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Establishment of compatibility is anecessity in re alarm systems. Asimple comparison of voltage andcurrent draws is insufcient in de-termining if a piece of equipmentis suitable for use with various realarm systems. With the advent ofmicroprocessor based equipmentand digital communications, signal-ing protocol becomes a major factor.For example, a monitor modulemade by a manufacturer will beprogrammed for use with certainprotocol. Substituting a physicallyidentical module with differentprotocol will not necessarily oper-ate properly within the re alarmsystem. Different re alarm manu-facturers operate with differentprotocol. Therefore substituting aphysically similar module may ap-pear to be workable in a quiescentcondition, but there is a substantialchance that the module may notsupervise itself or properly signalan alarm condition.

Compatibility Requirements This area is often misunderstoodand can present a serious problem.Establishment of compatibility isrequired for 2-wire smoke sensors/detectors, electronic initiating de-vices/sensors, addressable monitorand control modules, noticationappliances, and releasing solenoids.4-wire smoke detectors are in theprocess of being included sincesome panel power supplies havebeen found to supply voltages out-side the operating limits of thesedetectors.

Each panel manufacturer issues anNRTL listed/approved compatibil-ity document that lists the devicesthat are compatible with his corre-sponding control panel. The panelInstallation/Operating Manualcould also contain this informa-

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The ABCs of Fire Alarm Systems - Part XIIICompatibility

By Anthony J. Shalna 2009 Principal IMSA Representative to the Automatic Fire Alarm AssociationPresident: Southeastern Signalmen of Massachusetts

Retired Approvals Manager: Gamewell-FCI by Honeywell

tion. A smoke sensor manufacturermay also publish a compatibilitydocument that is NRTL listed/ap-proved.

If the device in question is not listedin these documents, it isNOT COM-PATIBLE.

If the installer intends to re-use ex-isting 2-wire smoke detectors, theexisting detectors must be listed inthe compatibility document.

Compatibility for 2-wire conven-tional smoke detectors is not simplya matter of comparing current rat-ings of the detectors and initiatingcircuits. Unlike a contact devicethat places a short circuit across theinitiating device circuit, the 2-wiredetector, when it goes into alarm,presents an impedance across thecircuit that is low enough to placethe circuit into alarm, but not toolow to prevent enough current tohold the detector in alarm, keepthe indicating LED lit, etc. This de-pends on the area of intersection ofresponse curves of both the detectorand initiating circuit. All these cal-

culations are also involved in deter-mining the capacity of the initiatingcircuit as to the quantity of detectorsthat may be installed on it. The com-patibility documents/manuals alsostate this information.

A major pitfall of retrofitting ismixing of different quantities ofdifferent models or brands of 2-wiredetectors in the same circuit. Unlessthis combination is listed in an NRTLdocument, any mixing of models/brands would violate the listing. Noone can predict what combination ofmodels/brands/quantities wouldwork properly. Only a qualied testlaboratory could verify that.

Another area affecting compatibilityis smoke level compensation. Newgeneration of microprocessor-baseddetectors have the ability to adjusttheir own sensitivity to compensatefor dirt build-up in the detector orgradual changes in the ambient

environment. Re-installation ofcompensated detectors could resultin unwanted alarms and subsequentfrustration by the building owner.Sometimes a smoke detector manu-facturer will purchase control panelson the open market, test his detectorswith these panels, have the resultsveried by an NRTL, and publishthe information in his own docu-ment. If you choose to use deviceslisted in a document published by asmoke sensor manufacturer rather

than by the panel manufacturer, beaware of a possible problem. Thepanel manufacturer will assume noresponsibility if the devices are notlisted in his own document, sincethe detectors, by others werentfurnished by him, or havent beentested by him. The reasoning hereis the panel manufacturer has noth-

CompatibilityRequirements

This area is oftenmisunderstood

and can present aserious problem.

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Continued from page 34

ing to gain and everything to lose by allowing instal-lation of a product not sold by him. Also, since thepanels tested were purchased on the open market bythe detector manufacturer, there is a possibility thatthe individual tested panel may have been damaged,improperly stored, or is from a production run thatexhibited quality assurance problems, etc. This couldeventually result in litigation that would only be settledin the courts.

No requirements have yet been established regardingthe useful life of smoke sensors, but the National FireAlarm and Signaling Code, NFPA 72, calls for reaccep-tance testing when equipment is replaced, etc. Compo-nents age with time, lter screens may become cloggedor partially clogged, materialsbecome brittle with age, etc. Planon replacing any smoke sensorsthat fail the reacceptance test.

Also, remember the big question:How many computers or cellphones do you use that are as oldas these detectors?

Notification Appliances These devices sound straightfor-ward and far less complicated thansensor installations, but the latestpanels, depending on line voltageextremes and tolerance build-up,may present operating voltagesthat range outside those of the

notication appliances.

The ADA requires synchronization of ashes for strobelights under most conditions, always wherever morethan one strobe is observable at the same time. This isdue to the fact that certain rapid ash rates have beenknown to cause epileptic seizures in persons prone tothis afiction. Older installations may have to be re-engineered with this requirement in mind.

The ABCs of Fire Alarm Systems Part XIII . . . Continued from page 34

Current ADA requirements may also affect mountingheights of appliances, so existing appliances may haveto be relocated.

Until recently, some jurisdictions have required that,after an alarm and before system reset, that the audiblesignals be silenced, but the strobes must continue toash. Its now being presented to them that, to a hear -ing impaired person, a ashing strobe is an evacuationsignal. Therefore, this regulation is in conict with thecodes.

Manual Pull Stations Pull stations in microprocessor-based systems likewiseare involved in the signaling protocol requirement.

In addition, with existing con-ventional pull stations, eventhough protocol is not an issue,

older stations may not conformto Americans with Disabilities Act(ADA) requirements in regard tothe maximum force required tooperate the station, and mount-ing heights. Previously it was feltthat a higher mounting heightwould discourage maliciousalarms by putting them out ofreach of smaller children, butADA requirements require loca-tion of stations at a lower heightthat could be easier to reach byan individual in a wheel chair.

In short, compatibility could become a real problem,especially in retrots. This adds more importance tohaving certied personnel performing the planningand supervision of the installation.

In Short . . .

Compatibility couldbecome a real

problem, especiallyin retrofits.

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