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The aquastat connections and system wiring differ for
heating only and heating/cooling systems. Heating only sys-
tems only require one aquastat, while heating/cooling system
require two, one for heating and one for cooling. Heating/
cooling systems require extra relays to provide an isolated cool-
ing signal to the heat pump and to disable radiant in-floor heat-
ing zones while in cooling mode.
typical wiring diagram for a heating only setup, while
000576CDG
depicts a heating/ cooling wiring diagram. These
drawings represent a basic system, in which heating is the de-
fault mode and cooling has priority. It is recommended that the
system be designed by a qualified system designer to ensure
proper functionality.
TABLE 2
shows typical settings for the aquastats. With
these settings, Stage 1 will activate when the tank temperature
reaches the activation point. If the load is too great, the tank
temperature will continue to drop when heating (rise when cool-
ing) until Stage 2 is activated. As the tank temperature stops
dropping and begins to increase when heating (decrease when
cooling) , Stage 2 will turn off before Stage 1, rather than at the
same time as Stage 1. There are three main advantages to this:
Less aquastat probe lag leading to reduced overshoot as the
tank temperature rate of change is reduced when only
Stage 1 is active.
Prolonged Stage 1 runtime leads to increased overall effi-
ciency as Stage 1 has a higher COP than Stage 2.
Reduced number of compressor starts.
The settings may be changed as desired; however Stage 1
setpoint for heating should not exceed
cooling setpoint should not be set below
these setpoint limits will cause the heat pump operating pres-
sures to approach the safety control settings, possibly causing
nuisance shut downs.
TABLE 2 - Typical Aquastat Settings
HEATING AQUASTAT
Stage 1
Item
°F
Setpoint
115
Delta
5
Activation *
110
COOLING AQUASTAT
Stage 1
Item
°F
Setpoint
45
Delta
5
Activation *
50
*Activation is indirectly set by the Setpoint and Delta
values
NOTE:If only floor zones are being heated, it is highly rec-
ommended to drop each of the heating setpoints by 15°F
(8°C) for increased efficiency.
02 JULY 2009
Drawing 000575CDG
show a
drawing
120°F
(49°C); Stage 1
43°F (6°C).
Exceeding
Stage 2
°C
°F
°C
46
105
41
3
5
3
43
100
38
Stage 2
°C
°F
°C
7
50
10
3
5
3
10
55
13
It is recommended that a buffer tank with electric elements
be selected to provide auxiliary / backup heat. The tank ele-
ment thermostat can be set to maximum, allowing the electric
elements to be controlled by an external contactor placed in the
power supply connections. The contactor can be connected to
Stage 2 of the heating aquastat via a 0-2hour timer.
drawing 000575CDG or drawing 000576CDG.
CONTROL TRANSFORMER
The low voltage controls for all model voltage codes ex-
cept code 5 (575-3-60) are powered by a 75VA class II trans-
former. The transformer has a resettable breaker on the secon-
dary side for circuit protection. Should the breaker trip, locate
and correct the problem and then reset the breaker by pressing
in on it. 575-3-60 units have a 100VA transformer with primary
and secondary fuses for circuit protection.
SAFETY CONTROLS
The heat pump has two built in safety controls which are
designed to protect the unit from situations which could damage
it should the operation of the refrigeration circuit fall outside the
allowable operating range.
A. Low Pressure Control
The low pressure control monitors the compressor suction
pressure and will shut the compressor down if the refrigerant
evaporating pressure becomes too low, risking the danger of
freezing conditions in the evaporator.
There are (3) main reasons why this control would activate
in response to the operating conditions of the unit while operat-
ing in heating mode:
1. Low or no outdoor loop flow.
2. Low Outdoor loop entering liquid temperature.
3. Dirty or fouled Outdoor loop heat exchanger.
B. High Pressure Control
The high pressure safety control monitors the compressor
discharge pressure and will shut the compressor down if the
condensing pressure becomes too high.
There are (3) main reasons why this control would activate
in response to the operating conditions of the unit while operat-
ing in heating mode:
1. Low or no Indoor loop flow.
2. High Indoor loop entering liquid temperature.
3. Dirty or fouled Indoor loop heat exchanger.
The unit contains a control board that monitors the safety
controls and operates the compressor accordingly. Refer to
APPENDIX A
for control board specifications. The low pressure
control is connected to LP1 and LP2. The high pressure control
is connected to HP1 and HP2.
The control board also has provisions for a flow switch.
The flow switch is unused from the factory and a jumper wire is
placed across the FLOW SWITCH terminals. If a flow switch is
desired, the jumper can be removed and the two leads from the
flow switch can be connected to the FLOW SWITCH terminals
on the safety board. The flow switch is ignored for 30 seconds
on compressor startup to allow time for flow to be established.
The high and low pressure controls are monitored at all times,
the compressor will not be able to start if either of them has a
fault.
Page 7
Refer to
Boreal Geothermal Inc.
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