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I had no idea the economizer calibrated 3 minutes after start-up. Good to know

Pull the access panel off the economiser hood and verify actuator operation. Also red service lite should be on on uem board. When putting in test mode and nothings working, disconnect the j6 plug on the ucp board, this way u are in control and bas is out of the picture.

Runs mechanical cooling upon start up with no attempt to operate economizer

Trane units will run the economizer-If the economizer does not satisfy the supply air temperature in about 5-10 minutes, it WILL bring on a stage of cooling to try to satisfy the supply temperature demand - it is 55*F I believe. If you have ROVER software and the Tool, you can view the device and REALLY see whats going on. If your economizer is not equiped with barometric relief or power exhaust- your not getting enough air change through the economizer for it to be able to work. Start up the unit from a warm load, Put a temperature probe in the supply duct and see if you are getting 55* F, if you are not, the mechanical cooling IS going to run. Hope this helps.

0 Degrees

Originally Posted by Westernpatech

Replaced both sas & oas. Still running mechanical cooling below 30 degrees

Voyager and Precedent units are designed to run mechanical cooling to 0 degrees F ambient.

Replaced both sas & oas. Still running mechanical cooling below 30 degrees

Check out this site for Trane info http://hvac.amickracing.com/RTU%20Tr...%20RTU%20info/

Supply air sensor is the problem.Get new SAS or pull OAS and use it.

Was not waiting three minutes for test mode, that explains it operating intermittently.

FYI, it does not matter if you have dry bulb, reference, or comparative. In test mode it will still work and it also ignores all sensors.

I just want to make sure that you know you have to wait approximately 3 minutes after powering up the unit before you start stepping through test. The economizer actuator is calibrating during this time, if you don't wait it will skip over economizer and step through mechanical cooling and heat.

In test mode it's opening on first test? Yes or no or is this the sometimes?

What is the Model No. and Serial No.

What type of control do you have. Reliatel or Microtel.

What is the indoor temperature.
What is the COOL set point.
What is return air temperature.
What is OSA Humidity.
What is return Humidity.
What was the position of the economizer.
What was the Supply air temperature.

Do you have comparative enthalpy control or just outdoor dry bulb.

Have you checked the OSA sensor and compared temperature versus resistance and finally voltage drop.

There are many times when the performance of the sensor has degraded and will not respond correctly. Even a simple 3 degrees off will cause an erratic behavior if the OSA conditions are stable.

The supply air sensor also should be checked.

There are several people who visit this site who have more experience with this unit than I do, so give them time to chime in too.

Check where the economizer's wiring harness plugs into the unit's wiring harness. If the unit doesn't "see" that an economizer is connected, then it operates as though there isn't one, and it sounds like that's what yours is doing most of the time. Bad connection at the plug, or the wires to the plug. Could be loose, dirty, corroded,etc....

Trane economizer troubleshooting

Trane YCD060 operating mechanical cooling @ 25 degrees. Run test mode economizer operated once out of several times