Re: Can't Mix Smoke Models....really?

["mbbaker@xxxxxxxxx" <mbbaker@xxxxxxxxx>]

As I understand it, UL and other NRTL's test smoke detector / control
panel compatibility to determine the limits of both.  These tests add
more and more detectors to the circuit until they fail so that it can
be determined where that failure point is.  For example, the result of
a test may be that no more than 10 smoke detector "X" may be used on
any one circuit of control panel "Y".  Each test is conducted using one
make and model of smoke detector.  They don't mix makes and models on
the same circuit, therefore, the manufacturer isn't making any
warrantees as to the reliability of mixing different types of smoke
detectors on the same circuit.

The test is described in UL 864 8th edition:

25.2 For control unit-smoke detector compatibility considerations, the
operating voltage of an initiating device circuit is determined while
the control unit is operating at each of the conditions specified in
items A - E as follows:

A. Rated primary and secondary input voltage and rated load conditions.

B. Overvoltage conditions of ac input with no load on the control unit,
the initiating circuit disconnected from the end-of-line device and the
standby power source disconnected.

C. Overvoltage condition of the standby input voltage with no load on
the control unit, the initiating circuit disconnected from the
end-of-line device and the primary power supply disconnected.
D. Brownout voltage level of ac input; standby supply disconnected with
maximum rated load connected to the control unit.

E. Primary ac supply disconnected, standby voltage adjusted to 85
percent of rated voltage, and maximum load connected to the control
unit.

25.3 The operating voltage of a two-wire smoke detector is considered
compatible with an initiating device circuit if the detector's
operating voltage range coincides with or overlaps the initiating
circuit rated voltage range at both the high and low end.