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IM 1131-2

Water Piping

Glycol Solutions

WGZ units are designed to operate with a leaving chilled fluid
temperature from 15°F (-9.4°C) to 60°F (16°C). Leaving
chilled fluid temperatures below 40°F (4.6°C) result in suction
temperatures at or below the freezing point of water and a
glycol anti-freeze solution is required. The use of glycol in the
evaporator will reduce the performance of the unit. The
reduction in performance depends upon the glycol
concentration and temperature. This should be taken into
consideration during initial system design. Glycol in the
condenser will have a negligible effect on performance
because glycol at these higher temperatures will perform with
characteristics similar to water.
Daikin Applied recommends a minimum concentration of 25%
be provided on all glycol applications. Glycol concentrations
below 25% are too diluted for long-term corrosion protection
of ferrous metals and corrosion inhibitors need to be
recalculated and possibly added to the system.
Chiller capacity, flow rate, evaporator pressure drop, and
power input for glycol solutions can be calculated using the
following formulas and reference to

Table 2

for ethylene

glycol and

Table 3

for propylene glycol. Test coolant with a

clean, accurate, glycol solution hydrometer (similar to that
found in service stations) to determine the freezing point.

Note:

Ethylene and propylene glycol ratings are outside the

scope of AHRI Standard 550/590 certification program.

Capacity

is reduced compared to that with plain water. To find

the reduced value, multiply the chiller's capacity when using
water by the capacity correction factor C to find the chiller's
capacity when using glycol.

Flow

-To determine evaporator gpm (or T) knowing T (or

gpm) and capacity:

For Metric Applications

-- Determine evaporator lps (or T)

knowing T (or lps) and kW:

Pressure Drop

- To determine glycol pressure drop through

the cooler, enter the water pressure drop graph on

page 14

the actual glycol flow. Multiply the water pressure drop found
there by P to obtain corrected glycol pressure drop.

Power -

To determine glycol system kW, multiply the water

system kW by factor K.

Table 2: Ethylene Glycol Correction Factors

Table 3:

ropylene Glycol Correction Factors

Condenser Water Piping

Arrange the condenser water so the water enters the bottom
connection of the condenser. The condenser water will
discharge from the top connection. Failing to arrange the
condenser water as stated above will negatively affect the
capacity and efficiency.
Install pressure gauges in the inlet and outlet water lines to the
condenser. Pressure drop through the condenser should be
measured to determine flow on the pressure drop/flow curves
beginning on

page 14

. Vibration eliminators are recommended

in both the supply and return water lines. Install a 20-mesh
strainer in the inlet piping to the condenser.
Water-cooled condensers can be piped for use with cooling
towers, well water, or heat recovery applications. Cooling
tower applications must be made with consideration of freeze
protection and scaling problems. Contact the cooling tower
manufacturer for equipment characteristics and limitations for
the specific application. Head pressure control must be
provided if the entering condenser water can fall below 60°F.
The WGZ condenser has two refrigerant circuits with a
common condenser water circuit. This arrangement makes
head pressure control with discharge pressure actuated control
valves difficult.
If the tower water temperature cannot be maintained at a 60°F
minimum, or when pond, lake, or well water that can fall
below 60°F (15°C) is used as the condensing medium, special
discharge pressure control must be used. A water recirculating
system with recirculating pump as shown in