Honeywell L641AI039, L641BI004, L641B1012, L641BI020 Product Data

L641

FEATURES

DESCRIPTION

SURFACE CONTACT

THERMOSTAT

PRODUCT DATA

• 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 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 fan­coil control systems.

• 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)

EN0R8444

L641 SURFACE CONTACT THERMOSTAT

DIMENSIONS

SPECIFICATIONS

INSTALLATION

Dimensions in

millimetres (inches in brackets)

Supply

voltage

: 230 V~, 50...60 Hz

ORDERING SPECIFICATION

Switch action : S.P.D.T. Type 1CL
Switch rating : 4(2) A, 230 V~
Temperature

setting range
Differential : Approximately 10 K non-adjustable
Surface

temperature
range

Ambient
temperature
range

Mounting : L641A mounts directly onto cylinder

Dimensions : 44 x 79 x 54mm (1.73" x 3.11" x

Wiring : 3 terminals with wiring clamps,

: see table

: 0 to 95oC

: 0 to 70oC

using fixing strap provided
L641B mounts directly onto pipes
using fixing springs provided

2.13")
(w x h x d)

2

Model Application Temperature

Setting Range

L641Al039 Cylinder

Thermostat

L641Bl004 Low Limit Pipe

Thermostat

L641B1012 High Limit Pipe

Thermostat

L641Bl020 High Limit Pipe

Thermostat

Min, 40 to 80 o C

Min, 10 to 40o C

50 to 95oC

40 to 95oC

Mounting

The L641A cylinder thermostat should be mounted 1/4 to 1/
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.

3

IMPORTANT

1. The installer must be a trained service
engineer

2. Disconnect the power supply before beginning
installation

Wiring

Cover removal Wiring to terminals

EN0R 8444 2