11
NXW REVERSIBLE CHILLER INSTALLATION MANUAL
Field Connected Water Piping cont.
Before final connection to the unit, the supply and return
hose kits must be connected to each other, bypassing
the unit, and the system flushed to remove dirt, piping
chips and other foreign material. Normally, a combination
balancing and close-off (ball) valve is installed at the return,
and a rated gate or ball valve is installed at the supply. The
return valve can be adjusted to obtain the proper water
flow. The valves allow the unit to be removed for servicing.
The proper water flow must be delivered to each unit
whenever the unit heats or cools. The proper flow rate
cannot be accurately set without measuring the water
pressure drop through the refrigerant-to-water heat
exchanger.
A 3 GPM flow rate per ton [0.054 LPS per kW]
of cooling capacity (2.25 GPM per ton [0.0404 LPS per
kW] minimum) is required.
NOTE
: The placement and connection of the water
circulating pump(s) must be taken into consideration prior
to designing the final water piping systems.
Closed Loop Tower/Boiler Systems
The water loop is usually maintained between 60°F [15.5°C]
and 90°F [32.2°C] for proper heating and cooling operation.
This is accomplished with a cooling tower and a boiler.
To reject excess heat from the condenser water loop, the
use of a closed-circuit evaporative cooler or an open type
cooling tower with a secondary heat exchanger between
the tower and the condenser water loop is recommended.
If an open type cooling tower is used without a secondary
heat exchanger, continuous chemical treatment and filtering
of the water must be performed to ensure the water is free
from damaging materials.
CAUTION: Water piping exposed to outside
temperature may be subject to freezing.
Open Loop Well Water Systems
Installation of an open loop system is not recommended
without using a secondary heat exchanger unless water
quality guidelines are met.
Earth Coupled Systems
All supply and return water piping should be insulated to
prevent excess condensation from forming on the water
lines. Ensure pumping system is capable of providing
adequate flow rate at the system pressure drop, 3.0 GPM
per ton [0.054 LPS per kW] (source side) is recommended.
Antifreeze in the loop is strongly recommended.
Heating with High Source Temperatures
Heating water with a water to water unit using high source
temperatures can lead to operating conditions that fall
outside of the system operating range. The condition
occurs when the loop (source) temperature exceeds 70°F
[21.1°C] with a full flow of 3 GPM per ton [0.054 LPS per
kW]. Under this scenario, the evaporating temperature can
fall outside of the compressor operating window.
To allow the system to operate correctly, restricting the
source side flow when the evaporating temperature
exceeds 55°F [12.7°C] is recommended. One way of
accomplishing this is to use a flow-restricting valve on the
source loop circuit that is controlled by the evaporating
temperature. Locate the sensing device on the refrigerant
inlet of the evaporator. In dual circuit systems, the company
recommends monitoring both circuits and controlling off
the sensor that reads the highest temperature.
As an alternative to the evaporating temperature, the
suction line temperature can be monitored with the same
control capability. In this control, temperature should be a
maximum of 65°F [18.3°C].
