Service Bulletin

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GENERAL DESCRIPTION

The McNab Model M5RS-A a five-pin relay is a direct replacement for the M5RS. The M5RS-A has the same form, fit and function and is trip point calibrated. Our present design uses electronics instead of a mechanical design. The unit may be installed at any attitude. The unit is used in McNab salinity models IC/D6, IC/D2RM, IC/D5, M-ATC, MM-ATC and IC/D10, (see photo A05-14 IC/D5 5RS is the left relay in the photograph).

It has come to our attention, that some substitute relays supplied by distributors do not have adequate trip point sensitivity to signal alarm when the salinity value is above target chemistry value. Specifically they have onesixth the voltage sensitivity to meet the specifications of the original equipment. Presently (2006) the Navy part number will in some cases unintentionally supplies the out of specifications relay. The out of specification sensitive relay should be immediately replaced by one that throws between 4 to 5 volts. The salinity system will not alarm at all with the wrong relay.

APPLICATION

The M5RS-A functions as the critical pick up voltage trip point relay. When over-salinity occurs, this relay sends an alarm/dump signal. The purpose is to alarm the engineering staff of unsanitary drinking water and/or contaminated main boiler feed water. It is critical to the mission of the ship that these units operate properly.

SPECIFICATIONS

A99-34B Rev D