220VAC on the supply pins, but no indication LEDs on

[as1988]

PLC: Mitstubishi FX3G 24MR/ES

 

There is 220VAC coming to the PLC supply pins, but no indication LEDs are switched on and there is no 24VDC service supply.

This PLC is used to control the sauna.

Before dismantling PLC, is it possible that there is some unmet condition that is preventing PLC from starting?

 

 For example, if Emergency stop is activated and wired to the PLC input, can it prevent PLC from starting? Just a reminder, there is 220VAC at the L and N pins of the PLC.

 

 

[Gambit]

you are supplying 24V to the terminals below, but these already provide 24V!!!!

[as1988]

42 minutes ago, Gambit said:

you are supplying 24V to the terminals below, but these already provide 24V!!!!

It is not outside 24VDC that are being supplied to the PLC.

 

24VDC are supplied by the PLC and then distributed further - it is, so called, service power supply.

 

 

[Gambit]

ok than maybe there is a short,

only connect the power on top L/N. If the power LED doesn't turn on the unit is broken.

[as1988]

2 hours ago, Gambit said:

ok than maybe there is a short,

only connect the power on top L/N. If the power LED doesn't turn on the unit is broken.

Ok, thank you.

[Ron_S]

The 24 vdc is not normally wired like that.

It's not good practice to parallel supply's.

[as1988]

21 hours ago, Ron_S said:

The 24 vdc is not normally wired like that.

It's not good practice to parallel supply's.

There is just one 24VDC power supply and it is the PLC's service power supply. 

[Ron_S]

Well all the outputs are being supplied by it.

The plc 24vdc is very low amps.

 

Go over that and the supply shuts down.

Edited September 11, 2021 by Ron_S

[glavanov]

When 24V service power suply of Fx series is overloaded or short circuit the green power and red error leds are solid ON. Program led OFF. and you can see the error by GXW2 with PLC diagnostics function.

It happened to me with Fx3U, not sure for Fx3G series.

Problem might be elsewhere... PLC AC-DC converter, blown AC fuse or, AC line...

Edited September 13, 2021 by glavanov

[as1988]

On 13/09/2021 at 0:23 PM, glavanov said:

When 24V service power suply of Fx series is overloaded or short circuit the green power and red error leds are solid ON. Program led OFF. and you can see the error by GXW2 with PLC diagnostics function.

It happened to me with Fx3U, not sure for Fx3G series.

Problem might be elsewhere... PLC AC-DC converter, blown AC fuse or, AC line...

Thank you, much appreciated.