John Wood Takagi - 320H-520H - Manual (Page 19)

19
Pump Control Connection
The 520H model can be used to control a recirculation
pump. Proper pump control helps to preserve the life of the
system and saves energy as well: The water heater pump
control port is a “normally open dry contact", and therefore
needs additional components to properly control a recircu-
lation pump. To control a recirculation pump, connect the
pump to the “Pump connector" in the 520H as shown in the
diagram below. (In an Easy-Link system, connect the pump
ONLY to the “PARENT" unit.) The pump is to be connected
using suitable relays shown in the diagram below. Please
make sure the relays are properly rated for the recircula-
tion pump. Using the 520H models internal thermistors as a
temperature control, the recirculation pump will only turn on
when recirculation is needed.
CAUTION
In an Easy-Link system, the pump must
be connected to the “Pump connector"
in the “PARENT unit" only. If the pump is
connected to any of the “CHILD units", the
pump will not work.
Recirculation
pump
Connect to this
“Pump connector"
Power supply
for relay
Power supply
for pump
120 VAC
220 VAC etc
120 VAC
220 VAC etc
for relay
Thermal
relay
These components
are NOT included
with the water
heater and are
external to the
unit. They must be
acquired separately.
Pump Control Modes
The 520H provides the four types of the pump control
modes. The pump control modes are selected by changing
DIPswitch settings. The DIPswitches that change the pump
control modes are located in the right bank of DIPswitches
in the upper-left quadrant of the computer board in the
520H. (see below.) These 4 modes only affect pumps that
are connected to the 520H pump control (pg. 19)
Right bank of
DIPswitches
A) Recirculation Control: No. 5 ON
Feature: Maintaining temperature in a standard recircula-
tion loop, providing hot water in a quicker amount
of time.
Function: The pump is only set to run when the tempera-
ture of the water in the recirculation loop is more
than 5C° (9F°) below the set temperature of the
water heater. The pump will run for about 1 min-
ute every 30 minutes to determine whether the
water temperature in the entire recirculation loop
is more than 5C° (9F°) below the set temperature.
If the water temperature is more than 5C° (9F°)
below the set temperature, the pump will remain
running until the water in the loop reaches the
set temperature. Otherwise, the pump will stop
for another 30 minutes. If the inlet thermistor of
water heaters detects that the water temperature
is more than 5C° (9F°) below the set temperature
before those 30 minutes have elapsed, the pump
will activate immediately and remain running until
the water in the loop reaches the set tempera-
ture.
B) Storage Tank Circulation Control: No.6 ON
Feature: This is to ensure a higher rate of recovery for
storage tank applications.
Function: The 520H heats the water 3°C (5.4F°) higher
than its set temperature. The circulation pump
between the storage tank and the water heater
will continually remain running. After set temper-
ature has been reached in the storage tank, the
520H will fire off and limit the water flow rate to
less than 9.8 l/min (2.6 GPM (US)), to continually
monitor the temperature throughout the system.
Note: In this mode, the pump will continually remain
running.