Thanks all for the advices recently on humidifier installation.
I installed an Aprilaire Humidifier 550 this weekend.
A useful link is here:
Most of the installation is straightforward. The only tricky part is the 120V wiring for the Humidifer Transformer:
- The A50 relay (the previous contractor installaed it) was not functioning. from my reading and talking to installer, they hate the A50 relay.
- I have 1991 Tempstar furnaces (x2), and it was a challenge to find the 120V to hook up the transformer. I wired the 120V circuit to a "switched" terminal, which means the transformer is powered only when the blower motor runs. In my case (for those familiar with Tempstar circuit board), I used a voltmeter and watched the furnace go through a cycle and probe to see which terminal turns on with the blower on. I found #1,#4, #5.
#1 & #4 are "upstream" from the blower circuit (#5) so I removed the jumper wire from #1 and #4 and make new connection with a winged nut. (They adise not to wire directkly into the blower motor circuit and I am not sure why not because the transformer draws very little current anyway).
I also took (alot of ) time to clean and vacuum the burners and heat exchangers... about a cup of black soot and tar removed. I used a 1/2" hose (clear type) attached to a vacuum machine to clean the furnace.
ANYWAY WORKS GREAT!!!