Spdt relay

Discussion in 'Electrical Forum discussion & Blog' started by jdanw, Jun 4, 2012.

  1. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    I'll go for that: We don't understand exactly what you are trying to do. Give more information. But I would reserve relays strictly for controlling high draw motors where a standard switch would be short lived or very expensive.

    I often hook up submersible pump pressure switches to control the pump via a relay. The pressure switch contacts then carry very little current and the heavy relay does the millions of cycles they are designed for.
  2. jdanw

    jdanw New Member

    Messages:
    22
    Location:
    Wichita, KS
    First let me say, that the equipment is bought and nearly impossible to get me to completely start over, so I need to work with what I have, for the most part. Dampers are inline and installed, Fan is installed. It's just the wiring that need to be completed. I understand an appreciate what you are saying JW, but I just want the system to run. Let me worry about makeup air, whether the system accomplishes the goal,. I need to know how to get it wired correctly.

    OK, the objective is to ventilate two bathrooms with a single inline fan and control via N.O. dampers. I do not want both bathrooms being ventilated every time the fan is on. That's just the way we want it.

    The reason my electrician acquaintance suggested the relays is the damper power. We need to make sure that only 120V gets to the fan, so that power has to originate from the same source and not from two separate circuits (right? again, his words). I could wire the fan with 3-way timers, but how to get the power pulled off for just one damper? Hence the use of relays.

    So, if all of the wiring is in the outer insulation, it is a cable and will be complaint, right? When it exits this outer insulation, and hence the cable, it needs to be in an approved enclosure, right? (just like the rest of the house wiring , into a covered box) I was going to suggest the transformers be attached to a metal box as they are typically mounted, with the line voltage side in of course, but how about mounting them to an enclosure that JW suggested, with the relays mounted in the enclosure and all wiring in cable or boxes. And everything with a ground will have one and it will be connected (I think my original timers do not, so no ground there). Is that what I am hearing?

    Please, Please help me figure this out with the equipment I have. It seems the parts are being used for what they were designed for, so it's just the installation now right? I am in the process of re-insulating my attic and want to get this wrapped up, so I don't have to go up there and trample the new insulation.

    Thanks again...Drawing to come today...
    Last edited: Aug 24, 2012
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
    Have you got your permit for this job yet? Will it be inspected as it is required by law?

    You have made a few statements in your post above that has me wondering if your intent is to make this installation with safety thrown out the window and the world be damned.

    There is a lot more to what you are attempting than what you want to consider. You are sold on a foolish idea and will not listen or even discuss what the flaws are. You simply state that you are going forward with or without help.

    Is the fan large enough to vent both baths at one time? The one you mentioned earlier in this thread is not and will be a failure.

    All conductors of a circuit must be contained in the same cable or raceway and this includes the hot neutral and equipment grounding conductors. One wire of a conductor cannot be used and the rest left unattached as this will cause heating.

    What has happened to that electrician you had giving you advice, did he quit?
  4. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX
    Play it safe

    Really the short here is to build it the safest way that you can.

    I would put all of the electronics in a properly enclosed box.

    It may not meet code and it may not need to be inspected, but it should for the protection of your family.

    Where I live you can do as you please in your own house, For the most part.

    If you do have a insurance claim then it would be best to have it up to NEC code, even if not required.

    If you have questions about how it should be wired then consult your personal electrician.

    If it was me I would have a fart sensor to open the proper vent and have the fan turn on automagically.


    Just be safe playing with electricity.
    Last edited: Aug 24, 2012
  5. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    What makes relays inherently dangerous? Not that you need one to control a 1.7 amp load...

    But if he puts it in a heavy UL box and mounts it on an exterior wall, thats pretty safe, providing he knows the wiring theory.

    But again, wishing to over-design and go no need "tech" is not a good place to play in the house. Grandmas timer works clean. Also they have electronic switches with adjustable off delays. I built a box for a 20HP sander with a on delay timer for the 5hp dust collector, so not to smoke the panel. Already blew up one transformer outside and had a nice small forest fire.
  6. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,529
    Location:
    North Carolina
    It is my professional opinion that what you had before you started doing anything is 100% better than anything you are trying to accomplish. If your idea was so much better can you explain why it is not on the market and being installed in every home now.

    The fan you are planning on using is not big enough for one bath and you plan on using it on two baths. It won’t amount to a fart in a whirlwind should both baths being used at the same time. Sometimes what we want we cannot have and what you propose is one of those things you can’t have simply because it won’t work

    If your friend was an electrician he would have already told you this isn’t going to work. It is true that if the fan is supplied from one branch circuit it would only get 120 volts but if there is only one fan how is it to get anything other than 120 volts? I don’t understand the dampers or the need for them.



    Maybe. All conductors meaning the hot, neutral and equipment grounding conductors that supply either the relays, transformers, dampers, or the fan must be in the same cable or raceway. You can’t use one conductor of the cable to supply anything, you must use all the conductors in the cable.
    Not only must it be in an enclosure it must be secured to the enclosure by an approved method. The enclosure must be approved for the purpose for which it is used.
    [​IMG]
    Yes the transformers can be in a NEMA enclosure but it must be large enough to allow free air for cooling. Be sure that the transformers are approved for installation in attics as most are not due to the extreme heat in attics during summer months.

    The equipment is not being used as they are designed for. You are trying to design something to use them on which is different.
    There is nothing about the equipment or the installation that will pass an inspection and this is why I have asked you if you are planning on getting it inspected.

    You have come up with some sort of abstract idea and have closed your mind to any discussion about your project and in my opinion demanding that someone just tell you how to make it work.
    The truth of the matter is it is not going to work as has been pointed out to you in this thread many times but you are not listening.
    You even made the statement that you are not going to change your mind no matter what anyone says so I see no point posting anything more in this thread.

    Can’t hardly wait.
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