LRL wrote: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)
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1 Gig radios or 802.3af/at devices should report:Pair 1: OK
Pair 2: OK
Pair 3: OK
Pair 4: OK
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If the cable diagnostics reports pair length mismatches this is an indication of damaged cable that has been kinked or stretched. - REPLACE IT