Need Help Wiring Relay for Bathroom Timers

Discussion in 'Electrical Forum discussion & Blog' started by umchemist, Aug 13, 2013.

  1. umchemist

    umchemist New Member

    Messages:
    2
    Location:
    Ontario
    Hi Everyone,

    First time poster and really in need of some basic help. I am able to perform simplewiring, but I need help understanding how a particular relay fits into the picture. The below setup was installed by the electrician when we bought the house, unfortunately I had to relocate the box and move things around due to some new construction. Although I wrote down the wiring, I lost that paper and now am at a loss trying to reassemble this circuit.

    I want to be able to turn on the bathroom fan from either timer, each of them would share the same circuit as the relay. When a timer expires, the relay breaks the circuit and the fan turns off. If both timers are in use, the last timer to turn off breaks the circuit and turns off the fan.

    Each bathroom has one outlet box, and within each box there is a light switch for two halogen bulbs and the timer (ie. Two devices per OB in each bathroom).

    The exhaust fan is an Lifebreath 155 HRV that has a panel which contains a dry contact point, for operation by mechanical timers. I am using the Lutron digital timers via the relay to control this contact point. When powered, the relay completes the dry contact point to turn on the HRV.

    The timers are Lutron MA-T51MN-WH, multi-location requiring a neutral.

    I would use the normal HRV timers by Lifebreath, but I can’t as I only have a two wire line run to the bathroom OB’s and not a three wire line needed for those timers. As such, I am assumedly forced to use the dry contact point.


    As always, thanks for any help.
    Exhaust Wiring.jpg
    Last edited: Aug 13, 2013
  2. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    Lifebreath 155HRV doesn't seem to be a simple exhaust fan, but rather a heat exchanger. The mfr data on the Lutron MA-T51MN doesn't show a low-voltage output that would directly interface with a relay having a 24VAC coil, that being the Omron G7L-2A-etcetera-etcetera

    Is there a 24VAC supply that we are not aware of?
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,045
    Location:
    Cave Creek, Arizona
    The relay does not show a "neutral" wire and it cannot operate with just one wire going to it. But, since the timers apparently control the transformer, you connect the hot wire to the outlet, and BOTH timers. The neutral/white goes to the transformer, wherever it is, and the outlet. The "switched" leads from the timers are connected together along with the "hot" wire to the transformer.
  4. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    If you really wanted to get hard-core about it, there are dual-coil relays available, so that the outputs of the two countdown timer switches are not connected together.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,045
    Location:
    Cave Creek, Arizona
    As long as the timers have a common feed, there is no problem having their outputs in common.
  6. Murphy625

    Murphy625 Member

    Messages:
    150
    Location:
    Michigan
    Seems to me that your control timers are 120 volts but the relay that activates the fan wants a 24 volt signal to the coil.. That's easy enough as 24 volt transformers are very common for doorbells and heating systems, etc.

    You would simply wire the timers to send power to the transformer which would then send 24 volts to the relay, which would then close for fan operation.

    I also agree with AJ.. so long as the timers are on the same 120 volt leg, there should be no issue with making them common together.. It would form what is called an "And/Or" circuit.. if timer 1 is on, and timer 2 is on, OR if timer 1 is on or timer 2 is on, then the circuit is TRUE and the fan should run.
  7. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    What I'm curious about, is whether the countdown timer switches are capable of functioning over a wide range of input voltages. It is not uncommon to see solid-state electronics that can be supplied with anything from 10 volts to 250 (the idea here being that the switches might function on 24 VAC, making their outputs compatible with the relay in the diagram)
  8. Murphy625

    Murphy625 Member

    Messages:
    150
    Location:
    Michigan
    Not from the literature I was just reading.. They are 120 volts only and the output comes from the input power. So, 120 in, 120 out...
  9. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,559
    Location:
    North Carolina
    The original poster has not commented in five days about a unit that one needs a college education to install. This is not your average bath fan that we see every day so most of the advice given in this thread would not apply.

    If the original poster does not post within the next couple of days this thread will be closed
  10. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    Well, that's not the closure I ever hope for. It doesn't seem possible to connect the puzzle pieces without a 24 VAC source, and it's difficult to envision one located in a bathroom.
  11. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,559
    Location:
    North Carolina
    Do some research on the system, I have only saw these installed by a HVAC person including the switching system
  12. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,444
    Location:
    Houston, TX

    Why would you need a college education to install this Fan ?

    A person only needs to RTFM...

    And have a little smarts, or call a pro.

    And the pro may not have a college education, but can do it properly.
  13. Wet_Boots

    Wet_Boots Sprinkler Guy

    Messages:
    798
    Location:
    Metro NYC
    I want to know how what appears to be a whole-house heat exchanger winds up doing duty as a bathroom fan. :confused:
  14. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,559
    Location:
    North Carolina
    This was a nice attempt to say that this is far beyond a DIY job
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