Lochinvar 1, 000 through 2 warranty Integral Bypass, BYPASS VALVE - Synchronization

INTEGRAL BYPASS

	HOT
	WATER
BYPASS VALVE	OUTLET

PRIMARY PUMP HEAT

EXCHANGER

SECONDARY

HEAT

EXCHANGER

COLD

WATER

INLET

FIG. 40 Bypass Piping with Valve Actuator and Pump

temperature conformal coating to prevent any corrosive damage to the copper tubes or cast iron headers from the low pH condensate. The protective coating is brown in color and covers both the headers and finned tube surfaces. The secondary heat exchanger is designed to maximize heat transfer efficiency by fully condensing flue products. The inner jacket that houses the secondary heat exchanger is designed to collect the flue gas condensate and discharge it from the jacket.

This appliance contains an integral bypass and circulating pump that connects the primary and secondary heat exchangers. A floating-point automatic bypass valve regulates the flow of water through the bypass between the two heat exchangers. The valve is a butterfly type valve with an EPDM seat and a 24 VAC gear driven motorized actuator. The appliance’s internal Excel-10 controller senses inlet water temperature to the primary heat exchanger and provides a 24 VAC signal to open or close the valve as required. Operation of the bypass is based on an assumed flue gas dewpoint temperature of 130°F (54.4°C) as referenced in the ANSI standards. The dewpoint of flue gasses becomes the minimum acceptable inlet water temperature for the primary heat exchanger. Sustaining water temperatures in the primary heat exchanger above the dewpoint prevents formation of flue gas condensate on the primary heat exchanger. The Excel 10 establishes a dead band around the 130°F (54.4°C) setting of +1.8°F (2°C). This means the actual temperature can vary positive or negative approximately 2° around the 130°F (54.4°C) minimum desired setting. The variable input rate of the burner from 25% to 100% will also affect the position of the bypass valve as it adjusts to maintain primary heat exchanger (Bypass) temperatures above the 130°F (54.4°C) setting. The inlet temperature to the primary heat exchanger is displayed by the command display and provides the Excel 10 the adjustment point for the bypass valve. The inlet water temperature to the primary heat exchanger generally should not remain below the minimum dewpoint temperature for more than approximately five minutes. In this case, the inlet temperature to the primary heat exchanger is

rarely below 125°F (51.7°C). The actuator on the bypass valve will take between a minimum time of 180 seconds up to a maximum time of 300 seconds to move from a “full closed” position to a “full open” position or vice versa. Operation of the bypass valve actuator assures that water temperature in the primary heat exchanger is maintained high enough to prevent condensate formation on the primary heat exchanger.

BYPASS VALVE - Synchronization

As the main power is switched on and/or when the run/stop switch is placed in the “RUN” position, the bypass valve will go through a synchronization process to establish a reference point for opera- tion. After the initial synchronization on start-up, the bypass will resynchronize in approximately 2 week intervals of normal operation. This resynchronization will only occur in an off cycle operation of an installed appliance. During the synchronization process the Excel 10 controller will overdrive the valve actuator to a full closed position. This establishes a reference point to assure quicker response to variation in inlet water temperature. The bypass valve operates best when it can start operation from a full closed position. A status point mode of Byp Synch will be indicated in the Command Display as the actuator on the bypass valve is overdriven to the closed position for synchronization.

29