Finned copper tube gas boilers & water heaters – Boiler Manual16Figure 7B Multiple Outdoor UnitsGENERAL PIPING REQUIREMENTSImproper piping of this boiler/water heater will voidthe manufacturer’s warranty and can cause boilerfailure resulting in flooding and extensive propertydamage! Excessive water hardness causing scaling inthe copper heat exchanger tubes is NOT coveredunder the manufacturer’s warranty. See Table 8.Excessive pitting and erosion of the internal surface ofthe copper heat exchanger tubes is NOT coveredunder the manufacturer’s warranty if the result of highwater flow rates. See Table 7. Return watertemperatures below 140oF, 60oC will result in heatexchanger damage from excessive condensationvoiding the manufacturer’s warranty, see Primary/Secondary Piping. See Figure 9.Shut off valves and unions should be installed at theinlet and outlet connections of the boiler/hot waterheater to provide for isolation of the unit shouldservicing be necessary.Freeze protectionInstallations in areas where the danger of freezing exists are notrecommended unless proper freeze protection is provided. Thefollowing precautions MUST be observed:1. A continuous flow of water through the unit MUST bemaintained! The pump responsible for flow through theboiler/water heater must run continuously!2. An ethylene glycol/water mixture suitable for the minimumtemperature that the unit will be exposed to must be used. Thepump must be capable of producing a minimum of 15% moreflow and overcoming a 20% increase in head loss.Domestic watersystems must be isolated from the water heater by the use of aheat exchanger or other approved method.3. If the unit must be shut off for any reason the electric, gas andwater supplies MUST be shut off and the unit and its pumpcompletely drained.Improper outdoor installation of this unit can causeboiler failure voiding the manufacturer’s warranty!Relief valvePipe the discharge of the pressure relief valve as shown in Figure 9.Never install any type of valve between the boiler/water heater and the relief valve or an explosion causingextensive property damage, severe personal injury ordeath may occur!Flow SwitchThe flow switch supplied with the boiler/water heater must be wiredto the terminal strip in the control panel to prevent the boiler fromfiring unless there’s adequate water flow through the unit. The flowswitch must be installed in the supply piping adjacent to the boileroutlet connection.Failure to properly install the flow switch may resultin damage to the boiler/water heater heat exchangervoiding the warranty!HEATING SYSTEM PIPINGGeneral piping requirementsAll heating system piping must be installed by a qualified technicianin accordance with the latest revision of the ANSI/ASME Boiler andPressure Vessel Code, Section IV, and ANSI/ASME CSD-1, Standardfor Controls and Safety Devices for Automatically Fired Boilers. Allapplicable local codes and ordinances must also be followed. Aminimum clearance of 1 in, 25 mm must be maintained betweenheating system pipes and all combustible construction. Allheating system piping must be supported by suitable hangers not theboiler. The thermal expansion of the system must be considered whensupporting the system. A minimum system pressure of 12 psig,82.7 kPa must be maintained.Heating boiler piping connectionsThe supply and return connections should be sized to suit the system,per Table 6.Table 6 Supply & Return Pipe SizingInputMBHSupplysizeReturnsize2500 - 5000 4" FLANGE 4" FLANGEPump requirementsThis low mass boiler requires a continuous minimumwater flow for proper operation. The boiler pump must besized to overcome the head loss of the boiler and the near-boilerpiping in order to achieve the required temperature rise. Table 7provides the heat exchanger pressure drop and temperature risefigures. The temperature rise across the boiler must never exceed35oF, 19.4oC. The adjustable pump delay turns the pump on each