Trane RTAC 375

[Dr Death]

This chiller had historic intermittent phase loss and phase reversal faults on comp.1A . New site to us ,so isolated comp. thro' Techview. Comp 2B now refuses to start due to phase loss or phase reversal issue. Checked fuses ,contactors etc, CTs have equal resistance and are within spec. Replaced starter module , no improvement . Anyone help ?
Also ,during testing, found 3 of the 4 comps to have meg readings as low as 4 to earth and 20 meg between windings (star/delta with closed transition).
The other comp is 250+ meg to earth so would rule out moisture etc.
Any help gratefully received .

[serviceman]

7 0 0 0 0 Current Transformers

7-1. General

Each compressor motor has all three of its line currents monitored by torroid
(doughnut) current transformers. These currents are normalized with respect
to the Rated Load Amps of the respective compressor and thus are
expressed in terms of % RLA and in Amps. The currents are “normalized”
through the proper selection of the Current Transformer and the unit configuration.
CTs are selected based on the motor RLA. Refer to Table 7-1.
The current transformers provide the input for five basic functions of the
starter module:
1. Current overload protection using a programmed % of Rated Load Amps
versus time to trip characteristic. The steady state “must trip” value is
140% RLA and the “must hold” value is 125% RLA. The starter Module
will trip out the compressor, and the Main Processor (MP) will then shut
down the other compressor on the same refrigerant circuit (if applicable).
The appropriate diagnostic codes will be displayed.
2. Loss of Phase Current. A phase loss due specifically to lack of Current
Transformer inputs is not looked for during transition (which lasts for 3
seconds in software) and is additionally delayed 2.8 seconds. As such,
the diagnostic will not be called out any sooner than 5.8 seconds after
transition even if it occurs immediately at start. Additional, two of the
three current inputs also serve the Phase Rotation circuits. If this circuit
(monitored immediately after start), outputs an inconsistent value to the
module (due to loss of one or both of its inputs), a diagnostic of either
Phase Loss (steady output) or Phase Reversal Protection Lost (varying
output) will occur with a maximum delay of 1.2 seconds after start

[Dr Death]

Thanks for taking the time to reply. If the CTs resistance is consistent and in spec it should therefore read the correct current. In the time it takes to trip it is not possible to see what reading the controller sees.Is there another way to check them? Would the low meg readings be screwing things up ?

[sefuss]

Silly question here but have you tried ringing and speaking to Tranes technical guys ive found them quite good when ive needed some trane chillers problems resolving give them a ring 08457165162
hope you fix your problem

[Dr Death]

When I tried that they wanted an order number to send an engineer. Revenge I guess for what 'we' do to them !

[Lowrider]

When I tried that they wanted an order number to send an engineer. Revenge I guess for what 'we' do to them !

What did "you" do to them than?

did u check to see if all contactors fully close and open?

[goshen]

Hi there the compressor module wont let u start the comp if there isnt a current reading within 8 ms or more of start command ,i would reccomend checking your toroides for the correct ressistance ,if this checks out ,and u check the connectiones of the comp and contactores ,u could temporarely disable phase protection and check compressor,before doing this make sure all i mentioned above checks out ,
u might have a bad contactor coil ?
good luck!

[Dr Death]

Oh the joys of working for the competition !!

[choochoo!]

if the compressor contactors don't try pulling in then try H.P switch as this will bring up phase loss fault.

[moideen]

This chiller had historic intermittent phase loss and phase reversal faults on comp.1A . New site to us ,so isolated comp. thro' Techview. Comp 2B now refuses to start due to phase loss or phase reversal issue. Checked fuses ,contactors etc, CTs have equal resistance and are within spec. Replaced starter module , no improvement . Anyone help ?
Also ,during testing, found 3 of the 4 comps to have meg readings as low as 4 to earth and 20 meg between windings (star/delta with closed transition).
The other comp is 250+ meg to earth so would rule out moisture etc.
Any help gratefully received .

RTAC is special chiller. When you replace any sensor,transducers,thermistors, modules you can’t restart the chiller without upgrading the system by using trane software. This software, trane will not give to others. Authorized trane person will do this job. So your replaced module will not work. In your case, this type alarm will occur(without the reasons of phase failure and revers rotation) due to the defect of starter module,ct,contactor and contactor auxialry.
Did you check the contactor and auxiliary? In idle period starter module should get signals from contactor auxiliaries (NO, NC of contactor relay).

Moideen-Dubai