We just had a new feed water tank put into our boiler room. On the controller for the motors we have a tempeture controller that is powered with 120 volts. It recieves a 4-20ma inputed from a level sensor and sends a 4-20 ma signal to a to a valve in order to allow water to fill the tank. The Temp contoller has a set point value on it and when it goes below a certain level it opens the valve. The problem is that it everyonce in awhile the current value shoot up high sticks there which in turn tell the valve not to open and then our tank eventually runs out of water. I called tech. support on the controller and he said they are really sensitive to noise. The cable being used is 2 pairs of 18 gauge wire with a bare ground all wrapped in a shielded cable. The bare cable is grounded. Could it be that noise is traveling on that ground.