Trane RTAA fault code (8A)

[coopcam]

Hello, I am working on a Trane model- rtaa240yxd01a1cofe ...the code is (8A)...if I recall it states if the entering chilled water temp falls to 2 degrees below leaving temp for 100seconds it locks out on this code...I have veified the actual cwtemp entering and leaving and we are well within range...43Lwt,49Ewt...the read out on the display says 45leaving, 46entering...I believe the sensors nees calibrated, I am not sure if they can be or how to do it...I would appreciate any info you could give me,

Thank You....ser# (u93hi7413)

[fixerup]

Check your water flow on the evap barrel. Sensors could be bad but I would bet low water flow.

[usaf hvac retired]

+1 for water flow ...
The sensors cannot be calibrated...
Also I have seen this happen before, when the chiller starts with a low heat load and the entering water wasnt much warmer than the setpoint.

[chillrdude]

After verifying the flow with one gauge, I would replace the sensors, they come as a matched pair, when you install the entering water sensor make sure you don't stick it in so far that it touches the refrigerant tube.

[ON-CALL]

Pull Out Sensors And Put It A Cup Of Ice Water And See What Your Temp Is To See How Bad Out Of Cal. They Are.

[coopcam]

Thanks for the input....I will call Trane tomorrow and find out what Delta P should be on it....if I am in range I will replace sensors

Thanks Again

[Randy S.]

I had one that would do this after it cycled off for lack of a load.

This was an 80 ton RTAA, mfg'd. 2001, I seem to recall.

I was able to run some trends on the DDC and discover that the inlet was lower than the outlet briefly during the off cycle as chilled valves went full open. This is a low load flat line kind of system where the chiller is much bigger than the actual load due to "engineering" data. If the chiller was starting up at the same time, the fault would occur. The band-aid fix was to spread the start differential way, way out, to give the loop more time to stabilize, yet still be able to carry the low load.

If this is going on while running, I'd be for checking the sensors.

[joegrind]

had this problem once! the bas would shut the pump down on a sched. therefor opening flow switch and stoping chiller.. BUT>>> the flow switch was stuck closed and it would fault this code

[Carnak]

I will take Fahrenheight Seconds for $500 Alex