John Wood Takagi - 910 - Manual (Page 14)

14
Pump Connnection
The 910 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 addi-
tional components to properly control a recirculation pump.
To control the recirculation pump, connect the pump to the
pump terminal in the 910 as shown in the diagram below.
(In a multi- unit system, connect the pump ONLY to the
PARENT unit.) The pump is to be connected using suitable
relays shown in the diagram below (the pump terminal is
essentially only a dry contact. An external power supply and
relays are required to operate the pump). Please make sure
the relays are properly rated for the recirculation pump.
Using the 910 internal thermistors as a temperature control,
the recirculation pump will only turn on when recirculation
is needed.
CAUTION
In a multi-unit system, the pump must be
connected to the "Pump terminal" in the
"PARENT" unit only. If the pump is con-
nected to any of the "CHILD" units, the
pump will not work. These components are
NOT included with water heaters and are
external to the unit. They must be acquired
separately.
Connect to this terminal.
This is the pump terminal.
Power supply for relay
Power supply for pump
120 VAC 220 VAC etc
120 VAC
220 VAC
etc for
relay
Thermal
relay
Recirculation
pump
These components are NOT
included with water heaters and
are external to the unit. They
must be acquired separately.
Pump Control Mode
The 910 provides the four types of the pump control
modes. The pump control modes are selected by chang-
ing DIPswitch settings. The DIPswitches are located in the
upper bank of DIPswitches in the lower-left quadrant of the
central computer board in the 910. (See picture below)
Upper bank of DIPswitches
A) No. 4 ON: Recirculation Control
This mode is for providing hot water as soon as possible like
a recirculation usage. The pump is only made to run while
the temperature of the water in the re-circulation loop is not
close to the set temperature of the water heater. The pump
will run for about 1 minute every 30 minutes to determine
whether or not the water temperature in the whole recircula-
tion loop is lower than 5C° (9F°) from the set temperature. If
the water temperature is lower than 5C° (9F°) from the set
temperature, the pump will remain running until the water in
the loop gets up to the set temperature. If not, the pump will
stop for another 30 minutes. If the inlet thermistor senses
that the water temperature is lower than 5C° (9F°) from the
set temperature before those 30 minutes have elapsed, the
pump will activate immediately and remain running until the
water in the loop gets up to the set temperature.
B) No. 5 ON: Storage Tank Circulation Control
The 910 will heat the water 3C° (5.4F°) higher than its set
temperature (unless the 910 is already set at its maximum
temperature of 85°C (185°F)). This is to ensure a higher rate
of recovery for storage tank applications. The circulation
pump (from storage tank to 910) will always remain on.
C) No. 4 and No. 5 ON: Energy Conserving
Recirculation
This pump control mode is similar to the “Recirculation
Control mode”. However, once the heat requirement is less
than 7,440 BTU/h, the pump will turn off. The pump will
activate again when the temperature of the system is less
than 35°C (95°F) or after 20 minutes have elapsed from its
previous operation.
*If operating the pump in this mode, insulation is recom-
mended on the water piping.