Honeywell L641 User Manual
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
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