Honeywell L641AI039 Operation manual

EN0R8444
L641
SURFACE CONTACT
THERMOSTAT
PRODUCT DATA
FEATURES
•Versions available for use as a cylinder thermostat
in domestic hot water installations
•Versions 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)
•Approvals - B.E.A.B. (meets EN 60730)
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 and XE90 fan-
coil control systems.

L641 SURFACE CONTACT THERMOSTAT
EN0R 8444 2
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
temperature
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 mm
2
Mounting
The L641A cylinder thermostat should be mounted 1/4to1/3
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 40oC
L641B1012 High Limit Pipe
Thermostat 50 to 95oC
L641Bl020 High Limit Pipe
Thermostat 40 to 95oC
Wiring
Cover removal Wiring to terminals

L641 SURFACE CONTACT THERMOSTAT
3EN0R 8444
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 4
L641Bl004 4 4
L641Bl012 4 4
L641Bl020 4 4
Notes
1. The L641A should be mounted 1/4to 1/3of 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. 25oC 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

L641 SURFACE CONTACT THERMOSTAT
Honeywell Control Systems Limited Helping You Control Your World
Newhouse Industrial Estate
Motherwell ML1 5SB
United Kingdom
EN0R 8444
Summer/Winter
Changeover for 2-pipe
Fan-Coil Units
Note:
For wiring details
refer to the
appropriate XE70
or XE90 Product
Data sheet.
(ENOR8402, 8403,
8406)
Set to
25oCSet to 25oC
WIRING DIAGRAMS
L641A1039
DHWS ControL
L641B1012
L641B1020
High Limit
Terminal 2 used on Honeywell
Y-Plan systems
Heating Load
Timer
Fan coil
Unit
Heating Load and
existing controls
L641B1004 Automatic
Summer/Winter Changeover
XE90
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