Interoperate: Time Delay Relay, Intake Louver, Exhaust Fan, Smoke Detector, Hydrogen Detector, HVAC, Alarm Signals

Thread Starter


Joined Jan 12, 2022
Quite the title I've assembled there and yes, I'm attempting to get all the subject parts to interoperate through relays (if possible).

I've got a stand-alone, precast telecom structure with the subjects that are needing to work together. I'll do my best to best explain how all these will work together along. What I'm asking of the community is help with wiring everything together. If each of these parts worked independently, I'm certain I could get it done; however, they've all got to be connected.

1. (2) Time Delay Relays (Macromatic TE-8812U) - This relay will serve to operate the intake louver, exhaust fan and to also send out two signals for an alarm to an alarm monitoring center.
2. (2) Power Relays (IDEC RH1B-UAZC120V, SPDT) and (2) Relay Bases (IDEC SH1B-05) - These bases and relays will be used in conjunction with the smoke detector and hydrogen detector (1 relay and base for each).
3. (1) Intake Louver (Belimo TFB120)
4. (1) Exhaust Fan (GREENHECK SE1-12-432-A4X)
5. (1) Smoke Detector (GENTEX GN-503FF)
6. (1) Hydrogen Detector (SBS-H2)
7. (1) HVAC Unit (Bard W36A2-A10 3.0 Ton)
8. (1) 66-Pin Alarm Block
9. (2) 20A/1P circuit breakers - (1) for smoke detector, (1) for hydrogen detector
10. (1) 15A/1P circuit breaker - To operate both the intake louver and exhaust fan.

1. Simultaneously, operated by the time delay relay, the intake louver is to open and the exhaust fan is run once a day for ten minutes to clear the room. When the exhaust fan kicks on, a NO contact alarm is to be sent to the alarm block and clears (back to NC) when the relay turns off. If the time delay relay ever fails, a NO signal is to be sent to the alarm block.

2. In the event either the smoke detector or hydrogen detector go into alarm, the HVAC unit will shutdown. Which ever detector goes into alarm, smoke or hydrogen, a separate signal (opens on alarm) for each will be sent to the alarm block.

3. In the event only the smoke detector goes into alarm, the time delay relay is to be de-energized so the intake louver and exhaust fan do not run, also the HVAC unit will shutdown as well. A smoke alarm signal (opens on alarm) will be sent to the alarm block.

4. In the event only the hydrogen detector goes into alarm, the HVAC unit will shut down, the time delay relay energizes so the intake louver and exhaust fan run simultaneously. A hydrogen alarm signal (opens on alarms) and the exhaust fan timer signal (NO) will be sent to the alarm block.

I contacted support at Bard for the HVAC unit. I was told the smoke and hydrogen detectors can be wired in series using (2) separate SPDT relays so that if either detectors goes into an alarm, the HVAC unit will shutdown. The shutdown occurs within the HVAC control wiring; it's just the signal wires (open on alarm) that go back to the unit and breaks the 24V connection.

I'll admit I'm not proficient when it comes to controlling equipment with relays so I cannot even provide a wiring diagram of where I would start. But any help in the right direction would be greatly appreciated.


Joined Jan 27, 2019
Welcome to AAC.

Your narrative is good as far as it goes but it will be almost impossible to use it to integrate the parts.

My suggestion for a first step is to make a block diagram for each part labelling the inputs and outputs, and connecting them to their respective inputs and outputs. This doesn’t have to be a literal wiring diagram or account for internal interconnections, in fact it shouldn’t.

Instead, the parts that work as subsystems should be treated as black boxes with no concern for how they work internally, just what they do. Once you have this picture, you can start to build a state diagram focused on how the condition of each part must affect those they are directly connected to.

This combination will allow you do see how the parts must be physically wired together, what other logic (relays, etc) you will need, and if you have created a deadlock or other error condition with your logic.


Joined Nov 6, 2012
Without the Wiring-Schematics for each individual Machine/Device,
it's impossible to even begin working this out.
This includes any Manual or Automatic Control-Panels, or Status-Indicator-Panels, or
"Test-Operation-Panels" that may be desired or required.
The Environmental-Requirements, and Wiring-Code-Requirements must also be known.

With all of the above, the work can start,
usually resulting in multiple "re-dos", and lots of "figure-figures",
as all of the conflicts and requirements are worked-out,
and sometimes, all this figuring may even result in some very simple and elegant solutions.

Then, after everything is done and figured-out,
the whole mess must be accurately documented so that the poor fool that gets called-in
to fix some problem can make some sense out of it, and doesn't trash the whole thing.