Daikin UATYQ20ABAY1 [18/44] Air system

Translation from original instructions

Installation manual

We reserve the right to make changes without any prior notice.

UATYQ*Y1

Packaged Rooftop

4P522680-1

4.7 Air system

4.7.1 Internal air fans

Dependingonthecongurations,theremaybeonlysupplyfansoralsoreturnfansintheunits.

The fans are radial fans with reverse blades, with external rotor motor directly coupled to the impeller.

The radial fans are called "EC", with electronically commutated brushless motor. The fan is powered by mains AC

voltage, and speed control is obtained via DC 0-10V control signal coming from the microprocessor installed on the

unit.Thismakesitpossibletosettheairowratethroughtheparameterbeingdisplayed.

The motors have alarm signalling, which includes thermal overload protection, overcurrent, undervoltage, absence

ofoneormorephasesandseizedrotor.

The EC fans are not provided with a contactor and are constantly live as soon as the main disconnect

switch of the unit is closed.

4.7.2 Flow rate sensor for fans

Unitswith"EC"fansareprovidedwithadi󰀨erentialpressuretransducerthatdetectsthepressuredi󰀨erencebetween

theinsideandtheoutside(upstream)oftheintakenozzle.Theairowrateisproportional,foreachfan/nozzlepair,

tothesquarerootofthepressuredi󰀨erenceaccordingtotheequation:

where

- Q=totalairow[m3/h]

- n = number of fans in the unit

- k=constantaccordingtothefannozzle

- ΔP=pressuredi󰀨erencemeasuredonthenozzle[Pa]

Thecharacteristicconstant"K"forthenozzlesusedis:

- Fan of diameter 450: k = 217

- Fan of diameter 500: k = 281

- Fan of diameter 560: k = 350

Thedi󰀨erentialpressurevalueandtheairowratecanbeshowndirectlyonthedisplayofthemicroprocessorthat

carriesoutautomaticcontroloftheairowrate.

4.7.3 Airowsensor

Thisdevicepreventstheunitoperatingintheabsenceofairow.Thecontroliscarriedoutbyadi󰀨erentialpressure

switchthatmeasuresthepressuredi󰀨erencebetweenupstreamanddownstreamoftheevaporatingcoilandtheair

lter.Themicroprocessoralarmcomesonlaterthaninterventionofthesensor.

To check their operation, open the automatic circuit breakers of the compressors, from the microprocessor card

removetheterminalwiththecontrolsignalfortheECfan(foridentication,refertothewiringdiagram),andthen

switch on the unit. The microprocessor alarm should appear within a few tens of seconds.