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Ummm operating pressures please? Also any pressure switches?

I have a unit very similar to the one you describe except mine is a water cooled unit. This problem has shown up with my unit in the past and was the freeze stat. I'm betting yours has a freeze stat as well.

Bypass pressure switches and see how that works. If it has freeze-stats try bypassing that first.

You do know in tet mode all safeties are ignored. have you verified there isnt a ba d low, high or other switch bad

Originally Posted by jjmarquez84

Unsure if theres a tracer I know its not a conventional tstat. It has one of those zone tstats. Could it be the Tstat causing this problem?

It is not usual that a thermostat such as a BAYSEN019C would give you this type of problem. However with a model no of the RTU a matched thermostat can be identified and it sequence checked.

If it is a Tracer summit or Tracker system you would see a 5 wire stat where as only terminal 1,2, and 3 are necessary for the thumb wheel and zone sensor

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Understand the symptoms and you will find a solution.

What is the Model No for this unit. Does it use the old Microtel board or is it a Reliatel version. In any case It will be necessary to ohm out all sensors, OSA, RAS, and supply air sensor. If supply air sensor has a degraded performance where as an example it is reading a supply air temperature below set point it will cycle compressors.

I have also seen OSA sensor read a much lower reading than actual temp. What is the position of the economizer when you are suspecting trouble.

In addition it will necessary to read actual voltage drop versus actual sensor temperatures. An ice bath is very accurate to check them all. The truth is if they are older than ten years old, Just replace them- $9.00 each.

As far as verifying if this is a tracer system, this is very easy to tell. There would be a Com board which will support the BCU which you may have on site .

Good luck

Unsure if theres a tracer I know its not a conventional tstat. It has one of those zone tstats. Could it be the Tstat causing this problem?

Is it on a Tracer ? Conventional stat ?

Does the exterior unit have a temp control for fan and compressor cycling / defrost. Wondering if the sensor could be out of calibration or settings wrong which would shut off your exterior unit. Test mode at that point are bypassing controls which doesn't make sense unless it could get temps over that peak? What else could shut off the exterior controls in a five second delay on your system?

Trane 15 ton 2 stage cooling Given me hell!

I have a Trane two stage cooling & with an economizer 15 ton unit that’s isn’t wanting to cool at times. Pressures are good amps are good when everything runs. When it is in cooling mode the indoor blower stays running and the compressor and out door fans will start but after a 4 or 5 seconds the compressor and outdoor fans shut off. But when I go into test mode and let it run for a minute the unit cycles through normally. Basically when I run it in test mode it kind of resets itself and works for a day or two. Any ideas on what I might be dealing with guys?