APPENDIX
Appendix 1: Chrome Dome Collector Siting Aid is a tool for determining the best location for solar collectors in Florida. Its simplicity and ease of use in the field make it ideal for installation and service personnel. Appendix 2: FSEC Simplified Sizing procedure for Solar Domestic Hot Water Systems is an invaluable guide in sizing solar water heating systems in Florida. Appendix 3: Electric Water Heater Circuitry describes the electrical connections in a standard hot water tank with two heating elements. Appendix 4: Volt-Ohmmeter (VOM) or Multimeter Operation, provides basic information on VOM and multimeter operation and includes a standard temperature and thermistor resistance table for 3,000 and 10,000 Ohm thermistors. Appendix 5: Solar System Flow Rates describes two simple methods for checking solar system flow rates. Appendix 6: Tools for Service and Repair lists the tools and equipment that field personnel generally need to service a solar system. Appendix 1 Crome-Dome Collector Siting Aid
The Crome-Dome is designed to determine the best location for a solar collector. It will work well for any location in Florida, but it is not appropriate for use farther north than 31°N latitude (southern Georgia). A collector should be mounted in an area receiving sunshine during the entire year. The sun's path drops closer to the horizon during winter, and is higher in the sky during summer. The sun's lowest path, its highest path, and its position three hours before and after solar noon define the solar window. (See Figure 1.) The solar window is shown on the Crome-Dome by the heavy black lines on the sun path diagram. To use the Crome-Dome, stand a few feet in front of the proposed collector site facing south.* (Use a compass to determine south.) Holding the Crome-Dome base as level as possible, and several inches from your eye, look upward through the sighting circle. Align the cross hairs within the sighting circle with the lower edge of the solar window. If you can see any objects (trees, buildings) through the viewer that are within the solar window, these objects will shade the collector site. By aligning the collector location, your eye, cross hairs and object, (see Figure 2) you can read from the sun path diagram the times of day and times of year a particular object will shade the collector location. When checking for high angles (summer), tilt your head all the way back and peer through the viewer on the base of the Crome-Dome. The summer sun path goes almost directly overhead. *If you are on a roof, it is safer to squat or sit at the base of the collector location.
The Crome-Dome was invented by Dr. Charles Cromer, P.E. at the Florida Solar Energy Center in 1980. A-1 A-2 Appendix 2 Simplified Sizing Procedure for Solar Domestic Hot Water Systems
The following procedure was developed to size residential solar Water heating systems in Florida. eating See last page for limitation and assumptions. Hot water demand and tank size
Step 1. Using Table 1. Estimate daily hot water use (GALLONS) And select a nominal tank size (TANK SIZE). GALLONS TANK SIZE gal/day (1) gal Table 1. Hot water demand and tank size . Average GALLONS and minimum TANK SIZE based upon number of people: People 1 2 3 4 5 6 7 GALLONS Minimum TANK SIZE (Gallons) 20 40 40 40 55 66 70 80 85 80 100 100 115 120 (Add 15 gallons per person for each additional person.)
" Step 2. Using Figure 1, determine the proper cold water temperature (COLDTEMP) for location. COLD TEMP F (2) Figure 1. Cold water temperatures Region North Florida (12,2,3)* Central Florida (4,5,6)* South Florida (7,8,9)* COLDTEMP 68"F 72"F 76"F * Correspond to regions for the Florida model energy building code. A-3 Step 3. Calculate how much energy is needed (BTUNEED) to heat the water to 122ºF. BTUNEED = 8.34 x GALLONS x (122-COLDTEMP) x Standby loss factor BTUNEED = 8.34 x _________ x (122 - _________ ) x _________ (Step 2) (Table 2) (Step 1) * See last page for explanation. _____________ Btu/day BTUNEED (3) Table 2. Standby heat loss from storage
Type of tank installation________ 1-in. foam or 2.5 ­in fiberglass (R = 8 ­ 9) 2-in. foam (R= 16-17) Standby loss factor____ 1.20 (Use linear interpolation to obtain standby loss factor for insulation materials having other R-values.) Table 2 is to be used for sizing systems with FSEC ratings. If SRCC rating is used and if There are no other backup tanks use a standby loss factor or 1.0. Example: A thermosiphon water heater with its storage tank containing a back-up element has an SRCC rating. There are not other back-up tanks for the system. In this case use a standby loss factor = 1.0. Example: The same thermosiphon water heater system is used as a preheater to another back-up tank. The element in the thermosiphon tank may not be connected. In this case use a standby loss factor from Table 2 corresponding to back-up tank insulation level. Collector Sizing
Step 4. Determine penalty factors that affect sizing. a. Select the System Factor form Table 3. b. Select the proper Tilt Factor from Table 4. c. Select the Orientation Factor from Table 5. ___________________ System Factor (4a) ___________________ Tilt Factor` (4b) ___________________ Orientation Factor (4c) Calculate the overall penalty factor(PENALTY) for the combination Of all three individual effects: PENALTY = System Factor x Tilt Factor x Orientation Factor PENALTY = ___________ x ________ x __________ (Step 4a) (Step 4b) (Step 4c) ___________________ PENALTY (4c) Table 3. System Factor System configuration________ Direct system with no heat water exchanger. Indirect system with a heat exchanger between collector and storage tank. Systems with SRCC system certification and QNET rating. __System Factor__ 1.29 1.30 1.00 A-4 Table 4. Tilt factor
Tilt angle 0º to 3º 3º to 7º 7º to 12º 12º to 16º 16º to 20º 20º to 25º 25º to 30º 30º to 37º 37º to 43º 43º to 59º Collector tilt Roof pitch 0 1 in12 2 in 12 3 in 12 4 in 12 5 in 12 6 in 12 8 in 12 10 in 12 12 in 12 Roof tilt 0º 4.8º 9.5º 14.0º 18.4º 22.6º 26.6º 33.7º 39.8º 45.0º North Florida 1.25 1.15 1.09 1.05 1.02 1.00 1.00 1.01 1.04 1.08 Tilt Factor Central Florida 1.22 1.14 1.08 1.04 1.01 1.00 1.00 1.01 1.05 1.10 South Florida 1.19 1.12 1.06 1.03 1.01 1.00 1.00 1.02 1.06 1.12 Table 5. Orientation Factors
Collector orientation South or nearly south Southeast or southwest East or west Orientation Factor 1.00 1.15 1.40 Step 5 Calculate the rating requirements of the solar system (RATREQD) To provide 70% of the annual hot water energy needs using the formula: RATREQD = BTUNEED x 0.70 x PENALTY RATREQD = ___________ x 0.70 x ___________ (Step 3) (Step 4) ________________ Btu/day RATREQD (5) Step 6. For the collector selected, record the thermal performance rating at the intermediate temperature (BTURATING) in Btu/day and the gross collector area (GROSSAREA) in square feet from the required FSEC label. Collector Manufacturer _______________________________________ Model No. _________________________ Thermal Performance Rating at the Intermediate Temperature (Btu/day) Or SRCC QNET or QNET equivalent* Gross Collector Area (ft2) Estimate the number of collectors needed using: ________ (Step5) NUMBER = RATREQD BTRUATING = ________ (Step6) Select the actual number of collectors to be used. This is the nearest Whole number to (6c). The total area number of the collector array is: TOTAL AREA = NO. COLLECTORS x GROSAREA ________________ ft2 TOTAL AREA (7b) ________________ NUMBER (6c) ________________ Btu/day BTURATING (6a) ________________ ft2 GROSSAREA (6b) Step 7. ________________ NO. COLLECTORS(7a) TOTAL AREA = _____________ x ____________ (Step 7a) (Step6b) * For those systems that are SRCC certified use the SRCC QNET rating here. Systems with only FSEC test and certification may get an equivalent SRCC QNET from Testing & Operations on request. A-5 Based upon the actual number of collectors to be used, compute the Solar fraction (SOLAR FRACTION): SOLAR FRACTION = 0.70 x NO. COLLECTORS NUMBER = 0.70 x __________ (Step 7a) = _____________________ SOLAR FRACTION (7c) (Step 6c) If the solar fraction (Step 7c) is less than 0.65, the collector array is undersized. Consider either adding another collector or using a different model/size collector. This procedure has several constraints: 1. 2. The procedure is valid only for Florida The procedure is based on sizing solar systems to provide between 65% and 75% of the heating load; i.e., a solar fraction of between 0.65 and 0.75. A solar fraction of 0.7 is estimated to be optimum for most installations and, in particular, for solar collectors with a tilt angle of approximately 20º -25º (mounted parallel to the 4-in. -12 or 5-in12 pitched roofs that are common in Florida). The 20º - 25º collector tilt angle provides for an aesthetic installation and meets 100% of the hot water needed in summer and 50% in winter. Systems can be sized to maximize lifetime saving by providing a larger solar collector that will produce a solar fraction of 0.9 or higher. At high annual solar fractions however, the production and waste of excess heat during the summertime needs to be considered. To minimize collector size for high annual solar fractions, the collectors can be installed at a tilt angle of between 40º and 40º. Optimization of these types of systems is beyond the scope of this simplified sizing procedure. To achieve this solar fraction, the collectors will need to be installed at a tilt angle of between 40º and 50º The hot water delivery temperature of 122ºF in step 3 was obtained by FSEC from analysis of two years of actual experimental data. The 122ºF delivery temperature is consistent with Florida Law, which requires that hot water thermostats be set no higher than 125ºF. It is also consistent with electric water heater energy consumption data as measured by Florida Power and Light Co. Automatic dishwashers may not clean dishes very well at 122ºF. However, most dishwashers have a cycle that Uses an electric element in the dishwasher to boost water temperature to about 140ºF. 3. This form was developed by Subrato Chadra with the assistance of David Block, Mukesh Khattar, David LaHart, Tim Merrigan, Jerry Ventre and Ingrid Melody. A-6 Appendix 3
Electric Water Heater Circuitry The following illustration shows the electrical connections in a standard hot water tank with two heating elements. Each electrical supply line has a potential of 115 volts measured to ground and 230 volts measured across the two lines. The illustration shows where the high-limit protector is located in the circuit. It also shows how the upper thermostat is used to prevent operation of both heating elements simultaneously. First, power travels through the high-limit protector: a double-pole, single-throw (DPST) snapaction device. When the water reaches a predetermined temperature (about 180°F), this device opens both contacts of both lines at the same time, which cuts all power to the heater. To restore operation, the reset button must be pressed. At the output side of the high-limit protector, the circuit splits and forms the parallel circuits that lead to the two elements through their respective thermostats. The upper thermostat is a doublepole, double-throw (DPDT) bimetal type, designed so that when one of the contacts is closed, the other is open, and vice versa. This thermostat is always in operation. Depending on the demand for hot water, it supplies power to either the upper or lower element, but never to both elements at the same time. The lower thermostat is a single-pole, single-throw (SPST) type and controls the lower element. Before this lower element can be energized, the upper thermostat must be "satisfied" (even though the lower thermostat contacts may be closed). A-7 Appendix 4 Volt-Ohmmeter (VOM) or Multimeter Operation
The volt-ohmmeter (VOM) measures voltage and resistance. (Some VOMs also measure current but current measurements are not needed in controller troubleshooting.) VOMs have either an analog or a digital readout. The analog display uses a needle pointer on a scale. The digital display gives an LCD numerical reading. Both types of meters operate from batteries and usually have a battery low indicator to signal when new batteries are needed. The meter contains two probes with wire leads, one black (the common or ground lead) and one red (the positive lead), which plug into color-coded receptacles on the meter. For detailed information about operation of the meter, refer to the VOM manual. Check the VOM before each use: 1. Turn on the power switch. If the battery replacement indicator signals low batteries, replace them before continuing. 2. Set the function switch to "ohms," and set the range switch to a mid range around 0 to 20K ohms. (Note: K equals 1,000 and V refers to volts.) Connect the probe wires to the proper receptacles and touch the red probe to the black probe without contact with your body. The meter should read zero (0) or 0.00 (digital), showing continuity. If it does not, adjust to zero. If the meter doesn't respond, check the battery supply for a blown fuse. Two types of thermistors (sensors that change resistance with changing temperature) are generally used in control systems ­ the 3,000 (3K) ohm and the 10,000 (10K) ohm. Table 1 lists the usual VOM settings for measuring resistance; Table 2, for measuring AC voltage; and Table 3, for measuring DC voltage. Thermistor resistance should match temperature as closely as possible, as shown in Table 4. To be accurate, disconnect the thermistor from the circuit before measuring it. Table 5 lists the resistance setting for a positive temperature coefficient resistance temperature device (RTD) that uses 1,000 (1K) ohm sensors. Resistance Measurements with the VOM
Remember any circuit must be disconnected to measure its resistance. Table 1 Measuring Resistance with the Volt-Ohmmeter
Measuring Resistance Resistance Resistance Resistance Resistance Resistance In the Range of Minimum Maximum 0 199 200 1,999 2,000 19,999 20,000 199,999 200,000 1,999,999 2,000,000 19,999,999 Function Switch at Ohms Ohms Ohms Ohms Ohms Ohms Range Switch at 20000 2K 20 K 200 K 2M 20 M Multiply Reading by 1 1,000 1,000 1,000 1,000,000 1,000,000 A-8 AC Voltage Measurements with the VOM
· · · · Never measure circuits containing over 700 volts AC. Always make measurements from one line to the other (this is measuring in parallel). Never insert probes in series with a line. If the voltage is unknown, start with the highest range on the VOM. Table 2. Measuring AC Voltage with the Volt-Ohmmeter
AV Voltage AV Voltage AV Voltage AV Voltage AV Voltage AV Voltage In the Range of Minimum Maximum 0 0.19 0.2 1.9 2 19.9 20 199.9 200 700.0 Function Switch at AC 0.7 kV AC 0.7 kV AC 0.7 kV AC 0.7 kV AC 0.7 kV Range Switch at 200 mV 2V 20 V 200 V 2 kV Multiply Reading by 0.01 1 1 1 1,000 DC Voltage Measurements with the VOM
· · · · Never measure circuits containing over 1,000 volts DC. Always measure in parallel with the lines. Never insert probes in series with the circuit. If the voltage is unknown, start with the highest range on the VOM. Table 3. Measuring DC Voltage with the Volt-Ohmmeter
DC Voltage DC Voltage DC Voltage DC Voltage DC Voltage DC Voltage In the Range of Minimum Maximum 0 0.19 0.2 1.9 2 19.9 20 199.9 200 1,000.0 Function Switch at DC 1 kV DC 1 kV DC 1 kV DC 1 kV DC 1 kV Range Switch at 200 mV 2V 20 V 200 V 2 kV Multiply Reading by 0.01 1 1 1 1,000 Current Measurements with the VOM
Amperage measurements are not needed in the troubleshooting of controllers. Even if your VOM measures only up to 1 A safely, do not use it as an ammeter placed in series with the pump or motor valves. Some VOMs have extended 10 A ranges, but even these may be damaged if the circuit has a low-resistance short. Possible Causes for Thermistor Malfunction
To check the thermistors in a solar DHW system, disconnect the thermistor leads at the controller. Remember also, a change in temperature changes thermistor resistance. Make sure the pump is not cycling on and off, changing measurement conditions. A-9 Open Circuit If the VOM measures an open circuit (an infinite resistance reading), either the sensor is bad or the associated wiring is broken somewhere along its length. A break may occur where the wire crosses a sharp edge of the building or where it has been bent. Run new wires if the break cannot be found and repaired. High Resistance A high, but not infinite, resistance may also indicate a bad sensor or lead wire. Disconnect the sensor from the lead wire and check the resistance at or near room temperature. The resistance should measure at or near 3K or 10K, depending on thermistor rating. Short Circuit A shorted circuit can also indicate a bad sensor or contact in the associated wiring. This is indicated on the VOM by a zero reading, which shows continuity between the lines. Drift On rare occasions, thermistor resistance drifts to the wrong value for its temperature and it must be replaced. This drift is usually due to aging and can be checked with the VOM. Refer to Table 4 of thermistor temperatures. When resistance readings are correct or nearly correct for various temperatures, the thermistor is working properly. There may be resistance in the wiring. To check the associated wiring, use a jumper to short across the sensor. The ohm resistance of the wiring itself should go near zero. If the resistance still exists, make sure all connectors are clean and no breaks with resistance contact are found. If none of these are found, to eliminate the wiring resistance, replace the wiring. A-10 Table 4. Temperature and Thermistor Resistance
Temperature (°F) Thermistor open Thermistor shorted 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 77 78 80 82 84 86 88 90 3000- Thermistor Infinite 0 10,400 9,790 9,260 8,700 8,280 7,830 7,410 7,020 6,650 6,300 5,970 5,660 5,370 5,100 4,840 4,590 4,360 4,150 3,940 3,750 3,570 3,390 3,230 3,080 3,000 2,930 2,790 2,660 2,530 2,420 2,310 2,200 10,000- Thermistor Infinite 0 32,660 30,864 29,179 27,597 26,109 24,712 23,399 22,163 21,000 19,906 18,876 17,905 16,990 16,128 15,315 14,548 13,823 13,140 12,494 11,885 11,308 10,764 10,248 10,000 9,760 9,299 8,862 8,449 8,057 7,685 7,333 Temperature (°F) 92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 124 128 132 136 140 144 148 152 156 160 165 170 175 180 185 190 195 200 210 3000- Thermistor 2,100 2,010 1,920 1,830 1,750 1,670 1,600 1,530 1,460 1,400 1,340 1,280 1,230 1,180 1,130 1,040 953 877 809 746 689 637 589 546 506 461 420 383 351 321 294 270 248 210 10,000- Thermistor 7,000 6,683 6,383 6,098 5,827 5,570 5,326 5,094 4,873 4,663 4,464 4,274 4,094 3,922 3,758 3,453 3,177 2,925 2,697 2,488 2,298 2,124 1,966 1,820 1,688 1,537 1,402 1,280 1,170 1,071 982 901 828 702 A-11 Table 5. Temperature and RTD Resistance
Temperature (°F) 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 Resistance 861.8 890.5 919.2 948.7 978.2 1008.7 1039.0 1070.3 1101.5 1133.6 1165.6 1198.7 1231.5 1265.4 1299.1 1333.9 1368.5 1404.1 1439.5 Temperature (°F) 35 45 55 65 75 85 95 105 115 125 135 145 155 165 175 185 195 205 215 Resistance 876.1 905.1 933.9 963.7 993.4 1024.0 1054.6 1086.1 1117.5 1149.9 1182.1 1215.4 1248.4 1282.5 1316.5 1351.4 1386.2 1422.0 1457.7 A-12 Appendix 5 Solar System Flow Rates
Determining flow rate Determining approximate flow rate through the collector loop can help you identify problems in the system such as faulty pump operation, clogged or restricted pipes or failure of the check valve to open properly. Here are two simple methods for checking the solar system flow rate. Method A This method uses the "siphon principle" to keep water in the collector loop when the city water pressure is shut off. First, you must purge air from the collector loop. Also, you must vent the storage tank to the atmosphere to prevent a vacuum from forming during the following steps. Refer to the following illustration. a. Turn off the back-up heating element (to avoid burning out the element should the water level drop to the element's level). b. Ensure all air is purged from the collector loop and close or plug any valves (air vents or vacuum breakers) that may admit air into the pipes. c. Close the shutoff valve in the cold water supply line to the tank. d. Open the PT relief valve on the storage tank. e. Attach a hose to the boiler drain on the return line from the collector(s). Drain off a few gallons of water so the standing water level is below the top of the tank and not in the hot and cold supply pipes. If you have a clear plastic hose, you can easily see the water level. When the level is about 1" below the top of the tank, stop the draining process by elevating the open end of the hose above the top of the tank. Leave the boiler drain open. f. Close the isolation valve between the return line boiler drain and the tank. g. Lower the open end of the hose to just above the standing water level in the tank. Allow the level to come to equilibrium. h. Place a vessel of known volume (a gallon milk jug works well) where it can receive all the discharge from the hose attached to the return line boiler drain. Keep this container as close to the water level line as possible to minimize static head influences on the flow rate. i. Manually turn on the pump and use a stopwatch (or the sweep second hand on a wristwatch) to measure the time required to fill the vessel. j. Turn off the pump. Use this formula to calculate the flow rate: A-13 k. Close the return line boiler drain. Open the shutoff valve in the cold water supply to refill the tank. Bleed off the entrapped air through the PT relief valve, and close it when the tank is full. 1. Open the remaining valves to return the system to normal operation. This avoids prolonged stagnation in the collector loop. Method B Another less accurate method can be used when the system is plumbed in such a way that you cannot follow Method A. a. Determine how much water the collector can hold (volumetric capacity). If the collector has been certified by FSEC, you can find this information on the FSEC Summary Information Sheet. b. Turn off the pump and allow the collector loop pipes to cool down to equilibrium (and the collector to heat up). A-14 c. Put your hand on the return pipe near the tank and turn on the pump. When you feel the "slug" of hot water warm the area under your hand, start timing. (Again, use a stopwatch or the sweep second hand on your wristwatch.) Continue timing until the pipe starts to cool down again. d. Calculate the approximate flow rate by dividing the volumetric capacity reported on the Summary Information Sheet by the time measured (gallons/hour or gallons/ minute). Flow Rates and Water Stratification in Solar Tanks Flow rates also have a direct correlation to system performance. Low flow rates in single-tank direct systems result in better overall system performance. Low circulation does not mix up the water in the solar tank and thereby enhances stratification. When water circulates through the collectors and returns at a low flow rate, the hottest water will migrate to the upper portion of the tank. The colder water at the bottom of the tank will not mix with the returning collector-heated water. Thus, the bottom water being fed to the collector is the coldest water in the tank. This in turn improves the collector's efficiency because the colder the inlet temperature, the more efficient the collector panel. To improve system performance by using lower flow rates and better stratification, follow these guidelines: a. Use a flow rate of approximately 0.01 gallons per minute per square foot of collector panel (e.g. 40 square feet of panel x 0.01 = 0.4 gallons per minute). b. Use dip tube diffusers on your cold and hot ports. You can make these by heat closing the end of the dip tube and drilling holes near the end ­ so the water exits sideways instead of downward. c. Return the solar heated water at least 8 to 10 inches below the top heating element. A-15 Appendix 6 Tools for Service and Repair
To avoid costly delays, repair and service personnel must arrive at the scene fully prepared and outfitted. Listed below are the recommended tools and equipment for diagnosis and repair of DHW systems. All tools must meet OSHA guidelines. Bucket, 5-gallon plastic Brush, flux Brush, wire Chalk-line reel Compass Crimping tool Cutter, copper and PVC Drill, battery operated Drill, electrical Drill bits, assorted size set, high speed steel twist Drill bits, 3/4" to 3" set, steel hole saw Drill bits, 3/8" to 1" size set, power wood Extension drill Extension cord, 100' Extinguisher, fire (A:B:C: rated) Flashlight, industrial Glasses, safety Gloves, work Gun, caulking Gun, soldering Hacksaw Hammer, claw Hand pump, or small air compressor Hex key sets, standard and metric Hose, rubber 25' Inclinometer Knife, utility Ladder, extension 24' Lamp, heavy duty trouble Level, 24" Level, magnetic torpedo Mask, dust Mirror, inspection Multimeter or voltmeter Nut driver set, standard and metric Pliers, diagonal cutting 6" Pliers, locking 10" Pliers, needle nose 8" Pliers, 6" Pliers, slip joint 8" Plumb bob Pop riveter A-16 Pressure gauge, testing Putty knife Rope, safety 3/8" x 100' Saw, hand 8 point, general purpose Saw, skill Saw, miter Screwdriver, angle Screwdriver set, electronic Screwdriver set, Phillips Screwdriver set, standard Sensor stimulator Slate, nail cutter Shears, industrial Shoes, non-skid Socket wrench set Torch, acetylene Torch, propane Vise, mechanics Vise grips, 10" Water meter key Wire strippers Wrench set, Allen Wrench, adjustable Wrench, pipe 10" Wrenches, open-end kit, 5/16" to 3/4" A-17