PRODUCT DATA
FEATURES
Version available for use as a cylinder thermostat in
domestic hot water installations
Version available for use as a pipe thermostat in fan-
coil applications
Version available for use as a pipe thermostat in frost
protection applications
Version available for use as a pipe thermostat to limit
the supply water temperature in underfloor heating
and solid fuel systems
The S.P.D.T. switching action is accomplished by a
snap-action MICRO SWITCH which is actuated by a
bimetal temperature sensing element
The desired temperature control point is set by the
clearly scaled temperature selector on the front cover
Wiring terminals are easily accessible
Tamperproof temperature setting (L641B)
Screwdriver slot temperature setting, with optional
manual setting knob supplied (L641A)
CE approved
DESCRIPTION
The L641 is a surface contact thermostat designed to sense
the water temperature in storage cylinders and water pipes,
and to provide temperature control, temperature limiting, and
temperature feedback functions.
L641A mounts directly onto domestic hot water cylinders and
can be wired to directly switch a wet central heating
circulating pump, or boiler, or to operate spring return and
motor open/motor close zone valves.
L641B mounts directly onto a pipe and can provide high limit,
low limit or frost protection in wet central heating systems or
automatic summer/winter changeover in XE70 fan-coil control
systems.
L641
SURFACE CONTACT
THERMOSTAT
l641-en0r8444-uk07r0515
L641 SURFACE CONTACT THERMOSTAT
DIMENSIONS
SPECIFICATIONS
INSTALLATION
Dimensions in millimetres (inches in brackets)
Supply voltage
230 V~, 50...60 Hz
Switch action
S.P.D.T. Type 1CL
Switch rating
4(2) A, 230 V~
Temperature
setting range
see table
Differential
Approximately 10 K non-adjustable
Surface
temperature
range
0 to 95oC
Ambient temp.
range
0 to 70oC
Mounting
L641A mounts directly onto cylinder
using fixing strap provided
L641B mounts directly onto pipes
using fixing springs provided
Dimensions
44 x 79 x 54mm (1.73" x 3.11" x 2.13")
(w x h x d)
Wiring
3 terminals with wiring clamps,
accepting wires up to 1.5 mm2
Approvals
L641 is CE, RoHs and WEEE
compliant. For regulatory information,
DoC / CoC number D0005. Product
must be wired as shown for CE
compliance
Mounting
The L641A cylinder thermostat should be mounted 1/4 to 1/3 of
the way from the bottom of the domestic hot water cylinder
after removing a section of the insulation and cleaning the
surface.
The L641B pipe thermostat should be positioned less than
0.6 m (2') from the boiler, or on a supply pipe to a fan-coil
unit, close to the 3-port control valve.
IMPORTANT
1. The installer must be a trained service engineer
2. Disconnect the power supply before beginning
installation
ORDERING SPECIFICATION
Model
Application
Temperature
Setting Range
L641Al039
Cylinder
Thermostat
Min, 40 to 80 o C
L641Bl004
Low Limit Pipe
Thermostat
Min, 10 to 40o C
L641B1012
High Limit Pipe
Thermostat
50 to 95oC
Wiring
Cover removal Wiring to terminals
l641-en0r8444-uk07r0515
2
L641 SURFACE CONTACT THERMOSTAT
DHW Storage
Tanks/
Cylinders
(see note 1)
High Limit
Underfloor
Heating
Systems (see
note 2)
High Limit
Solid Fuel
Systems (see
note 2)
Low Limit
Frost
Protection
(see note 3)
Fan-Coil Unit
Summer/
Winter
Changeover
for 2-pipe
units (see
note 4)
L641Al039
L641Bl004
L641Bl012
Notes
1. The L641A should be mounted 1/4 to 1/3 of the way from the bottom of the cylinder.
2. The L641B should be mounted less than 0.6 m (2') from the boiler.
3. The L641B should be mounted on the boiler return pipe and used in conjunction with the T4360A FrostStat.
4. The L641B should be set to approx. 25o C and mounted on the supply pipe close to the 3-port control valve
such as to sense the water temperature even when the valve is closed.
APPLICATION
High Limit
For Underfloor Heating
For Solid Fuel Systems
T4360A FrostStat
Limit Control in Pipes
D.H.W. Storage Cylinders
and Tanks
Low Limit
For Frost Protection of
Exposed Pipework
L641A1039
Water Temperature Sensing and Control
3 l641-en0r8444-uk07r0515
L641 SURFACE CONTACT THERMOSTAT
WIRING DIAGRAMS
L641A1039
DHWS ControL
L641B1012
High Limit
Terminal 2 used on Honeywell
Y-Plan systems
Heating Load
Timer
Fan coil
Unit
Heating Load and
existing controls
Contacts C and 1 break on
temperature rise
L641B1004
Low Limit
(Frost
Protection)
Connected to override existing
time and temperature controls
Contacts C and 1 make on
temperature fall
L641B1004 Automatic Summer/
Winter Changeover XE70 series
Typical wiring
XE70 Series
SUMMER / WINTER CHANGEOVER FOR 2PIPE FAN-COIL UNITS
Summer / Winter chanfg
Honeywell Control Systems Limited Helping You Control Your World
Newhouse Industrial Estate
Motherwell ML1 5SB
United Kingdom
l641-en0r8444-uk07r0515
Loading...