automating garage exhaust fan

[jb garage]

Hi guys. I'd like to control my exhaust fan with more than a simple home depot 'on at x degrees' thermostat.

Ideally, I'd like something that could have more than one parameter.

Like off at 70 degrees AND off if garage reaches same temperature as outside. For example if it is 80 degrees outside, the garage will never reach 70 degrees and the fan will run continuously not good.

Any ideas what kind of system I might could use to program something like this?

 

[Git]

You could do that with Homeseer software running on a computer or there is an opensource version (OpenHab) but I don't have any experience with that

With HomeSeer you would obviously need a couple of temp sensors along with a device to turn your fan on or off. It may get spendy if this is all your going to plan on doing with it

We have a couple of whole house fans that we run at night in the cooler weather along with an outside temp sensor. If the temp gets above 70 degrees, it will turn the fans off

Example Event:

If the device (temp sensor) changes and becomes a range value of 70 to 105 degrees, then set devices (attic fans) to off

 

[matt_i]

If you get a PLC (programmable logic controller) you can write whatever logic that you can think of.

There are "brick" PLCs available from Automation Direct which have free software in the $100 range.

There are also some limitations, imo iit woud be easier to have temp switches (like a thermostat) which come on and off at your setpoints rather than having an analog voltage that's proportional to the temp. Its not that the PLC is incapable of dealing with analog signals but it needs a special module to deal with them.

You could also have time-of-day conditions and also have timers set so that if its running for X number of hours something is probably wrong and it should stop.

I used to see a lot of people saying "aurduino" as the automation controller of choice but I don't see that as much any more. I work with industrial automation in my day job so I'm already familiar with the PLC.

 

[jb garage]

Wow thanks guys. Some great leads. Some reading to do now.

 

[75gmck25]

Arduino is very popular as an automation controller, since it is very well supported and very flexible, but you would have to figure out a lot yourself. It can be programmed to monitor a large number of inputs, and then control/feed a large number of outputs. However, you are the one who will have to figure out the interfaces, what to monitor, the logic of what actions to take, etc.

If you are comfortable with computer programming you might really find Arduino useful, but it is not a turnkey system. It is more like buying a really flexible toolkit, not a final solution.

Bruce

 

[The One]

You could go fully mechanical with relays.

 

[rattle_snake]

You can buy off the shelf differential temp controllers, but I have found the best solution is a simple timer. The outdoor temperatures are predictable in relation to time and indoor temps.
To removed heat, I run exhaust fan after sundown when outdoor temp has dropped significantly, and again at 4-5am when it is the coolest outside.

Logic;
Q:Is it always cooler outside at 11pm-5am?
A: yes
The exact temperatures don't really matter.

Been doing it in garage, shop and barn for several years. Works F@#$'n great and is cheap/easy. I have plotted temp data in my shop thread if interested. Can be over-ridden easy, just push of button, to clear smoke or whatever.

$20
https://www.homedepot.com/p/Defiant...ch-with-Screw-Terminals-White-32648/300524126

I started down this path with writing code on a microchip dev platform with two temp sensors, with the intent of running fan when temp differential was greatest. it was basically always at the same time, hence the timer solution. No need to worry about sensor locations, wiring, s/w corner cases and so on.

 

[jb garage]

That makes a lot of sense Justin. I have a sensor plotting thermostat in the garage right now. I noticed mine starts pulling away at 11am.

By 5pm my garage can be almost 10 degrees warmer than outside, so I might have it go on earlier in the afternoon. But then on again after dark and also in the early am.

How many programs a day does that let you set?

How many hours a day (total) do you end up running your fan?

 

[Git]

I just pulled up the 10 day weather forecast for Chandler Arizona and it looks like the current overnight temps are 78-79 degrees with the daily temps around 105.

Is it even worth running any fan in those conditions? By 8 A.M. your at 85 and by 9 your at 90

 

[rattle_snake]

Not sure your location and climate. Suggest adding location to your profile.

Anyhow, the one listed I think supports 7 programs (on and off) which is likely more than you need. I use a different brand/type for my shop that has a 220V variable speed exhaust fan.

I change the settings somewhat through the seasons based on observations. Before I had A/C, I would run fan 4 hrs (10pm to midnight) and then 3-5am in the hottest part of the summer. When I was in the shop in the evening and outdoor temp dropped a few degrees below indoor, I would just manually turn it on. The next scheduled (10 to mid) event would turn it off automatically if needed.
Other times a year only need an hour or two in the morning when temp differential is large.

link to some data.
https://www.garagejournal.com/forum/showpost.php?p=6506317&postcount=334

You will need a decent sized intake vent to run the fan autonomously with doors and window shut. Good luck.

 

[rattle_snake]

I just pulled up the 10 day weather forecast for Chandler Arizona and it looks like the current overnight temps are 78-79 degrees with the daily temps around 105.

Is it even worth running any fan in those conditions? By 8 A.M. your at 85 and by 9 your at 90

Good question. given the average temp, an other wise uncooled but insulated shop would be over 100* inside all the time. blowing 80* air in for a few hours lowers the average temps, especially when a hot vehicle is parked inside. As sunrise time changes it makes sense to adjust to the min outdoor temp as needed. running fan this time of year at 9am isn't helpful.

It's not going to make it comfortable, but lowers the peak (not average) temp about 10* or so. It was the only cooling method I had, so better than nothing.

Edit; well, I had 2 swamp coolers but I found them mostly useless and just a humidifier. Automatic exhaust fan is way more effective. YRMV.

 

[jb garage]

Dallas Texas. Yes rattlesnake hits it on the head, the fan won't make it comfortable in that weather, but less miserable. Garages can be like greenhouses. They trap the heat. Ad some ventilation to make it bearable.