Control Fan From HVAC and AVR

[EmagSamurai]

I'm not sure how many of you guys frequent AVS as well, but hopefully posting this question on both forums isn't an internet posting foul. It occurred to me this morning that this was more of a home automation question than a theater question.
 
I would like to wire up my room exhaust fan to come on automatically when either my AVR/PJ or my HVAC is on. I think I figured out how to do it, but I'd like a sanity check. Here's the relay I'd like to use. It seems perfect since the coil is rated 10VDC to 30 VDC so it will handle both the 12 V AVR trigger as well as the 24 V thermostat voltage.
 

 
If I use two of these, I think I can connect the coil of one to the AVR/PJ 12V trigger, and the coil of the other to my HVAC thermostat. Then connect the contacts in parallel to supply the fan. Something like this.
 

 
Here's the part I'm not too sure about. I think this is how I need to connect the relay to the thermostat (relay coil between C and G on my thermostat). 
 

 
Anyone know if this is correct? Am I overlooking something? I've found one site that mentions the thermostat controls the fan during cooling, but the heat pump will control the fan during a heat cycle. Is that true? If so, this may not work as I'd hoped although it's unlikely I will want any heat in my theater.
 
Also, does anyone see any issues with both the HVAC and the AVR/PJ energizing the fan at the same time? Since it's being fed from the same 120 V leg, I can't see that it would be a problem, but it's worth asking.
 
Thanks in advance!
 

 

[BraveSirRobbin]

Pretty sure those relays triggered via your thermostat are 24 volt AC (i.e. not DC) so not sure if that relay in a box that you specified would work.

 

[EmagSamurai]

That's a good point. I'd assumed it was 24 VDC, but you are correct. Fortunately, that relay will accept 10-30 VDC, 10-30 VAC, or 120 VAC. I'd rather be lucky than good any day

 

[tmbrown97]

You're going about it all wrong... that's just way too easy like that!  What you need to do is upgrade your HVAC to a connected one that talks to your home automation controller; also have that home automation controller watch for the status of your AVR via a globalcache itach and if either one is running, have it send a command to turn on the fan either via UPB or ZWave or one of those technologies.
 
You can't do this for $25; you need to invest at least $2K and start a much larger project!
 
  :rockon:

 

[EmagSamurai]

:lol:  Funny stuff!
 
I'm normally not the one to go with the simple solution if there's a more complicated and more expensive alternative. Unfortunately, budget dictates I go with the boring...... um..... cost effective.... route this time.

 

[Ira]

You may want to go to Functional Devices' web site (the manufacturer of the relay-in-a-box) and look at either RIBU2C or RIBU2S2, or some of the other RIB's that have two or more relays in the same box, rather than two separate boxes.
 
Also, you can do a lot better on price than Graingers if you are going to buy it online...
 
http://www.energyequipment.com/search.php?search_query=RIBU2C&x=17&y=19
 
The above link has the RIBU2C for substantially less than Graingers RIBU1C, and you only need one RIBU2C.
 
The RIB's are great relays (as are the other Functional Devices relays, like the track mounted ones).

 

[EmagSamurai]

Awesome! Thanks for the tip. I didn't realize they had any with multiple relays in the same box. And good point about Graingers. That was just a name I was familiar with, but a little Google searching turned up some MUCH lower prices. I was surprised at the difference.