Operating instructions

10
operate the control components may occur.
B. Remote Hydronic Controls
The GW240, and 360 use tandem compressors (two
connected together) configured as stage-controlled with
separate Y and Y2 inputs with an adjustable time delay for
the Y2-controlled contactor. Consult the instructions
packaged with the remote hydronic controls for proper
mounting and operation of the hydronic controls.
Important – If one remote hydronic control operates
multiple heat pumps, the control wiring of the heat pumps
must be isolated with isolation relays to avoid excessive
voltages or overheating and premature failure of the control
components.
Power is supplied to the remote hydronic control from the R
and X terminals on the heat pump terminal strip.
A single-stage hydronic control (heating Aquastat) on a
storage tank or a wall mounted thermostat may be all that is
required for simple heat-only systems. The contact on the
hydronic control closes and provides 24Vac to the Y
terminal. When using a hydronic control, insert the
temperature sensor approximately 1/3 of the way down into
the storage tank. Set the hydronic control setpoint to 110-
115
o
F typical, and set the differential to 15
o
F to avoid short
cycling.
CAUTION – The setpoint of the hydronic control must
limit the LWT from the heat pump to a maximum of 120
o
F
to avoid premature failure of the compressor.
A cooling hydronic control (Aquastat) can be mounted on
the water supply line, as shown in Figure 4. This control
acts as a low limit, which shuts the heat pump down when
the cooling water reaches the setpoint (e.g. 45
o
F).
Changeover from heating to cooling can be achieved in two
ways: 1) a manual toggle switch to select the heating or the
cooling hydronic control (Aquastat), or 2) a cooling
thermostat which powers the coil of a single pole/double
throw relay to select the heating hydronic control (normally
closed contact) or the cooling hydronic control (normally
open contact).
Note – Always wire the system to shut down (Anti-short-
cycle) between a heating and cooling mode changeover, or
nuisance trip-outs could occur from changing modes “on
the fly.”
For Zoning applications, any number or types of
thermostats, Aquastats, or switches can be used with an
independent power supply (typically a 24-volt transformer)
to activate specific zone controls. These zone controls are
normally either a zone pump (Figure 4) or zone valves
(Figure 5). End switches on the zone valves can be used to
control a pump relay when the zone valve is open. The
pump relay then activates a common pump, which supplies
any number of zones. Example: the fan coil in Figure 4
could be supplied by the same pump as the radiant floor
system if zone valves were used instead of two pumps.
C. Controller
The heat pump controller receives a signal from the remote
hydronic control, initiates the correct sequence of operation
for the heat pump, and performs the following functions:
1) Compressor Anti-Short Cycle
2) Compressor Control
3) Ground Loop Pump
4) Compressor Staging
5) Hydronic Circulator Pump Control
6) 4-Way Valve Control
7) Compressor Lockouts
8) System Diagnostics
9) 24Vac Fuse
10) Plug Accessory
11) Alarm Output
12) GW360 Compressor Overload Modules
1. Compressor Anti-Short Cycle
An Anti-Short-Cycle (ASC) is a delay period between the
time a compressor shuts down and when it is allowed to
come on again. This protects the compressor and avoids
nuisance lockouts for these two conditions;
1. A 70 to 130-second random time-out period occurs
before a re-start after the last shutdown.
2. A 4-minute/25-second to 4-minute/45-second random-
start delay occurs immediately after power is applied to
the heat pump. This occurs only after reapplying power
to the unit. To reduce this timeout delay while servicing
the unit, apply power, disconnect and reapply power
very quickly to shorten the delay.
2. Compressor Control
When 24Vac is applied to the Y terminal on the controller
wiring block, the controller decides, based on lockout and
anti-short-cycle periods, when to turn on the compressor
contactor. The M1 output of the controller energizes the
contactor(s) until 24Vac is removed from the Y terminal.
3. Ground Loop Pump / Ground Water
Initiation
On ground loop systems, a M1 output from the controller
will energize the contactor to start the compressor and the
ground loop pump. On ground water systems, the M1
output will also energize the ground water solenoid valve
through the “Plug Accessory” connector.
4. Compressor Staging
GW240 and 360 have staged compressors controlled with
separate Y and Y2 inputs. The M1 output of the controller
energizes the first compressor contactor and begins the
time-out of the time delay (adjustable 10 to 1000 seconds;
factory set at 10). After the time-out delay, a Y2 input can
energize the 2
nd
compressor contactor. Note – Ensure
there is always a delay time between the operation of the
two compressors to avoid nuisance low-pressure lockouts.