[Amps] time to death in the event of a blower failure

[Jeff Blaine]

Thanks Gary,

I am familuar with those.  The similar button-type is used on the HVAC stuff.  They are easier to get than the TO220 sized which seems to be a single-supplier thing.  

The button type is larger but I am thinking that it would be easy to cut a hole in the chimney and mount it through the side.  Otherwise, it’s the same benefits as the other switch...

73, Jeff ACØC
www.ac0c.com


From: Gary Smith 
Sent: Monday, November 08, 2010 11:47 AM
To: Jeff Blaine ; amps at contesting.com 
Subject: Re: [Amps] time to death in the event of a blower failure

Pick a temp figure you like everything to come to a halt at.  Then head for a appliance part store and ask for a dryer safety cutout sensor at that temp figure.  They are available in either one then cut off, or off then on.  The guy behind the counter won't understand the app, but he will know about the switch.
73, Gary...wa6fgi



----- Original Message ----- 
  From: Jeff Blaine 
  To: amps at contesting.com 
  Sent: Sunday, November 07, 2010 8:27 PM
  Subject: [Amps] time to death in the event of a blower failure

  The traditional monitor for a failed blower is a air pressure sensor.  But this is harder to implement with a variable speed fan arrangement.

  I was working on a fail-safe for this case and thought a solution.  Wanted to run that idea by the board to see what the comments are...

  Here’s the idea...

  1. The cut-out mechanism would be one of these TO220 sized bimetal switches.  They are available in a variety of trip points.  

  2. The switch has no electronics inside and should be RF immune.  

  3. The switch can be set in the chimney near the silicon wall and would not significantly impede airflow.

  4. The switch has a very low thermal mass and will switch quickly.

  5. Even with a failed blower, the tube would be dissipating tons of heat and convection would ensure heat-up of the switch.

  73, Jeff ACØC
  www.ac0c.com
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