Local distributor says Macurco no longer manufacturing CM-15A. New unit is CM-E1. I breezed through the manual at the distributor's counter looking for a reference to the snap-in battery on the PC board, found nothing about why it was there, its life span, voltage, or part number. Counter person was no help.
What purpose does the battery serve, despite a reference to connecting it to a UL listed alarm panel, which would already have a battery backup?
Does the battery get charged from the alarm panel's12-VDC?
The unit is to be ceiling mounted or wall mounted according to the fine-print instructions, hence high up on the wall.
I've always wall-mounted the CM-15A about 5' 10" above the floor, the height at which many of our noses are busy taking in air.
In one house I used the 5' 10" height in hallways and other locations where there was "awake" activity, near all sleeping areas, and at a lower level INSIDE all the bedrooms adjacent to the bed, wall mounted between the bed and the bedroom door, in effect bringing the unit closer to their noses. Though Massachusetts Building Code does not require the detectors to be placed within the bedrooms, this particular customer wanted one in each of six bedrooms.
My understanding of CO is that when produced, it is from a hot source, thereby rising upwards, but as it cools it begins to drop, and mix further with the ambient air, and then can flow anywhere within the house predicated on the normal air flow patterns of the house. It therefore seems reasonable that the best height to mount is at the height of the air that we are about to breathe.
To exaggerate, it would seem that the best place to mount a CO detector is on my nose, or as close as possible!