A.O. Smith AWH-35, Instruction Manual

Page: 18 / 48

15. All components in the hot water supply system must be
adequately sized to meet peak water flow requirement
16. When the HPWH unit is installed above the storage tank
install a Tee fitting at a high point in the outlet water line
leaving the unit. Install a purge valve, or if required by local
code, a T&P valve (temperature and pressure relief) in a
branch of the Tee fitting that can be used to purge air from
the HPWH unit during start up. See Figure 7 and Figure 8.
17. DO NOT install a (T&P) relief valve in the outlet line of the
HPWH unit unless required by local code.
18. Dielectric unions should be installed a the inlet and outlet
water lines to the HPWH unit.
19. All HPWH water piping must be insulated.
SINGLE TANK CONFIGURATION
The HPWH must be plumbed to storage tank. The maximum
stored water temperature the HPWH unit can produce in the
storage tank is 140°F (60°C). Figure 7 shows a typical storage
tank piping configuration. Tank ports must be large enough to
handle the peak water flow rates through the water heating
system. See Piping Diagrams on page 4 1 for detailed piping
diagrams.
SUPPLY
DUCT
DIGITAL TANK
THERMOSTAT
HPWH
Purge Valve or T&P
(purge air from system)
ISOLATION
VALVES
T&P VALVE
OPENING
HOT
OUTLET
REMOTE TEMPERATURE
SENSOR OR MECHANICAL
TANK THERMOSTAT
COLD
INLET
INLET
(RETURN)
OUTLET
(SUPPLY)
STORAGE
TANK
Figure 7
TWO TANK PRE HEAT CONFIGURATION
When water temperatures above 140°F (60°C) are required the
HPWH and storage tank are piped in series (upstream) with a
backup water heater. See Water Temperature on page 10. The
backup water heater will raise the temperature of the preheated
water to the final system temperature required. Figure 8 shows a
typical preheat piping configuration.
18
DIGITAL TANK
THERMOSTAT
HPWH
HOT
OUTLET STORAGE
TANK
BACKUP
WATER
HEATER
(OPTIONAL)
COLD
INLET
SUPPLY
DUCT
PRE-HEATED
WATER OUT
ISOLATION
VALVES
PRE HEATED
WATER INLET
REMOTE TEMPERATURE
SENSOR OR MECHANICAL
TANK THERMOSTAT
Purge Valve or T&P
(purge air from system)
T&P VALVE
OPENING
INLET
(RETURN)
OUTLET
(SUPPLY)
Figure 8
CONDENSATE DRAIN LINE
The HPWH unit must be plumbed to permit condensate drainage.
Drain piping connected to the HPWH unit should be a minimum
3/4 inch PVC or equivalent. A condensate trap must be used to
overcome the internal vacuum to permit proper drainage. See
Figure 9 below for recommended drain trap dimensions.
The condensate must be discharged to a suitable drain. If a drain
is inaccessible, use a condensate pump.
HPWH
UNIT
6.00
3.00
3.00
CONDENSATE TRAP
(All dimensions in inches)
Figure 9
STANDARD TANK THERMOSTAT
Standard tank thermostats (Aquastat) already installed in the
storage tank may be used instead of the factory supplied Digital
Tank Thermostat if desired. Ensure the standard tank thermostat
is installed the lower third of the tank. Wire the existing tank
thermostat to the HPWH terminal strip. See Standard Tank
Thermostat Wiring on page 38 .