24VAC common 1769-OF4

[Narlin]

[FONT=&quot]My proposed new proportional valve diagram powers from 24VAC – 10VA (not DC) and it uses a 2-10V DC control signal. The wiring diagram shows connected the control signal DC common (neg) to the 24V AC common. [/FONT]
[FONT=&quot]Q1? If I connect the common of a 1769-OF4 to a 24VAC neg side, might I damage the OF4?[/FONT]
[FONT=&quot]Q2? Wouldn’t the AC signal, even on the common side, introduce noise to the 24V DC?[/FONT]

 

[Mickey]

I'm not sure what would happen but it does not sound good to me.

I would install an isolator.

 

[widelto]

+1 for mickey.

 

[Narlin]

I am looking for a different actuator.

 

[bernie_carlton]

Do you have a link to data on the actuator? Without knowing the data on the actuator I really can't form an opinion.

If the manufacturer shows it (the AC source and the DC reference) as a valid setup I'm not too concerned.

 

[Narlin]

LinK http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CB4QFjAAahUKEwjO9q7OwIHIAhXOPB4KHUgjAU4&url=http%3A%2F%2Fwww.belimo.us%2Fbelimo%2Fmedia%2FTechnical_Documents%2FCharacterized_Control_Valve%2FCCVTechDoc.pdf&usg=AFQjCNEbS0sGnmjSJGRKq2l-jR7RZq0WxA&sig2=QPeuHePwJ_tOZf9XYcVKaQ

If the link works? Belimo is brand. Document is CCVTechDoc.pdf. If link doesn't work, google belimo with that pdf and it will be on top.
Page 51 of 126. also Sec1:51. Same page. I don't care 2 to 10V or 4-20mA.
I called Belimo US and spoke with a Tech who said "if your controller uses half-wave its OK, but if it uses full-wave it could be a problem"
I know what that refers to wrt non-switching power supplies, but not wrt switching PS. In other words, he didn't help me.
If you could look at their wiring diagram and comment.
I'm on the East Coast and its dinner time. I'll check in a few hours.

 

[Contr_Conn]

note 3: on the same page:
Actuators may also be powered by 24 VDC.

So why not to use DC?
But I would use isolator in any case

 

[Narlin]

I wasn't attentive to the DC power option. I wonder why the tech didn't mention that? An isolator would work. Automation Direct has an FC-11 for only $90 that purports to pass thru 4-20mA. This actuator goes really slowly and so only uses 10VA - maybe a little more with DC power, but insignificant. There is a 5A power supply in the box.
In general, AC commons are connected to GND and should be stable, but i have seen plenty of ripple current and wouldn't normally connect things up that way .

 

[ASF]

I have used this type of valve before powered from both AC and DC, both worked. Although the 0VDC and 24VAC Neutral were both grounded so in principle it makes no difference whether I'm putting an AC ground or a DC ground on it - they're both bonded to earth.

Having said that, as Contr_Conn suggested, it's far better to just run it off DC so you don't spend the rest of your life explaining to anyone who comes along looking at the system after that it's OK, the manual said to do it that way

 

[BobB]

Belimo are quite common and I have no problems with them. I run the 24VAC side through an isolation transformer and the 4-20ma signal straight out of an Omron PLC analogue card. Neither the secondary neutral of the isolation transformer of the negative of the 24VDC switch mode power supply are grounded but are allowed to float otherwise isolation is lost.