Raypak HI DELTA 302B Installation & Operating Instructions Manual

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Raypak HI DELTA 302B Installation & Operating Instructions Manual Manual pdf 16 page image

16Failure to exceed 105ºF (41ºC) within 7 minutes mayresult in the premature failure of the hot surface ignit-er, remote flame sensor, burners and heat exchanger.It can cause operational problems, bad combustion,sooting, flue gas spillage and reduced service life ofthe vent system. The bypass allows part of the heaterdischarge water to be mixed with the cooler heaterreturn water to increase the heater inlet temperatureabove 105ºF (41ºC). This precautionary measureshould prevent the products of combustion from con-densing in most installations. Warranty claims will bedenied when condensation occurs.Cold water operation issues are applicable to bothcold water start and cold water run applications. Coldwater operation for 7 minutes or less on start-up isacceptable. Where cold water starts will last longerthan 7 minutes or where cold water operation is con-tinuous, provisions must be made to mix highertemperature outlet water with the colder inlet waterand thereby raise the inlet temperature to at least105ºF (41ºC) within the 7-minute time limit.Cold Water StartsFrequent (more than once a week) cold water starts,wherein the inlet water temperature remains below105ºF (41ºC) for more than 7 minutes, must have coldwater start protection. Known protection methods con-sist of mixing heated outlet water with the inlet waterwith a bypass to raise the inlet to 105ºF (41ºC) or high-er. Once the system is heated up and has return watertemperatures of 105ºF (41ºC) or higher, the mixing ofoutlet water with inlet water is no longer needed andthe bypass can be shut off. If the bypass is not shut offas the system heats up, the outlet temperature maycontinue to climb and actuate the high limit, therebyshutting down the heater. Thus an automatic valvesystem, such as a three-way proportional valve or amodulating two-way valve to control the bypass,should be utilized.Cold Water RunCold water run differs from cold water start in that thesystem water entering the heater remains below 105ºF(41ºC) continuously. Typically, this is the case in swim-ming pool heating and water source heat pumpapplications as well as some others. If the systemwater is kept in a narrow temperature range, a perma-nent manual bypass can be employed and manuallyadjusted to achieve an inlet temperature of 105ºF(41ºC) or higher. An injector pump arrangement mayalso be utilized to keep the heater loop at or above105ºF (41ºC). An injector pump approach has theadded value of being able to adjust to changes in thesystem water coming back to the heater take-off.Temperature & Pressure GaugeThe temperature and pressure gauge is factory-mounted in the in/out header.Hydronic HeatingPump SelectionIn order to ensure proper performance of your heatersystem, you must install a correctly sized pump. Ray-pak recommends using a 20°F ∆T as design ∆T. (∆T isthe temperature difference between the inlet and out-let water when the heater is firing at full rate). If a ∆Tof larger than 20°F is necessary, see Table H andTable I for flow rate requirements.Table H: Heater Rates of Flow and Pressure Drops10°F T 20°F T 30°F T 40°F T Min. Flow Max FlowModelNo. gpm P (ft) gpm P (ft) gpm P (ft) gpm P (ft) gpm P (ft) T gpm P (ft) T302B 50 3.3 25 0.8 N/A N/A N/A N/A 20 0.5 25 90 9.8 6402B 67 5.8 34 1.4 22 0.6 N/A N/A 20 0.5 34 90 10.0 7502B 84 9.1 42 2.3 28 1.1 21 0.6 21 0.6 40 90 10.4 9652B N/A N/A 55 4.1 36 1.8 27 1.1 27 1.1 40 90 10.8 12752B N/A N/A 63 5.7 42 2.6 32 1.5 32 1.5 40 90 11.3 14902B N/A N/A 76 8.3 50 3.8 38 2.2 38 2.2 40 90 11.7 17Notes: 1. Basis for minimum flow is 20 gpm or 40°F ∆T. Basis for maximum flow is 90 gpm. Flow switch will not operate if flow is lessthan 20 gpm.2. Rear-mounted pumps may provide higher flow rates on smaller models than the system requirements.NOTE: Individual and multi-boiler Cold Water Startsystems require the use of a 20°F ∆T boiler pump.NOTE: To ensure proper operation, use 20°F ∆Tboiler flow rates when designing the heating systemloop pump.