chiller mekanik
10-27-2007, 12:27 AM
Hello all,
First order of business, Cerus Tech support has been "top shelf" as they have tried to help me in every way.
Readers Digest version:
The vfd is for a tower fan.
The 4-20 ma signal comes from a 19XR. I've installed three of these drives so far on 19XR's with total success. This one is special.
I have verified the signal with two meters. The vfd even reads the signal as 20 ma while the drive is in bypass.
But, switch it to drive & the signal on the screen will read about 12 ma while it is actually 20 ma, therefore it only runs at about 31 hz.
If you disconnect the load wires from the drive, it will see the 20 ma signal & go to 60hz. Its because of this that its the mfrs position that this is a problem caused by the magnetic field from the load wires that is bleeding over to the signal wire. In other words, an installation problem.
The signal wire is stranded shielded cable. I even replaced it once to rule out anything wierd. Its ran on its own path & its not strapped to the conduit for the load or the line wires.
The load & line wires are in seperate conduit.
The shield is connected at the drive end & is not connected at the chiller end. Per mfrs instructions.
I've tried everything I can think of including things I wouldn't ordinarily try.
If its an installation problem, fine. Somebody just tell me what it is.
First order of business, Cerus Tech support has been "top shelf" as they have tried to help me in every way.
Readers Digest version:
The vfd is for a tower fan.
The 4-20 ma signal comes from a 19XR. I've installed three of these drives so far on 19XR's with total success. This one is special.
I have verified the signal with two meters. The vfd even reads the signal as 20 ma while the drive is in bypass.
But, switch it to drive & the signal on the screen will read about 12 ma while it is actually 20 ma, therefore it only runs at about 31 hz.
If you disconnect the load wires from the drive, it will see the 20 ma signal & go to 60hz. Its because of this that its the mfrs position that this is a problem caused by the magnetic field from the load wires that is bleeding over to the signal wire. In other words, an installation problem.
The signal wire is stranded shielded cable. I even replaced it once to rule out anything wierd. Its ran on its own path & its not strapped to the conduit for the load or the line wires.
The load & line wires are in seperate conduit.
The shield is connected at the drive end & is not connected at the chiller end. Per mfrs instructions.
I've tried everything I can think of including things I wouldn't ordinarily try.
If its an installation problem, fine. Somebody just tell me what it is.