BYPASS PIPING ASSEMBLY
The primary and secondary heat exchangers are interconnected with a bypass and pump mounted in 2 1/2 inch (63.5 mm) diameter copper pipe. All access to the piping is from the rear of the appliance. On initial start up, all air must be removed from the bypass piping to ensure proper water flow through the appliance. The bypass piping has an air bleed cock located on the discharge side of the internal pump. This bleed cock should allow any trapped air in the internal piping to be purged from the piping before operation. The bypass piping also contains a flow switch to sense operation of the circulating pump, bulb wells for temperature sensors and a relief valve(s).
INTEGRAL CIRCULATOR
FIG. 41 Bypass Valve and Actuator Assembly
The appliance has an integral circulating pump mounted in the bypass piping. The pump has a 3/4 H.P. motor wired for 120 volt, single-phase operation as shipped. The on-off operation of the circulating pump is controlled by the Excel 10 controller. The pump will start and run continuously when the power switch is in the “ON” position and the run/stop switch is in the “RUN” position. A flow switch installed in the bypass piping assembly proves water flow.
Optional Intermittent Pump Operation
On-Off operation of the circulating pump is available as an option. Cycling of the integral pump is controlled by the Excel 10 controller. The pump will start on a call for heat and a flow switch installed in the bypass piping assembly proves operation. After the burner cycles off and the call for heat is satisfied, the pump will continue to operate for a timed period to remove any residual heat from the combustion chamber before the pump is turned off. If the ambient temperature at the temperature sensor for the Excel 10 drops below 45° F (7.2° C) the circulator pump will turn on to help prevent freezing of the heat exchanger.
BYPASS - Initial Set-up of Maximum Water Flow
On initial start-up of the Intelli-Fin the maximum water flow to the two internal heat exchangers must be manually set before the automatic operation of the bypass begins.
Setting temperature rise on an Intelli-Fin with an automatic bypass is accomplished by disconnecting the power leads to the bypass actuator at the multi-pin connector on the rear of the appliance, declutching the actuator drive and manually closing the bypass valve. Manual adjustment of the bypass must not be attempted if the 24 VAC power leads are connected to the terminals on the appliance, the appliance is operating or if there is any torque on the bypass valve by the actuator. Disconnect the 24 VAC power leads to the valve actuator. The declutch button on the actuator must be pushed down and held in the depressed position to disengage the gear driven motor that operates the valve. The declutch button must push in easily without forcing its movement. If the button does not easily move when pushed, the valve is under torque. Forcing the declutch button in will cause non-warrantable damage to the actuator. Torque can be removed by disconnecting the power leads to the valve actuator. With the declutch button fully depressed, move the actuator handle till it is perpendicular to the piping. This fully closes the bypass valve. The position of the handle is the same as the position of the butterfly in the valve seat. With the bypass fully closed, all inlet water flows through the secondary heat exchanger and then through the primary heat exchanger. No water will flow through the bypass at this time. Turn the appliance on and allow the burner to come on and fire at full rate (100% of input as shown on the Command Display). Adjust the field-installed ball valve in the outlet piping from the appliance to achieve the proper temperature rise for your specific model. Adjustment to achieve this temperature rise ensures a maximum of 90 GPM to the bypass and pump when in operation.
