Aprilaire 700M and Armstrong Ultra 80 furnance

Greetings. I need some assistance with wiring my new humidifier. I have purchased an Aprilaire 700M and it is installed on a Armstrong Ultra 80 oil fired furnace. The furnace is approximately 25 years old.

I have completed all of the installation except for the wiring the humidistat and actual humidifier. I am not very good at reading schematics and am asking for detailed instructions to ensure I wire it correctly. I also have a transformer that came with the humidifer as well.

As a side note, I replaced an old Sears humidifier and it was wired directly to the fan blower motor. I understand that this will not work with the Aprilaire.

I have attached pictures of the furnace to provide a visual so hopefully someone can assist me. Thanks in advance.

 

Welcome to the forums.

How was your Sears unit wired..... with a transformer ?

You have a basic heating system with no control board. The only way to connect your humidifier is to use a current sense relay like the model 50.

Aprilaire-50-Sensing-Relay-24-volt/dp/B002T0ZTNC

 

the Sears was connected directly with the blower motor. 110v as far as I know. Is there anyway to use the transformer that was included with it to connect it? thanks for the reply.

 

You can connect the supplied transformer to the blower motor.

Otherwise you'll need to supply the new transformer with power and use the #50 switching relay.

 

Ok, so i connect the hot and neutral from the blower to the transformer and then I hook the white and black from the transformer to what? Sorry if I am being too naive.

 

No problem....

Since the wiring between the transformer, humidistat and humidifier is AC.... there is no polarity.

 

Awesome. thanks for the drawing it really helps. I will connect it in the morning. Thanks again!

 

Well that didn't work. Just burned up the transformer.

 

The wiring diagram is correct. I'm not sure what happened there.
Was something shorted on the 24v side ?

 

Wired it per the diagram, and when the blower kicked on the transformer smoked and arced. Not sure what else to do.

 

That sounds like the voltage was higher than 120v applied to the transformer. Usually an oil fired furnace will use a 120v blower motor but maybe yours is different. It will need to be checked.