Hello guys,

so I have 3 wires all 24VAC that I need to setup a system of logic gates for.
Wires A B C only get 24V when the respective system is powered (A = Heat, B = Fan, C = Air conditioning, D = Common (24VAC always on))
I am thinking relays since it is 24VAC.

Here's what I need in text form:
We'll call it wires A B C D
If (A or B is 24V) AND C is 0V then output 24V from D to the new device

That's it. If either the Heat or the FAN is on, then output power but only if AC is not on!

Hope that makes sense.

 

I was drawn the logical control diagram to shown the conception that you want and we can try to use the bjt or logic ic or relay or mix them to reach your requirement.

 

It looks good! Now comes the hard part, finding 24vac components.

I live in Denver so we have microcenter and allied electronics to my knowledge.

 

The main requirement really is longevity and price. I don't mind soldering components and such. I just want something I can set and not worry about ever breaking (not for a few years)

 

They sale what you need at most any part house that sales parts for hvac

 

Here's a circuit using 24VAC SPDT relays that should do what you want:

 

would something like this suffice?

https://www.grainger.com/product/GRAINGER-APPROVED-Enclosed-Fan-Relay-6AZU4

 

would something like this suffice?

https://www.grainger.com/product/GRAINGER-APPROVED-Enclosed-Fan-Relay-6AZU4

That should work if you need that high a current rating.

 

Lol like i said you reinventing the wheel

Just make sure you get the right one they come in 24 volt made for what your doing
you get heat AC and fan

 

Lol like i said you reinventing the wheel

Just make sure you get the right one they come in 24 volt made for what your doing
you get heat AC and fan

I'm not reinventing the wheel... I'm trying to turn on something but only when fan or heat is on, not AC

 

I don't necessarily need the high current rating but it's really hard to find 24vac coil relays.

That should work if you need that high a current rating.

 

Those are 24 volt and the come like you want they come in the same combination
as crutschow drew up in his post all in one black box.
24 volt ac coil and all
And they sale then at any good AC supply house

I don't now where your at but I live in ky probably 10 store stock them.
but they come in spdt and up you can get them that do most anything you'd need
or get 3 and do it like crutschow drew

 

Those are 24 volt and the come like you want they come in the same combination
as crutschow drew up in his post all in one black box.
24 volt ac coil and all
And they sale then at any good AC supply house

Awesome!

 

I don't now where your at but I live in ky probably 10 store stock them.
but they come in spdt and up you can get them that do most anything you'd need
or get 3 and do it like crutschow drew

And also as close as the local Graingers, even if it means buying from the internet.