Carrier 30GT series low suct pressure switch

[doodlehill]

I have several 30GT carrier chillers to maintain. Several of these chillers don’t have a low side suction pressure switch to stop the compressor on a loss of suction. They are instead equipped with a “Loss Of Charge” switch that is connected to the discharge. What I have found a problem with the TXV or solenoid valve will cause compressor burn out on these machines.

Connecting the switch to the low pressure side will cause the compressor to trip during the initial 10 sec pump down cycle. We have confirmed through the provided documentation that the switch is supposed to be connected the high side of the compressor.

I have not been able to locate a low pressure safety on any chiller of this series. I am planning on installing low pressure protection on these machines in the very near future.

I would like to know if any one has seen a single module solution to resolve this. The switch will have to be disabled during the initial start up of the compressor and not cycle the compressor on a actual low suction situation.

[hvac3901]

i don't remember everything about the 30gt. but i believe the level of charge (LPS) is not a physical point in the system, the level of charge is monitored via thermistor input to the unit controller.

[doodlehill]

This i checked into and there is a safety that applies only to EXV units that will shut the compressor down on a high superheat if that condition exist for 5 minutes.

I went to all our chillers of this type today and confirmed that they will not shut down loss of suction.

[trimble]

Those machines don't require a low pressure switch. The saturated suction temperature thermistor will monitor suction temp and shut down the unit on low suction temp if low on charge. The micro will also monitor superheat and trip if needed. These units have been out for 20 years and not having a low pressure switch is not an issue.

[airworx]

traneman is correct. the processor board will monitor all thermistors and if there is a problem will shutdown chiller. also you cannot just wire in a low pressure switch. these units will pump out on startup. which would trip low pressure switch. now you could use a bypass relay parrell to pressure switch, but your wasting your time the processor will take care of any problems.

you need to go to carrier and get a service manual for your machine. youll have a tough time working on them without it.

also you may want topurchase the flotronic monitor software so you can hook up your laptop to unit and view all the thermistor , water and refrigerant tempertures and pressures.

[doodlehill]

I will check into it only one out of 8 or our TXV equipped machines have thermistors. I think it origonally had EXV's and some one decided to put TXV's in it.

[hvac3901]

the txv installation makes sence although i don't know what it does to the exv logics. the early exv's had serious problems due to having only 750 steps in the mechanism, later they used 1000+ steps (i think 1400 steps) and they had better internals.

airworx,
depending upon which of the flowtronic sries he has he may or may not be able to use computer to check it out. flotonics one with comfortview will not work out. flotronics II is good for it.

[airworx]

doonehill. not all models have thermistors and exv (flotronic)
some models come with txvs.

[trimble]

Airwox is correct. Not all models of the early 30GB / 30GT chillers had EXV's and thermistors.

[carriertech1]

Don't try to outsmart the system software. The system will trip on high suction superheat long before it will trip on a ad on low pressure switch. If you are losing refrigerant
check you quarter inch oil equalizer lines on the bottom of each compressor they leak all the time. You realy can't add on a low pressure switch

[doodlehill]

We aren’t loosing charge we burnt out 3 different compressors this year because of solenoid valve failures. We haven’t been able to make a TXV controlled chiller shut down on superheat.

[airworx]

i would check to see if the discharge gas hi temp switch is not stuck closed. also why is solenoids failing. are compressors pumping down and not shutting off. i would go to carrier and get a service manual for this machine. very difficult to work on if not experienced on flotronic equipment without manual.
also check into flotronic monitor so you can hookup a laptop to machine you can tell a great deal more of whats going on.

if you just can't figure out whats causing these problems you could install a lowpressure switch with a bypass time delay wired in parrallel to pressure switch but i would rather repair the problem instead of manifesting a solution.

[Dallas Duster]

Is your oil pressure switch not catching it?

[consolidmech]

I have the SOMs on the 30 GB & GT series . Post M/N & serial. Is it a 30 GT flotronic 1 with the two digit screen or is it a Flotronic 11 with the expandend screen.

[Luisito]

Don't try to outsmart the system software. The system will trip on high suction superheat long before it will trip on a ad on low pressure switch. If you are losing refrigerant
check you quarter inch oil equalizer lines on the bottom of each compressor they leak all the time. You realy can't add on a low pressure switch


hi carriertech or other user, can you help whit flotronic II,
necessarily I quit both EXV and put two TXV and now works, but when cutting by temperature it leaves error 38.39 but not cut the refrigerant flow. Can be quit configuration EXV and be put it TXV?
i have this module HK50AA023 Flotronic II whit module keyboard display HSIO, this HSIO have 6 funcion keys, 12 num keys and LCD 8 characters
i read manual of Colortronic 30gtn-4t, google it, is something similar a flotronic II and i read in the manual can change this function.

tanks ALL!

sorry but my poor English, if you want talk me in MSN djluis@hotmail.com.ar

[Luisito]

I have the SOMs on the 30 GB & GT series . Post M/N & serial. Is it a 30 GT flotronic 1 with the two digit screen or is it a Flotronic 11 with the expandend screen.


what is SOMs?, i havent Model and number serial, i have manual operation and says FLOTRONIC II fase 3, the display is LCD 1 Line 8 Character

[innovative]

Hi

we also have Carrier chiller 30GT and recently we chnage the Expansion valve from dome type to canister type and now we are facing a error code 59 which say Low Charge switch (LCS) we tried all the possibility but after 5 to 7 minutes system stop working. kindly let me know if anyone has come up with this type of problem.

regards

Ashfaque

[Dallas Duster]

Are you sure it`s not a bad switch ? The switch is actually reading the hugh side of the system so the system would have to be below 7 psi to open and produce the alarm.

[innovative]

Are you sure it`s not a bad switch ? The switch is actually reading the hugh side of the system so the system would have to be below 7 psi to open and produce the alarm.


"switch is fine , now i feel i must change the dryercore , but that is not the issue i believe.

[volt]

Check your service bulletin history for that machine.

I believe there is some updated software for all 30GT's that were manufactured before 1997. (EPROM chip)

I don't recall anything regarding the type of issues you are having, but I always start with the basics of bringing the machine up to the most current software version, and make sure your configured correctly before making any kind of changes.

[innovative]

Check your service bulletin history for that machine.

I believe there is some updated software for all 30GT's that were manufactured before 1997. (EPROM chip)

I don't recall anything regarding the type of issues you are having, but I always start with the basics of bringing the machine up to the most current software version, and make sure your configured correctly before making any kind of changes.
so you feel that we should update our software , and again do the setting?

[volt]

Some of the 30GT machines were sent out of the factory with "Generic" programming. This was the reason for the bulletin and software updates.

Not saying your machine is one of them, or that a software update will fix your issue but it's worth looking into IMO

As far as checking configuration for your application. I always do that because you never know who has been tinkering.

[innovative]

thanks for your valuable feedback , i will look into this.

[Gibbo]

Your loss of charge switch is meant to be on the high side and is set about 5-7 psi. You should be able to check if its the switch or connection to main board at fault, i take it there is refrigerant in this circuit.

[innovative]

Hi

today we chnaged the dryer core as well for the unit but it give the same error code number 59 which is nothing but LCS " loss of charge Switch" how and why this happen can anyone pinpoint the mistake , what is the solution for this.



Your loss of charge switch is meant to be on the high side and is set about 5-7 psi. You should be able to check if its the switch or connection to main board at fault, i take it there is refrigerant in this circuit.

[Dallas Duster]

Did you ohm out the switch? What country are you from ? Explain exactly where the switch is located?

[innovative]

I will get it check again but i checked and it was fine. what is the reason it gives such error (LCS)

can anyone tell me what need to be done to solve this issue?




Are you sure it`s not a bad switch ? The switch is actually reading the hugh side of the system so the system would have to be below 7 psi to open and produce the alarm.

[Dallas Duster]

It means that if the switch is good and it is located correctly then you have lost your charge and I don`t mean some of it I mean all of it.

[innovative]

I have not ohm it but if you say so i will do it, we are located in Dubai ( UAE) the loss of charge is connected with discharge line in circuit A.

[Dallas Duster]

What kind of pressure do you have on the discharge ?

[innovative]

250 psi

What kind of pressure do you have on the discharge ?

[Dallas Duster]

I would ohm the switch out at the plug connector in the control panel. The LAST resort would be to jump it temporarily and see if this makes the alarm go away but DO NOT leave it that way if alarm goes away. Jump it at the board.

[innovative]

what do you mean by kind of pressure ? definately it will be gas pressure in discharge line


What kind of pressure do you have on the discharge ?

[Dallas Duster]

There should be a refrigerant access fitting on top the the compressor head. The loss of charge switch is reading that discharge pressure. A loss of charge switch isn`t going to open with 250 psi on it.

[innovative]

i will get the it check tomorrow since we are close now , what is the pressure
it should start with and give me an idea how should be rectify this issue.



There should be a refrigerant access fitting on top the the compressor head. The loss of charge switch is reading that discharge pressure. A loss of charge switch isn`t going to open with 250 psi on it.

[Dallas Duster]

The loss of charge switch is the most unused component of the chiller. It doesn`t care if the EXV or TXV is closed. It doesn`t care if the liquid line driers are plugged. It is only there to open in the case if you lose your refrigerant charge. Hard to say what your pressures should be.

[innovative]

why this loss of charge happen? we have charged the gas after replacing the old ExP valve still we get this error,
what do you do to recharge the loss of charge switch?



The loss of charge switch is the most unused component of the chiller. It doesn`t care if the EXV or TXV is closed. It doesn`t care if the liquid line driers are plugged. It is only there to open in the case if you lose your refrigerant charge. Hard to say what your pressures should be.

[Dallas Duster]

I would replace it if you have replaced everything else at least it is the least expensive option. Good Luck.

[innovative]

Hi we have issue with chiller 30GX-328-AO-338-NEE and it give the error code 14 , 16 and 52 , can anyone help me to rectify this error and let me know why this happen.

[Dallas Duster]

Hi we have issue with chiller 30GX-328-AO-338-NEE and it give the error code 14 , 16 and 52 , can anyone help me to rectify this error and let me know why this happen.

Start a new thread if your looking for help. How long have you been doing HVAC work ?

[innovative]

If we replace the switch do you think it will work ?

[Dallas Duster]

I would bypass the switch first to confirm the replace if it fixes it. You will know pretty quick if bypassing it fixes it.

[innovative]

last three years and we never face this problem , we work with many diffrent chiller but this time we are stuck with this issuee

[innovative]

i will do the same tomorrow and see how it goes,

[Dallas Duster]

Try bypassing the switch first then get back with me.

[innovative]

Hi we have issue with chiller 30GX-328-AO-338-NEE and it give the error code 14 , 16 and 52 , can anyone help me to rectify this error and let me know why this happen.

[innovative]

we did replace the switch still it is not resolve, now it stop circulaion of the gas from Exp valve.

[volt]

Is the access port that the switch is mounted on seeing system refrigerant pressure?

Is the schrader core being depressed by the switch?

If the switch is mounted on a valve, is it open slightly?

Did you check the switch at the main circuit board connection?

[pureroundcircle]

If you really want the suction pressure switch Grainger does make a kit to add one on, though I think you would probably need some sort of time delay with it for your application. Just happened to run across that while looking for something else a few days ago.

part # 6MD66