Lennox Rooftop Units with enthalpy sensors 1

[cpan]

Hello,

I'm work in building commissioning. There are some roof top units with an modulating outside air damper. I would like to verify that the damper is modulating properly, however there is no test option on the controller located in the unit. Does anyone have any recommendations? Thank you.

 

[willard3]

Without a control sequence, you will not know. Find the original Engineer.

 

[cpan]

A few of my co-works suggested that I trip the enthalpy sensor by turning a can of compressed up upside and spraying it. It should work.

 

[ChasBean1]

Measure return air temp/humidity and outdoor air temp/humidity and calculate enthalpy from each. This time of year you'd find outdoor at higher enthalpy than return most of the time (northern hemisphere, 45° parallel or below). Ensure the OA damper is at its minimum position if OAE is higher than RAE.

Set the DAT set point high (e.g., 85°F). Cool the OAT sensor with ice (or as you mention, by spray can) and the dampers should modulate toward full outdoor air.

 

[cry22]

you should use fixed position for RTU's OA control. You cannot maintain the correct levels of OA without air flow measurement on RA/OA (too much or too little). your SF could be pulling most of the air form OA intake when modulating. AND you will have room overpressure problems.

 

[cpan]

Thanks for the input everyone. Much appreciated.