48 Volt Dc Reading 7 Volts From Negative to Chassis

Thu Jul 25, 2019 xi:24 am

Configuration Defined-48V DC Bombardment and Earth
Telecom and wireless networks typically operate on 48 volt DC power. But unlike traditional 12 and 24 volt systems which have the minus (-) side of the battery connected to ground (i.east. called negative ground systems), telecom batteries accept the plus (+) side of the battery connected to ground, called a positive ground system, besides designated equally "negative 48 volt". In this configuration the minus side of the battery becomes the "hot" conductor and the + is no longer hot, rather it'southward at zero potential as it is connected to basis and referred to as the "common" or "render" wire. Despite its complexity and propensity for confusion, described below, "neg" 48 volt is the common selection in DC ability for wireless networks.

History
Why is the positive side of the DC circuit connected to ground in telecom applications versus negative basis used, equally used, in automotive and other industrial dc systems?

Back in the day, when Telephony equipment was existence developed, 48 was the chosen organization voltage considering it's considered safe "low voltage", and reduced amperage requirement of equipment powered at this voltage. This allowed utilize of smaller gauge wires, while still being capable of carrying power over long wire runs with minimum voltage drop as a per centum of the operational voltage. The early phone systems were configured as negative ground, this all the same resulted in corrosion on the conductors acquired by electrolysis when the + wires were subjected to wet (you can encounter evidence of this condition on your car battery where the corrosion builds up over fourth dimension on the + last postal service). To remedy this problematic condition, the systems were changed to positive ground and the destructive galvanic corrosion was eliminated by the cathodic protection provided by grounding the + side of the circuit.

Precautions
This positive footing configuration does not cause polarity to change, plus (+) is still plus and carries a positive charge with respect to the negative (-) terminal or minus. Many a brusque circuits have occurred when installers assume that when changing to positive ground, polarity changes equally a result, non true! Regardless of ground reference, connecting (+) plus to (-) minus volition nevertheless result in either a brusk excursion or reverse polarity to equipment.
Some other factor that can cause confusion (and potentially sparks) is employ of red & black colored wires. In negative ground systems, carmine is universally understood as hot and +, in positive footing, this "red wire" is no longer hot, merely is nonetheless +. Then y'all can imagine an installer continuing there with a black wire in one hand and carmine wire in the other looking at the input terminals on a "neg 48 volt" transmitter that are marked "HOT" and "RTN" request himself "What goes where?" Answer is: black to plus and red to minus, which is a fleck counter-intuitive. Thus, we recommend a common color be used for both conductors and the wires labeled with the polarity.

Another word of caution on system integrations that mix positive and negative footing equipment, Ground Isolation must be maintained between these operating system to prevent short circuits and equipment compatibility problems. In add-on, there is the event of continuity between chassis footing and organization basis; they can be common or may be isolated (called a floating footing).

NOTE: The but switch we brand that is rated for negative 48V is our WS-26-400-IDC. The ability supply in it has polarity protection so if you hook it up backwards information technology only volition not power up and not damage it. Since the unit of measurement is for positive and negative DC sites the color code of the DC input terminals is coded for positive DC sites as they are most common.

WS-26-400-IDC is this model: https://www.netonix.com/wisp-switch/ws-26-400-idc.html

Thu Jul 25, 2019 4:47 pm

A common exercise to reduce confusion on systems with both positive and negative grounded circuits is to employ iii colors.

The IEC standard for this is:

Positive: dark-brown
Mid-wire (neutral): blueish
Negative: grey

Still, as with passive PoE, there is a defacto standard using colors more commonly on manus:

Positive: red
Mid-wire (neutral): white
Negative: black

When this setup is used and your terminals are colour coded cerise and black, white is the only color that does not friction match

Negative grounded systems use red and white - red connecting to cherry terminals and white connecting to blackness terminals
Positive grounded systems utilize black and white - black connecting to black terminals and white connecting to scarlet terminals

Thu Jul 25, 2019 5:00 pm

Yes but the real trouble is people volition use one of our non ISOLATED DC switches similar the WS-8-150-DC / WS-12-DC/ WS-12-250-DC / WS-26-500-DC and simply think if they flip the polarity it will piece of work.

Well the switch volition power upwards simply as soon equally you provide power to a radio on the tower that has POE DC negative bonded to rail / chassis / belfry then POOF y'all fried the switch and maybe the radio.

Virtually radios WISPs apply such equally UBNT / MIMOSA / Cambium / IGNITE all bond POE DC negative to chassis basis and the shelter has positive bonded to ground and the cabinet ground and belfry grounds SHOULD E'er BE BONDED and then when you power up the radio you lot create a Dead Short - POOF

At negative DC sites you must utilise the WS-26-400-IDC.

Y'all E'er bond shelter / box / AC Service ground to tower footing arrangement else you volition also blow up equipment with GROUND CURRENT (Ground Loop) passing through the switch to the radio to the tower to the tower ground.

READ THE POSTS BELOW:
https://forum.netonix.com/viewtopic.php?f=17&t=5495&p=29602&hilit=Rules+of+thumb#p29602
https://forum.netonix.com/viewtopic.php?f=33&t=5496&p=29621&hilit=Well-nigh+DC+chargers+as well+bond#p29621

Thu Nov 04, 2021 four:41 pm

We are putting in a WS-26-400-IDC in a -48v site powered via an Eltek rectifier. The site has 24 & 48v hardware that will be powered via the Netonix, and other -48v hardware including backhaul radios and a switch.

I accept questions about how this should be grounded. Currently the positive ground on the rectifier and -48v hardware (switch and backhaul radios) is grounded to the tower ground every bit information technology should be on a -48v site

Should the ground on the Netonix be continued to the belfry ground also? What about the positive 24 or 48 items that it powers on the tower? Nosotros are concerned about creating a span betwixt the - and + polarities that might crusade issues and I would but like some explicit guidance on the best practices for this configuration.

Mon Nov 08, 2021 v:02 pm

dscott wrote:We are putting in a WS-26-400-IDC in a -48v site powered via an Eltek rectifier. The site has 24 & 48v hardware that will exist powered via the Netonix, and other -48v hardware including backhaul radios and a switch.

I accept questions well-nigh how this should be grounded. Currently the positive footing on the rectifier and -48v hardware (switch and backhaul radios) is grounded to the tower ground as it should be on a -48v site

Should the basis on the Netonix be continued to the belfry ground as well? What nearly the positive 24 or 48 items that it powers on the belfry? Nosotros are concerned about creating a bridge betwixt the - and + polarities that might cause issues and I would simply like some explicit guidance on the all-time practices for this configuration.

If you are using a WS-26-400-IDC at a negative DC site you do not need a rectifier, it is designed to accept -48V as it has an isolated power supply and if you hook it up backwards information technology will not harm this unit like it would the WS-12-250-DC or WS-26-500-DC which volition fry if hooked up backwards or will fry in one case you become to power radios as they exercise not take isolated power supplies. If y'all claw the WS-26-400-IDC up backwards information technology merely volition not ability up.

As far as what you can power with this unit you need to verify our POE pin-outs to insure your device volition accept the ability/polarity we are providing on the pivot outs.

Our POE pin out polarity is in the spec sheet and in many posts like this mail

viewtopic.php?f=six&t=1178#p8809

48 Volt Dc Reading 7 Volts From Negative to Chassis

"Negative" 48 Volt Power: What, Why and How

"Negative" 48 Volt Power: What, Why and How

Wiring sites with both positive and negative grounded system

Re: "Negative" 48 Volt Power: What, Why and How

Re: "Negative" 48 Volt Power: What, Why and How

Re: "Negative" 48 Volt Ability: What, Why and How

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