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cwwilson721

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Reply with quote  #51 
Notice the hinged 'arm' the original used? Think of it as a 'stroke multiplier". If you need a longer 'moment arm', that's about the best way to do it.

GaryBIS

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Reply with quote  #52 
Hi,
I had a go at making a prototype stagnation temperature vent using the bimetallic spring from the automatic foundation vent -- added the description and test to the bottom of this page:

http://www.builditsolar.com/Tests/StagVent/StagVent.htm

It works pretty well.  Starts opening at about 190F and well open by 230F.

Would like to hear what people think of it.

I have somewhat mixed feelings -- it does appear to be a reliable and simple way to provide venting, but it also adds some complication and time and money to a collector build.

Gary
SolarInterested

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Reply with quote  #53 
Gary it was interesting to see this "The initial windup or tension you put on the bimetallic spring allows you to adjust when the vent will open -- a nice feature." I had thought it would be more complicated so it's nice that it's that simple.

As for the bottom vents would there be any advantage to having a one way valve similar to your thermo-siphon collector, thin plastic film on hardware cloth?

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GaryBIS

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Reply with quote  #54 
Hi CW,
It does seem like having some kind of poly film "valve" on the bottom vent would be good.

It is nice that the bimetallic strip does not have any fixed temperature range.

I asked for a quote from the company you mentioned with the linear temperature driven actuators -- will see what they come back with.

Gary
Ky-Jeeper

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Reply with quote  #55 
http://www.simplysolar.supporttopics.com/post/show_single_post?pid=1281413882&postcount=22
cwwilson721

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Reply with quote  #56 
Quote:
Originally Posted by GaryBIS
...I have somewhat mixed feelings -- it does appear to be a reliable and simple way to provide venting, but it also adds some complication and time and money to a collector build.

Gary


Yes to time, money, and complication to a build. You need to weigh it against the possibility of a CPVC meltdown (if you use that material as your medium transfer), the possibility of a steam or overpressure event, or if you REALLY like "Old Faithfull" spewing from your collector when you pull in the driveway after a visit to Grandma's House for tea and crumpets. How cheap is your glazing? Will it take longer and cost more to build these into the frame while in initial construction? Or will replacing the glazing be cheaper and faster? How often DO you stagnate?

What if during the more spectacular event, the family dog happens to walk underneath? Hot water shower, indeed.

You have to make the decision yourself, based on your own setup and needs.

If it costs $15, a couple of holes in the framing, and an extra 15min and some stiff wire...Why not? Mandatory? No.

(Unless the guvmint reads deese forums and this post...)

cwwilson721

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Reply with quote  #57 
Quote:
Originally Posted by Ky-Jeeper
http://www.simplysolar.supporttopics.com/post/show_single_post?pid=1281413882&postcount=22


If you have power available, actuators, fans, step motors, even a plastic pool toy inflator can be used to open vents, lift the glazing, or whatever. That's fairly easy.

What if you have a power failure (not just grid, but for some reason, your PV failed, too) while you're away for lunch, work, or shopping? Stagnation event will quickly follow, and...

I'm a REAL fan of the "actuator lifting the glazing'. That'll vent REAL quick. But, it requires an 'external power source', whether electrical, hydraulic, or pneumatic. It will also cost a bit, in both money and time during construction.

The basement auto vent bi-metallic spring attached to a top vent or both top and bottom vents seems to be a good non-powered solution. Fairly cheap, easy to even 'add-in' to and existing built collector, and non-powered. 
Garage_Hermit

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Reply with quote  #58 
Hi, Gary,

Quote:
Would like to hear what people think of it.


I think it is real neat !

When U consider the time & effort that goes into a collector, this device looks like a really good investment !

(no self-respecting turbofan would be seen without one of these "additional air intake doors" !)

G_H



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cwwilson721

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Posts: 303
Reply with quote  #59 
Possible improvements:

  • Slot-type opening, with hinged metal sealing to outside of frame (Gasket?) and spring inside of collector. Have the spring push the vent 'up' from the inside to open, with a linkage wire down to a bottom vent that opens to the inside of the collector (both open "up"). Harder to insulate
  • Vent plug/slot having guide holes with rods to guide it 'up', with no hinge. Spring w/linkage to bottom vent same. when hot, spring pushes under the plug, pushing it up. When in normal operation, top of plug can be bigger than the hole, sealing it. This version would allow full insulation/etc. Needs longer 'moment arm' to push the plug high enough.
stmbtwle

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Reply with quote  #60 
I'm not sure if this is the "best" system but IMO it's probably one of the simpler.  A small computer fan in the bottom of the collector powered by say a 10w PV panel (cheap) and a snap switch located in the top.  A "flapper" vent at the top.  When the snap switch trips the PV panel will power the fan at full output to bring in outside air, pushing the hot air out the vent.  The only moving parts are the fan and the flapper, and it's independent of outside power.  If the sun isn't shining yes the PV won't work, but the collector won't overheat, either.
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