Daisy Chaining Kidde Smoke Detectors Problem

Hello:
Boy, I have just finished spending several hours trying to figure out what is wrong, and am still stumped. Would really be most appreciative for any thoughts on the following:
My son moved into a 30 year old house a few weeks back. The house has 3 AC wired-in Rittenhouser smoke alarms. (anyone ever hear of these, or possibly know what voltage is supposed to appear on the red interconnect wire when tripped ?)
No real way of knowing, but it wouldn't surprise me if they were originally put in when the house was built, some 30 years back. But they are possibly newer ?
The three units apparently are wired to communicate with each other; I guess that if one goes off, they all are supposed to go off. They have a third, Red, wire daisy chaining from one to another.
Didn't really think they did this daisy-chaining concept to fairly recently, so was a bit surprised to see it.
I just put in 3 new Kidde Model PI 2000 (dual, photoelectric/ionization) alarms. Also AC wired in. The "seem" to work fine.
But, if I hook up the red wires to daisy chain them together, they all keep going off, sequentially.
Disconnecting the red wires, reverts them back to apparently normal operation.
The house is a bit far from me, and won't be down there again for a week or two. I mention this, because I "now" think that it might have been a good idea to put a meter on the red wire and check if there is any voltage on it ?
My undertstanding with the Kidde units, although I am not really sure, is that there should normally not be any voltage on the red wires (relative to ground) unless one of the units is tripped. Should have checked.
Guess I assumed that the daisy chaining "concept" would be the same for the old units as it is for the new ones ?
** Is it possible that these old Rittenhouser units have the red, daisy link, wire always hooked up to some voltage, or...? **
Am I possibly missing anything when I wired them in ?
Any thoughts on what might bwe the problem, and how to correct it would be most appreciated.
Thanks, Bob
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Have you tried eliminating 1 SD at a time, powering back up, and seeing if things behave? In other words, Tie the 2 reds together, and then disconnecting the SD from power?
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Trace all the red wires, find out where they go.
Are they just all hooked together or are they going to some other unit or something with voltage on it.
MC
P.S. Do not interconnect different manufacturer units, use all same when interconnecting units.

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Are you sure that you found all of the existing smoke detectors? Check the attic and the basement. Those Kiddes will go off if there is another brand connected to them. Try and trace out the wiring. Find out which one is the first in the chain and then identify the second and third. Then connect the first and second to see if they go off and go from there.

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The sensors in smoke detectors are only good for a couple years. So, you're right to replace them. Wish I was more help.
--

Christopher A. Young
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Are you sure you found all the old smoke detectors? There could still be an old one hidden in the attic or basement or some out of the way location. If there is still an old detector on the line somewhere it could be incompatabile with the new ones and causing them to go off.
Steve B.
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