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Replacing the 240-COe detector with the new 250-CO

You will need the GE Security 250-CO with 250-CO-PLT Adaptor Plate Kit for Replacing 240-COe.

So you have a 240-COe carbon monoxide detector which is beeping, to notify you it has reached the end of its service life. You have learned that his model has been discontinued and has been replaced by the newer 250-CO detector. While this is a direct replacement model, there are a couple of differences between the two. Here we will illustrate the differences and how they pertain to the replacement installation. The first difference between the two models is their physical size. The newer unit is more compact than the older unit, and as such will not completely cover the likely unpainted section of wall left behind by the larger footprint of the old 240-COe detector. For installations where aesthetics are important, there are adaptor plates available which are large enough to cover the footprint of the old detector, and allow you to mount the new 250-CO directly to this adaptor plate.

The second difference involves the wiring, or more accurately the additional trouble relay included with the 250-CO. For this we refer to the wiring diagram provided with the 250-CO installation instructions:

While the 250-CO is a 4-wire detector, here we see 6 wires being used; however only 4 of these wires are to be connected to the alarm panel, and the same 4 wires currently connected to the 240-COe will be reused. Two of these wires are used to power the detector (marked PWR+ & PWR- on the diagram) and the other 2 are for connecting the detector’s alarm relay to the alarm panel’s zone terminal connections (shown in the upper left hand corner of the diagram.) The difference here is the additional relay connection shown on the right hand side of the diagram (note these connections are labeled simply “T” for trouble on the actual detector, and do not use the markings shown on this diagram.) This trouble relay activates to indicate a trouble condition upon lost power, CO sensor cell trouble or cell end-of-life. While it is recommended this relay is connected as shown above, (so that the 250-CO may report any trouble condition to the alarm panel) this connection is optional. if left disconnected the detector will still sound it’s built-in sounder and the LED will flash amber to notify you of any trouble, just as the old 240-COe would.

Should you decide to take advantage of this new feature, you must use 2 additional short lengths of wire to bridge the alarm and trouble relays as shown in the diagram. Any small gauge (24-18 AWG) wire may be used. Note the end-of-line resistor pictured in the diagram, this resistor is specific to the alarm panel and as such you must reuse the resistor being used with the currently installed 240-COe detector. In many cases alarm installers will place this end-of-line resistor at the alarm panel, to save time. While this technically defeats the purpose of the resistor, (which is to supervise the wiring and prevent tampering of the same) it is not a critical function for a life-safety device, (as opposed to burglary protection devices) and as long as that resistor is somewhere on the line the system will operate correctly. Therefore if the 240-COe currently has this resistor installed, reuse it with the new 250-CO. If it is not installed at the existing detector, then you may proceed with the rest of the installation and simply omit this resistor.

It is important to note when wiring the alarm relay, that while the wires on this relay do not have a polarity, depending on your alarm panel either the NO & C terminals (as pictured) or the NC & C terminals will be used. Note which of these two configurations the existing detector is using, and use the same when installing the replacement 250-CO. If the end-of-line resistor is placed at the detector, and you will not be wiring the trouble relay in your installation, then place the resistor on the NC or NO terminal of the alarm relay (otherwise place it as shown in the diagram.) Once the wiring for the relay(s) is complete, you need only attach the power wires to the detector. If installed correctly the detector will flash a green LED every few seconds to indicate it is operating normally. The installation is now complete.

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