Dual Air-Temp Gauge for On/Off Switch Automation?


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Old 06-01-14, 05:10 PM
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Question Dual Air-Temp Gauge for On/Off Switch Automation?

I'm attempting to bring a concept to life to help with my Garage Heat Mitigation Projects.

I'm going to install a fan to vent hot air out of my garage and draw cooler air in through vents near the floor on the cooler side of the house in the evening/night.

I don't want the fan just running all the time (there will, inevitably be a period of time in the morning when it's cooled down enough inside the garage from the fan going all night maybe that it will be hotter outside for a while, and I would not want it running then).

I don't want to have to keep turning it on and off (I will inevitably forget it, and leave it going at some point).

I could put it on a timer, but the timer would have no idea of the actual temp difference (between inside the garage and outside the house), and I would need to keep adjusting the timing of the timer as the season goes along.

So, I want to create a system that has two thermometers;
one inside the garage (at the hottest place inside the garage, I think),
and the other on the outside of the house (at the cooler spot where air will be taken in).

Then, I want an on/off switch of some sort that will simply pay attention to the two thermometers; if the outside temp is cooler than the inside temp, turn the circuit on.

Do any of you know of a product out there that already exists that can do this kind of monitoring/switching, and/or, if not, do you have any ideas for how to piece different things together to come up with something that will do this for me?
 
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Old 06-02-14, 01:35 PM
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....................
Am I crazy?
 
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Old 06-03-14, 09:19 AM
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You could use a regular line voltage cooling thermostat inside and a remote capillary thermostat for outside temp. Not aware of anything premade for application.
 
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Old 06-03-14, 09:34 AM
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@ PJmax

OK. So, with those two items together, would I be able to create a system like I'm talking about?
Any chance you could give any more pointers on such a thing?
 
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Old 06-03-14, 09:40 AM
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I'm out on the road. I'll post more info, in depth, tonight for you.
 
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Old 06-03-14, 09:56 AM
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Sweet. Thanks a lot. ....................
 
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Old 06-03-14, 05:13 PM
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You would need a thermostat inside the garage so that the fan only came on when a certain temperature is exceeded. For that you would use a line voltage cooling thermostat. The following is just one thermostat. You can search for others.
Thermostats | Robertshaw®Line Voltage Thermostat Cooling, SPST Switch | B210940


For outside sensing I'd use a remote bulb thermostat that activated below a set temperature. The following is just one. There are many that will work. Keywords are SPDT switching, remote bulb, 120vac use. I'd check for bargains on ebay too.
WHITE-RODGERS Thermostat, Remote Bulb - G1679063

Here's one on Ebay......
New Johnson Controls A19ABC 4c Remote Bulb Temperature Control | eBay



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Old 06-03-14, 08:44 PM
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Wow, thanks!
So do I understand it correctly that, in the way you have suggested it, both would need to be true, and that would result in the circuit being connected?

In this case, I wouldn't be able to fully get what I imagined, BUT, if I do this AND add in a timer, I could probably acheive at least a 90% equivalent..... right? I mean, I don't really need to have it going all night long anyway.....probably just a few hours in order to get a significant enough amount of cooling, I guess, right?
 
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Old 06-03-14, 08:56 PM
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You could easily add in a timer.
 
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Old 06-04-14, 05:45 AM
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....and if I did, that would go to the left of the thermostats in your diagram, right?
 
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Old 06-04-14, 08:36 AM
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All three devices need to be on for the fan to work so it can go anywhere in the chain.
 
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Old 06-04-14, 10:08 AM
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OK...yep, I get that part.
I was just meaning that, there's no reason for me to be sending electricity through the thermostats at all if it's outside of the desired time anyway. So, I could just put the timer between the source of electricity and the thermostats. Right?
 
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Old 06-04-14, 10:21 AM
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Sure.... makes perfect sense.
 
 

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