Honeywell L641A User Manual

L641A - Cylinder Thermostat

Installation Instructions

The L641 is a water temperature thermostat designed for surface mounting on domestic hot water cylinders. It is supplied complete with mounting strap for rapid and easy installation, so draining of the system or tapping the cylinder is not necessary. The desired temperature control point is set by the clearly scaled temperature selector on the front cover.

Features

Specification

50	60	50	60	•	Snap action SPDT Micro	Switch Action:	SPDT, Type 1 CL.
40	70	40	70		Switch™.
	80°C		80°C			Switch Rating:	230V~ 4(2)A 50...60Hz
				•	Wiring terminals are easily
	min		min			Temperature Setting Range: 40...80°C
					accessible.
				•	Tamperproof temperature	Differential: Approximately 10°C non-adjustable
L641A1039		L641A1039			setting.	Ambient Temperature Range: 0...55°C

• Optional manual setting	Cylinder Surface Temperature Range: 0...95°C
knob supplied

1

Mounting Position

2

Pre-insulated cylinder

preparation

The cylinder thermostat

Remove a section of

should be mounted to

insulation as specified.

of the way from the bottom

Clean cylinder surface

80mm

of the cylinder.

to ensure good surface

contact.

to

45mm

Height

3

Cover Removal

4

Wiring

8mm

max

Caution: Isolate

power supply and

make safe before

wiring the unit to

prevent electric

shock and equipment

damage. Installation

should be carried

out by a competent

person.

Cover installation is the reverse of above

5

Wiring Diagram

All wiring must be in accordance with I.E.E. regulations.

Use connections C and 1 when			L641
system operation is required on
temperature fall
* Terminal 2 used on										*
Y-Plan systems
			C		1				2
230V~
50..60Hz	3 AMPS

Heating Load

Timer/Programmer

Use heat resisting flexible cable rated at 85°C.

A switch, having contact separation of at least 3mm in all poles, must be incorporated in the fixed wiring as a means of disconnecting the supply.

The thermostat is a class II (double insulated device) requiring no earth connection.

The heating system must be appropriately fused with a fuse rating of no higher than 3 amps.

For use in normal domestic environments.

EMC compliance considerations

Keep AC mains supply/load cables separate from signal wiring. Refer to Code of Practice EN61000-5-1 and -2 for guidance.

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6	Mounting	Fixing hooks		7	Fixing Strap and Hooks
					Cut strap to size (if required) to ensure
					thermostat is held firmly against cylinder.
	Pre-formed insulation
		Important Note:
		Ensure good clean
	Hot Water	surface for thermal
	Cylinder	contact.
					Screw hooks into strap and link together
	Locate mounting strap in cover slot				to secure around cylinder.
8	Temperature Setting (Tamperproof option)			9	Optional Manual Setting Knob (Non tamperproof option)

Normal set point 60°

Important Note:

Ensure slot in knob is aligned with arrow then push home firmly

What is a cylinder thermostat? …an explanation for householders

A cylinder thermostat switches on and off the heat supply from the boiler to the hot-water cylinder. It works by sensing the temperature of the water inside the cylinder, switching on the water heating when the temperature falls below the thermostat setting, and switching it off once this set temperature has been reached.

Turning a cylinder thermostat to a higher setting will not make the water heat up any faster. How quickly the water heats up depends on the design of the heating system, for example, the size of the boiler and the heat exchanger inside the cylinder.

The water heating will not work if a time switch or programmer has switched it off. And the cylinder thermostat will not always switch the boiler off, because the boiler sometimes needs to heat the radiators.

Cylinder thermostats are usually fitted between one quarter and one third of the way up the cylinder. The cylinder thermostat will have a temperature scale marked on it, and it should be set at between 60°C and 65°C, then left to do its job. This temperature is high enough to kill off harmful bacteria in the water, but raising the temperature of the stored hot water any higher will result in wasted energy and increase the risk of scalding.

If you have a boiler control thermostat, it should always be set to a higher temperature than that of the cylinder thermostat. In most boilers, a single boiler thermostat controls the temperature of the water sent to both the cylinder and the radiators, although in some cases there are two separate boiler thermostats.

IMPORTANT: No user serviceable parts.

This product and its associated documentation and packaging are protected by various intellectual property rights belonging to Honeywell Inc and its subsidiaries and existing under the laws of the UK and other countries. These intellectual and property rights may include patent applications, registered designs, unregistered designs, registered trade marks, unregistered trade marks and copyrights. Honeywell reserves the right to modify this document, product and functionality without notice. This document replaces any previously issued instructions and is only applicable to the product(s) described. This product has been designed for applications as described within this document. For use outside of the scope as described herein, refer to Honeywell for guidance. Honeywell cannot be held responsible for misapplication or the product(s) described within this document. Manufactured for and on behalf of the Environmental and Combustion Controls Division of Honeywell Technologies Sàrl, ACS-ECC EMEA, Z.A. La Pièce 16, 1180 Rolle, Switzerland, by its Authorised Representative Honeywell Inc.

Honeywell Control Systems Ltd.

Arlington Business Park, Bracknell

Berkshire, RG12 1EB

Technical Help Desk: 08457 678999 www.honeywelluk.com

42007492-001 R6

© 2010 Honeywell International Inc.