Hot Gas Reheat; Hot Gas Bypass; Internal 2-Way Water Valve - Bosch LV Series Installation And Maintenance Manual

18 | Options

Hot Gas Reheat

(Available on size 015 and larger)
LV series heat pumps size 015 and larger can be
provided with hot gas reheat for active
dehumidification. In operation hot gas reheat
dehumidifies space by cooling the air and
removing moisture and then reheating the air back
to a neutral temperature using waste heat from the
compressor. The net effect is to decrease the
relative humidity of the space without changing
the sensible temperature.
The major components of the hot gas reheat
option are the hot gas reheat coil, the reheat
solenoid valve and the control circuit. When the
control circuit energizes the heat pump in reheat
mode, the heat pump will operate in the cooling
mode. The hot gas solenoid valve diverts the
compressor discharge gas to the reheat coil which
is mounted downstream of the unit evaporator.
This hot gas re-heats the cooled air coming off of
the evaporator.
To function, heat pumps with hot gas reheat must
be controlled by both a thermostat and a
humidistat (or a combination thermostat/
humidistat). The humidistat must provide a dry
contact closure on a rise in humidity above set
point.
Note that the ability of the reheat coil to reheat
cooled air back to a neutral temperature is
affected by the water temperature of the system.
At water temperatures of 85 deg F, the reheat coil
can recover 95% to 100% of the sensible capacity
of the evaporator. At water temperatures below
60 deg F, the reheat coil can only recover 5% to
25% of the sensible capacity of the evaporator.
Refer to the unit wiring diagram for control circuit
details.

Hot Gas Bypass

(Available on size 024 and larger)
The hot gas bypass option can be used to reduce
cooling capacity in low air temperature
applications such as applications with a large
percentage of outside air.
As the air temperature entering the unit drops, the
suction pressure and evaporating temperature
start to drop as well.
8 733 905 683 (2013/04)
At an evaporating temperature of 40°F the hot gas
bypass valve will start to divert a portion of the hot
compressor discharge gas to the low temperature
liquid entering the evaporator coil. This hot gas
serves to warm the evaporator coil and reduces
the cooling capacity of the heat pump.
Note that the hot gas bypass valve is inoperative
in the heating mode.

Internal 2-Way Water Valve

In many applications, including variable pumping
and well water installations, a motorized water
valve is required on the heat pump water circuit.
On the LV series this water valve can be factory
mounted and wired internally to the unit.
The LV series internal water valve option features
a 24VAC motorized water valve rated to 450 psig
working pressure. This valve is wired to open on a
thermostat call for compressor operation (heating
or cooling) and will remain open as long as the
thermostat calls. The valve can remain seated with
up to 20 psi of back pressure on all sizes.
The valve consists of two main parts: the valve
body and the actuator. The valve body is brazed
into the leaving water line of the heat pump and is
a permanent part of the unit. The valve actuator
can be easily removed from the valve body for
service.
Refer to the water side pressure drop table in the
troubleshooting section of this manual to
determine the appropriate pressure drop across
the heat pump with and without the water valve
option.
Note that the 2-Way Water Valve option will add
additional pressure drop between the water in
and water out connections of the heat pump.
Note that this water valve cannot be used as an
isolation valve.
Subject to change without prior notice
LV Heat PumpSeries
LV Heat Pump Series