Remote test feature. Ampac Discovery

DISCOVERY PRODUCT GUIDE

3.4 Remote test feature:

This feature, available on all Discovery detectors and the call points, is enabled from the control panel by changing the state of a forward command bit. On receipt of the command the detector is forced by electrical means into an alarm condition. After a delay of up to 20 seconds due to signal processing, an analogue value of 85 is returned, provided that the detector is functioning correctly. This value is sustained until the forward command bit is changed back to its original state, after which a period of 20 seconds is required for the detector to return to its normal analogue value.

The manual call point is different in that the receipt of the command bit will cause the call point to generate the interrupt sequence, followed by a sustained analogue value of 64. The call point resets when the forward command bit is changed back to its original state.

3.5 Rejection of transient signals:

All Discovery detector algorithms are designed to give low sensitivity to very rapid changes in the sensor output, since these are unlikely to be caused by real fire conditions. This is achieved by digital low-pass filtering of the sensor values which optimises the rejection of false alarm sources while maintaining the response to fire.

The filter parameters depend on the mode selected and for some modes the filtering is minimal. The filtering has no significant effect on the response to fires but does affect the way in which detectors respond to transients and to step changes of smoke or heat.

This is seen in the “minimum time to alarm” given in individual detector specifications. These times represent the time taken by the detector to reach the alarm condition when responding to a large step change in input.

3.6 Interchangeability:

Any Discovery detector may be replaced by any other type in the range. For example, if a smoke detector proved unsuitable in a particular application, it could be simply replaced with a heat detector set to the appropriate mode, provided that the maximum floor area coverage does not exceed that specified by

BS5839: Part 1 or other local code.

Discovery detectors can also be used to replace XP95 detectors and again, it is possible to change types, e.g. smoke for heat or vice versa. Factory-new Discovery detectors are set to mid range, equivalent to XP95, and the flashing LED feature is disabled.

Notes

1.

The control panel must not have a drift compensation algorithm activated when interrogating

Discovery detectors.

2.

When replacing an XP95 detector with a Discovery detector ensure the control panel configuration is modified accordingly.

Servicing Note

The “minimum time to alarm” referred to above is important when detectors are tested in situ, for example using aerosol test gas. A delay in response may be apparent.

Warning: all detectors are supplied with a red cover to protect against dust. The covers should be left in place until commissioning of the system when they should be removed. If, however, further building work is anticipated after commissioning, the covers should be replaced and alternative fire protection arrangements made. When the system is handed over all covers should be removed.

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