Experienced problem regarding Rosemount 1151 DP Pressure Transmitter.
Transmitter is installed on condense tank for oil fired boilers. It transmits signal to water level indicator and PR 2312 limit switches responsible for automatic work of condense pump and high/low water level alarms.
Just suddenly everything stopped working. All limit switches are indicating 0.0% signal and water level indicator is stable at 76%.
I checked all limit switches, their parameters, supply and input and didnt find anything wrong. Supply as well as input is 24 VDC on all of them. Power supply is also working fine receiving 220 VAC and transmitting 24 VDC to limit switches and pressure transmitter.
I disassembled Rosemount 1151 DP from condense return receiver and checked it on bench. Applied pressure corresponding to 4 mA and 20 mA and also found nothing wrong. Signal changes correctly between 4 and 20 mA.
I installed it back to condense system and again no signal is coming to switches. Checked it by fluke and found that transmitting signal is less than 4 mA all the time no matter what pressure is inside the tank. Actual reading was 3.89 mA. Voltage on + and - was 21 VDC.
Kindly asking for any help regarding this problem because now i have no idea what is wrong and what is the cause.
Attaching connection diagram. Optional water level signal to ECR is absent, jumper is put between 278 and 279.