Applied Air DFL 035, Technical Manual

29

Sequence of Operation – Return Air Units

Signal from remote control I to AdaptAire 

Controller D, sets operational parameters 

for dampers B and C, and burner. Damper 

operation can be manual, building pres-

sure or mixed air temperature.

Return air dampers B, and outside air 

dampers C, are interlocked to move  

together. As one opens, the other closes. 

As the return air dampers open, allowing 

more return air to enter the unit, the out-

side air dampers move toward the closed 

position, decreasing the amount of outside 

air. Pressure sensor and flow station J, 

senses change in return airflow and signals 

AdaptAire Controller D.

Modulating gas valve H, regulates gas  

supply in response to signal from AdaptAire 

Controller D. AdaptAire Controller D, var-

ies signal based on input from room tem-

perature sensor F, discharge temperature  

sensor G, and airflow sensor J. Gas valve H 

can provide approximately 4% to 100% of 

rated burner capacity.

P000621

Guide Specification – Mixing Dampers With  

                                    Return Air Flow Station

Unit(s) shall have outside air and return 

air dampers with modulating actuator 

controlled by AdaptAire DDC control 

system (Patent #7,059,536). The AdaptAire 

DDC control system shall have capability 

to digitally control the outside air quantity 

from a nominal minimum of 20% to 100% 

with integrated gas valve control at all room 

concentrations of CO2.
The return air inlet shall include a self-

calibrating flow measuring station with a 

grid of velocity pressure probes with spacing 

no greater than 12” over the entire face of 

the return air opening and sampled every 

second. Samples are averaged to provide 

smooth, accurate data that is delivered to 

the AdaptAire DDC control system every  

second. The DDC control system shall 

be capable of electronically displaying 

the return air/outside air ratio within 5% 

accuracy at all damper positions.

The AdaptAire DDC control system shall be 

capable of controlling mixing dampers in: 

(Choose One)

Manual Mode:

 The “Manual” mode allows 

manual positioning of the outside air (O.A.) 

damper and return air (R.A.) damper by 

changing the damper position setpoint.

Mixed Air Temperature Mode:

 The “Mixed 

Air Temperature” mode shall provide auto-

matic control of the mixed air temperature by 

modulating the outside air (O.A.) damper and 

return air (R.A.) damper to maintain the mixed 

air temperature setpoint. 

Building Pressure Mode:

 The “Building Pres-

sure” mode shall provide automatic building 

pressure control by modulating the outside air 

(O.A.) damper and return air (R.A.) damper to 

maintain the indoor building pressure setpoint. 

As the building pressure decreases below the 

setpoint more outside air will be introduced.