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Outdoor reset also improves comfort control and
extends the life of the burner and boiler. Without reset,
system temperatures are maintained too high during mild
weather. This produces uncomfortable space temper¬
atures and causes unnecessary cycling of the burner.
Systems without reset are susceptible to expansion
and contraction caused by large changes in water
temperature. This causes annoying noise and excessive
system wear. Outdoor reset reduces these undesirable
effects by maintaining lower and more constant water
temperatures. The W964F Aquatrol System senses both
outdoor temperature and discharge water temperature.
As outdoor temperature changes, the Aquatrol resets the
boiler water, following a selected ratio.
ON-OFF AND PROPORTIONAL +
INTEGRAL (P+l) CONTROL
The Honeywell W964F Aquatrol System is designed to
provide any commercial building with reliable, effective
control over hydronic heating systems. The Aquatrol has
field selectable on-off burner control or P+l control of a
motorized 3-way mixing valve.
ON-OFF CONTROLOF BOILERS WITHOUT DOMESTIC
WATER HEATING COILS
On-off control of burners to reset the boiler water
temperature is used mostly with the smaller commercial
boilers. The W964F directly controls the operation of the
burner through output contacts, thereby controlling the
temperature of the discharge water.
W964F P+l CONTROL OF LARGER BOILERS AND OF
BOILERS WITH DOMESTIC WATER HEATING COILS
P+l control is used to reset the discharge water
temperature by positioning a motorized mixing valve.
This valve bypasses return water around the boiler and
mixes it with the correct amount of water leaving the
boiler to provide the required temperature of water being
discharged from the valve into the heating system. Mixing
valves are used with reset systems for three important
reasons:
1. Boilers with domestic water heating coils must be
maintained at a preset minimum temperature to provide
the capacity to serve the domestic water needs of the
building.
2. The manufacturers of many large fire-tube boilers
require the boiler to be maintained at a present
temperature (usually 170 F to 190 F [77 C to 88 C])
regardless of domestic water heating coils.
3. P+l control of motorized 3-way mixing valves
provides much moreaccurate control of discharge water
temperature than either on-off control of burners or
conventional modulating control of mixing valves.
With P+l control, there is zero offset of the required
discharge water temperature. In other words, the actual
discharge temperature does not fall below or rise above
the discharge temperature required by the reset sys¬
tem. This closer temperature control produces more
comfort and more energy savings than on-off or mod¬
ulating control.
In new installations with the Aquatrol, any of the
Honeywell series 60 actuators, such as the M644A-E, are
used with V5013A.B mixing valves. In retrofit of older
installations using W902 reset systems, the W964F may
be used to control existing series 90 motors without
internal balancing relays (M944B,E or M945B,C,G).
APPLICATION VERSATILITY
All hydronically heated buildings, including those
with uncontrolled radiation, controlled radiation, or
variable air volume can benefit from the W964F
Aquatrol System.
UNCONTROLLED RADIATION
The Aquatrol System can be used to provide out¬
door reset in buildings with uncontrolled radiation,
which includes standing radiators, baseboards and
convectors.
The Aquatrol controls the building's space tem¬
perature and is less expensive than zone control. The
Aquatrol saves energy by reducing overheating and
providing night setback during unoccupied periods.
CONTROLLED RADIATION
The W964F can also be used to provide outdoor
reset in buildings with controlled radiation, which in¬
cludes fan coils, unit ventilators, unit heaters, radiator
valves, and terminal reheat.
In these applications, the Aquatrol improves space
temperature control by providing water at a tem¬
perature very close to the heating requirements. The
zone and room thermostats fine tune the water flow for
precise temperature control.
Reset ensures lowered heating water temperature as
the weather becomes milder. This can speed the
changeover from heating to cooling on a two-pipe fan
coil system. (Water over 90 F [32 C] must not be sent to
the chiller.)
VARIABLE AIR VOLUME
In variable air volume cooling with perimeter heating
applications, the W964F provides controlled heating
of perimeter zones and reduces the conflict between
the heating and cooling systems. Additional energy
savings can be gained by using the built-in night
setback.
If questions arise regarding this product, contact your local distributor or Honeywell representative.
Honeywell Inc.
International Sales Offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland,
1885 Douglas Drive N.
France, Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A.
Golden Valley, MN 55422-4386
PRINTED IN U.S.A.
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