) requires raising and lowering the head pressure above and below the 19 MAINTENANCE AND TROUBLESHOOTING Refrigerant Leak Test If a leak is suspected in an HRU, a leak test must be performed. There are two methods for testing that are effective on HRUs that are encased in a two-part foam such as the Enviro-Temp unit. They are pressure –drop test or leak soap (or bubble) test. Since the foam insulation gives off a gas that fools halide detectors, they are of little or no use in testing for leaks. The pressure-drop test involves pressurizing the HRU with nitrogen to the working pressure (450 psi) and sealing the system for 24 hours. If there is a loss in pressure, a leak can be presumed. The bubble test involves pressurizing the HRU and testing for leaks by covering the suspect areas with an approved leak soap and searching for the sign of bubbles. Since every Enviro-Temp unit is pressure-and leak-tested at the factory, the chance of a leak is very remote. Be certain to properly test the system prior to removal or replacement. Cleaning, Descaling Water Tubes There are two methods of cleaning the water tubes of the E$P units, depending on the type of unit used. The mechanically-cleanable unit (E-341-XX-C-*, the “C” means mechanically cleanable) can be brushed with a wire brush. This can be done by isolating the water supply to the HRU, relieving the water pressure, and removing the access plugs at the rear or the unit. Once the tubes have been brushed and all scale materials have been loosened, flush the water tubes with fresh water, re-install the access plugs and return to service. The circulator pump should be shut off during this operation and all air must be bled from the water circuit when returning the unit to operation. Be certain to use an approved pipe sealant on the threaded access plugs when re-installing to prevent water leaks. equipped with isolation and access valves. The isolation valves should be shut off and the access valves opened. The chemical descaler can be pumped through the water tubes until the tubes have been thoroughly cleaned. Once the tubes have been properly cleaned the system should be thoroughly flushed with fresh water to remove any descaler and sediment. Again, upon returning the system to operation, all air must be bled from the water circuit, so that pumping action can be resumed. The need for cleaning of the water tubes can be determined by testing for heat exchange (see Performance Testing in this section). The frequency of cleaning required will depend upon the hardness of the water, hours of operation, and the temperature of the water. Periodic monitoring and testing of the system is usually the best method of establishing a cleaning schedule. Chemical de-scaling of the HRU can be accomplished using a metal-safe descaler. If this method is used, the “water in” and “water out” lines must be Winterization for Freeze Protection If the HRU is mounted in a non-conditioned space subject to freezing conditions, and is connected to an air conditioner or other unit that will not be operated during the winter months, it must be protected from freezing. Since the HRU is a water filled appliance, it is subject to freeze damage. Be certain the HRU is equipped with a freeze protection control that has been properly tested prior to anticipated freezing conditions (See Freeze Protection Thermostats in Electrical and Controls section). Remember, if a power outage occurs, the freeze protection control system will be rendered useless. NOTE: THE SUREST METHOD OF FREEZE PROTECTION IS TO DRAIN THE SYSTEM. BE CERTAIN THAT ALL AIR IS REMOVED FROM THE SYSTEM BEFORE RETURNING THE SYSTEM TO OPERATION. IF THE SYSTEM IS DRAINED FOR FREEZE PROTECTION, THE PUMP SHOULD BE ELECTRICALLY DISCONNECTED AS A SAFETY MEASURE, TO PREVENT THE POSSIBILITY OF DRY RUN. 20 This manual is produced by Turbotec Products, Inc., and is intended to be used as an aid to installation of Enviro-Temp Heat Recovery Units. Various applications may require installation designs or methods differing from those described in this manual. For special applications consult Turbotec or other qualified personnel for assistance. Tu r b o t e c P r o d u c t s , I n c . 651 Day Hill Road Windsor, CT 06095 Tel: 860.731.4200 Fax: 860.683.2133 Headquarters 914-916 25th Street, SE Hickory, NC 28602 Manufacturing Plant 1-800.394.1633 www.turbotecproducts.com sales@turbotecproducts.com ETIOM-1108