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48-500W PoE 802.3af Voltage

I've been looking through the tech specs, but it doesn't detail the PoE 802.3af voltage? It does for the 802.3at PoE+, but not basic PoE?

 

Appreciate it's a standard, but can someone confirm what voltage range is covered?


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Re: 48-500W PoE 802.3af Voltage

It does both 802.3at/af (auto sensing). Max voltage is 57V, with a max draw of 34.2W. Anyhow, see the datasheet HERE. I'm currently powering UBNT and non-UBNT 802.3af gear off my US-48-500W.

 

Oh, fwiw, up to 27V passive, max 17W. If that mattered at all.

 

Cheers,

Mike

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Re: 48-500W PoE 802.3af Voltage

It does both 802.3at/af (auto sensing). Max voltage is 57V, with a max draw of 34.2W. Anyhow, see the datasheet HERE. I'm currently powering UBNT and non-UBNT 802.3af gear off my US-48-500W.

 

Oh, fwiw, up to 27V passive, max 17W. If that mattered at all.

 

Cheers,

Mike

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Re: 48-500W PoE 802.3af Voltage

Thanks for the reply Mike.

 

I read the datasheet, but didn't see anything about the voltage for 803.2af? In particular, does it cover 48v?

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Re: 48-500W PoE 802.3af Voltage


@WannabeMKII wrote:

Thanks for the reply Mike.

 

I read the datasheet, but didn't see anything about the voltage for 803.2af? In particular, does it cover 48v?


You're welcome.

 

It actually provides slightly over, 50-57v, to account for line drop, which is common with many vendors.

 

Cheers,

Mike

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Re: 48-500W PoE 802.3af Voltage

Hi Mike. Ah, OK. So we've a device that requires 48v, would 50v cause any issues?

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Re: 48-500W PoE 802.3af Voltage

[ Edited ]

@WannabeMKII wrote:

Hi Mike. Ah, OK. So we've a device that requires 48v, would 50v cause any issues?


The 802.3af standard requires that devices support up to 57V of power, so its perfectly within spec.

 

Cheers,

Mike

 

ADDITION: for example, see HERE. Actually for 802.3at but has 802.3af info.

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Re: 48-500W PoE 802.3af Voltage

That makes sense, but in theory, could the extra 2v potentially cause an issue?

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Re: 48-500W PoE 802.3af Voltage


@WannabeMKII wrote:

That makes sense, but in theory, could the extra 2v potentially cause an issue?


Well, if the device is 802.3af compliant, it would be designed to support up to 57V so when it's receiving 50V that would be within the device's own spec. So I'm a little confused. We are asking about 802.3af compliant devices right?

 

Cheers,

Mike

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Re: 48-500W PoE 802.3af Voltage


@UBNT-MikeD wrote:

Well, if the device is 802.3af compliant, it would be designed to support up to 57V so when it's receiving 50V that would be within the device's own spec. So I'm a little confused. We are asking about 802.3af compliant devices right?

 

Cheers,

Mike


Sorry, I'm not trying to cause confusion, it's just the product we're potentially going to be powering is 802.3af, but they also advise that it requires 48v and if something goes wrong, I don't want to be stuck with a £1,200 paperweight...

 

So you see my situation and reasoning for the questions?

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Re: 48-500W PoE 802.3af Voltage


WannabeMKII wrote: Sorry, I'm not trying to cause confusion, it's just the product we're potentially going to be powering is 802.3af, but they also advise that it requires 48v and if something goes wrong, I don't want to be stuck with a £1,200 paperweight...

 

So you see my situation and reasoning for the questions?


Fair enough. As I've said, if it's 802.3af compliant it would be fine. That is my personal opinion (even knowing it's 50v output). They do have to support the input range to be compliant to the active PoE standard. There is the signature detection process when you first connect the device. If it isn't compatible then it will not power up. 

 

If it was passive 48v only, with no support for active PoE (802.3af/at), it would usually require some form of proprietary PoE injector. It would not power up if it was a proprietary method. 

 

Do you mind me asking what the device is? If you'd prefer, feel free to PM me. I could double check with the hardware team.

 

Cheers,

Mike

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Re: 48-500W PoE 802.3af Voltage


@UBNT-MikeD wrote:

@WannabeMKII wrote:

Hi Mike. Ah, OK. So we've a device that requires 48v, would 50v cause any issues?


The 802.3af standard requires that devices support up to 57V of power, so its perfectly within spec.

 

Cheers,

Mike

 

ADDITION: for example, see HERE. Actually for 802.3at but has 802.3af info.


This is super helpful to understand.  I was looking at the AP Pro and it says 48v, but then this said 50V, so I was a bit concerned.  Though it seemed silly that the AP Pro wouldn't be compatible with the Unifi Switches.

 

Thanks.

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Re: 48-500W PoE 802.3af Voltage


@UBNT-MikeD wrote:

Oh, fwiw, up to 27V passive, max 17W. If that mattered at all.


Wait 24v "passive" PoE on UniFi switches goes up to 27V?

 

I thought 24V ubnt devices wouldn't accept more than 25V-26V or so without letting the smoke out?

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Re: 48-500W PoE 802.3af Voltage

I have ran a few things on a DC load around 28 volts .  I'd be afraid to get to close or over 30.

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