RS485 substitutes...

silentboarder69 · Nov 23, 2013

Hi,
I'm doing an installation of an air source heat pump system for a customer. In the specs, the user interface, heat pump and cylinder need a cable connecting each other. This is specced as RS485. My local supplier doesn't stock this, can I use 1.0mm 5 Core PVC Flex 3185Y?

Thanks in advance,

Rick

Rockingit · Nov 23, 2013

Er....confused. RS485 is a protocol, not a cable type. Are you sure you're reading the manual correctly?

silentboarder69 · Nov 23, 2013

The required controller cable is a shielded MODBUS cable RS485, for example a 4 core 1mm² 24 AWG (Nominal impedance 120Ω) Foil and Braid, which can be purchased from Dimplex as an accessory.

Rockingit · Nov 23, 2013

RS-485 - Wikipedia, the free encyclopedia

Rockingit · Nov 23, 2013

silentboarder69 said:
The required controller cable is a shielded MODBUS cable RS485, for example a 4 core 1mm² 24 AWG (Nominal impedance 120Ω) Foil and Braid, which can be purchased from Dimplex as an accessory.

OK....what you need to install is a shielded data cable. RS485 works at very low voltages (>< 200mV) and at very high speeds. If the manufacturer is recommending a particular type, as above, then the easiest thing is to buy it (or find an exact equivalent on line and buy that much cheaper).

Robotstar5 · Nov 23, 2013

Belden probably have something suitable - link

Jimsparky · Nov 23, 2013

Belden 9841. 1 * twisted pair.

rmaynard · Nov 23, 2013

I always use belden for communications on boiler and air handling systems

Guitarist · Nov 23, 2013

silentboarder69 said:
The required controller cable is a shielded MODBUS cable RS485, for example a 4 core 1mm² 24 AWG (Nominal impedance 120Ω) Foil and Braid, which can be purchased from Dimplex as an accessory.

Do that then.

FAA Greenie · Nov 24, 2013

My local supplier doesn't stock this, can I use 1.0mm 5 Core PVC Flex 3185Y?

Whatever you buy, don't use the above!!

As said above the 458 is a data cable, basically used for transmitting digital info from one device to another, or several others at high speed. These cables are impedance matched to the equipment they are linking (like Tv aerial cables do) so will have a higher impedance that 5 core flex.

In a nutshell, you need to find the right cable.....