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Outdoor Air
- 20°F and Below
Pump P1 and P2 are operating in parallel. P3 is on standby and remains
off.
Outdoor Air - 20°F and Below 40°F
System moves into a partial heating load requirement. The 50/50
system allows for P2 to be shut down by an outdoor reset, leaving the
system at 50% flow capacity and operating at a 50% pumping reduction.
Valves are positioned by the reset schedule or a relay connected to
P2.
Outdoor Air - 40°F and Below 60°F
Here is the most striking cost difference between a 50/50 design
and a conventional 4-pipe system. Rather that 100% of the chilled and
hot water flow being circuited by two pumps rated for 100% of their
respective flows, the 50/50 system efficiently delivers 4-pipe capacity
with half of the pumping requirement. The unnecessary full flow requirement
during a marginal day is eliminated. The chiller is brought on line
by outdoor reset. Valves are also positioned by the outdoor reset schedule
or a delay connected P2.
Outdoor Air - 60°F to 80°F
When heating is no longer required, the boiler is shut down along
with P1. Since only a partial cooling load is required, P2 circulates
50% of the total flow. Valves are positioned by the outdoor reset schedule
or a relay connected to the pumps.
Outdoor Air - 80°F and Above
Design day cooling allows for both P1 and P2 to be operating in
parallel delivering 100% of the chilled water flow. Valves are positioned
by the outdoor reset schedule or a relay connected to the pumps.
The 50/50
system allows design day operating costs to be incurred only when necessary.
By using half of the normal main size, with a double Riser Heat Exchanger
in each unit, the 50/50 system delivers only the load required for each
season, substantial reducing installation and operating costs.
Remember:
The pumps on a 50/50 system are up to 50% smaller than those found on
a conventional 4-pipe system.
Up to 85%
of the time a fan coil unit is operating at less than full capacity.
The 50/50 system allows you to realize significant operational savings
during this time.
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