3D Connexion mD4000-b heatInG seQuence OF OPeratIOn

Manual 2100-574
Page 10 of 23
MD4000
decidesLead
unit
Spyder1 is lead
SignalsSpyder2
aslag.
Spyder2 is lead
SignalsSpyder1
asLag
DCAmp load is read and
convertedto building load
withthe equation DCA *
106.4-.2455= BTUH
Calculate
AvailableCooling
(AC)for 1 econ Availablecooling =( SP-
MTD-OAT)*1.08*Airflow
IfAC > BL
CalculateMAT
StartEcon 1
StopEcon 2
StopBlower 2
Yes
No
Calculate
Availablecooling
for2 econ
IfAC*2 > BL
Yes
No
StartLead
Compressor
StartLead Blower
No
IsOAT suitable
forCooling
Yes
IfOAT <= SP-MTD
andEnthalpy is below
curve(ifequipped
DetermineBuilding
Load
CalculateMAT
StartEcon 1
StartEcon 2
StartBlower 2
CalculateMAT
StartEcon 1
StartEcon 2
StartBlower 2
IsRT
aboveSP
Yes
No
StopLead
Compressor
IsRT
above or
belowSP
No
Yes
Calculateadjusted
buildingLoad
(BL)
MATwill be adjusted to take
intoaccount deviation from
setpoint
BL+((RT-SP)*Airflow*1.2)
IsRT
BelowSP
No
Yes
IsRT
AboveALarn
Setpoint
Yes
StartLag
Compressor
No
Allowecon
operationwith
Compressor
No
Yes
StopEcon 1
StopEcon 2
Stop Blower 2
Is2nd comp
Allowed
Yes
NO
MD4000-BCESDC/MD4000-BESDC
W/ AC UNITS W/ DC CONTROL
ECONOMIZERS
OAT= Outdoor Air Temperature
BL= Building Load
MDT= Minimum Temperature Differential
RT= Room Temperature
SP= Setpoint
AC= Available Cooling
heatInG seQuence OF OPeratIOn
Note: All heating sequences for air conditioners with
electric heat or heat pumps will automatically operate
in Alternating Lead/Lag/Lead/Lag sequence even if
controller is set to Non-Alternating for cooling with or
without economizers.
1. Air Conditioners with Electric Heat
1st stage heating set point is the dead-band (db) below
the 1st stage cooling set point (the SP entered into the
program). The dead-band is adjustable from 2-40F, and
factory default is 27F.
2nd stage heating set point will operate at same inter
stage differential as set for cooling mode.