Siemens RCCB trips even while inductive motor is off

There is a thermal overload shown in the schematic. How come this is not fitted?

Nicelectrician: You wrote in your first post:

We use a normal 4x1.5mm cablet (3power 1ground).

by which I understand you provide L1, L2 and L3 and an earth/cpc to the autoclave.

But the image you show of the RCCB shows L1, L2, L3 and a neutral - to the far right of the four terminals top and bottom - there is a black conductor going in and not out. This indicates to me that the autoclave requires a four wire 3 phase supply - L1, L2, L3 and N plus an earth/cpc.

The fact that the RCCB trip test button does not work also indicates the N is absent.

I think then that you should check the installation instructions to confirm whether a Neutral is required - because I reckon it most certainly is.

At the stage of the autoclave process, the sterilisation has been completed and the chamber and its contents are now being rapidly cooled by a number of cycles of vacuum pump on, vacuum pump off(hold), vacuum pump on, VP off(hold)... see:


If the autoclave uses a water cooled cooled jacket system to reduce the the chamber temperature, there is either a small water pump being turned on/off to circulate cold water or an electrically operated solenoid valve is opening/closed to do it. The pump or valve may be the only electrical part of the autoclave which require a Neutral. The absence of the supply neutral only becomes a problem then the first time they are energised by the autoclave's computer/controller.

(For my EF colleagues, I suspect there are other light current loads using a neutral, the net effect being a virtual neutral is produced which is good enough for them until the higher current required by the pump/solenoid I mentioned in the previous paragraph disturbs its potential wrt the lines and earth and then transient leakage currents trip the RCCB or the residual current over the 3Ls and N through the RCCB sense coil - the virtual N being on the load side of the RCCB -or something along these lines.)

Hello All

Thank you for your quick response. First I need to apologize, I did not check in person the electric cabinet until now. I will have to fire my "electrician" or re-evaluate him. He told me incorrect information which I provided to you EF. I have attched the whole manual, from page 178-196 are the electric diagrams.

Also the RCCB does indeed feed not just the motor but other components, L1 and L3 goes to other components. I will check them personally later. I tested the motor the insulation is ok and the loads are balanced when I tested the motor outside the machine.



So from now on, I will provide tested information by me.

Again huge thanks to Marconi and everyone who are at this moment teaching me with just comments on the problem.

Best regards to you all

Ahh one more thing this is an Indian low-cost machine, I already told management that this machine is not new but used or it got wet during shipment, the motor is not by close new, not even second hand, super used. They told me to just keep repairing it to make it operative.

Thanks again

Page 179/196 details how the 'Power Fail' signal is produced. Monitor its state at the relay and also at the input to the PLC.

The Autoclave does require a Neutral so a 5 wire cable to it.

Have you really connected N to ground at the output of the RCCB? That would not be right to do.

There is a power supply filter which may have failed/is failing - has the problem only just started after a period of trouble-free operation? (see the page with the wiring diagram which shows the RCCB).

Do the checks suggested and of all other power supplies eg: 24V ac and 24 dc. Pay particular attention to check and test components I suggested and others which only come into use after the Sterilise phase has ended and the cool down starts eg: vacuum exhaust valve.

I am off to bed now.

Nicelectrician: What is/will the autoclave used for please?

The same transformer that provides the supply to the 'Power fail' relay has another secondary coil which provides the 24V ac for the various electrically operated solenoid valves(V1 etcetera). The load of one or more of these valves being energised could be loading the transformer such that the voltage to the 'Power fail' relay has a temporary dip, opening it's contacts briefly, and then recovering to close the contacts - yet the PLC detects the brief opening of the contacts and assumes a 'Power Fail' has happened.

Check the output voltages of the secondary coils and also any marking for the voltage rating of the primary coil - is the primary suited to 208V or is it a 220V/230V/240V primary?

marconi said:

Nicelectrician: What is/will the autoclave used for please?

Click to expand...

It is used for all kinds of materials, steam sterilizer. Clothing, cleaning, etc. Materials for a cleanroom.

marconi said:

The same transformer that provides the supply to the 'Power fail' relay has another secondary coil which provides the 24V ac for the various electrically operated solenoid valves(V1 etcetera). The load of one or more of these valves being energised could be loading the transformer such that the voltage to the 'Power fail' relay has a temporary dip, opening it's contacts briefly, and then recovering to close the contacts - yet the PLC detects the brief opening of the contacts and assumes a 'Power Fail' has happened.

Check the output voltages of the secondary coils and also any marking for the voltage rating of the primary coil - is the primary suited to 208V or is it a 220V/230V/240V primary?

Click to expand...

The situation is that the RCCB actually trips.

Have you carried out any tests on the RCCB in case that is at fault?

You have not answered whether the supply has a neutral.

Also you have not confirmed whether the neutral at the RCCB has been 'grounded' which I said was wrong.

You have not yet measured any voltages as I asked.

:-(

Sintra said:

Have you carried out any tests on the RCCB in case that is at fault?

Click to expand...

I dont have much tools to test, The only option to "test" that I have is to change it. I m already planning to do so. But if you know a method to troubleshoot the RCCB I m all ears.

Best regards

The RCCB may not be faulty. It is certainly not correct and potentially dangerous to connect - as said in the image below the lower terminals in #18 - the neutral from the RCCB to earth/ground (especially since there is a filter in the supply lines - forgive me but I will not explain why).

The wiring diagrams I have looked at show no neutral coming out of the RCCB only one going in to it - see page 178 of 196 in manual.

Could you/your company not buy one of these:


The autoclave requires a 5 wire supply providing L1, L2, L3, N and E - HAS IT!!!!!!!!! If it does not then the first thing to do is provide a 5 wire supply with a neutral.

I am becoming exasperated with you hence the bold annoyed text.