Domestic Water Heaters; Water Velocity Control - Lochinvar 000 - 2 Installation And Service Manual

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
495,000
645,000
745,000
985,000
1,255,000
1,435,000
1,795,000
2,065,000
36
Rise °F
15
19
22
18
23
26
32
37