HP Power Supplies in Parallel

[algerdes]

"Don't ..." seems to be a word people use a lot, not only around their children, but also around here when it comes to use multiple power supplies.  There comes a time when "Don't" doesn't cut it!

I'm mounting 3 HP HSTNS-PL18 power supplies in one cabinet, then connecting all three together in a bus/parallel setup.  All 12vdc power (vdc +) will come from one bus bar and all 12vdc negatives (vdc -) to another.

I know that this has been done with the larger Meanwells, and in HP server racks where these very units are combined.  The Meanwells don't require it, but ... I am trying to figure out if the HP PS units require a common control line.  If so, which of the connections on the back of the PS gets connected to each?

If you have used multiple HP Server PS units, in a bus/parallel, did you have a third line connected between each PS?

Thanks in Advance!

ALG

[gunther]

One thing to keep in mind is that if one of the power supplies fails in a way that causes that supply to short VCC to ground, the rest of your supplies will not like it.   Best case is they shut themselves down, worst case is a Lotta amps from the other supplies all going through a short that is probably glowing red and burn things.

[algerdes]

A thought to keep in mind, for sure.  Thanks.

[pixelpuppy]

causes that supply to short VCC to ground, the rest of your supplies will not like it.   Best case is they shut themselves down

I'm pretty sure that all power supplies which support paralleling also have over-current protection built in.  

Anything is possible, I guess, but that is a failure mode that is extremely unlikely in the real world.  

worst case is a Lotta amps from the other supplies all going through a short that is probably glowing red and burn things.

That's what fuses are for.   If you don't fuse your high-current DC power feeds then that's a risk you choose to take.

[algerdes]

My thought process is something along the same.  The scenario of Vcc going to ground must have been taken into account when multiples of these are put into a server.  It is time to find the schematic for them and look for a shutdown system.

Besides, every power supply I have had "go bad" simply opened up.  I don't have one instance of a short.  Then again, we must plan for it.