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  1. Our climate here is very dry, so humidity is not...

    Our climate here is very dry, so humidity is not an issue. In fact it only gets hot when we get the hot Santa Ana desert winds, along with which comes 10% humidity.

    Sounds like the worst case...
  2. So if I happen to be gone during the two hours...

    So if I happen to be gone during the two hours they shut off the condenser, the HVAC will be running (probably on 2nd stage) the whole time, using up energy without doing any cooling? I guess that...
  3. Sure, here you go:...

    Sure, here you go:...
  4. Got it - it'll continue to circulate air...

    Got it - it'll continue to circulate air throughout the house, it just won't be conditioned - right?



    Yes, makes sense - will have to see how this plays out in actual usage.
  5. So the HVAC system will know to shut off after...

    So the HVAC system will know to shut off after the condenser has been cut off?
  6. Hmmm, this is exactly what I am worrying about -...

    Hmmm, this is exactly what I am worrying about - what happens to the "system" if the power to the condenser gets cut off. Doesn't the system somehow know when the condenser has been shut off (low...
  7. Yes, this is in line with what our provider (SCE)...

    Yes, this is in line with what our provider (SCE) reserves the right to do - up to 6 hours of "off" time per day. In the past year they have never exceeded 4 hours at a time, and all but that one...
  8. Thanks for the quick response! From what I read...

    Thanks for the quick response! From what I read on their website, when they shut the AC off, it's usually for about 2 hours - so that should alleviate any concern about damage?

    Regarding whether...
  9. Any risk from power company cycling my condenser on and off?

    I am considering signing up for my power company's rewards program, which allows them to turn off my AC remotely whenever they have a high load on their system, in exchange for crediting me $200 a...
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    Got it, so that means RH of < 60% for 75F...

    Got it, so that means RH of < 60% for 75F outside... Today the RH here is 9% :).
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    Thanks beenthere. I haven't considered the extra...

    Thanks beenthere. I haven't considered the extra dirt loading on the filter and coil, that pretty much puts an end to this idea!
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    True, good point. But if I could (which I can't)...

    True, good point. But if I could (which I can't) supply the cooler outside air right to the return, wouldn't that be better than recirculating and cooling the 80F air that is in the house?

    It...
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    I guess I look at it analogous to a car (maybe...

    I guess I look at it analogous to a car (maybe it's flawed). They say if you get into a hot car that's been sitting in the sun, to first run the AC with the windows open, to "push out" all the...
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    Thanks shophound! My original question was not...

    Thanks shophound!

    My original question was not so much "use the AC or a wholehouse fan?", because the latter takes too long.

    What I wanted to confirm was that under the conditions I listed...
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    Thanks guys, this all makes sense. Regarding...

    Thanks guys, this all makes sense. Regarding running a mechanical fan, yes, I know it is more efficient. But it's a large house, and when it heats up to 80F, it takes like three of four hours to...
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    Run AC with windows open?

    If it's 80F in the house when I come home from work, and 75F outside and low humidity (around 20%), is there a pro or con to keeping the windows open while I run the AC to cool the house off?
    ...
  17. Bad, bad, Key1, generating his own data... But...

    Bad, bad, Key1, generating his own data... But please do share it :).
  18. Ah, OK, I see what you are getting at. The key...

    Ah, OK, I see what you are getting at. The key (no pun intended) word here is primary - so you are saying that Key was trying to find the primary source of restriction, or conversely, to show that...
  19. I think I see what you are getting at, and if so,...

    I think I see what you are getting at, and if so, then we are not disagreeing (I don't think :) ). All I was trying to say was that if you increased your return area, you would reduce your total...
  20. Ha, I am not so sure - I think you take the...

    Ha, I am not so sure - I think you take the "obsession" prize :).



    Hmmm, I don't understand - when you simulated adding more return, your system static dropped from 0.98 to about 0.78 - isn't...
  21. Key, you and I seem to have the same obsession...

    Key, you and I seem to have the same obsession (some might say we are pathetic :) ), but to answer your direct question above, my thoughts are that your test results do not confirm that your system...
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    Thanks Dash, that would explain it. My Manual D...

    Thanks Dash, that would explain it. My Manual D is a few years old.

    You wouldn't happen to have a current flex duct friction loss chart handy, would you? :). I'd like to update the equations in...
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    Manual D and Flex Duct

    I am finishing up my efforts to "model" my existing duct system, using values from Manual D, as a precursor to trying to find the most effective changes to make in order to reduce my static.

    My...
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    0.22" static in the return duct (without a...

    0.22" static in the return duct (without a filter) seems like a lot of resistance. I also have a high static system (about 0.9"), of which 0.25" is in the return with the filter. It drops to 0.15"...
  25. Dan, I didn't see your e-mail address in the...

    Dan,

    I didn't see your e-mail address in the profile, but I posted my e-mail in a message to you, so if you get a chance, send it over! I spent a couple of hours last night setting up the basic...
  26. Suggestions for duct analysis software?

    I am looking for software where I can input my as-built system, and have it tell me what static pressure I can expect with the existing ductwork and system cfm. Then I'd like to try changing some...
  27. I am just a homeowner, but like Key1, I try to...

    I am just a homeowner, but like Key1, I try to learn as much as I can. So a couple of thoughts:

    First, I have no doubt that Mr. Davis has measured some 90% furnaces to be running at 50%. But I...
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    I'm just a HO, but it sounds like what he...

    I'm just a HO, but it sounds like what he measured was exactly what you asked him to measure - pressure drop in the ductwork. By measuring before the filter on the return side, he measured the...
  29. Yup, we're birds of a feather then :). I'm...

    Yup, we're birds of a feather then :). I'm putting my worries about my static on the backburner for the holidays, but I'll attack it head on in January.
  30. Key1, are you still worrying about your 0.7"...

    Key1, are you still worrying about your 0.7" static? I thought that Trane told you in their lengthy one-word answer that the 0.5" limit is without a coil, and can be increased to 0.8" when a coil is...
  31. I'm having a hard time picturing this. These...

    I'm having a hard time picturing this. These numbers would suggest that you have twice the resistance on the return side as on the supply side; i.e. your return duct and filter have two times the...
  32. They are reasonably tight; certainly not...

    They are reasonably tight; certainly not "stretched", but also not kinked or loosely placed like I saw on many other installations.



    Yes, I appreciate this concern, shophound. My thinking was...
  33. Well, don't take my numbers too literally :). I...

    Well, don't take my numbers too literally :). I am still struggling with the bouncing Magnehelic needle (although I just received their pressure snubber that is supposed to fix that), so I made the...
  34. Dash, Thanks for the reply. I see what you...

    Dash,

    Thanks for the reply. I see what you mean about lower static downstream due to the vanes, but I am surprised by no change in the plenum static. Does this mean that my TESP will not reduce...
  35. I was pondering the same thing, as I with the...

    I was pondering the same thing, as I with the door open, I have airflow coming in before and after the probe (probe is in the return plenum). But I convinced myself (maybe foolishly) that the...
  36. Yes, I often feel like Chevy Chase - "This is not...

    Yes, I often feel like Chevy Chase - "This is not longer a vacation. It is a quest!". I feel like I am on a quest to have the lowest static in CA :).



    Interesting. I guess what I do see is...
  37. Understood. I have Manual J calcs that show the...

    Understood. I have Manual J calcs that show the heat load and cooling/heating cfm requirements for each room. Like you said though, I have no way of verifying if the right cfm is being delivered to...
  38. Made some more static measurements, help me interpret

    As you recall from my other thread, I am struggling with excessive static in my system (0.95" at 1800 cfm):

    http://hvac-talk.com/vbb/showthread.php?t=184924

    I have lowered the cool airflow to...
  39. KEy1, if you are still looking for a source,...

    KEy1, if you are still looking for a source, e-mail me, and I can give you some pointers on where to find them.
  40. Ah, we must have been posting at the same time! ...

    Ah, we must have been posting at the same time! Thanks Dash!
  41. Thanks Key, very interesting. If I interpret the...

    Thanks Key, very interesting. If I interpret the data correctly, the data would suggest that 2" vanes can actually result in MORE pressure loss than just a radius fitting with no vanes. Of course...
  42. Dash, I found a contractor (not the original...

    Dash,

    I found a contractor (not the original installer), who is willing to install Ductmate ProRail vanes, but he is asking if I want the 2" or 4" versions :confused:. What size is typical for...
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    You are right, my system is 5 ton, but I have the...

    You are right, my system is 5 ton, but I have the blower set to 1600 cfm in order to reduce the static. And this kind of airflow is typical of a 4 ton system, isn't it?
  44. If I had to do it again, I would have gone with a...

    If I had to do it again, I would have gone with a smaller system for sure, but Manual J suggested 5 ton cooling, from which everything else was sized accordingly. I guess the "design" conditions...
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    For what it's worth, I have a system running at...

    For what it's worth, I have a system running at 1600 cfm (~ 4 tons), with two 16" flex duct returns (each about 10' long) from two 20x25" filter boxes, and I have a fairly high static in the returns....
  46. Sorry to steal the quote from another thread, but...

    Sorry to steal the quote from another thread, but it appleis to this one:



    I have to say that every time I get wrapped around the axle worrying about my high static and how much work it'll take...
  47. I'm using Model 2001, 0-1.0". I called Dwyer...

    I'm using Model 2001, 0-1.0".

    I called Dwyer today, and they suggested that I get a "pressure snubber", which I think is basically an orifice to dampen out the fluctuations. I ordered one and...
  48. Key1, That is good data, and seems to be in...

    Key1,

    That is good data, and seems to be in line with what I saw in my system.

    One other thing I am going to try is to take off one of my 10" ducts at the plenum, and see how the static will...
  49. Dash, I appreciate your feedback, and will ask to...

    Dash, I appreciate your feedback, and will ask to have turning vanes added. Thanks!
  50. It did not change between 1 filter and 2 filters...

    It did not change between 1 filter and 2 filters removed - both configurations resulted in -.15/+.70, so 0.90 ESP.
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