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Heating
Hydronic
Whenever a "W" (heat) call is received from a hydronic zone, the corresponding "OUTPUT" lug on the zone
controller circuit board is energized with source voltage (see comments under the "Installation and Hookup"
section of this manual). When the Tank Temperature Sensor indicates a temperature is not at the desired levels,
the system controller sends a compressor on (Y OUT) call to the Geo unit, signaling the geo unit to start and the
main pump to turn on.
Forced Air
When the air stat servicing the forced air coil loop sends a "W" call, it starts the forced air coil pump (BT >
80°F) and furnace/air handler blower (F-G). When the coil pump is plumbed as shown on HH120, the buffer
tank fluid must be circulated through the geo with the use of the main pump. The Buffer Tank Controller
software ensures that whenever the coil pump is required, the main pump is on as well (not applicable in "B"
mode).
Chilled Water (cooling)
During the water chilling operation, the zone controller and zone pumps are inactive. When the buffer tank is
being chilled, the OT (outdoor temperature) sensor is utilized to determine if a 2-stage heat pump will operate
in "stage 1" or "stage 2". The OT sensor is not utilized to adjust the target tank temperature during chilled
water operations. Rather, the temperature inside the tank is maintained at a certain set point. From the factory,
this set point is 50°F (Operational differential is 4° F) but can be adjusted anywhere from 40°F to 60°F with the
use of a PC computer and the appropriate software. The cooling operation requires a "Y" signal from the
thermostat servicing the forced air coil loop. When this happens, the buffer tank controller outputs a "Y" to the
heat pump. It also outputs an "O" to the heat pump signaling the heat pump's reversing valve to reverse
refrigerant flow. If the heat pump is a 2-stage unit, first stage cooling (Y1) will be the usual operating condition.
The buffer tank system controller will only send a second stage cooling call (Y2) to the heat pump if unusual
conditions occur, such as:
1. The outdoor temperature is greater than 90° F
2. The expiration of SOT timeout if the outdoor temperature is less than 90° F
3. During buffer tank heat-to-cool "turnover" if the tank temperature is warmer than 60° F
See the attached charts for a further explanation of how the controller reacts under different operating
conditions.
Efficiency Feature Pertaining to an Idle System
Without a room-thermostat initiated call for heat, the Buffer Tank controller will allow the buffer tank
temperature to fall below the target temperature if the outdoor temperature is above a designated temperature
(See: Maintain Tank Target Less Than OT). This can allow for greater system efficiency during moderate
outdoor temperatures. The factory-set designated temperature where this feature is allowed is 10° F. However,
using the appropriate software (available from Electro Industries) this temperature can be adjusted up or down
as desired.
System Pump discussion:
A-Coil Pump and Main Pump: B & C Mode Only
This paragraph relates to the main pump and A-Coil pump relationship during standby mode operation.
In the case of mode B, the standby heat source is a fossil fuel furnace, therefore neither the main pump nor the
A-Coil pump are allowed to operate during standby mode operation (no water is being heated).
In the case of Mode C, the standby heat source is an auxiliary boiler, therefore both the A-Coil pump and the A-
coil pump will operate if there is a requirement for the A-Coil pump (forced air demand and BT > 80°F). This
functionality in mode C allows for proper operation in regards to suggested plumbing shown on HH120.
02/22/2012
17
HI114
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