121 controller when setup for 2 pipe system will not heat or cool

Issue

A Xenta 121-FC controller setup as a 2 pipe system will not heat or cool even though the terminal load is showing a demand.

Product Line

TAC Vista

Environment

Xenta 121-FC

Cause

The Xenta 121-FC does not have a water temperature sensor wired into the device

Resolution

For this functionality to work automatically, a water temperature sensor must be wired into the U1 terminal on the FC-121.

The other alternative is to set the supply temperature via the SNVT nviSourceTemp. This can be done from a supervisory system that is feeding the water to the 121-FC.

To use the SNVT nviSourceTemp as a solution the correct heartbeat will be require to be set in the 121-FC.

Here is a link on how to set that up