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

NFPA 72-2002 4.4.2 Compatibility. All fire detection devices that receive their power from the initiating device circuit or signaling line circuit of a fire alarm control unit shall be listed for use with the control unit.

NFPA 72-2002 C.1 Directly connected system smoke detectors, commonly referred to as two-wire detectors, should be listed as being electrically and functionally compatible with the control unit and the specific subunit or module to which they are connected. If the detectors and the units or modules are not compatible, it is possible that, during an alarm condition, the detector's visible indicator will illuminate, but no change of state to the alarm condition will occur at the control unit. Incompatibility can also prevent proper system operation at extremes of operating voltage, temperature, and other environmental conditions.

Happy holidays,

Mike

-- Michael B. Baker, SET Michael Baker & Associates, Inc. PO Box 737 Gladstone, OR 97027-0737

503-657-8888 v 503-655-1014 f ET News(r)

Thanks, Mike.

If I'm getting this right, it explains why the detectors need to be compatible with the panel. That I understand....

What I'm not getting though is why the panel would suggest that any detectors connected need to be identical models. Is it a real technical issue, or maybe something just regulatory?

I'm just trying to figure out if I need to buy another one for a matching set, or if I'm functionally alright with this mixed pair.

Thanks!

What the manufactuers are worried about is each manufactuers units voltage and amperage characteristics are slightly different from the others and they are worried these differences can cause smokes to false, and or fail to operate in a timely manneror draw too much power off loop andkeep other smokes from activating. I have taken over many systems were nothing matches and everything works and functions but I have seen false alarm problems. Personally i try to keep everything the same for inventory purpose just makes it easier .I have never seen a panel fail to function even were there have been real fire situations It is more of a liability worry of the manufactuer. how ever they never take into concideration the cost of changing every device in a system especially when a detector is no longer made and 3 or more smokes need changed then costs start getting expensive.I magine what it would cost to change out a sytem with 100 smokes to my knowledge UL nor any one else has ever bothered to look into this situation to see if it really effects panels etc. But from what i see in the field it does not and one has to wonder is to just to sell more smokes that this rule is in place.

I never had this be and issue before. Smoke detectors become obsolete at any given time. Why not just test each unit, then you can determine whether this is just the panel manufacturer's suggestion? Please post your findings.

Jim Rojas

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.

The tests you quoted have nothing to do with compatibility. Operating voltage doesn't mean compatibility. It has more to do with the current draw of the two-wire smoke in alarm condition, and whether that increased current from a particular smoke is sufficient to cause an alarm on a particular control panel's circuitry.

I've looked at a couple of panel instruction manuals, and although they all list which two-wire smokes are approved for use with those panels, I don't see anything that prohibits mixing those approved smokes on the same circuit. I don't see any logical reason why it should make any difference.

When multiple two-wire smokes are connected on the same zone, the only one that counts is the first smoke to go into alarm. When that first smoke trips, it places the entire zone into alarm until manually reset: the other smokes no longer do anything useful at that point. So, if there are three different brands of two-wire smokes on the same zone, and all are approved for use with that panel, then any one of those smokes is capable of causing an alarm. Once it does, the other two smokes no longer matter. In fact, they probably don't even do anything, since many two-wire smoke zones can only supply enough current to power one smoke detector in alarm condition.

Finally, if there were any problems with mixing different brands on the same zone, it would become obvious during testing. I'll bet no one has ever seen a smoke fail to operate as a result of mixing approved smokes on the same zone.

- badenov

In this case, compatibility is a function of voltage *and* current. The smoke detector consumes the same amount of energy always. If the voltage available to the smoke detector sags then current increases because energy is conserved (remains constant). P = IE. The UL tests take these to their logical extremes to determine the failure point.

The literal intent here is that the test only includes one make and model at a time. No one has paid UL to test different combinations of devices on the same control.

I agree with you. Two-wire smoke detectors will shunt the circuit once they operate and who cares? A fire has been reported! Someone else pointed out that this goes to liability. If I were to mix makes and models on the same 2-wire circuit and a tragedy were to occur, I may be liable because I knew better than to mix makes and models on the same circuit.

Before using common sense in this case, buy errors and ommission insurance.

Happy holidays,

Mike

Point is moot in this case since the 2WT-B is not an audible...

But, what about line reversal?

We used the 2100AT's for quite a while and now > mbbaker said:

Hi Mike:

It's amazing to me that it's taken this long for someone to address this issue. There are many installations (Vancouver not being the least of the cities represented)where "mixing" makes and models of smoke detectors occurs. It becomes more and more prevalent as the systems get older and other servicing companies get involved. What's really amazing is that a number of companies aren't aware that smoke detectors are "cross listed" to a particular control and I've seen numerous installations where properly labelled detectors (ULC, FM, UL) are "mixed in" with no thought given to compatibility. A few of our customers have gone so far as to request that we not mention it to the apartment managers if we're called in to service a particular system!! I've always responded with: "Would you compromise your own family's safety? How can you ask us to willingly compromise someone else's??" Besides which, my insurance company would have "kittens" and I quite enjoy our unblemished record (and the low premiums that go with it).

I suspect this is a non-issue, since I haven't seen control panel instructions that say, "Use up to 7 Brand A two-wire smokes per zone, but you can use 15 Brand B two-wire smokes per zone." It's always "Use any of the following smokes, and use a maximum of X per zone." Which leads me to believe the specs have to be pretty much identical.

I remember that UL has "compatibility identifiers" for two-wire smokes; the usual ESL/System Sensor two-wire smokes are compatibility identifier A, as I recall. I don't have a copy of UL 268, but perhaps the answer lies there.

In any case, I still don't see where it says we can't mix and match smokes that are all on the approved list for a particular control panel. The 268 and 864 standards don't require a single brand of smoke, as far as I know. NFPA 72 doesn't require it either. The panel manufacturer's instructions don't prohibit mixing and matching either. And as others have pointed out, it is necessary during the life of a system to replace older smokes with newer models, unless you're going to claim that all the smokes have to be replaced whenever one goes bad.

You may consider it to be the "literal intent" of the standard, but I think that's guesswork on your part.

If you know any engineers at the panel manufacturers or smoke detector manufacturers, it would be interesting to hear their views on this subject.

Don't leave home without it!

- badenov

Perhaps if you knew anything at all about the subject you could have done so sooner rather than regurgitate what others have already posted, pretending to actually know the suibject matter.

How do you mean the reversal is nhandled differently, Joe?

Regards, Robert L Bass

Bwhahahahahahahaha!!! Now *this* is the Robert I remember. The one that resorts to childish responses that lack wit and humour. What'sa matter, Robert?? Even my newest apprentices know better than to add another splice in an attic like you recommended doing when installing a door contact in cold weather. Rest assured this is one that *will* be "regurgitated" frequently to demonstrate your lack of experience as an installer (I'll bet it even makes the Goofy Site). You are typical of many actually. They've passed and met all the licensing requirements (you held a CT L-5 from 1989 to 2000, an L-6 from 1985 to 1989) but don't know "diddly" when it comes to real world installation and service. Sure, you can quote from "the book" all you want (you've even been caught plagerizing the Sentrol Installation Handbook), but when it comes to "hands-on" experience I doubt you have more than five years under your belt (if that).

And you *still* haven't fixed your pop-up problem. Tsk!!!

he cant fix it..its an income,the one that pay for his Viagra pills so that the third world country girl he manage to bring here don't leave...

On the 2000at the line is simply reversed and the smoke do their own thing as far as sounding. Use the RR-2 Module.

With the 2wt-ab the line reversal relay supplys the pulsing for the coded output (Use the RRS module)

If you use the RR-2 on a 2wt-ab all you get out of the smokes is a steady whine.

Using the RRS Mod you get all the smokes sounding in synchronization (sp?).

snipped-for-privacy@comcast.net wrote:

Thanks Joe.