plc control - hvac system

outputs(0-10 V).

analog

You have a couple of unanswered questions. First, how much current does each valve draw? Second, how much current does your PLC analog module have available? Note that a relay is simply a switch, and your valve appear to be proportional, relying on a variable DC level to control their flow rate. Relays are not going to do what you want. It is very likely that you will need an analog amplifier or current buffer to increase the output current so that it can operate all 8 valves successfully. A low impedance buffer amplifier is the ticket. Then the single output can drive the amplifier, which will have a much higher input impedance, and the amplifier will drive the valves.

Cheers!

Chip Shults

thank you very much for replying, i know that each valve has got a power consumption of 3 watts, but i don't know the max amperage capacity that the plc can handle. anyway thank you very much.

it helped..

Irshaad

The 0-10v signal will not be supplying the 3 watts to each valve- that will likely be a separate 24V (or whatever) supply. You need to find out the input impedance of the valves and compare it to the PLC's output capacity. Wade