Trane RTU

[griz]

I am dealing with 15, 20, and 30 ton voyager units. They are controled by tracker ddc. It is my first pm on the equipment. My problem is when I run the step test I can not get the econimizers to open. It is happening to all 6 RTU's. I can't even get the damper to open using min pos pod. I am wondering if maybe control system overriding step test. 42 degree outdoor ambient and mechanical cooling running.

[dmd-marc]

Regardless the economizer should fully open in the test mode. It is the second step.
1.fan
2.econo
3.cool 1
4.cool 2
5. heat 1
6. heat 2

If you have just reset the unit by turning on and off the disconnect, it takes a little time even in the test mode for the econo to open. Or go into the tracker programming and command the econo's to open. There is min pos setting in the programming section of the tracker. Go into it and move it up. Good Luck

[jayguy]

the signal to drive the damper does seem to be slow like dmd said. i would reccomend the resistor method first...no questions about whether you accidently skipped the step or not. if that does not seem to work then try the troubleshooting below. do you have "dry bulb, reference or comparitive enthalpy"?

from the "MICRO-M-2D" manual:

Test 1: Verifying UCP communication with UEM.
If the ECA is not driving the dampers, measure the DC voltage output from the UCP. This is measured between UEM connector P11-11 which is connected to J1 on the UEM, and P15-5 which is connected to J5 on the UEM. The voltage measured while the ECA is driving open should be approximately 1.7 VDC. When the 90 seconds have elapsed, and the dampers should be fully open, the voltage will change to approximately 5 VDC. The LED on the UEM glows continuously when the ECA drives.

Test 2: Verifying that the ECA is functional.
Step 1.
With power applied to the system, in any mode, verify presence of 24 VAC between ECA terminals TR and TR1. If 24 VAC is not present, a wiring or terminal problem is present.
Step 2.
Jumper terminal TR1 to terminal CCW, ECA should begin to drive open. Should be at fully open position after approximately 90 seconds. Remove jumper from
CCW terminal.
Step 3.
Jumper terminal TR1 to terminal CW, ECA should begin to drive closed. Should be at fully closed position after approximately 90 seconds. Remove jumper from both terminals.

If after completing Test 1, and the ECA functions in Test 2,
the UEM has failed. If 24 VAC is present in Step 1 (Test 2), and
ECA did not drive as specified in Steps 2 and 3, ECA is
defective. Replace ECA.

good luck

[shelby]

on some yoyagers with ucp controls SOMETIMES (but not always) if tracer summit or tracker is controlling the unit you will never get to test the economizer through test mode it skips right over it , so what I do when I do a maintenance is. shut power off, temporarily un plug the wiring harness that links the ucp to the TCI board and plug the stand alone plug back in ( as if the unit were running stand alone without being controlled by BAS) then step it through test mode and the econo and power exhaust will work in test mode . Remember to switch the plugs back around or you will not be able to see it on your tracker panel. I have seen this happen on 99-05 voyager 3's more so than on the smaller tonnage voyagers or just increase the min pos on tracker or drive econo open on summit, however there is no fix for this so don't worry about it!!!!I have wasted enough time troubleshooting,changing boards and they still will do the same thing, newer units are now reliatel and don't have this problem hope this helps

[john77420]

on all trane voyagers if you power down the unit and bring it back on the econonizer will always go into test, it will slightly open and then shut. also check at the ucp that the plug going to the economizer it plugged in right, i had a unit that was 10 years old that never had the economizer plugged in at the ucp, i would check that.

[overhaul]

Have had a couple voyager series rtu's do strange thinks for me also. Contacted our train offfice in are area and talked to our guy. He by chance had stacks of main processer boards under his desk and recommend all 17 units get new boards under warrenty because there is a problem , just no body wants to a admit it like usual! May be worth looking into ,I experianced the same thing drove me nuts until I got the straight anwser. Also maybe try disconnecting low voltage wiring and putting unit through test mode to see what happens?

[griz]

Thanks everyone, indeed when unit is powered off by disconect and then powered back on the damper begins to drive then imidiatly closes. It has dry bulb reference. you say to jumper from tr1 to cw and ccw, does this mean that terminals cw and ccw receive a 24 vac signal from board under normal opperation?

[jayguy]

24vac drives the economizer motor open and closed

the drybulb settings are on the UEM board:
Switch 1 off, Switch 2 off: 60F
Switch 1 off, Switch 2 on: 55F
Switch 1 on, Switch 2 off: 65F
Switch 1 on, Switch 2 on: not used

the economizer will open the economizer if SA is above 55F and close it if the SA is below 50F. so even if the OAT is below the drybulb settings, the economizer may not be open very far if any at all.

if your OAS (outdoor air sensor) has failed, the economizer will go to minimum position and not modulate. this would possibly explain the reason for the mechanical cooling at such a low outdoor air temp.

OAS at 41F: 25,510 ohms, 50F: 19,960 ohms, 62F: 14,560 ohms, 71F: 11,600 ohms.

[griz]

thanks alot Jayguy, I will give er a shot

[harrelson]

you need to disconect the com link to the tci and try the test mode