Bell & Gossett DN0145D HS Vacuum Heating Units Series HVTM - Manual (Page 2)

2
DESCRIPTION AND INST ALLATION
The Series HV vacuum heating units are designed to serve the
dual purpose of pumping accumulated condensate back to
the boiler feed tank and maintaining vacuum in the conden-
sate system. This vacuum will draw air out of the system
on start-up and facilitate the flow of steam thru the heating
system.
One pump/vacuum producer/discharge valve assembly con-
trols both the condensate discharge and the production of
vacuum. Two pump (duplex) units have a second assembly for
backup and to provide extra capacity to handle peak loads.
Various electrical controls are offered to meet system require-
ments. These controls are normally supplied as part of the
assembled unit and a wiring diagram is furnished with the unit.
Refer to this electrical diagram as required.
The units respond to both changing condensate levels and
system vacuum requirements.
In operation the centrifugal pump circulates water (conden-
sate) thru the multi-jet nozzle creating multiple jets of water
entering the venturi. These jets entrain air and gasses creating
a smooth steady vacuum in the nozzle body and in the con-
densate system. The air and gasses are separated in the
receiver and vented to atmosphere.
Low system vacuum or high water in the receiver will start the
pump to create vacuum and circulate water.
The discharge valve is opened by means of a solenoid in
response to the condensate level float switch. Controlled
opening of the discharge valve holds sufficient back pressure
in the nozzle body that the vacuum producer continues to
function even when discharging condensate (simultaneous
rating).
When the vacuum and float switches have been satisfied and
the pump stops, the check valve in the nozzle body closes,
preventing the return of air and water to the system.
An internal orifice permits the vacuum in the receiver and in
the system to slowly equalize. Note that the vent line on the
Series HV requires a check valve to prevent return of atmos-
pheric air to the receiver. Without the check valve and orifice,
a system could develop high vacuum upon cooling holding the
check valve closed and thereby preventing flow of condensate
into the unit.
STRAINER
CONTROL PANEL
VENTURI
AIR VENT VALVE
FLOAT SWITCH
RECEIVER
MOUNTING PADS FOR DUPLEX
CENTRIFUGAL PUMPS
CENTRIFUGAL PUMP
MULTI-JET NOZZLE
DISCHARGE
MANIFOLD
SOLENOID
DISCHARGE VALVE
DISCHARGE
CHECK VALVE
VACUUM GAGE
DSK-1330
FIG. 1 SERIES HV VACUUM UNITS 25,000-60,000 EDR
AIR VENT
RECEIVER INLET
MULTI-JET NOZZLES
VENTURI
NOZZLE
BODY
CENTRIFUGAL PUMP
DSK-1328
SOLENOID
DISCHARGE
VALVE
FIG. 2 SERIES HV VACUUM PRODUCER