System Sensor DH400 Smoke Duct Detector Insider Tip

The other day I was installing the last two items on a new addressable fire alarm system for the a Military Base.  When I went above the ceiling to inspect the existing smoke duct detectors I found two P270-1000I.  Now these are a direct copy of the System Sensor DH400 smoke duct detectors.  Manufactured by Totaline these ion smoke detectors are now obsolete. 

The objective was to connect these smoke duct detectors to the new System Sensor RTS151 remote magnet test switch.  (The RTS151 replaced the RTS451) Well, when you use System Sensors test switch with the DH400 you will need to install a test coil (model COIL400) in the duct detector housing.  The test coil is mounted directly next to the ion detector head and acts like a magnet when power is applied.  So in short the magnet at the test switch closes contacts to the smoke duct detector circuit board which then allows 24VDC to the test coil.  Once the coil is powered up it sets the detector head into alarm.

Pretty easy right?  Well, in normal situations yes.  But here is the issue.  Once we had everything installed and ready to go we tried a test at the System Sensor RTS151 and to our suprise, nothing.  I called System Sensors tech support and double checked the wiring.  Everything was right and tech support told me the boards were bad and needed to be replaced.  Now here is what we found.  Although the P270-1000I is a direct copy of the System Sensor DH400 they used a different ion smoke detector head.  Now, since the head is not the same model it requires the placement of the test magnet in a different place.  About 1" - 1 1/2" away from the regular test area.  Once I realized this I marked the test area of the ion smoke detector head with a Sharpie and removed the head and base.  I then screwed the base back down to the housing making sure to line up the sharpie mark with the newly installed test coil.  Now that the test area of the detector head and the test coil are lined up it was time for another test.

I had my technician place the magnet on the system sensor RTS151 and we created a succesful alarm condition on the duct smoke detector.  It just goes to show you that common sense can sometimes play a bigger role in troubleshooting.