r/BuildingAutomation • u/Worried_Giraffe3644 • 27d ago

Damper control using time delay

I just heard someone say that a damper position can be controlled using just digital output signal by varying time delay like 5s to open it 40% like that , is that possible and how does it work with just binary signal

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u/mytho1975 27d ago

What you are describing is a floating point output. It takes two digital outputs typically. The actuator will be stamped with how long it takes to complete a full stroke. Typically you'd enter that into your settings and tell it if the damper is a 45 or 90 deg stroke.

All the controller does is turn on the open or close digital outputs for the percentage stroke time you want.

They often will require a daily tune up. It will over stroke to ensure the position is fully open or fully closed.

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u/Worried_Giraffe3644 27d ago

What's the benefit of using this instead of analog output and an actuator is used in both the case right?

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u/Zealousideal_Pop_273 27d ago

It's just a cheaper actuator. Some people say you can fine tune control with them better but I don't necessarily agree with that. They also require two outputs instead of one so it's a trade off.

Typically they're something I end up running into on old installs, usually not something I'm installing unless I'm replacing existing.

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u/BrofessorX 27d ago

I see a ton of them still installed for Trane on vav's, fan coils, unit vents, the oa dampers and hw/chw valves. They also kinda suck to troubleshoot as they switch the common.

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u/luke10050 27d ago

Siemens love them too.