probes on Carrier 30GX chiller

[Yuri B.]

Hello.
Maybe someone know how the controls manages to calculate suction superheat - there is a suction pressure transducer but no suction temperature sensor ?! Is EXV position not guided, to any extent, by the SH here?

[james10]

Hello.
Maybe someone know how the controls manages to calculate suction superheat - there is a suction pressure transducer but no suction temperature sensor ?! Is EXV position not guided, to any extent, by the SH here?
The 30Gx calculates discharge superheat


Electronic Expansion Device Module —

The electronic

expansion device module has 4 inputs and 2 outputs.
It receives signals from the PSIO- 1 module and operates the
electronic expansion devices. The electronic expansion device
module also sends the PSIO- 1 module the status of its
4 input channels

[Yuri B.]

Could you share with me the full document from which the extract has been pasted ? (if only the doc. refers to Carrier chillers - not to EXVs' control in general)

[james10]

Could you share with me the full document from which the extract has been pasted ? (if only the doc. refers to Carrier chillers - not to EXVs' control in general)
PM me your e-mail and i'll mail you

[Yuri B.]

Thanks James.
Have searched the whole thing thoroughly today ( the chiller) - no suction temp sensor on it. On its main board there are OAT, water-in, water-out temp sensors, on the compressor protection board - discharge temp, and motor temp. sensors. How it calculates the SH (if does it at all) - seems to remain a mistery to me.

[james10]

Thanks James.
Have searched the whole thing thoroughly today ( the chiller) - no suction temp sensor on it. On its main board there are OAT, water-in, water-out temp sensors, on the compressor protection board - discharge temp, and motor temp. sensors. How it calculates the SH (if does it at all) - seems to remain a mistery to me.
The psio module reads the discharge temp, suction pressure/temp(through suction transducer) and leaving water temperature this through the art of electronics and the sofware installed then sends this information to the expansion valve driver module(exd) the exd then interprets this information and opening the exv to the desired position
just re-read your your post the unit calculates discharge superheat and your correct there is no suction temperature thermistor as there is in effect no suction line as the compressor is mounted directly on top of the cooler the base of the compressor is in effect the suction line the discharge superheat is calculated through suction pressure and discharge temperature the software converts these two parameters to read discharge superheat if you check the discharge superheat on the psio and deduct 17 (if memory serves me right) this will be around the same figure as your traditionally measured suction superheat

[Yuri B.]

From what I have learnt tommorrow/ today on the cite about the Carrier : Discharge SH = Discharge T - Saturation Condensation T

At air T 6 C and when water-in was 16 C water-out was 14 C on the "bad" system the DSH was about 0C. I suspect it is short of gas.

When the system switched off on alarm, I turned on the other , "good" system. At water-in 15 C water-out 13 C its DSH was about 6 C. This system keeps doing the work for the both.

[Gibbo]

Low discharge superheat is not SOG.
The readings you have are they from the carrier display or have you measured this.

[Gibbo]

discharge superheat setpoint is normally 11 C

[Yuri B.]

By Gibbo

The readings you have are they from the carrier display or have you measured this.The readings were from the display.

While the good system drove the water T down from 13 C to 10 C (SP), DSH was indeed about the value you have mentioned : 6 C to 11 C.

But on the bad system (which had tripped on "low suction T" finally), at the point when water out T was 13 C DSH here was even not positive but mostly negative ! To raise the DSH the controls
1. started frantically the fans - driving SCT down (because DSH = DT - SCT).
2. closing EXV
By that the evaporation P went abruptly down. The controls sensed too low suction T (suction T is directly derived from the evaporation P ), the system tripped on the low suction T.

I am beginning to think now, there are uncondesables in the latter system, Hi P transducer senses higher T than would be the T correspponding to uncontaminated 134a, and so is trying - wrongly - to lower SCT.

PS. Subcooling was very good : 15 -20 K.

[Gibbo]

If you constantly have low DSH below 11 c then the EXV will start to close and if it closes enough you will have low suction temperature alarm.

[Yuri B.]

Thank you, Gibbo, and James, I did not know about this parameter's value in the controls logic (how could I , without its description?). Maybe you can send me the manual (in which this particular value is at lest mentioned) ?

[Gibbo]

The control of the EXV and discharge superheat is mentioned in the controls manual under the section of EXV control, however the configuration of the discharge superheat setpoint is done by the Carrier Factory or Carrier Service only. I believe James sent you the controls manual.

[Yuri B.]

Sorry, Gibbo, all I have is this:


5.13 - Compressor ......compressor.
5.14 - EXV control
The electronic expansion valves (EXVs) control charging and
the refrigerant flow in the evaporator, maintaining the optimum
evaporator throttle and a correct discharge superheat. Opening
the valve permits reduction of the throttle, and thus improves the
heat exchange in the evaporator. This opening can be limited to
maintain the condenser subcooling and correct superheat,
avoiding liquid slugging at the compressors and ensuring
operating stability.
5.15 - Motor cooling valve control
The temperature ...pressure.

Very general information.

[james10]

in the manual i sent you it descrribes how to test the exv at 25/50/75/100% positions open and closed to get an alarm description
press 1 stat
the unit will show how many active alarms there are
scroll down
when the unit shows the alarm code press the expand button think its labeled exnd
the alarm description will then scroll along the top of the screen very slowly

[Yuri B.]

There is not HSIO-11 interface on the chiller.

[Yuri B.]

Helll, cannot paste the images....

[james10]

Helll, cannot paste the images....
What type of control do ouy have then?
Phase 1 Global HSIO/PSIO (Flotronic 1)
Phase 2 Global Pro-Dialog (Black Screen)
Phase 3 Global Pro-Dialog plus (Grey screen)

[Gibbo]

sounds like you have a pro dialog GX. Phase 1 has flotronic 2 based controls Phase 2 has a black display board and pro dialog control. Phase 3 has a cream coloured display board and is pro dialog control.
There is a slight difference between phase 2 and phase 3 exv/dsh control.
if you go to http://eto.carrier.com/lit.asp scroll down to 30 GX and pick whichever version you need and download the controls manual.

[Yuri B.]

Pro dialog plus. And through this interface it is only possible to open or close EXV - no possibility of choosing a % of opening in test mode.

The system should be short of gas. At start, after reset (system have stayed several hours out of work), with the compressor yet cold, the system kept EXV almost closed, trying to lower DSH. After another low suction T alarm and the immediate reset of it, copm has gotten heated up, discharge T was now increased, system was not more busy keeping DSH down, EXV was now alloweed to be opened - it did so up to 100 %! Evaporation T (P) did not increased much by that, however, motor T rose up to more than 90 C. I wisely turned it off.

The system is surely short of gas.

[Yuri B.]

By Gibbo:

if you go to http://eto.carrier.com/lit.asp scroll down to 30 GX and pick whichever version you need and download the controls manual.

Information they give there is on my, serviceman, view hiighly unhelpful.
How to get access to service menu?

[Gibbo]

Service menu is password protected for Carrier Service techs only.

[serviceman]

if you need the password to the configuration menus and services are provided will gladly