Lochinvar 495 Domestic Water Heaters, Water Velocity Control, Required Temperature Rise, Table Q

Hydronic Heating Boilers and Domestic Water Heaters

DOMESTIC WATER

HEATERS

This section applies only to those units used to supply potable hot water for domestic use. The hot water supply boiler 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. Hot water supply 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

IMPORTANT: To ensure proper velocity through the 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 of velocity through the tubes. Excessive pitting or erosion in the tube is caused by too high of velocity through the tubes. Take care to measure temperature rise and maintain a velocity as follows:

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-Q. 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 985,000 - 2,065,000 Btu/hr.

5.Common manifold piping for multiple unit installations will require larger minimum pipe sizes and tank circulating tappings to ensure proper flow. See TABLE-R.

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-Q.

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.

Required Temperature Rise

Based on heating potable water with a hardness of 5 to 25 grains per gallon and/or total dissolved solids not exceeding 350 ppm, see Water Chemistry, page 37.

TABLE - Q

Temperature Rise Chart

Btu/hr Temperature

Input Rise °F

495,000 15

645,000 19

745,000 22

985,000 18

1,255,000 23

1,435,000 26

1,795,000 32

2,065,000 37

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