EN2R-9005 0406R3-NE
2
DESCRIPTION OF DEVICE FUNCTIONS
Aquastats thermostats
Honeywell manufactures a coprehensive range of water
temperature thermostats (trade name Aquastat) for controlling
and limiting boiler water temperature in hydronic heating
systems.
These sensitive, fast response devices are available in either
direct, panel or surface mount versions.
Sensing element
The liquid filled sensing element, including well or sensor
assembly, responds to temperature changes of water in a
heating system.
The sensor element has a diaphragm type power head
connected to a tube type capsule, through a small bore
capillary.
Expansion of the liquid, which completely fills the sensing
element, is the means of motion of the diaphragm.
The sensor assembly, used on the surface mounted aquastat,
envelopes the sensing capsule by means of an aluminium
heat shield for better heat conduction, an insulator of
glasswool and a mounting bracket.
Control mechanism
The control mechanism is mounted into the thermoplastic
housing. The mechanism transfers the motion of the
diaphragm to a snap action switch (Micro Switch) and also
provides the facility to adjust the temperature level on which
the Micro Switch has to operate.
The mechasnism consists of a two piece lever with calibration
screw, a plastic actuator for the switch, a cam and shaft for the
set-point adjustment, a loading spring for cam and levers and
a pad with pushplate to transfer the diaphragm motion to the
lever.
Knob with scale and index
The plastic knob with scale and index enables the user to
adjust the Aquastat on a selected temperature setting within
its range. The knob fits on the cam and stays on it due to the
force of the spring on the nave of the knob.
This spring force enables the installer to pull the knob from the
cam without the use of tools.
The hole in the knob and the shaft of the cam are provided
with a flat side which allows mounting of the knob only in one
position in order to maintain the calibration.
The plastic index will be fastened by means of two M4 thread
forming screws on the housing.
Micro Switch
The Micro Switch mechanism is also mounted into the plastic
housing. the mechanism consists of a snap action spring type
PL with contacts and a moveable or a fixed and a stationary
contact bracket.
The Micro Switch mechanism is intended to control electrically
a burner, a relay, etc. in dependency of the temperature
changes in a heating system.
On choice the Micro Switch mechanism can be delivered with
the following contact arrangements:
•
S
ingle
P
ole
S
ingle
T
hrow,
C-1 breaks on temperature rise
•
S
ingle
P
ole
D
ouble
T
hrow,
C-1 breaks on temperature rise.
C-2 makes on temperature rise.
The contacts are connected to 6.3 mm terminals which are
extending from the outside of the Aquastat housing.
Cover and conduit entries
The housing(s) of the Aquastat can be provided with conduit
boxes which are provided with holes to fit Pg 13.5 conduits.
To obtain easy wiring possibilities these boxes can be
mounted or disconnect without the use of tools (hook in
approach).
The conduit box is locked with the front cover, which is
fastened by means of an M3 thread forming screw. Also the
top cover is locked by the front cover.
Set-point stops
On request, the Aquastat can be delivered with a high and low
limit stop. The purpose of these stops is to provide the user
with the facility to choose a maximum and/or minimum setting
on the scale.
The stop is situated on the rear side of the setting knob.
Adjustment is only possible after removal of the knob.
Manual or tool reset
On request, the Aquastat can be delivered with a manual reset
or a tool reset feature.
The tool reset feature is covered by the front cover.
Operating of the reset button is only possible after removal of
the front cover.
The manual reset button potrudes the front cover of the
Aquastat and resetting can be done without the use of a tool.
Adjustable differential
On request, it is possible to deliver the Aquastat with an
adjustable switch differential.
The adjustable switch differential feature consists of a plastic
adjusting dial with pointer, which is connected to a moveable
contact.
Turning of the dial changes the contact gap of the Micro
Switch and thus the differential.
The dial is situated under the front cover or behind the panel.
Adjustable differential feature is only applicable on
controllers
and
recycling limit controls