# Running PoE with UPS dc



## Anoth (Oct 27, 2021)

I would like to add one new UPS dc protected outlet ckt and one existing ethernet PoE cat7 cable parallel in one existing conduit around 20 feet to an existing outside network breakout 12 inch junction box. The ups ckt addition is for for three 45w PoE injector brick loads to sit in that box (for 3 other downline PoE splitters switches) and one PoE cat 7 from a PoE switch on that same UPS source (existing poe camera). 

Considering the existing 3/4" conduit, perhaps using 14awg cable with existing cat7 ethernet or use single THHN conductors for 120vdc if necessary for sizing space. Cordcaps and ground.

Not AC.

All PoE work for below a roof eave for breakout from an IT closet below which is thru 8 inches of 1915 brick with one existing 3/4" emt. One LB and an offset emt connector in a straight run vertical to the existing JB can. Injectors are Ubiquiti poe-50-60-w for context. 1500va UPS off the shelf inside closet powers a couple ethernet switches.

Any caveats or experiences?

120vdc
48vdc

Thanks!


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## MikeFL (Apr 16, 2016)

Members: OP is legit. Please contribute if you have experience/ wisdom/ advice to share. Thanks!


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## SWDweller (Dec 9, 2020)

Sorry I have never tried to sheild DC voltage from communications. Would not know where to start.


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## Almost Retired (Sep 14, 2021)

SWDweller said:


> Sorry I have never tried to sheild DC voltage from communications. Would not know where to start.


me neither. if the dc is clean and steady will it actually impact the comms?


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## McClary’s Electrical (Feb 21, 2009)

I don’t understand the concern. A standard POE injector at the point of use is not sufficient? Use CAT 8 if you’re worried about voltage drop. It’s good for 40 gigs at 330 ft. POE should not be a problem


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## McClary’s Electrical (Feb 21, 2009)

Never mind I re read it and it makes more sense. There should be no concern about using Thhn. It’s 600 volt insulation has nothing to do with AC or dC, you’re fine. I would be more concerned with your choice of ubiquity than a thing else. lol.


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## paulengr (Oct 8, 2017)

McClary’s Electrical said:


> Never mind I re read it and it makes more sense. There should be no concern about using Thhn. It’s 600 volt insulation has nothing to do with AC or dC, you’re fine. I would be more concerned with your choice of ubiquity than a thing else. lol.


Why? Ubiquity is one of the best systems out there unless you want to waste money on Dragonwave.

When Ubiquity started at the time the Atheros chipset was known to have vastly more capability than if you just used it as a WiFi 802.11A/B/G as intended. Ubiquity got far more bandwidth and power out of it and did meshing almost before anyone else using Atheros chips in sort of “raw” mode. Their radios were small and inexpensive. The only real downside is the Atheros chipset wasn’t particularly good at not bleeding all over the band. That was 15 years ago or more. They cleaned up the channel issues and have perfected MIMO to the point where Dragonwave is now the underdog. Wireless ISPs out West use thousands of them.

I’ve used it all the time in 24x7 continuous operations. No issues.

The only complication is the original Airmax is the original product. Unifi is the old Motorola Canopy system. Unifi LOOkS like it requires a server to work and initially it does but once set up it doesn’t need it except for maintenance. Airmax is just solid.

There are minor issues that you run into from time to time but there are always easy workarounds.

Most good commercial/industrial radios use PoE. It’s just easy. As far as voltage drop it is not a problem up to the limit on Ethernet (100 meters). The injectors modulate/control the output so voltage dips within UL standard conditions (110 V +10%/-15%) are designed in.


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## cuba_pete (Dec 8, 2011)

Anoth said:


> I would like to add one new UPS dc protected outlet ckt and one existing ethernet PoE cat7 cable parallel in one existing conduit around 20 feet to an existing outside network breakout 12 inch junction box. The ups ckt addition is for for three 45w PoE injector brick loads to sit in that box (for 3 other downline PoE splitters switches) and one PoE cat 7 from a PoE switch on that same UPS source (existing poe camera).
> 
> Considering the existing 3/4" conduit, perhaps using 14awg cable with existing cat7 ethernet or use single THHN conductors for 120vdc if necessary for sizing space. Cordcaps and ground.
> 
> ...


You'd be hard-pressed to have any problem with high-frequency interference as long as your cat7 connectors are properly terminated/bonded. Common mode interference could be reduced by using electrically-common grounding/bonding connections i.e., using the same source for all of the devices and grounding/bonding them in a single-point configuration (this is above and beyond). This way you'd hit the three big ones: ground, bond, and shield.

If you're really that interested or concerned you can take readings with/without before/after each device is connected to the system, and include the network active/inactive, etc. A short real-world white paper/report could be added to the ET Electrical Resources section. Scope readings would likely be most beneficial.


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## Anoth (Oct 27, 2021)

Thanks for the replies. I like this site!

As a veteran industrial automation electrician, instrumentation / SCADA programmer and IT Systems Analyst for 40+ years I still concern myself with conduit fill rules. Shielding one end and traditional grounding. And especially surge.

In this question I was trying to wrap up a big network branch changeover with 120vdc from a UPS (THHN) along side one or two flat cat8. to fill a 3/4" 15 foot section up from an IT PoE closet switch area inside an old brick house & into an outside metal 12x12 junction box up at 1st floor eave and beyond. 

My concern was:

Interference - no AC, so no code issues I figured.
Ability to fit the three 120vdc UPS fed conductors and ethernet 48vdc PoE cables in an existing 3/4" emt straight run.

The jb will have a 6 outlet strip, perhaps no necessary surge protection there. This strip will power:
Ubiquiti USW-MINI, which feeds ethernet to Ubiquiti POE-50-60-W (3) to run to 3 areas' USW-FLEX partners that pass PoE to multiple cameras and UAP-IW-HD and UAP-FLEX-HD AP's, and other non PoE devices along the way. All cat.8. The PoE and other ethernet devices are temporarily running ad hoc and work fine at cat.6e. The brick house being 105 years of age I am lucky to have good quality receptacles but had at one time very bad store bought wifi capability. 

By using trunk branches to form hard wire uplinks from a UDM-US/UAP collection along with Ubiquiti BEACONs the wifi is now a strong durable and managed MU-MIMO 4x4 mesh for a full property in/out connect ability. 

Concerns in shielding with adequate bonding to a single ground will be the next step in planning, so 2 IT equipment sources each with it's own location, via one ethernet run inside as a backbone between each location with UPS around 1500va (2 services) where somewhere grounding might need to be isolated...there will be no AC except the UPS's source ckts. I also have to figure in cable internet service's bond which is foreign. Additionally no 120vac powered cameras will be in the mix. They will remain wifi only.

Thanks, the semi-pro Ubiquiti IS quirky.. but the cost/IPS/IDS and console outweighed home wifi inadequacy and a whole property surveillance high frame rate speed runs nicely.

So my next research will be good grounding (mostly PoE cat. 8 runs) outside along the exterior eaves under a 105 yr. old tin roof (lightning target possibility). All of this outside routing of alot of endpoints is mainly at 2nd floor eaves. This will keep inside devices most likely in the servers/service entry (cable) UPS and the second closet 120vdc UPS source as the outside section.

CHEERS!


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## splatz (May 23, 2015)

Anoth said:


> Interference - no AC, so no code issues I figured.
> Ability to fit the three 120vdc UPS fed conductors and ethernet 48vdc PoE cables in an existing 3/4" emt straight run.


All due respect this is just some over the top overthinking, like next level stuff even for an IT guy. 

I would bet dollars against doughnuts that, code issues aside, you'd never be able to measure any difference in performance / error rates at gigabit, with Cat6 UTP running alongside THHN for 15' drawing only enough 120VAC current to power the power supplies for the IT equipment. Like so skeptical that you'd have to show me rather than tell me. I have lighting control systems that have cat5e UTP running inside 480/277 VAC panels that haven't so much as burped in going on ten years. Now navigating the code to make it compliant, there was a little bit to that, and a bit of back and forth with the inspector. 

I missed where you're getting 120VDC from your UPS rather than 120VAC, but there's nothing that lets you off the hook for code requirements because the power is DC rather than AC. (Now it may get you off the hook with interference, but that's not a code issue.) Using a listed class 2 power supply lets you off the hook for a lot of things but it's not like it's exempt from the code, so much so that sometimes you have more flexibility just wiring the low voltage power limited as if it were line voltage and not using those differences. But this is almost certainly not a listed class 2 power supply.


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