thermal Overload

[marc5180]

Got called to a breakdown today on a millenium recip chiller. Circuit 1 was tripping on the compressor thermal overload. I checked the amps and got around 24 for each phase. The sight glass seemed to be bubbling a bit too much so connected guages and got 4 bar on the suction and 12 on the discharge. I know this is a little low but i wouldn't have thought this would have caused the compressor to trip on thermal overload so decided to look at the oil.
As there is no oil sight glass at the bottom of the compressor, how can i tell if the compressor is short of oil, is there a guage that i can buy for this purpose?

[Brian_UK]

Nice set of readings Marc but which refrigerant

Can you get a set of oil pressure readings at all?

Other than that I suppose you could pump down the compressor and pull the drain/level plug to measure how much is in there. Remember of course that some of it will be around the system.

The other thing is that it is normally the refrigerant that keeps the motor cool, if you are that short of oil you could be getting close to seizure.

[marc5180]

Oh yeah sorry its on R407c
Can't get a set of oil pressure readings as far as i'm aware, so I think i will pump the unit down as you say and then measure the oil that i get out of the compressor.
Any idea how much i should get out if the charge is correct?

[Brian_UK]

Nope, sorry. Is there a level plug on the side perhaps?

If not then it's back to the phone and the makers/agents for the info.

[marc5180]

I went back to the chiller today, couldnt pump it down as it kept tripping on the thermal overload after a few seconds, so i decided to decant it. I removed 19kg of R407c (standing charge was 21kg) also i found a sight glass for the oil on the side of the compressor, it had been painted over and looked like a bolt The oil level was under a 1/4 full so i added 2 litres until it was just under half.
Whats the next things to check after i get the gas charge and oil charge correct? Not really used to working on these big semi hermetic compressors or chillers, so any help would be appreciated.
Marc

[frank]

Whats the next things to check after i get the gas charge and oil charge correct? Not really used to working on these big semi hermetic compressors or chillers, so any help would be appreciated.
Marc

Give me a ring, pay my wages, expenses, buy me lunch and a beer after and I'll come up and fix it for you

[philjd26]

hi, i would be careful when adding oil , because as ther was a shortage of gas you may have a lot of trapped in the condenser, so when you pressure test and charge it up come back a few days laterv and check it out

[gsxr1340]

Hi Marc,
what york millenium recip was it, if you tell me what chiller it is, i will try and help, and try and give you some pointers to navigate through the millenium controller, it will tell you whats failed if you look in the alarm history buffer, and you can look at the operational data when it failed,

[marc5180]

Give me a ring, pay my wages, expenses, buy me lunch and a beer after and I'll come up and fix it for you

No need to be facetious Frank.

[marc5180]

Hi GSXR the model was a YCAM B/300 TUV. The chiller is around 10 years old and the controller seems pretty basic compared to the newer ones.

[frank]

No need to be facetious Frank.

It was a genuine offer of help my friend.

[The Viking]

You say that it's pulling 24 Amp, what's the overload set at?
And have you checked what current it's pulling when the overload trip?(best done with a peak load recording clamp meeter)

Sometimes the overloads themselves gets "tired" and trip even if the load is well below the set limit.

[gsxr1340]

Hi Marc.
does your ycam have soft start on the compressor, I have had these s/starts fail and drag the compresor down on thermal trip on start up.

[borley]

Hello Marc
if the high compressor current was caused by mechanical damage due to low oil level, then the damage has allready been done and by adding more oil won't reverse mechanical damage.
What is the motor rated current? what is the overload set point?have you checked the supply voltage 415v+-10%accross all phases. check the contactor for continuity accross the contacts. check all the power cable connections in the panel and in the compressor terminal box.
cheers
Shaun

[marc5180]

Went back to the unit today and recharged with the correct amount 21KG of R407c. On the overload on the contactor it doesnt have a set point that you can adjust, (see pictures) I measured the current on the other compressor ( circuit2) and that was also pulling around 25-26amps each phase.
After recharging i went to start up again and straight away i got the thermal overload fault flash up on the compressor again.
I noticed that inside the compressor terminal box there was a module, so i swapped this with the other compressor hoping that this could be the cause but once again it wasn't.

I noticed something in the control panel that i'm not familiar with and can only think that its some kind of current relay so when the amps get too much or too little it cuts the power to the fan/compressor. In the 2nd picture above the compresssor and fan contactors, the white box type thing on L1 it looks burnt but it doesn't look like it's just happened, it looks like an old fault but if not could this cause the fault?

[airconadam]

Ihave had the soft starts fail on these and it looks like the compressor is going to jump out of the unitcouldnt of been good for it. But would that make it go off on thermal overload??

adam

[gsxr1340]

Hi marc, the ycam does not have o/loads as you well know they are thermally and fuse protected, the white box with the blue front in the picture is your mains income fuse holder, and it does look very black, on line 1, check phase across this item. did you find a soft start mounted underneath or on the rear of your mains panel. the items on the front of the contactors are front mounted auxillary contacts, did you check the resistance across the thermistors which are wired on to the module you swapped, as it might be the sensor not the module.

[marc5180]

I didnt see a soft start but looking what wiring diagrams were there, i did notice on them soft start was mentioned several times. All i can guess is that it is behind the compressors , where the condensor and fans are located because i've seen them mounted there before. Iv checked that no cables are loose.
I spoke to a guy from York about it and he asked me if there was a red light on the main PCB, i told him that there was so he suggested that the fault therefore was either being caused by a HP fault or a current relay causing it to go off, but since i dont know what one looks like i'm stuffed I'v looked on the wiring diagrams but they are all in german and as i can read German they're no use

[gsxr1340]

Hi Marc, all the diagrams are the same, but when you look at the legend if you read across the discription of the item it is in german and french and spanish, and english, but its hidden amoungst the foreign lingo to,does the compressor actually run(how long), does it hum, vibrate, does the second stage part wind contactor pull in,

[marc5180]

Hi Marc, all the diagrams are the same, but when you look at the legend if you read across the discription of the item it is in german and french and spanish, and english, but its hidden amoungst the foreign lingo to,does the compressor actually run(how long), does it hum, vibrate, does the second stage part wind contactor pull in,

It varies sometimes it runs for up to 20mins but recently its been running for literally seconds before it cuts out. The compressor sounds fine and i have heard the second part come in only twice. This unit hasnt been run for a few months, its used as a backup but will be needed in the next few weeks whilst they move one of the main chillers

[gsxr1340]

Mark, it sounds to me like the thermistors maybe failing, check the resistance with the thermistor on the other compressor, I cant see the compressor winding getting over heated within a few seconds of run time, or check your control feed/voltages to the control module from your control board.
I have also had these not dropping the second stage part wind in and running on one winding. which does get the winding warm enough to trip the thermal.

[borley]

Hi again marc
If the compressor is only thermally and fuse protected and you keep getting a thermal o/l fault on the display, I would check the motor protection module that you have shown in picture 1.
Although you have swapped this module with a known working module, the fault may lay with the thermistor embedded in the motor windings.
To check this you can measure the thermistor resistance against the thermistor on the working compressor. Or you can check that the modules control contact is closed when there is power to the module.
The module will have a live and neutral terminals,thermistor terminals and a normally open and closed contact terminals. with a power supply to the module and the thermistor connected check that the control contact is closed, or you could temporarily bridge out the control contact on the module and then try to run the compressor. if the compressor runs then the fault lies with the thermistor.
I have had these fail before.
also check that all the thermistor terminals are tight, Even if slightly loose they can cause false readings and cause the module to trip.

SORRY GSXR1340 JUST REPEATED WHAT YOU HAVE SAID

cheers
Shaun

[marc5180]

How do i know which is the thermister sensor though? On the module it is labelled L,N 1,2,12,10,14,11, i worked out that L1 fed 11 so both are live and and the two black wires 3rd and fourth down on the picture, are at the side of the 3 phase power each on their own terminal, 12 isnt used and i'm not sure what 10 and 14 are.

[dkemper]

Mark,

Does the second compressor have the same wiring on it's motor protection module?

From your pics and description, it looks like the module is expecting 3 embedded thermistors and it's only wired with two.

Have you checked the oil for traces of acid and have you tested the motor with a megohm meter? Never hurts to verify the condition of the motor itself.

As others have said, this really sounds like a failed/failing thermistor in the motor.

You'd have to get the specs on the module, but you might be able to bypass a failed thermistor with a fixed impedance resistor.

Also, as mentioned, monitor the system closely when you do get it restarted for returning oil. Excessive oil in the compressor is often a really bad thing. Starting the system, pumping it down and restarting a few times will often return much of the oil to the compressor.

[philjd26]

hi,why not dry run it for a bit disconnect your tails from the compressor contactor, just to make sure all the controls are working up to scratch,if you have a lower voltage control cuircut keep an eye on the voltage to make sure the transformer is keeping a good swupply as controls come in...

rgrds phil

[borley]

From left to right:L AND N is the power supply to the module. Next two terminals (black wires) thermistor. Next terminal(not in use) normally closed contact. Last two terminals, common and normally open contact (control circuit)
cheers
Shaun

[marc5180]

How did you know that Shaun?

If the two black wires are the thermister then what resistance should i be getting across them? Should i just go off the other module? Also if i find that the thermister is faulty then how do i go about changing it id its embedded in the compressor windings?

[joel]

hi...

you should not charged additional oil to a system,unless having a leak,specially at the condenser...

drain some oil and investigate...mechanical wears might be the reason.(drain the oil to a thin and white cloth,serve as a filter.)

[marc5180]

Does anyone know how i would change the thermister if i find that its faulty, If its embedded in the compressor windings?

[borley]

Hi Marc
I know that due to experience and by the photo you supplied. You will probably find that the black wires are wired to a terminal block positioned alongside the main motor connections. You can compare the resistance to a known working compressor thermistor. If you find that the thermistor is faulty then you would have to remove the compressor and send to a motor rewind company to install a new thermistor. I personally would MEGGAR the motor windings to make sure they are all ok, if ok then I would bypass the motor protection module and fit a thermal overload to the main contactor and wire the controls through this. Unless anyone else has a better idea.
Cheers
Shaun

[GHAZ]

Hello marc looks like its a copeland compressor with INT69TM module , you have L and N to power up the module 1 and 2 are thermisters 11 is control circuit in 12 is alarm or fault lamp conection, 14 is control circuit out to next safety, to check thermisters you need to take off the brass strap on the terminal plate and then take the reading from top to pins because they are one pair, and then the bottom two pins, they should be roughly the same, around about 150 to 300 ohms when cold.

[joel]

sir,

try to take the other compressor module and install it to the one with having problem. before re- installation, check if the module is having same condition.

might be the module is giving problem.



l

[borley]

Hi Marc
when you check the thermistor resistance, disconnect the thermistor wires from the terminal block and test from the wire ends and not from the module terminals or the terminals on the compressor, as there may be poor connections that will give a false reading.
cheers
Shaun

[Brian_UK]

Marc, details here about these motor protection modules which may help with your understanding of them - I know I had to do a bit of reading up when I first saw the things....

http://www.cmpcorp.com/Kriwan_Products.asp

[C Bagtas]

Hi marc,
could you check the fla of the compressor,if higher than that you drawn you have problem in your compressor,isolate the compressor electrical supply and test it by megger 500v if you get 5 mega ohms above it is still good because that is wet winding.

[marc5180]

Hi marc,
could you check the fla of the compressor,if higher than that you drawn you have problem in your compressor,isolate the compressor electrical supply and test it by megger 500v if you get 5 mega ohms above it is still good because that is wet winding.

What do you mean by wet winding?

[marc5180]

Sorry its taken me so long to reply i only went back to the chiller this morning.
I'l explain what we got through today
Checked the resistance across the windings of the compressor and got 0.5 ohms on both compressors. Then we mega'd the windings with 500v and the readings came back clear.Linked out 1 and 2 on the module and checked the resistance across the internal thermisters. On the working compressor one we got 420 ohms and as the compressor ran it droppped 3 ohms but on the faulty side we got 234 ohms and ran it up and it dropped over 20ohms quickly.
Next we wired the working compressors thermisters into the faulty sides module but it still brought up the thermal overload fault straightaway, so we've now ruled out the thermisters.

Next we checked all pressure switches were operating ok which they were, then we moved onto the soft start which was located inside the condensor.
It looked like it had been disconnected, the power came through a capacitor then to a contactor and back out to the compressor contactor bypassing the soft start.
Dont know if anyone knows if there is a current transformer on these but we couldn't find one and the drawings weren't much use but thats another story.

Just as we were getting ready to give up, we decided to start it one last time and it ran for over 2 hours just before i left to come home. We must have started it up over 10 times during the day and it wouldn't run for more than 10 seconds, so why now would it decide to run. I'm going back tomorrow to run it up again and stay with it too see it it faults. All i can think is that it must have been a looses connection. Any ideas?

[borley]

Hi Marc
you don't seem to have completely eliminated the module. If I were you I would either test across terminals 11 and 14 to make sure that it does not open when the compressor trips, or bridge out the controls on terminals 11 and 14 and see if the compressor runs. if the contact does not open as the compressor trips, or the compressor trips withe the terminals bridged out then the fault must be caused by something else, BUT if the contact does open and causes the compressor to trip then the problem still lies with the module.
Make sure all connections are tight and good, also check that the supply to the module is ok and is not dropping or being lost.
A suggestion in electrical fault finding: First determine which component (ie. PLC, pressure switch, relay motor protection module etc) is causing the problem, by testing which contact within that component is breaking the control circuit, then you can investigate what has caused that component to fail. For example you are checking the thermistors on the module but you are not sure that the modules contact is opening causing the trip, therefore the thermistor may be fine...MAKE SURE THAT IT IS THE MODULE THAT IS CAUSING THE TRIP.

Cheers
Shaun

[marc5180]

When the compressor runs i have power on 11 because that gets its feed straight from the live on the module. Not too sure wether there was power on 14. Am i right in saying if there is power on 14 when the compressor has tripped then the module is fine and it isnt going off on the sensor fault?

[borley]

Hi Marc
If there is power on terminal 14 then the module's internal contact ( n/o between 11 and 14) is made therefore the module is ok. if the thermistor is faulty or the windings get hot then the contact will open between 11 and 14, and close between 11 and 12.
I don't recall but do you have an electrical drawing for this chiller?
cheers
Shaun

[marc5180]

Hi Shaun, yes there is a drawing on the back of the control panel although lots of extras have been added and some taken away by the looks of the wiring inside the chiller. Its very hard to follow the diagram. When the compressor trips out, there is power on 14 of the module.

[borley]

Hi Marc
Just to make sure you could disconnect one end of the thermistor from the module, the contact between 11 and 14 should then open, when you reconnect the thermistor the contact should close. If this is the case then it looks like something else is causing the compressor to trip. Check what happens to the working compressor module. Could you take a picture of the drawing and post it on this thread?
Cheers
Shaun

[marc5180]

Yes i'll take a few pictures on Monday when i'm back on site and post them here.
Marc

[Pooh]

Marc
if you are getting a feed out on terminal 14 of the thermistor unit then it is the thermistor that is faulty in the compressor, from the readings you got when you checked the thermistor resistance then there is definately a problem. If the thermistors are faulty it will require a compressor rebuild as there is no way of replacing the thermistors as they are part of the stator windings. have you tried shorting out terminals 11 and 12 on the module and seeing if the compressor will run. If you do this make sure you monitor the run amps. If the comp runs check the suction superheat as the fault may be a faulty expansion valve which is causing to much superheat which is causing the comp torun hot.

Ian

[marc5180]

Hi Marc
Just to make sure you could disconnect one end of the thermistor from the module, the contact between 11 and 14 should then open, when you reconnect the thermistor the contact should close.

Can i do this live? I mean it wont blow up the module or anything like that when i reconnect it will it?

[marc5180]

have you tried shorting out terminals 11 and 12 on the module and seeing if the compressor will run. If you do this make sure you monitor the run amps. If the comp runs check the suction superheat as the fault may be a faulty expansion valve which is causing to much superheat which is causing the comp torun hot.

Ian

Hi Ian, 11 is Control circuit in 12 is alarm or fault lamp conection and doesn't have anything connected to it. How would connecting 11 and 12 make it run? Do you mean 11 and 14? Controll in and out.
Also when i went back to the unit Friday morning (the chiller hadnt been run since wednesday evening) and started it up, it tripped straight away before it even started up. The power to the crankcase was left on though. Although when the chiller was running on wednesday for over 2 hours i checked the pressures, temperatures and superheat and all were fine, i also checked each side of driers and TEV to check for any blockages. All seemed ok.

[joel]

sir,

try this,
measure the good thermistor resistance. ( the one that compressor is running ) then, have a resistors that with same value..connect it to the module that is not running.

pls be aware to the compressor current.
check your crank case temperature before start up.

[marc5180]

I've linked out control in and control out this morning (11+14) and the compressor ran fine but as soon as i reconnect 11 and 14 the thermal overload fault comes up. I stayed with it whilst checking amps and compressor temperature for over 2 hours.

[borley]

Hi Marc
What you have just done is what I suggested a while ago. The contact between 11 and 14 should be closed for the compressor to run, you have proved this by bridging out the terminals 11 and 14 and the compressor ran, therefore when the bridge is removed and the compressor trips means the contact is opening. So it looks like your thermistor is faulty after all. Just to make things clear for you, with the power off the module terminal 11 is the common, 12 is the alarm (if required) and is normally closed, 14 is the control and is a normally open contact. So when power is supplied to the module on L and N and a healthy thermistor is connected to 1 and 2 then 11 and 12 should open and 11 and 14 should close completing the control circuit.
As Ian and I have said you cannot replace the thermistor without rewinding the motor.
The thermistor protects the motor windings from over heating from by current overloading and loss of cooling to the windings due to loss of refrigerant or high superheat. If you leave the module bridged out you can protect the motor from over current by fitting an overload to the compressor contactor, but this will not protect against lack of cooling, This is a decision and risk that you and the customer need to decide upon.
Cheers
Shaun

[marc5180]

Hi Marc
What you have just done is what I suggested a while ago. The contact between 11 and 14 should be closed for the compressor to run, you have proved this by bridging out the terminals 11 and 14 and the compressor ran, therefore when the bridge is removed and the compressor trips means the contact is opening. So it looks like your thermistor is faulty after all. Just to make things clear for you, with the power off the module terminal 11 is the common, 12 is the alarm (if required) and is normally closed, 14 is the control and is a normally open contact. So when power is supplied to the module on L and N and a healthy thermistor is connected to 1 and 2 then 11 and 12 should open and 11 and 14 should close completing the control circuit.
As Ian and I have said you cannot replace the thermistor without rewinding the motor.
The thermistor protects the motor windings from over heating from by current overloading and loss of cooling to the windings due to loss of refrigerant or high superheat. If you leave the module bridged out you can protect the motor from over current by fitting an overload to the compressor contactor, but this will not protect against lack of cooling, This is a decision and risk that you and the customer need to decide upon.
Cheers
Shaun

Hi Shaun as you can imagine the customer wants to leave it bridged out, rather than pay the price to send the compressor away. It is only used as a back up and it is also being replaced sometime next year, , so i think i will suggest the overload for the time being although i cant see it being used much over the coming months.
Thanks for all your help its really been appreciated.
Cheers