Trane rtaa low evap temp alarm

[Bstang27]

I have a trane rtaa 125 chiller. Both compressors trip on same alarm. Starts up in 2 min the female loader in energized then the suction psi drops has well as the low suction temp set point witch is set to default 22 degress. No glycol in chiller. 11 degrees sub cooling with clear site glass. All 5 fans running 80+ degress ambient temp. 7 to 10 psi differential on entering and leaving water flow. Sometime might run all day other time trips within 3 min of start. Thinking bad suction evap sensor ?????? Any suggestion please

[Six]

Both circuits sounds like low water flow.

[Bstang27]

Sorry alarm is low suction evap alarm

[Bstang27]

Even though I have a diferential and flow switch is made. Theres about 10 other rtaas on location with same installs piping pumps etc.... Could loaders be possible or looking to deep into it

[Six]

They're notorious for eating sensors but if I were you I would do my due diligence and make sure I have at least minimum flow,

Yes condemning unloader solenoids is a bit premature.

[Six]

Minimum flow on that chiller is 150 GPM.

If you're only getting a 7 psi diff. then you're close to the minimum GPM

[Bstang27]

Should the diff be greater. What is recomened for theses rtaas. Gonna check strainers on pumps tomorrow. Someone prior changed one sat suction temp sensor on circuit 1. I was told they come as a pair with the suction temp sensor. Have you ever seen the board giving the wrong pulse signal to the loaders or is that rediculous.

[Six]

The pair is the suction temp sensor ( located at the back of the compressor ) and the suction saturation sensor ( located after the EEV ) per circuit. SSH measurement


So if you change them you will have 4 sensors to change out.

As far as your flow there is a chart on that chiller that you can access online.

Typically I don't usually trust the mounted gauges if there installed and use my one trusty gauge I keep on my truck to get accurate measurements.

It may be sensors but both circuits bringing up low evap. sensor alarms on the same Chiller would justify a look at actual GPM.

[Healey Nut]

Duhhhhhh if there both tripping it aint the sensors , check the common denominator ............Flow !!!!!!!!!!!!!!!!!!!!!!!

[Six]

Duhhhhhh if there both tripping it aint the sensors , check the common denominator ............Flow !!!!!!!!!!!!!!!!!!!!!!!

Healey Nut what are the models of the two Austin Healeys in your avatar.

There is a guy locally that sports around in a yellow frog eyed sprite.

[Healey Nut]

Red one ...64 3000 Mk 3 BJ8
Green one ...67 3000 Mk3 BJ8

[Six]

Red one ...64 3000 Mk 3 BJ8
Green one ...67 3000 Mk3 BJ8

Did you do the restoration or did you acquire them in that shape ?

Are they hard to find parts for ?

[ryan1088]

Just because a flow switch is "made" doesn't ensure that there is water flow or sufficient water flow. Differential pressure switches aren't the most accurate things either. Proper flow switch adjustment sometimes requires some time and effort to get just right. Use the same pressure gauge when checking for pressure drop, there is a formula to tell you gpm. Get your post count up and apply for the pro membership, them you can have access to more information than you can possibly absorb.

[Healey Nut]

Did you do the restoration or did you acquire them in that shape ?

Are they hard to find parts for ?

Check my profile theres a bunch of pics there . Yes I did restore the green one and I am now doing the red one . Easy to get parts .

[Nuclrchiller]

Make sure entering and leaving water pressures are determined with one gauge, moved back and forth between the two. And be aware that a restricted, or plugged, evaporator will increase the pressure drop, giving a false indication of flow that is higher than actual. This is where knowing the entering and leaving water temps would be helpful.

[Bstang27]

whats the formula for gpm. what should the gpm be. Circuit 2 runs for 3min and off on low evap alarm. circuit 1 is running now for the past 2 hrs but when makes temp will be off on same alarm I have 7 psi difference between supply and return,flow switch abviousky is made. suction rftg 58dg sat evap temp 54.7dg,evap psi 92 psi cond psi is 173psi, entering wtr temp 62 and leaving is 58.7 f, thats on circuit 1. Circuit 2 starts and suction drops way down right away and goes off low evap alarm.

[Tech Rob]

Check the flow with ONE GAUGE!!! Use the search feature!!! How many times do we have to go over this?!?!

Sound familiar?

[Bstang27]

I did check with one guage. 7 psi difference.

[Healey Nut]

Heres a novel idea ........................ Call a pro !!!!!!!!!!!!!!!!!!!

[jpsmith1cm]

This seems more at home in Tech to tech chat.