Powered RB1100AH?

[LRL]

Has anyone powered an RB1100AH from the WS? The draw seems to be 12-13 watts, but I'm concerned about what ti will do full load. I know the fuses will pop at .75amps or about 18 watts

[sirhc]

Actually with 24V or 48V POE selected using pins 4, 5, 7, 8 you can power a radio up to 25+/- watts constant draw with no problem or 50+/- watts constant draw with 48VH using all 4 pairs.

In the image below I am powering an SAF 106 link.

CLICK IMAGE BELOW TO SEE FULL SIZE

SAF.png (112.67 KiB) Viewed 17729 times

[LRL]

I thought I'd read somewhere that the fuses were limited to 700-750mA. Is that correct? If that is, is that per pair or per conductor?
25 watts at 24v means slightly more than 1 amp(1.0416) . That would translate to 50w on 48v but that doesn't account for the two added pairs and their current capacity.

If I try to power a CCR-1009-8g-1s it powers up fine and runs for a while, but eventually it stops and powers for a second then off for a few, and so forth. This seems to me to be a resetting fuse. The UI shows the CCR is taking 17-19w, well under the 25.

I don't mean to be critical, just trying to get a firm understanding.

Thanks,

btw, love the power graph

[sirhc]

I thought I'd read somewhere that the fuses were limited to 700-750mA. Is that correct? If that is, is that per pair or per conductor?
25 watts at 24v means slightly more than 1 amp(1.0416) . That would translate to 50w on 48v but that doesn't account for the two added pairs and their current capacity.

If I try to power a CCR-1009-8g-1s it powers up fine and runs for a while, but eventually it stops and powers for a second then off for a few, and so forth. This seems to me to be a resetting fuse. The UI shows the CCR is taking 17-19w, well under the 25.

I don't mean to be critical, just trying to get a firm understanding.

Thanks,

No, the poly fuses are .5A +/- per pair constant draw with the ability to surge higher when needed. So this is why the 48VH ports using 2 pair for positive and 2 pair for negative are capable of 1.2A +/-.

Now the Ethernet transformers are limited to 720mA or .72A per pair. This means that "if" you draw more than .72A per pair on your POE for an extended time it will damage the Ethernet transformers.

Now manufacturers always have some margin of safety in their specifications so .72A is what they say they can handle all day everyday.

These Ethernet transformers are also the weakest link in a chain when a dead short occurs as .5A poly fuses are rated to deliver .5A all day everyday under normal temperatures (poly fuses are effected/influenced by temperature) but can handle well over 1A of inrush or surges which is obviously over the manufacturer's rating pf .72A.

We are looking into higher rated transformers but unless you dead short your switch for kicks you are fine.

Now with a ToughSwitch when I shorted a port at my WISP it most often fried the entire switch, however with the WISP Switch it will cause the switch to reboot if it is 48VH port and sometimes on the 24V and 48V ports as well but it will not fry the entire switch, at least not with our testing. You will however risk frying that port's Ethernet Transformer (roll the dice, obviously 48VH ports have the worst odds).

This is why I also make my installers un-power POE ports before they mess with the cable or radio on that port and always run a cable diagnostic BEFORE you restore power and NEVER restore power if the diagnostics report a "CROSS SHORT" meaning one pair is shorted to another pair or you will damage your equipment!!!

Regular airMAX radios should report:
Pair 1: OK
Pair 2: OK
Pair 3: SHORT (this is the positive pair)
Pair 4: SHORT (this is the negative pair)

CLICK ON IMAGE BELOW TO MAKE FULL SIZE

cd2.png (26.02 KiB) Viewed 17720 times

1 Gig radios or 802.3af/at devices should report:
Pair 1: OK
Pair 2: OK
Pair 3: OK
Pair 4: OK

CLICK ON IMAGE BELOW TO MAKE FULL SIZE

cd1.png (23.27 KiB) Viewed 17720 times

If the cable diagnostics reports pair length mismatches this is an indication of damaged cable that has been kinked or stretched. - REPLACE IT

[LRL]

Thanks for that clarification.

As I understand it then. The poly fuses are rated at .5amp and the transformers per pair are rated at .72amp. The formula for watts is volts X amps = watts.

In the 24V scenario the transformer rated limit is 24X0.72=17.28watts and the fuse limit would be 24X0.5=12watts

In the 48V scenario the transformer rated limit is 48X0.72=34.56watts and the fuse limit would be 48X0.5=24watts

In the 48VH scenario there are two pairs being used as positive and two used as negative, transformers rated limits are 0.72X2=1.44ampsX48v=69.12watts and the fuse limit would be 0.5X2=1ampX48v=48watts. I can see why 50+/- because the current change for a few watts either way is so little and given the safety margin not accounted for.

I don't see how the 24V is rated for 25watts given the equations above.

From the information you've given me I seem to be right at the limit on the RB1100 (fuse wise) and over the fuse limit and transformer limit enough on the CCR to understand why it was having difficulties.

[Dave]

On the RJ45 ports that have the 48HV, their are actually 0.75 amp fuses. No matter if you are running 24 or 48 volts, on the ports that have the 48HV option, you can pass up to 0.75 amps per wire pair (albeit the transformers are rated for 0.72 amps, the 0.75 amp fuse is as close as we can get).

So, on the 48HV ports, per wire pair, you can pass 36 watts at 48Volts, and 18 watts at 24 volts. For the non 48HV ports, the fuse it 0.5 amps, so you can pass 24 watts at 48 volts, and 12 watts at 24 volts. So, you can pass up to 72 watts on the 48HV using two pairs.

[LRL]

AH, that makes sense. Thank You for that.

[lligetfa]

per wire pair

Dave, could I please get clarification on what you mean by wire pair? Do you mean two conductors in parallel both carrying the same polarity (fe 4&5) or one + and one -?

Do you have a schematic drawing?

[sirhc]

per wire pair

Dave, could I please get clarification on what you mean by wire pair? Do you mean two conductors in parallel both carrying the same polarity (fe 4&5) or one + and one -?

Do you have a schematic drawing?

When he is saying per wire he is meaning the 2 wires of the same color bonded together.

There are 4 pairs in the CAT5 Cable

When using 48VH on the special ports
Orange - carriers positive voltage together - BONDED TOGETHER for DC voltage
Green - carriers negative voltage together - BONDED TOGETHER for DC voltage
Blue - carriers positive voltage together - BONDED TOGETHER for DC voltage
Brown - carriers negative voltage together - BONDED TOGETHER for DC voltage

When using 24V or 48V on any ports
Blue - carriers positive voltage together - BONDED TOGETHER for DC voltage
Brown - carriers negative voltage together - BONDED TOGETHER for DC voltage

DC.png (55.43 KiB) Viewed 17690 times

[sirhc]

Also those are recommended constant draw limits, meaning guaranteed to work and not damage your switch.

See below I have a 48V Standard in port 6 pulling 24-26 watts powering an SAF 106 link.

CLICK IMAGE TO SEE FULL SIZE

dc2.png (116.85 KiB) Viewed 17689 times