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Honeywell A4021 Series Product Handbook

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VALVE PROVING SYSTEM

PRODUCT HANDBOOK

A4021 Series

UNIVERSAL GAS VALVES

EN2R--9023 9705R0--NE

APPLICATION

The A4021 is a self--checking microprocessor based Valve

Proving System (VPS). The A4021 checks the effective clo-

sure of automatic shut--off valves by measuring the pressure

differential between two valves during the test sequence.

Subbase and pressure switch are required to complete the

system.

When during the test sequence of the A4021 a failing valve is

detected, the A4021 will go into a non--volatile lock--out sta-

tus, generates an alarm and prevents a burner start--up.

The intended application is for gas fired power burners and

other large capacity gas firing installations, where according

to the European norm EN676 a valve proving system can be

used as an alternative for pre--purging the combustion cham-

ber. And for installations with or without pre--purge with a

capacity of more than 1200 kW.

Subject to change without notice. Printed in the Netherlands.