Bryant 50YEW Design Manual page 38

Water-to-Water System Design Guide
Part III: Source Side Design / System Selection
Drawing 3-4 – Heating with water-to-water unit and cooling
with water-to-air unit application – units without internal source
pump(s) / single Flow Controller for both units: Drawing 3-4 is
used for water-to-water units without internal source pumps. The
Bryant Flow Controller includes one or two circulator pumps,
plus 3-way valves for purging air from the system. The use of
a separate water-to-air unit for cooling is the Bryant preferred
application when cooling is required (drawings 3-3, 3-4, and 3-5).
This application provides better and simpler control of the heating
and cooling system. Plus, pumps can be sized specifi cally for each
unit's fl ow rate (except drawing 3-4). When using only one set
of source pumps, as shown in drawing 3-4, care must be taken to
ensure that all combinations of unit operation are considered. In
other words, if both units are running (e.g. water-to-water unit is
making domestic hot water and the water-to-air unit is cooling),
the pumps must be sized so that both units have suffi cient water
fl ow. If it is not possible for both units to run with this type of
Drawing 3-4: Water-to-Water Source Piping -
50YEW (No Source Pumps) or 50PSW / GSW Units
- Water-to-Air Cooling (Shared Pumping with
Water-to-Water)
See drawings in section 2 for Load connections
36
arrangement (i.e. there is not enough fl ow), the water-to-air unit
compressor should be locked out when the water-to-water unit is
running via a fi eld-installed relay (water fl ow must also be stopped
through the water-to-air unit via a water solenoid valve). Since the
domestic hot water tank should be quickly satisfi ed, a momentary
disruption of cooling will be less noticeable than an interruption in
domestic hot water generation (domestic hot water priority). In
cases where the water-to-water unit will be generating domestic
hot water in the summer when the water-to-air unit is operating,
a mixing valve may be required to ensure that the entering source
water temperature to the water-to-water unit is not warmer than
the maximum temperature shown in the performance catalog
(50PSW/GSW units only). It is important to note that when
headering the ground loop outside of the mechanical room the
header must be a reducing type in order to be able to purge air
from the system at the Flow Controller 3-way valves. Reducing
headers are addressed later in this section.
Flow Controller
Note 2
P/T Port
Note 1
OUT IN
50YEW,
50PSW,
or GSW Unit
Load HX Source HX
(coaxial)
Bryant: Whatever It Takes.
To/From Ground Loop
Note 2
Water-to-Air
Unit
(Cooling)
Note 4,5
Notes 2,3
Water Out
Water In
P/T Port
NOTES:
1. P/T (pressure/temperature) ports are internal for
50YEW series units.
2. Source water piping must be insulated for closed loop
installations.
3. Unions are not necessary if residential swivel water
connections (60Hz units only) are used.
4. Pump selection (1 or 2) will be determined by size of
water-to-air and water-to-water units.
5. Pressure drop calculation should be made to determine if flow
rate is sufficient when both units are operating (e.g. forced air
cooling (water-to-air unit) and domestic hot water generation
(water-to-water unit). If flow is not sufficient, use two Flow
Controllers (see drawing 3-9) or lock out cooling unit when
water-to-water unit is operating to generate DHW.
6. Other components (additional ball valves, unions, etc.)
may be required for ease of service. This drawing
shows only minimum requirements. Your specific
installation will dictate final component selections.
7. Local code supercedes any piping arrangements or
components shown on this drawing.
04Oct07