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Scott Davis

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Reply with quote  #1 

Here are two options:

A snap disk fan switch like these for around $6.50:

https://www.pexsupply.com/pex/control/search?SEARCH_STRING=snap+disc

Most of us use this snapswitch for our hot air collectors.  It turns on at 110F and turns off at 90F:

http://www.pexsupply.com/White-Rodgers-3F01-110-3-4-Snap-Disc-Fan-Control-Cut-In-110-Degrees-F-Cut-Out-90-Degrees-F-14691000-p

Advantage: Cheap!

Disadvantage: You have to either run electricity out to your collector so the snap switch completes the circuit when it turns on, or use a relay.

Or

A differential sensor like this one for $133.00 (plus the cost of two sensors):

http://www.altestore.com/store/Solar-Water-Heaters/Differential-Temperature-Controllers/Delta-T-Hardwired-AC-Differential-Temperature-Controller/p6836/

Advantage: Plug and play - just plug your blower fan or pump into the unit. You only have to run a small gauge wire such a speaker wire out to the sensor on your collector.  Also, the differential controller will measure both your collector temperature and your thermal storage temperature, only running your pump when the collector is hotter, which makes it more suited to pumps for liquid (hydronic) collectors.

Disadvantage: Costs $126.00 more than the snap disk fan switch.


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DRDean

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Reply with quote  #2 
Scott, I wanted to share this option for temperature differential controllers.  Brian builds the controllers to order.  He has a fair number of controllers, solar trackers, etc:

http://www.mydtcstore.com/

Also, I purchased and Arduino board.  This little number is the way to go for customized control circuits.  It has a learning curve with programing, but there are some nice tutorials online.  Many programs are available online, written by others for specific purposes and available as open source code.  I have not spent the time I would like learning how to use it, but it can do soooo many things.

http://www.arduino.cc/

Dave.
taoswheat

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Reply with quote  #3 
I am using a neat temperature controller that includes a remote sensor, adjustable hysterisis, and a relay output to control fan or blower.  About $22 shipped.
http://www.ebay.com/itm/Digital-STC-1000-All-Purpose-Temperature-Controller-Thermostat-Aquarium-w-Sensor-/140756919030?pt=LH_DefaultDomain_0&hash=item20c5c422f6
JohnW
Taos
wyzarddoc

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Reply with quote  #4 
On my system currently in the planning stages I will use an arduino with solar panels to run both the arduino and the fans. Arduinos allow for inexpensive very flexible control of motors etc. Info can be obtained from http://www.arduino.cc/ add on boards for temperature, motor control etc can be found with software at http://www.adafruit.com/new/ and https://www.sparkfun.com/categories to name a few I have used. The system I am planning now will consist of a screen collector box connected to a rocket type heater. The planned system will use the collector during the day with the fuel box of the rocket bypassed. At night the rocket heater can be used if needed. 
Any suggestions are welcome
SolarInterested

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Reply with quote  #5 
wyzarddoc I've picked up an Arduino to fool around with and learn the code. I'd be interested in seeing your system and 'sketch' when it's built.

Mike

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Garage_Hermit

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Reply with quote  #6 
In the case of a fan, by far the best solution is to go for a temperature controlled fan: not only will it do what U state (turn on and off), but more importantly it will run "proportionally" faster as the temperature of your collector increases, which is what U should be looking for.  The fan comes with a temperature-sensor lead, generally limited to a few feet in length.

some good ones here...

http://datasheet.octopart.com/4312-EBM-Papst-datasheet-44855.pdf

I checked some prices on the web, some of them may look a bit more expensive, but the one I am getting is actually a lot cheaper than what I was originally off to buy elsewhere...  Plus it is far more compact.

Garage_Hermit

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doug9694

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Reply with quote  #7 
I had a furnace in a small room and the ceiling was around 110. I cut a vent above the
door to the room and used an adjustable switch that ran on the 24VAC control transformer of the furnace. It has both N.O. and N.C. contacts. When the heat got to 78 the contacts closed and 24VAC went to a relay that sent 110 house current to a fan at the vent opening and blew the hot air into a larger room. When the furnace went off the switch would open when the temp. went down to about 75.
You will use two of these. set one to open at 90 to shut off the latching relay that controls the fan. The other is used to turn on the latching relay at whatever temp you adjust the sensor to be. I have since moved 25 years ago. The relay and sensors where bought from electronics surplus stores that advertised in electronics magazines at that time. Now you can find places online.
Here are four advantages of this design I can see right away.
1. inexpensive
2. control over on-off set points.
3. Can use small wires to collector sensors.
4. Has both N.O. and N.C. contacts.
Scott Davis

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Reply with quote  #8 
Interesting Doug, thanks for sharing!
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moosemagicco

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Reply with quote  #9 
Scott Davis -

I was looking at your main page to see what you had done and saw that it is still "under construction".  That was quite a while ago.  I thought I had seen an update but can't find it anywhere.

Can you point us in the right direction?

Thanks!

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Scott Davis

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Reply with quote  #10 
Hi Moose,

Here is the main page:

http://www.n3fjp.com/solar/


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