PThree Power Supply Question

[rory 0]

I emailed them from end of last week but havent heard back yet, so thought I would ask here. Okay so I have a 12VDC PSU, will be plugged into a Surge Strip, then into a UPS with AVR .. it comes with a 2 prong power cord .. connected that to the 2 wires in the box already, but there is a green wire with one end of it screwed onto the back panel of the PSU metal case, says it is for earth ground.

 

Question is this, first there is no ground wire or pole available and wont be able to get one, but since it is being plugged into the AVR etc, is it really needed? Using Altronix in the past and even the OEM PSUs, never had to connect up an earth ground cable before. The documentation is pretty limited with the Pthree in this regard.

 

Thanks

Rory

[C7 in CA 0]

Is there another ground wire from the case to the control board of the PS? Or can you tell if the PS control board is isolated from the metal case?

 

I bet it will function ok without the ground connected. But problems will arise if the case becomes energized. In other words if a power lead became disconnected and was touching the metal case you would cause an electrocution hazard. Because without the ground the case would now have electrical "potential". Meaning if someone walked up and touched the case and the person was grounded somehow it could cause a shock. If the ground wire was connected to ground then the power lead touching the case should cause a breaker to trip. Eliminating the shock hazard.

 

If there is no building ground available it is unlikely someone walking up to the PS would be grounded, but somethings that could ground a person would be standing barefoot on a concrete floor, touching an electrical conduit, water pipe, gas pipe, ect.

 

I know some stuff about electricity but don't know a lot about electronics. But if the PS control board is also connected to the metal case it may reference that ground for voltage regulation or some other electrical magic these electronic devices do.

 

Does the AVR in the battery backup work without a building ground? What will you do with the ground prong on the power cord? I'm guessing no building ground means 2 prong outlets? In buildings without a ground I change out the outlet with a GFCI outlet. They are about 10 bucks here in the States and do a good job of protecting against shock. Plus it gives me some place for my ground prong. But I don't know if they give a proper ground reference for electronics that may need it.

[Lolo Wolf 0]

Rory, electronic devices/trans. that are supplied with 2-prong AC cords. refered to as double-insulated, are supposed to be specially designed and certified to guarantee safety even when overloaded or experiencing an internal component failure. They are common in consumer electronics and low-power equipment. However dependent on the class of the transformer and as C7 in Ca says, it is a good idea to bond metal boxes as there is a potential they could be come energized due to mechanical failure or tampering, I bond all my power boxes, hardwired to a dedicated circuit at the panel.

[rory 0]

C7, there is just the 2 prong lamp type cord that came with the PSU, no ground on it. The UPS etc are all standard 3 prong. The ground wire Im talking about is just a short green wire that has one end of it screwed to the back of the case, inside, and the other end is just bare. The room where it will be located is all carpeted. I dont know much of anything about high voltage unfortunately, and kind of paranoid about it also. Bottom line is I dont want a fire.

 

Lolo, I understand what you are saying, however down here most electrical is all messed up from lack of enforced codes, so it sounds like unless the building's electric is first redone, its probably not worth it in my case? The amount of bare live electric I saw as I was in the drop ceiling was frightening, almost got shocked several times! Guess thats why we dont ground the alarm panels down here. I use to get hit so many times up on the attics when doing alarms .. people just add in lights and such and leave the live wires tied together without any kind of protection.

 

I guess basically, is this any different than an alarm panel would be? If not then I think I will be okay with out it, in this case.

[C7 in CA 0]

Yep, I understand the ground you are talking about.

 

So the electrical outlets have 3 prongs? did you test the outlets for ground?

 

Use something like this to easily test outlets:

 

 

 

If the outlet has a good ground you can use this device to easily ground your devices:

 

 

You plug this into the outlet. The recessed hole you see in the middle is a screw that replaces the faceplate screw on the outlet to hold this in place. Then you use the wing nut to clamp your ground wire. It uses the ground prong of the outlet which would be better then nothing...

 

http://www.ditekcorp.com/product-details.asp?ProdKey=24

[CollinR 0]

I just got one of these the other day!!!

 

WTF were they thinking!

 

 

I don't think I'll be buying another unless they start showing this on the spec sheets.

[CollinR 0]

Think this may be designed in to prevent ground loops?

[Lolo Wolf 0]

Rory if you are crawlin through a attic and see bare wires tied together all over the place a good idea to move on, all splices should be boxed and (with faceplate/cover)... exposed to allow access, I too have encountered a lot of issues with addons from clients even splices buried in walls....trouble for sure and not worth my time to correct other peoples dangerous mistakes, aside from the liabilities your life is more important than a cam job. In so far as the 2prong plug you can use it, the green short ground marked earth is for bonding/protection, if you were to hardwire or attach to a conductive building surface or outdoor box I would bond. Remember in order for a lot of protection devices to function to spec they require a working building ground, most UPS have a diagnostic led to report a building wiring fault.

[rory 0]

Lolo, thanks, I'll give it a try, either way its probably better than the 4 channel OEM one that is there now.

 

Colin, what did you just buy?

 

C7, interesting .. guess I could check around town, see if anyone has one of those.

[RickA 0]

Or replace the two wire lamp cord with a three wire ground cord, is not going to help the original wiring, but helps if your using a well wired cicuit.

[CollinR 0]

I bet the plugin was an afterthought, it looks as though they intended for it to be hardwired in via conduit.

 

There is no way to secure the lamp cord either, you just have to tie it in a knot and not fully knock out.

[RickA 0]

Usually use a cord plug, can get them with grounded cords at electrical supply.

[CollinR 0]

Yeah but like every other supplier provides a grounded cord so when buying a Premere Power power supply you must add in that cost and the effort to aquire it.

 

Further I somewhat question if the device is even up to code, you have HV on the LV side of the barrier. The transformer doesn't mount with the primary directly connected to the barrier through a conduit, it has 14 gauge leads.

 

I think it's MG Electronics I have had good luck with in the past.

[Lolo Wolf 0]

Collin, you are correct on the hardwire, the HV should never be within contact distance to any LV and entrance should be isolated thru conduit with a provided knockout for entry-safe practice (HV wire could energize a LV wire due to a connector failure) aside from boxes Ive seen that and other mess before on sites ,lots of people doin improper HV lV wire mix within same conduit fills then they wonder why they get written on a inspection

[rory 0]

Ok yall lost me .. anyway, Ive used Altronix in the past without ever having to worry about this green ground wire, even with the 4 channel OEM PSU I just used it had none of that. I think Im going back to Altronix ..

 

When mounted to a sheetrock, wooden, or concrete wall, inside a building, will this green ground wire prevent fire and/or ground loops/interference; codes dont bother me as there really are none here. ..

[Lolo Wolf 0]

Rory, all the altronix outdoor nema boxes I use also have binding nuts for ground, the 2prong AC cord is fine as long as it is approved for the device and you keep the conects apart from the LV side of the transformer,if you choose to bond the box that is your choice, the last one I did called for separate entrances for the PTC outputs from the non-power limited, pulled the ac in on the other side keeping all AC in and LV out isolated three individual conduits, I use mostly Altronix and they have stood up well, used some 24vac Preferred Power Products for indoor work and their boxes are well thought out with provided knockouts and separation panel, glad to see you made it through that last big storm....

[rory 0]

Yep, I don't do any outdoor boxes though, this is all indoors.

 

Got a question though, why they made the knock outs on the Pthree so hard you need a hammer to break them through

 

I do like the Pthree's separated panel thing though. One of their techs was also a member on this forum at one time.

[Lolo Wolf 0]

smack it with a punch, for the altronix which doesnt provide them I just pull out the old Kwik stepper and put them where I want them anyway

[rory 0]

LOl .. first I was trying a screw driver and just jicking it like we do the holes in the alarm panels .. well that didnt work