Humidification System in Hospitals - How to Interlock

[ziptron]

The snippet below is from Standard Z317 - Special Requirements for Heating, Ventilation and Air Conditioning in Health Care Facilities

Can anyone provide a definition of what 'interlocked' means? The standard itself does not define it.

I understand that the intent of this interlock is to shut down the humidification system when the air-handling unit supply fan is off, but how must this be achieved? Must I use a physical electrical interlock snap switch and physically wire the fan and humidifier or can I program this requirement into a logic board which shuts off the humidifier when the system notices that the fans are off.

Any guidance on how 'interlock' can be achieved to satisfy this standard would be appreciated.

Thanks!

 

[EnergyProfessional]

Interlocking means exactly what you define it as. whne the fan turns off, the humidifier needs to stop.

They won't accept a pressure switch. I assume this is because a pressure switch may not work reliably in VAV systems with widely varying flows and consequently varying pressure differential when the fan runs. You could use a VFD reading, or have the controller that controls the fan also control the humidifier. the latter may not be reliable if the fan fails. The VFD can read power draw, so above a certain draw you could activate the humidifier.

 

[BenMacier]

You need to hardwire the steam supply with the fan power supply. So if one shuts down, the other one shuts off simultaneously.
Usually this would be done on the control cabinet of the AHU.