adccommunitymod (AutomationDirect) asked a question.
Created Date: August 27,2015
Created By: Bob S BN
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So I have a small application here, and wondering if I could get some past experience/insight. I need to install a temperature monitoring and controlling system. The monitoring system (type k TC, Solo Controller, Lights) will be a few feet from the TC, but the valve I need to control is 140 feet away by conduit. I had planned on using the 4-20ma output Solo, but they are out of stock. Can one get a reliable 0-10volt signal and 24vdc valve actuator power through the same conduit? I was looking at the 18ga 2 shielded twisted pair cable from AD. Or, I could run seperate power and control cables, but they would be in the same 3/4 " conduit. What's anybodies thoughts on this. Thanks,
Created Date: August 27,2015
Created by: scott.lawrence
I have one set-up in which a 4-20mA valve is about 80 ' from the enclosure, and it works fine using #14 THWN for both the power (+24v) and signal return.
the last time I checked the NEC, you can mix voltages/current in the same conduit
provided all wires shared the same insulation.
Created Date: August 27,2015
Created by: Bob S BN
Thanks for the reply Scott, but what I'm wondering about is using 0-10 volt signal instead of 4-20ma because AD is currently out of stock on the 4-20ma output SOLO controller.
Created Date: August 27,2015
Created by: scott.lawrence
in another application, we are using a 4-20mA signal to a steam valve, and at the valve itself, there is a 500 OHM resistor across the input terminal and the negative, effectively giving a 2-10VDC signal.... that valve is about 90 ' away from the panel.
Created Date: August 27,2015
Created by: Bob S BN
If I could buy a controller today that would output 4-20ma (like I would prefer to do) , the valve I am connecting to (belimo) also would require adding a 500 ohm resistor at the valve end to convert the signal to 2-10 volts that the valve is actually built for.
The problem is Automation Direct is currently out of stock of the SOLO SL9696-CRE controller that outputs a 4-20ma signal.
What I am wondering is if anyone has run 0-10 volt analog signal 140 feet in a conduit with nothing but the 0-10 volt and 24vdc valve power, because if it would work ok, I could buy the SOLO SL9696-LRE instead.
Created Date: August 30,2015
Created by: ControlsGuy
I 've run 0-10V sensors a hundred feet or more (which means the 24VDC and 0VDC are actually inside the shield with the signal wire) and it was fine. I'd prefer 4-20 for better noise immunity, but some sensors are only available in 0-10V, and it doesn't seem to be a problem.
I think you'll be fine, but just run enough wires to work on either 4-10ma or 0-10V, and try the 0-10V Solo. On the off chance it doesn't work you have 30 days to return it and by then the 4-20ma unit may be in stock, or you can order one from Auber Instruments (dirt cheap and seem to work fine).
Created Date: August 31,2015
Created by: Bob S BN
Thanks for the input. Since it took a while to hear from anyone that thought this might work, and the equipment relocation got moved out a couple weeks, I already had ordered the 4-20ma version, and if it ships anywhere near the Sept 9 date the AD website gave, all will be OK.
Thanks Again,
Created Date: August 31,2015
Created by: artonpaper
I have (some) experience with 0-5VDC on oil & gas well site pads powered from solar panels. Low power consumption is critical, hence the 0-5VDC as opposed to 4-20mA. 140 ft. has not been a problem.
Art
Created Date: September 07,2015
Created by: dieselvette
I 've used 0-10V in places it should never work (according to the masses) because of noise, and even in metal conduit with power conductors, etc. We only have a few rules: Always shielded cable, all shielding grounded at one common point, sensor-end or splices in shielding always insulated to prevent accidental contact to ground.
I think there are very few technicians who fully understand how to diagnose "noise " issues and they simply fix possible problems until the symptom goes away (ha, kind of like medical doctors). In theory 0-10V is more susceptible to noise, and I'm sure for some techs experience proves that, but I often wonder if using 0-10V is blamed more often than it should be.
Created Date: September 08,2015
Created by: artonpaper
Noise is very difficult to figure out.
Your experience is same as mine, doctors that is...
Art
Created Date: August 27,2015
Created by: Bob S BN
So I have a small application here, and wondering if I could get some past experience/insight. I need to install a temperature monitoring and controlling system. The monitoring system (type k TC, Solo Controller, Lights) will be a few feet from the TC, but the valve I need to control is 140 feet away by conduit. I had planned on using the 4-20ma output Solo, but they are out of stock.
Can one get a reliable 0-10volt signal and 24vdc valve actuator power through the same conduit? I was looking at the 18ga 2 shielded twisted pair cable from AD. Or, I could run seperate power and control cables, but they would be in the same 3/4 " conduit.
What's anybodies thoughts on this.
Thanks,