Connect with us

0-10V DC Signal

Discussion in 'General Electronics Discussion' started by JayJones, Feb 14, 2014.

Scroll to continue with content
  1. JayJones

    JayJones

    6
    0
    Feb 14, 2014
    I am sending a 0-10V DC signal to a Boiler to reset the hot water set point. At the boiler, I read the 0-10V signal on the boiler terminals with my meter but on the boiler display, it shows 0V. I took the wires off of my controller that is generating the 0-10V signal and attached a 9V battery and the boiler and my meter read 9.1 Volts. I have never seen this before and I don't understand the difference between my controller signal and the battery. Seems to me if the meter reads 0-10V, the boiler should see it. I tried 10V, 9V, 6V, 3V, and 1V from my controller and each time the meter read the corresponding Voltage but the boiler always read 0V. It is unshielded wire between my controller and the boiler but I would think if that were the problem, the 9V battery would not work either. Has anyone seen this before?
     
  2. davenn

    davenn Moderator

    13,585
    1,870
    Sep 5, 2009
    hi there
    welcome to the forums

    not really sure what your definition of a 0-10VDC signal is ??

    is it varying between 0V and 10V ... ie. sometimes its in between say 7V ?
    or is it a square wave switching between 0V and 10V ?
    or is it something else ??

    what is this "controller" ? is it designed to specifically work with this boiler ?

    some clarification might help us guys help you :)

    cheers
    Dave
     
  3. Laplace

    Laplace

    1,252
    184
    Apr 4, 2010
    Have you checked your wire for continuity? Short together one end and measure the loop resistance from the other end.
     
  4. JayJones

    JayJones

    6
    0
    Feb 14, 2014
    For energy savings, we reset the hot water set point depending on outside air temperature. i.e. as the outside air temperature go from 50 degrees to 30 degrees, I am going to change the hot water set point from 140 to 180 linearly. So at 120, I will send 0V. At 180, I will send 10V. At 160, I will send 5V, and everything in between. The boiler settings correspond to this so when it sees 5V, its set point will be 160, when it sees 7.5V, its set point will be 170. In my original post I wrote that I sent 10V, 9V, 6V, 3V, and 1V to the boiler and at the boiler my meter would read the DC voltage but the boiler would not read it.
     
  5. JayJones

    JayJones

    6
    0
    Feb 14, 2014
    As far as continuity, I took the wires off of my controller that generates the 0-10V signal and put a 9V battery in place of my controller and the boiler and meter(which is hooked to the boiler wire terminals) read 9.1 V. What doesn't make since is my fluke meter will read 0V all the way to 10V off my controller but the boiler doesn't see it so originally I thought something had to be wrong with the boiler but the boiler will read 9V when a 9V battery is connected. My question is if my fluke meter says my controller is outputting 9V DC, then how could that 9V DC be different than a 9V DC battery?
     
  6. JayJones

    JayJones

    6
    0
    Feb 14, 2014
    And thanks for the welcome!
     
  7. JayJones

    JayJones

    6
    0
    Feb 14, 2014
    Another thing I forgot to mention: I took the wires off of the boiler and hooked them to a variable frequency drive and the same 0-10V DC signal from the same output on the same controller sped up and down the VFD so I know the signal is there and the wires are good based on the fluke meter and the VFD but I also know the boiler will read a 9V battery. I don't know enough about DC electricity to diagnose any further. This should be just a signal with almost no current draw but I am wondering if the boiler input could have enough draw not see the voltage. I really don't know, I'm just searching for possibilities now.
     
  8. davenn

    davenn Moderator

    13,585
    1,870
    Sep 5, 2009
    because it works on a 9V battery its possible/probable that the controller isn't supplying enough current to operate the boiler circuit

    again I ask .... what is this "controller" ? is it designed to specifically work with this boiler ?

    is it the original controller or did the original controller fail and you were hoping that this one would do the job ?

    cheers
    Dave
     
    Last edited: Feb 14, 2014
  9. JayJones

    JayJones

    6
    0
    Feb 14, 2014
    Distech is the manufacturer of the controller (part# LN-PRG600). It is a generic controller with multiple inputs and outputs. It is part of a building management system. I write code in the controller to (in this case) control a hot water system. From this one controller, I turn off and on pumps, vary the speed of the pumps based on differential pressure in the water loop, open and close valves, enable and disable the boilers, and vary the hot water set point of the boilers. We do these systems on every commercial building we get and use these same controllers. The boiler runs on a 120V circuit, all I provide is an enable which is dry contacts to let the boiler know it needs to run and this 0-10V signal to vary the hot water set point.

    If My fluke meter reads 9V DC on a 9V battery and 9V DC from my controller, why wouldn't the boiler read the same? Is there anything in DC electricity that could explain this or is this on my controller or the boiler controller?
     
  10. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    Two meters can read a voltage differently if they have a different input impedance, and it then depends on the output impedance of the voltage source. Try this, read the voltage out of your controller with your fluke meter with a 1K resistor across the output. See how that affects the voltage reading. If so, it might be that the output impedance of the controller is too high and needs to be buffered.

    Bob
     
  11. duke37

    duke37

    5,361
    767
    Jan 9, 2011
    Measure the voltages when the boiler is connected.

    Have you got the polarity correct? Much more obvious if you use an analog meter.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-