Lochinvar 497 - 2067 Domestic water heaters, Water velocity control, Maximum Water Flow

Installation & Service Manual

7 Domestic water heaters

This section applies only to those units used to supply potable hot water for domestic use. The water heater must be installed with a storage tank.

This section contains specific instructions for those units used to supply domestic hot water. All warnings, cautions, notes and instructions in the general installation and service sections apply to these instructions. Water heaters are designed for installation with a properly sized storage tank. The use of a properly sized pump and the control of water velocity, as explained below, are important for correct operation of your water heater.

Water velocity control

To ensure proper velocity through the NOTICE heat exchanger, you must regulate the

temperature rise across the heat exchanger from inlet to outlet. Do this upon initial installation and periodically recheck.

The correct temperature rise across the heat exchanger ensures proper velocity in the tubes. This will yield long life and economical operation from your hot water heater. Excessive lime build up in the tube is caused by too low velocity through the tubes. Excessive pitting or erosion in the tube is caused by too high velocity through the tubes. Take care to measure temperature rise and maintain a velocity as follows:

Initial set-up of maximum water flow

On initial start-up, the maximum water flow through the heat exchanger must be manually set before normal operation begins.

TABLE - 7A

MAXIMUM WATER FLOW

CAUTION: The maximum flow rate through a water heater with a copper heat exchanger must be set to provide and not exceed the following flow:

Model	Maximum
	Flow
497, 647, and 747	55 GPM
987, 1257, 1437, 1797, and 2067	90 GPM

If higher flow rates are required through the water heater, an optional Cupro Nickel heat exchanger is available. Consult the factory for specific application requirements.

The heat exchanger is capable of operating within the design flow rates required for the water heater, storage tank(s), and connecting piping. Erosion of the finned copper tubes may occur if the flow rate exceeds the maximum allowable flow rate through the water heater. The maximum flow rate through the water heater must be adjusted. Maximum flow on Models 497 - 747 is 55 GPM and 90 GPM on Models 987 - 2067. Flow rate can be determined by measuring the temperature rise through the water heater when it is firing at full rate input.

48

	TABLE 7B
	Temperature Rise Chart
Model		Temperature
		Rise
497		15°F
647		19°F
747		22°F
987		18°F
1257		23°F
1437		26°F
1797		32°F
2067		37°F

1.With the pump running and the water heater off, the inlet and outlet thermometers should read the same temperatures. If they do not, an adjustment must be made to your final calculation.

2.Turn the water heater “On” and allow time for the temperature to stabilize. Record the difference between the inlet and outlet temperatures. This difference will be the “temperature rise”.

3.Compare the temperature rise on the heater with the required temperature rise in Table 7B. Should adjustment be needed, proceed as follows:

If the temperature rise is too high, the water velocity is too low. Check the following:

1.Check for restrictions in the outlet of the water heater.

2.Be sure all valves are open between the water heater and the tank.

3.Check the pump to be sure it is running properly and that the pump motor is running in the proper direction (see arrow on volute housing).

4.Be sure the installed circulation pipes between the water heater and storage tank are not less than 2 1/2'' in diameter on Models 987 - 2067.

5.Common manifold piping for multiple unit installations will require larger minimum pipe sizes and tank circulating tappings to ensure proper flow. See Table 7C on page 53.

If the temperature rise is too low, the water velocity is too high. Adjust as follows:

1.Slowly throttle the valve on the outlet side of the water heater until the temperature rise is steady at the required temperature rise as noted in Table 7A.

2.Sustained high water velocity and low temperature rise may result in pitting or erosion of the copper tubes in the heat exchanger. This is a non-warrantable failure. Temperature rise must be properly adjusted to achieve the specified flow rate.