Lochinvar 90, 500 service manual Three Way Valves, Boiler Flow Rates

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4Hydronic piping (continued)

Low Temperature Bypass Requirements

This piping is like a primary/secondary boiler installation with a bypass in the secondary boiler piping. Inlet water temperatures below 140°F (60°C) can excessively cool the products of combustion resulting in condensation on the heat exchanger and in the flue. Condensation can cause operational problems, bad combustion, sooting, flue gas spillage and reduced service life of the vent system and related components. The bypass allows part of the boiler discharge water to be mixed with the cooler boiler return water to increase the boiler inlet temperature above 140°F (60°C). This should prevent the products of combustion from condensing in most installations. The bypass should be fully sized with a balancing valve to allow for proper adjustment. A valve must also be provided on the boiler discharge, after the bypass. Closing this discharge valve forces water through the bypass. Start boiler adjustment with the bypass valve in the full open position and the boiler discharge valve half open. A small amount of the higher temperature boiler discharge water is mixed with the system water to maintain the desired lower system temperature. A remote low temperature range operator is recommended to control the boiler operation for temperatures lower than 100°F. This remote operator should be wired across the R and W terminals (see Room Thermostat Connection and Terminal Strip Instructions in Section 5 of this manual).

Three Way Valves

The installation of a three way valve on this boiler is not generally recommended because most piping methods allow the three way valve to vary flow to the boiler. This boiler is a low mass, high efficiency unit which requires a constant water flow rate for proper operation.

Low flow rates can result in overheating of the boiler water which can cause short burner on cycles, system noise and in extreme cases, a knocking flash to steam. These conditions can cause operational problems and non-warrantable failures of the boiler. If a three way valve must be installed, please pipe in a primary/secondary system. Based on boiler sizing and system flow requirements, this piping may still result in boiler short cycling.

Installation & Service Manual

Boiler Flow Rates

￿ CAUTION The maximum flow rate through the boiler with a copper heat exchanger must not

exceed 30 GPM.

The heat exchanger is generally capable of operating within the flow rates of a residential heating system. Should the flow rate exceed the maximum allowable flow rate through the boiler 30 GPM) an external bypass must be installed. The bypass should be fully sized with a balancing valve to allow for proper adjustment of flow. Flow rate can be determined by measuring the temperature rise through the boiler.

The basic guide for minimum flow in this boiler is based on a 40°F temperature rise in most installations. Lower flow and a higher temperature rise is acceptable if the boiler system is specifically designed for the characteristics of a higher temper- ature rise. A system not specifically designed for a higher temperature rise may experience overheating of the boiler water. This can cause short burner on cycles, system noise and in extreme cases, a knocking flash to steam. These conditions can lead to operational problems and non-warrantable fail- ures of the boiler. High temperature rise systems must be designed by a qualified engineer.

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Contents Models 90,000 500,000 Btu/hr Contents Checking equipment Please read before proceedingCodes Copper-fin =B=R Rating RatingsCopper-fin Specifications Gas connection pipe Copper-fin How it worksModels CWN270 Front View Model CWN399 Front View 422 Location of unit Determine unit location3Combustion Air Direct from Outside Determine boiler location6Combustion Air from Outside Single Opening Minimum Recommended Combustion AIR Supply to Equipment Room Vent Pipe Sizes VentingConventional Negative Draft Venting System Venting Less from Ridge From Parapet Wall Vertical Vent Termination ClearancesVent Materials Masonry Chimney InstallationSidewall Venting Number7CB with Vent Damper and Vent Damper Terminal Block Automatic Vent DamperGas Supply Gas Pressure Test Gas connectionsGas Connection Manifold PressureGas Piping Install Piping to ControlClockwise to raise regulator gas pressure, counterclockwise Gas Manifold Pressure Adjustment Procedure4Gas Supply Pressure Checking Gas Supply PressureTwo Stage Burner Control System Combination Gas ValvesVenting of Combination Gas Valves Relief Valve Water Flow Switch if equippedHydronic piping Low Water Cutoff if equipped Typical Heating Boiler InstallationsMinimum Required Flow For Heating Boiler General Plumbing RulesPiping of the Boiler System System Temperature Rise ChartCirculator Pump Specifications Heat Exchanger Pressure Drop ChartWater Connections Heating Boilers Only Circulator Pump RequirementsPrimary/Secondary Boiler Piping Boiler Flow Rates Three Way Valves4Primary / Secondary Piping of a Single Boiler Primary / Secondary PipingNot to Exceed 4 Pipe DIA or MAX. of 12 Apart 8Multiple Boilers Zoned with Circulators Boiler Operating Temperature Control Terminal Strip WiringPower Venter Connection to Terminal Strip Electrical connectionsOperating Temperature Control Temperature AdjustmentPump Wiring for a Heating Boiler Temperature Control Settings Locating Temperature ControlMaximum SET Point Determination Maximum Set Point DeterminationInlet Water Temperature Sensor Temperature Control SensorsMulti-Purpose Temperature Sensor Outdoor Air Temperature SensorInstallation of a Tank Sensor Water Heater Application Outdoor Air Reset OptionInstallation of a Remote Sensor Boiler Application Additional Temperature Controls Manual Reset High Water Temperature Limit Control Blocked Vent and Flame Roll-Out / Flame Interlock SwitchInitial Start-up Pre-start ChecklistStart-up 1Gas Valve 90,000 270,000 Btu/hr Models Lighting InstructionsTo Turn OFF GAS to Appliance Safety Shutoff Test For Standing Pilot Ignition SystemOperating Instructions Intermittent Pilot Spark Ignition System F9/M9 Safety Shutoff Test for Spark Ignition Pilot SystemFreeze Protection To Turn Off Gas to ApplianceFreeze Protection for a Heating Boiler System if required Water TreatmentRequired Temperature Rise Required Temperature RiseDomestic water heaters Domestic Water Heaters 90,000 500,000 Btu/hr ModelsPump Operation Water ChemistrySoftened Water Systems 1Single water heatersingle tank 2Single water heatermultiple tank 3Multiple water heatersingle tank Thermostat Settings Remote Sensor InstallationMinimum Pump Performance Heat Exchanger5Danger Warning Pressure Only Relief Valve Water Flow Switch if equippedThermal Expansion Cathodic ProtectionService technician Maintenance and annual startupOwner maintenance See the User’s Information Manual for instructionsMaintenance Check Relief Valve Check Expansion TankCheck Control Settings Check All WiringCombustion Air Adjustment Perform Start-up and ChecksInspection and Cleaning Procedure Inspect and Clean BurnerHeat Exchanger / Burner Access Clear Area Pilot Flame Adjustment ProcedureInspection of Heat Exchanger Waterways Water Circulating PumpGas Train and Controls Review with ownerTroubleshooting Pilot or replace Schematic Diagram F1 Unit DiagramsWiring Diagram F1 Unit 90,000 270,000 Btu/hr Models315,000 399,999 Btu/hr Models Schematic Diagram F9 UnitWiring Diagram F9 Unit Diagrams Diagrams Page Revision a ECO #C06290 initial release CFA-I-S Rev a 09/10
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