Aprilaire 600A Control Wiring

[LitlBob]

Hi guys, I'm new to the forum and hope you can help me solve my problem. I installed an Aprilaire 600A bypass humidifier and am having trouble with the automatic humidistat controller.I wired it exactly as the manual instructs but I can't get the solenoid valve to open. Terminal R and C are wired to a steady 24VAC. Terminals W/G and Cf are wired to a switched 24 VAC source via a transformer connected to the furnace accessory terminal(HUM).Terminals ODT are wired to the outdoor sensor. Terminals H are wired to the solenoid. When furnace is running I placed controller into test mode and can hear the relay pick up but there is no output volts (0.0 VAC) measured at terminals H. I do get a closed contact action across these terminals.If I switch the controller to manual with the manual resistor connected I get a steady 24 VAC across terminals H. Is controller defective or can I just wire a 24 VAC source in series with the H terminal and the solenoid?

[ckheat]

Although I used this forum quite a bit as a service tech years ago, I haven't used it in the several years I was in distribution management, I have just come back to it as a contractor and understand that to discourage DIY, they do not want these discussions taking place here. From my memory, I believe those terminals to be dry contacts unless you flip a switch on the humidistat board. Check your instructions again.

Thanks, CK Heat

[LitlBob]

Thanks ck heat, you were 100% on the money. The AB switch was in B position.
Needs to be in position A. When it was in B position I read a phantom 24VAC on terminals H due to high impedance voltmeter (Fluke 77). Not real voltage. System works O.K. now. Thanks for your help.

[jrbenny]

Although I used this forum quite a bit as a service tech years ago, I haven't used it in the several years I was in distribution management, I have just come back to it as a contractor and understand that to discourage DIY, they do not want these discussions taking place here. From my memory, I believe those terminals to be dry contacts unless you flip a switch on the humidistat board. Check your instructions again.

Thanks, CK Heat

Do not provide DIY assistance.

Consider this your freebie.