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Thread: Relay controlled fans from furnace

  1. #11
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    Quote Originally Posted by myspark View Post
    Perhaps OP needs to come back and clarify what exactly his intentions are. . . instead of going through all these hypotheses.
    perhaps

    Quote Originally Posted by myspark
    Not all SSRs are the panacea of all issues that are present in control circuits.
    true

    Quote Originally Posted by myspark
    They are sensitive to high temps unlike those time proven electro-mechanical relays that don't require heat sinks.
    not sure, i find many of the Omron SSR's rated at operating temp of 80C (176F). mechanical are subject to bad contacts, dirt, noise generation, slow rise/fall times, sticking contacts, etc etc.

    Quote Originally Posted by myspark
    I've wired giant forging furnaces and the work area is constantly around 103 F, 24/7.
    how big was the furnace? i find many of the Omron SSR's rated at operating temp of 80C (176F). but i suspect by theorized hypothesis that the OP does not have a operational high-temp problem to design around, but we should ask. in general, SSR's are preferred.
    Last edited by FionaZuppa; 08-07-17 at 04:35 PM.

  2. #12
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    How far you need to run, what is acessible, how easy it is to tie back to the furnace (120 or 24 volts) all impact what may be easiest way to do it. If these are at the end of a long main duct and is difficult to get back to furnace - maybe even use a pressure switch to sense increase in static pressure in the duct to start your fans. If your booster fans drop the static pressure too much, that won't work - they will just cycle on/off as pressure keeps cycling - but if you encounter that you have serious ducting issues and boosters probably aren't the answer either.

  3. #13
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    IMO, Boosters are the result of poor design to begin with.
    Tom
    TBLO

  4. #14
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    Quote Originally Posted by ptonsparky View Post
    IMO, Boosters are the result of poor design to begin with.
    I've seen them applied when a room is added to a house. The original system was not designed to feed the extra space and a booster is more economical than re-piping the house.

  5. #15
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    Quote Originally Posted by ptonsparky View Post
    IMO, Boosters are the result of poor design to begin with.
    where's the admins here to close you down? poor design has nothing to do with the OP's question

    and, OP only said "booster fans", but we really have no idea if its actually boosting anything, or its just the name of the type of fan being used. i have also seen "booster" fans used to suck hot air from top of cathedral ceiling and move it to another room(s). ceiling fans dont always work when, as example, such room has a hefty wood burning fireplace and this room gets way to hot, so you use "booster" fan (aka inline) to move that heated air around as needed.

    we dont know why such fans are being used, but i think OP has enough info to make an informed decision on what to do.

  6. #16
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    Quote Originally Posted by FionaZuppa View Post
    where's the admins here to close you down? poor design has nothing to do with the OP's question

    and, OP only said "booster fans", but we really have no idea if its actually boosting anything, or its just the name of the type of fan being used. i have also seen "booster" fans used to suck hot air from top of cathedral ceiling and move it to another room(s). ceiling fans dont always work when, as example, such room has a hefty wood burning fireplace and this room gets way to hot, so you use "booster" fan (aka inline) to move that heated air around as needed.

    we dont know why such fans are being used, but i think OP has enough info to make an informed decision on what to do.
    OP's mentioning of somehow tying them to the furnace is a big indication that they likely are boosting the air being delivered by said furnace though.

  7. #17
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    Quote Originally Posted by kwired View Post
    OP's mentioning of somehow tying them to the furnace is a big indication that they likely are boosting the air being delivered by said furnace though.
    as the saying goes, which is a 50/50 conundrum

    perhaps yes, and perhaps no, we suspect yes, but we dont know

    tying to the furnace relay only tells me the fans are used to move air when furnace is on, perhaps just to move air from one high ceiling into a more distant add-on room. i dunno.

  8. #18
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    Quote Originally Posted by FionaZuppa View Post
    as the saying goes, which is a 50/50 conundrum

    perhaps yes, and perhaps no, we suspect yes, but we dont know
    Based on other things mentioned, I think the odds of OP using them to boost air flow is higher then 50%.

  9. #19
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    Thank you all.

    I have a problem of designing things overly complicated. The independent control of the fans was to deal with rooms that get too warm and too cool, I wanted to better regulate.

    I also have an issue with too little make-up air that I needed to address, so if I made my controller (down the road) cognizant of pressure drop I could shut of the fans drawing the most air away from the basement.

    In the summer and winter I could boost different areas depending on what needed it.

    I really would have had no issues running 14/2 everywhere... At least the price had come down some. I also know how expensive ssr and relays are so as a cost saving measure it doesn't make much sense.

    When I get some sleep I'll respond to the points individually.

    Without adding a complication now there's also a small laser cutter with a huge impeller for smoke collection and exhaust. I can't run it until I deal with the duct issues and safely push that outside. But pressurized the house with make-up air when it's running isn't behind the possibilities.

    Thank you all again for the excellent ideas and viewpoints.

  10. #20
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    Excuse my ignorance but having never used a relay in a box I'm guessing there is not a need to install a barrier between the high and low voltages? Does that only apply to switches?

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