Carel networks = electric shocks ???

[Keef_Controls]

I've been working on some Carel networks in JS recently. From what i understand the network is RS485 based - however why do i get a mild shock off it ?? RS485 voltages should'nt exceed 5vdc really..

A few other people i've spoken to have noticed this aswell, i'd be interested to know the reason why..

[Chunk]

Hi.i`ve been told by Parasense engineer that the voltage feedback is normal but when you get a buzz of 70 volts up your arm it doesnt feel normal.i will find out tomorrow and post back.i was told why the voltage was there but i`ve forgotten.

[Keef_Controls]

I see Carel support have been posting on here today - maybe they will have the answer.

I also spoke to Parasense about it, and they say its normal too??

Glad its not just me thats noticed it though - i thought i was going mad, or at least completey ar*ed somthing up..

To me it seems really dodgy - i'm sure it goes against the CE / UL / health safety etc.. rules. RS485 is deemed as low voltage, no one expects a shock from it ! If i had a ****y ticker - 70 volts up your arm, unexpectantly may not have the best results...

[nike123]

It could be induced voltage in unshielded cables or static electricity. Did you measured voltage on that line?

[Keef_Controls]

It could be induced voltage in unshielded cables or static electricity. Did you measured voltage on that line?

Did'nt measure it - another engineer i know reckons its 110v.. Its not static - you can feel a definate buzz like a mains shock.

I'm sure its not induced voltage, if it was i'm sure i would have noticed it with other controllers. Also i dint feel anything when touching the screen - although the screen seems to be only connected to earth at the controller ends.

[Chunk]

Hi. I spoke to Georgio at carel and he says that the comms on the ir33 powerboxes has 50vac running through them.the cables should be sheathed so you dont get shocked.this is the case for all ir33 powerboxes and not ir33 standalone controllers which use 5vdc.I was also told dont touch comms cables when you are kneeling in water!! Thats technical support from the people who know.

[Keef_Controls]

Hi. I spoke to Georgio at carel and he says that the comms on the ir33 powerboxes has 50vac running through them.the cables should be sheathed so you dont get shocked.this is the case for all ir33 powerboxes and not ir33 standalone controllers which use 5vdc.I was also told dont touch comms cables when you are kneeling in water!! Thats technical support from the people who know.


So they are saying its normal to have 50vac running through the comms ? mmm - sounds even more dodgy..it really should'nt.

Do you know if the comms interface is opto isolated at the ir33 end - i'm fairly sure it is at the webgate end.

[Chunk]

now you are baffling me with science.our commissioning engineer said he only gets this problem in some stores due to improper earthing on the gateways,but because i dont get many problems with these controllers i have not spent too much time looking at them.to be honest i only get etc alarms,repair them and walk away and go play with the rdm`s.

[750 Valve]

RS485 is a standard comms protocol, it does not use any AC voltage, it uses 5 vdc supply and transcievers in the RX and TX lines, measure both to ground and you will get 5vdc approx biased to one line - like 2.4 and 2.6vdc, when comms fail you quite often see a higher voltage in one line like 1Vdc and 4vdc but will still be approx 5vdc. If you are seeing AC voltage its either induced due to improper shielding or if its carels design to have 50vac then it does not use RS485 comms protocol

[Keef_Controls]

RS485 is a standard comms protocol, it does not use any AC voltage, it uses 5 vdc supply and transcievers in the RX and TX lines, measure both to ground and you will get 5vdc approx biased to one line - like 2.4 and 2.6vdc, when comms fail you quite often see a higher voltage in one line like 1Vdc and 4vdc but will still be approx 5vdc. If you are seeing AC voltage its either induced due to improper shielding or if its carels design to have 50vac then it does not use RS485 comms protocol

Everything you say about RS485 is right - but i am sure this IS RS485. Cant find any looked obout the controllers yet - but the WEBGATE at the other end is using RS485, also 120R termination resistors have been fitted at the end of the network - normally done with RS485..

I do some more investigations tommorow on site i think...

[nike123]

I think that doesn't matter at what potential is comm line in relation to earth, it could be at any potential as long as tk+ and tk- are 5V from comm line and comm line is not grounded. That is how you could experience higher than 5V voltage if you touch comm line who is on higher potential in relation to ground because circuit is closing thru ground and not thru tk+ or tk-. Also, both tk+ and tk- could give you shock.
That is theoretically, what is really, I could not know without electrical diagram.