Replyevery time i jump the test pins compressor 2 comes on, then 1, then 1 and 2 together. there is something not letting it on. have you verified all the safeties? maybe there are some you didnt know about.
New Guest
We have a Trane Voyager A/C unit that switches immediately from circuit #1 to circuit #2, even in test mode is will skip circuit #1. It is currently controlled by Alerton with a VLC that acts as the thermostat. When alerton is signaling for Comp #1, Comp. #2 is running, and when it signals for both compressors to run only comp 2 is on. Circuit #1 is larger than Circuit #2 so on hot days it cannot keep up with the demand. This unit also has an economizing feature (factory installed). Circuit #1 appears to be fully functional both LPS and HPS check out and when we jump circuit #1 to run its pressures are spot on. The LED indicators shows that everything is fine. Trane recommended replacement of the control board, but that did not help.
Does anyone know if there is some preinstalled logic on the control board that is trying to run the unit efficiently and ignoring the commands from alerton?
Professional Member*
every time i jump the test pins compressor 2 comes on, then 1, then 1 and 2 together. there is something not letting it on. have you verified all the safeties? maybe there are some you didnt know about.
Professional Member*
I test mode all external control is ignored. Problem is internal to unit. Safety most likely for that Circut.
Regular Guest
is this an older voyager with the large ucm board or a newer reliatele with the small ucm board. the older boards can give weird test modes if there is a resistance accross the test termanals. on the ucm, there is a single plug that the test terminals go to. its a small 2 wire plug. look on the wiring diagram to determin which one. unplug the wires and short the pins direcly. if the unit doesnt follow test properly then its a bad ucm board. on a relitele unit it could also be a problem with the wiring that determins the unit setup.
Regular Guest
If older UCM board, did you check CTI Board? and with either board possibly holding out first stage due to econimizer, check if damper is opening there is also green/yellow LED on actuator to show if its in free cooling. TRANE also has a manual available for both UCP and the RTRM board that gives you all checkout procedures for the different cofigurations I highly recommend getting one, I heard they were giving them out for free now but not 100% sure.
Regular Guest
this is not necessarily correct .Originally Posted by vathicus
I worked on a 50 tonner years back ,I was performing the test at the ucm .
I was getting strange results like a compressor that would cycle on/off several times and the skipping the OP was talking about.
Trane tech support told me I had to plug it back in and perform the test at the TB , as it had a resistor there ,or something adding resistance ...
Don't believe me , call trane tech support yourself .
This is NOT true for all voyagers and I can't tell you why .
Any trane guys here know what I'm talking about
Regular Guest
Hey Mike that's an interesting subject about resistance on that terminal input. I have not experienced that before. But that's not to say that it's not possible. As far as I know even a slight resistance will put that UCM in the test mode. When in doubt I have always used a variable resistance decade box so an accurate command can be given which will put it immediately in its corresponding test mode based on the resistance value.
It sounds like you had an older series with a Microtel UCM, but still works with the same principle as the newer Reliatel.
As for the erratic operation of the compressors it will be necessary to check the supply, return, and outside air sensors and verify that they are with in range of there temperature/resistance value. An accurate way to check is with an ice bath. In addition the voltage drop should be checked which will give an accurate measurement of its performance.
Its possible that if the outside air sensor is reading a lower temperature it may try to economize first. Or possibly the supply air sensor is reading a lower air temp and holding out the additional compressor.
Like stated earlier the UCM board needs to be identified as their have been many revisions which have had improvements made along with control strategy changes.
Trouble shooting is not part of the repair..................understand the symptoms and you will find a solution
Professional Member
pull the j7 plug and check terminals j7-8 and 11 to ground for 5 vdc. if not the ucp board is bad
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