Initial Start-Up; Sequence Of Operation; Cooling Mode; Heating Mode - Bosch SM024 Installation, Operation And Maintenance Manual

SM Series Heat Pump

INITIAL START-UP

NOTE: Make sure all valves in heat recovery
water piping system are open. NEVER
OPERATE HR PUMP DRY.
1. Turn on the heat pump. The HR pump should
not run if the compressor is not running.
2. Turn HR switch to the "ON" position. The pump
will operate if entering water temperature to
HR is below 120° F.
3. The temperature difference between the water
entering and leaving the heat recovery should
be 5° to 15° F.
4. Allow the unit to operate for 20 to 30 minutes
to ensure it is functioning properly. The pump
should shut off when the water temperature
entering the heat recovery reaches 120°F.

SEQUENCE OF OPERATION

Cooling Mode

Energizing the "O" terminal energizes the unit
reversing valve thus placing the unit into cooling
mode. The fan motor starts when the "G" terminal
is energized.
The fan motor will take 30 seconds to ramp up
to operating speed and will run at fan only rated
air flow as long as there is no call for compressor
or heater operation.
When the thermostat calls for first stage cooling
(Y1) the loop pump or solenoid valve if present is
energized and the first stage of compressor
capacity starts. The fan ramps up to first stage
cooling air flow in 30 seconds.
Some options will have a built in delay, and
hence, compressor operation is not immediate.
See 'Options' sections for more detail.
When the thermostat calls for second stage
cooling (Y2) the second stage (or full compressor
capacity) is initiated. The fan ramps up to full
cooling air flow.
Once the thermostat is satisfied, the compressor
shuts down and the fan ramps down to either fan
only mode or off over a span of 30 seconds.
Revised 02-15
Note that a fault condition initiating a lockout will
de-energize the compressor irrespective of
which stage is engaged.

Heating Mode

The first two stages of heating (Y1 & Y2) operate in
the same manner as cooling, but with the reversing
valve de-energized. On a call for auxiliary heat
(W1), the fan ramps up to auxiliary heat air flow
immediately and the electric heater package is
energized along with the compressor.
As the thermostat is satisfied, the heaters will shut
off as soon as W1 is de-energized, and the
compressors will remain on until the thermostat
stages are satisfied.
If the unit compressor locks out for any reason
at this time, the electric heaters will continue to
function normally.
Once the thermostat is satisfied, the compressor
shuts down and the fan ramps down either fan only
mode or off over a span of 30 seconds. If
thermostat has two different output points one for
Auxiliary heat and a different one for Emergency
heat the two outputs must be terminated on W1
units equipped with one stage of Electric heat.
(Figure #115)
When using a 2-cool, 3-heat thermostat both the
W1 & W2 on the Heat Pump and W2 & EM on
the thermostat must be connected together via
a jumper. (See Figure#115)
Initial Start-Up | 43
6 720 220 406 (2015/02)