plc control - hvac system

[irshaad]

hello all, can anyone help me with the following problem.


my question is:

i'm using a controller, the satchwell IAC 600, it has got 4 analog outputs(0-10 V).
i need to connect 1 of these outputs to 8 modulating valves (0-10 V) . the
valves are to be connected in parallel.
is there any relay circuitry which i can use to interface the single analog
signal to the 8 modulating valves?

thanks.

--
Hasta Luego

Irshaad
(Faster than Bruce Lee)

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[Sir Charles W. Shults III]

i'm using a controller, the satchwell IAC 600, it has got 4 analog outputs(0-10 V).
i need to connect 1 of these outputs to 8 modulating valves (0-10 V) . the
valves are to be connected in parallel.
is there any relay circuitry which i can use to interface the single analog
signal to the 8 modulating valves?

thanks.

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

 

[irshaad]

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

 

[Wade Hassler]

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