Issue:
How does MV8 Supply Fan Speed effect the Fan Coil ECM fan motor?
Resolution:
The following parameters are seen at the ECM Engine Module
Hi 1
Md 1
Lw 1
E1M1
E2M1
AhM1
AlM1
Hi 2
Md 2
Lw 2
E1M2
E2M2
AhM2
AlM2
Changing the High/Med/Low/EH1/EH2 are the parameters for the 5 binary inputs on the Engine Module.
If you want to change the speed that t.he controller is going to use for Fan High and Fan Low, change parameter AhM1 (Analog high Motor1) speed and AlM1 (Analog low Motor1) speed. This will set the speed the motor will run at. Do the same for motor 2 if you have 1.
On the ECM board, there are three ways to remotely control the fan
-
IMC speed command (highest priority)
- High/Low speed based on AhM1 and AlM1 configuration parameters
-
Analog input speed command
- High/Low speed based on AhM1 and AlM1 configuration parameters
- This is used only for customer supplied control interface
-
Binary input speed command (lowest priority)
- High/Med/Low/EH1/EH2 speed based on HI 1/MD 1/LW 1/EHM1/EHM2 ECM configuration parameters
The UC400 is commanding the board using IMC communications. If you were to attach a potentiometer to the analog input and switches on all 5 binary inputs, the ECM board will continue to command the board using the IMC communications. Only when you are commanding the ECM board using only the binary inputs will the High/Med/Low/EH1/EH2 settings will be taken into consideration.
Supply Fan Speed Request (AV-63) is a calculated output. It is calculated based on the cooling/heating load or Supply Fan Speed BAS (MV-8) request. The output of AV-63 is in 1/3 increments across 100% (0, 33.33%, 66.67%, and 100%). This would be your Off, Low, Medium and High values for three speed fan operation. Setting this value to something other than the 4 pre-defined values, the control algorithm will either increase or decrease the value to the nearest pre-defined value.
As for MV-8, there are only four pre-defined operations, Off, Low, Medium, and High where
- Off = 0 RPM
- Low = AlM1
- Med = ((AhM1 AlM1) * .50) + AIM1
- High = AhM1
When the UC400 commands a speed to the ECM board, it will send a percentage to be running (0% - 100% where 0% is off, 1% is low and 100% is high).
Example: Low speed is a percentage of the overall difference between low rpm(ALm1) and high rpms (AHm1).
Lets assume that ALm1 is 500rpm and AHm1 is 1500rpm
This gives a difference of 1000 rpm.
If the you send a 15% or 1.5vdc, the fan will run at 650rpm.
15% of 1000rpm is 150rpm.
Min rpm is 500, add 150rpm and the fan will be commanded to 650rpm.
Basically what we are talking about is the slope of the line.