Horstmann ServicePlus S21 User Manual

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The Horstmann ServicePlus S21/S21R is a 24 hour programmer allowing
independent timing of hot water and central heating with up to
3 ON/OFF settings per 24 hours and a hot water boost button
and central heating advance override.
There is also a programming switch allowing permanent selection of:
OFF/ON/AUTO/ALL DAY.
Additionally, the ServicePlus programmer gives an advance warning
of the annual boiler safety check due date.
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1

Horstmann ServicePlus S21 Specifications

General

Type	Electronic Programmer
Display	LCD
Voltage	230V AC
Battery Backup	Yes
Number of Channels	2
Compatibility	Gas and Oil systems
Channels	2
Programming	7 Day
Load Rating	3A Resistive, 1A Inductive
Installation	Wall-mounted
Contact Rating	3A
Operating Mode	Auto, Off

Summary

The ServicePlus S21 and S21R Programmer

Manual Overrides

BOOST FUNCTION

Allows temporary 1-hour override for hot water, indicated by BOOST on display.

ADVANCE FUNCTION

Brings forward the next ON or OFF operation for central heating.

Channel Override Facilities

Setting the Time of Day

Setting the On and Off Times

Resetting the Programmer

General Information

BATTERY

Details on the programmer's long-life battery backup for retaining settings during power interruptions.

SERVICE AND REPAIR

Guidance on user serviceability and contacting professionals for faults.

What is a programmer?