RS485 - Black wire?

[TonyR68]

I had a service technician here yesterday on another issue. He advised that for the IntelliCenter RS485 connected devices only the green and yellow wires are needed. That is the case for my VSF pumps, but my MasterTemp heater and the IntelliChem use the black wire too. The installation manual for both reference the use of the black wire as part of the RS485 connectivity. What is the black wire used for? Heater seems to work fine without the black wire connected.

Any insight to address my curiosity would be much appreciated.

Thanks

Tony

 

[ajw22]

Black wire provides power for devices that are powered through their RS-485 link. It is not needed for devices powered in other ways.

 

[TonyR68]

Ok. Thanks. So not needed for MasterTemp or IntelliChem and should not be stated as such in the installation manual.

 

[Jimrahbe]

Tony,

The only place in the manual that says to connect only the Yellow and Green wires is for the IntelliFlo pump. (I don't know about the heater..)

Seems to me that you should either use the just the two wire, or 4 wire connection. Leaving off the just black (ground) make no sense to me at all, if the Red +15 volts is connected.

Thanks,

Jim R.

 

[TonyR68]

Yup. Neither the MasterTemp or the IntelliChem call for the red wire. Both specifically say only black, green, yellow.

 

[Jimrahbe]

Neither the MasterTemp or the IntelliChem call for the red wire. Both specifically say only black, green, yellow.

Tony,

Thanks, I did not know that...

I suspect they are just trying to tie the grounds together so that you don't end up with noise in the two RX-485 lines.

I can see where there might be an issue using the Red +15 volt line when it is not needed, but can't see any issue with using the Black ground wires. Most likely will work fine, without the black wire, but if the manual says to use it, I'd use it.

Thanks,

Jim R.