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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22627
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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I installed an Aprilaire 800 and I can't get it to start.

Customer Question

I installed an Aprilaire 800 and I can't get it to start. I'm using the nest thermostat and a relay to control the humidifier. I checked and I'm getting 24VDC to the hum terminals on the humidifier.
The Aprilaire power light is on and green, but the fill and steam lights are not on. When I turn it off the drain light comes on, and water drains out.
Any ideas?
Submitted: 1 year ago.
Category: HVAC
Customer: replied 1 year ago.
I forgot to mention it's set for 16A 240V. Dip switch 1 is on, 2-4 are off.
Expert:  BillyHvac replied 1 year ago.

I am very sorry your question has not been picked up yet.

I just logged on and found you had not been assisted.

Please let me know if you still need help and I will do my best. Please do not "Rate" as we have not worked toward an answer yet.

If you would like to proceed let me know by replying. Once again use reply..not "rate".

Customer: replied 1 year ago.
Yep, still looking for help. Thanks
Expert:  BillyHvac replied 1 year ago.

we should be ooking for 24v AC not DC...are you sure of that reading?

Customer: replied 1 year ago.
Pretty sure. I'm using my nest 2.0 to control it. I'll double check but I thought the board on the humidifier calls for open/closed, and ac will fry it. Im running the 24VAC signal to a6azu2 relay to get 24vdc, then to the humidifier. I think my actual reading was 23vdc.
Expert:  BillyHvac replied 1 year ago.

24dc is all internal to the humidifier. All control power is ac volts.

see page 10 HERE and tell me if you are using J12 terminals 1 and 2

Customer: replied 1 year ago.
I'm using J12 1 and 1. I basically followed the diagram here'm back in town in the morning and I'll check whether I'm getting ac or dc signal.
Expert:  BillyHvac replied 1 year ago.

if using J12 it is 24v ac. I also see you had main power as 220v not 120v?

Customer: replied 1 year ago.
220. I'll get a meter on j12 later this morning.
Expert:  BillyHvac replied 1 year ago.

thank you. Just keep me posted

Customer: replied 1 year ago.
Okay, thanks for your help so far. I confirmed I am getting 24VDC across j12. I also confirmed that the voltage is internal to the aprilaire 800. The j12 contacts are only looking for dry contact. I measured across the relay with the wire to the humidifier removed and got no voltage. I'm assuming once the relay makes the dry contact the 24 volts DC I'm measuring is internal to the humidifier. The power light is on to the humidifier and I'm getting no error messages. The drain light comes on when its drain but no other lights come on except the power light. Any ideas?
Expert:  BillyHvac replied 1 year ago.

if you jump j12 1 and 2 does the unit start?