Operation – Steffes HPB22 Owners Manual User Manual
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2. OPERATION
A. CONTROL SEQUENCE
•SPACE TEMPERATURE CONTROL
In its primary application, supplementing the output of a heat pump, the HPB is normally installed closely adjacent
to and downstream from the heat pump air handler. Installation ducting (see INSTALLATION section) allows the HPB
to draw off a portion of the supply air leaving the heat pump air handler, heat this air as required, and return it to the
supply duct downstream from the HPB. This ensures comfort while utilizing the efficiency of the heat pump.
•CORE CHARGING
The SFIII circuit board, serving as the master controller with its sensor in the outdoor air, normally determines what
level of charge is suitable for prevailing climatic conditions. Upon receipt of the utility off-peak signal, the master
controller operating in conjunction with a core temperature controller, initiates the appropriate core charge level. These
levels are determined in accordance with the following schedule:
CORE CHARGING SCHEDULE
(TABLE 1)
During core charging, heating elements are staged on and off in 7.3 kW increments (maximum).
SUMMER/WINTER
OUTDOOR AIR
CHARGE
kW INPUT FOR HPB (MAX)
CORE TEMP.
SWITCH POSITION
TEMP. (
o
F)
LEVEL
11
15
22
o
F (Nominal)
Winter
45
1
7.3
7.3
11.0
500
Winter
35
2
11.0
14.7
22.0
900
Winter
25
3
11.0
14.7
22.0
1350
Summer
35
1
7.3
7.3
11.0
500
Summer
25
3
11.0
14.7
22.0
1350
•SUMMER/WINTER SWITCHING
Heat calls are unlikely during summer months; but, for those owners interested in maintaining a reduced heating
capacity during off-season periods, a SUMMER/WINTER switch is provided (See Figure 1). Core charge levels will
vary according to the switch position (See Table 1).
Alternatively, owners may choose to simply turn the booster off during off-season periods by moving all 60 AMP
core charging circuit breakers to their off (down) position. The 15 AMP circuit breaker must be left in the on (up)
position for proper operation of other heating and controlled devices (See Figure 2).
•AUTOMATIC CONTROL SEQUENCE
Supply air tempering by the HPB is a function of temperature conditions being sensed by the space thermostat and
controllers provided with the booster. The space thermostat provided with the heat pump incorporates Stage 1, Stage 2,
and Emergency Heat control points. The effect of these control points, core charging requirements, and on-peak/off-
peak periods are summarized in Table 2, Table 3, and Table 4.