Carrier VVT

[242447]

I service a Medical Bld. that has a VVT system 30 ton Compressor for cooling and a boiler for heating. My question is the unit shut down on a SE 11 ERROR on the Monitor stat I checked the book and its said its a temp. high limit which mean after 10 mins if the supply duct temp. does not drop below 55 F the unit will shutdown. I Ohmed out the supply duct sensor and got a reading of 19 Mega ohms which I though was real high. I checked on the Monitor stat for that sensor Catagory 5 option 5 it showed FAILED does this mean that the sensor is bad or does it need to be recalibrated

[uke]

I would try to recalibrate sensor at first. On general, these sensors require recalibration every couple of years.

[Balibe]

The SE11 alarm is a Temperature Limit Alarm. If option 4.4 is ON, you will get this alarm if temperature exceeds the settings in 4.5/4.6/4.7/4.8. I would check these settings & see why you exceeded them.

HIGH/LOW TEMPERATURE LIMIT EXCEEDED (SE11)

Heating Mode — An alarm is issued when any supply air
sensor in the system is above the first or second stage
heating temperature limit (depending on which stages are
active).

Cooling Mode — An alarm is issued when any supply air
sensor in the system is below the first or second stage
cooling temperature limit (depending on which stages are
active).

Heat/Cool Mode Alarms are cleared from the system in two ways:
• Cycle power to the thermostat OFF, then ON.
• Reset the Unit Thermostat. Initiate a reset by switching
the Unit Reset to the ON (Category 7, Option 11).

The 10 minute timeframe on temperatures is not the same thing. This is the Cool/Heat Error Setpoints in Options 7.9/7.10. If these settings are not reached within 10 min, you will get an alarm of SE07 or SE08. The defaults for these are 0°F and 140°F, in all my years I have never seen anyone change these. I never do to prevent unnecessary alarms.