31
Installation & Service Manual
4
System piping
(continued)
Each appliance has a combination gas valve to cycle the gas
supply on and off to the burners. The combination valve
consists of a gas regulator and two valve seats to meet the
requirements for redundant gas valves. The valve has a gas
control knob that must remain in the open position at all
times when the appliance is in service. The gas control valve
has pressure taps located on the inlet and discharge sides of
the valve. Manifold pressure is adjusted using the regulator
located on the valve.
The manifold pressure is preset at the factory and adjustment
is not usually required. If the manifold pressure is to be
adjusted, follow the “Gas Manifold Pressure Adjustment
Procedure” for proper adjustment.
Combination gas valve
An alarm bell is available as a factory supplied option
on 150,000 - 300,000 Btu/hr water heaters. The alarm
bell is shipped separately for remote mounting and is
not weatherproof. If ordered on an outdoor unit, mount
the alarm bell inside a building. Refer to the wiring
diagram in the “Diagrams” section of this manual for wiring
connections.
Alarm bell (if equipped)
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.
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 storage tank. The use of a
properly sized pump and the control of water velocity, as
explained below, is important for correct operation of your
water heater.
Domestic water heating
NOTICE
These water heaters are provided from
the manufacturer with a single power
supply to the unit for operation of
both the standard cirulating pump and
controls.
All circulating pumps shipped with these units equipped
with the Pump Delay Systems are all bronze pumps to
ensure that no water discoloration can occur in an extended
off cycle of the pump.
Water velocity control
IMPORTANT
To ensure proper velocity through
the heat exchanger, it is necessary to
regulate the temperature rise across
the heat exchanger from inlet to outlet.
This must be done on initial installation
and periodically rechecked. With the
correct temperature rise across the heat
exchanger, you may be assured of the
proper velocity in the tubes. This will
yield long life and economical operation
from your water heater. Excessive lime
buildup in the tube is a result of too
little velocity in the tubes. Care should
be taken to measure temperature rise
and maintain a velocity as follows.
1. With the pump running and the hot water supply
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 4A. 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.
4. Be sure the circulation pipes between the
water heater and storage tank are not less than
2" diameter for a single appliance 150,000 through
300,000 Btu/hr installation.
5. Common manifold piping for multiple appliance
installations will require larger minimum pipe sizes to
ensure proper flow. See Table 4B.
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 (Table 4A).
Summary of Contents for Efficiency-Pac EW 150 -- 300
Page 47: ...47 Notes ...
