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Possible to chain multiple PDUs together?

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doodlepop_apc
Crewman
Crewman
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Possible to chain multiple PDUs together?

This was originally posted on APC forums on 11/19/2008


We have 2 AP7953 PDUs, although only 1 is currently in use (the other is a "cold spare" if you like).

However, we need more sockets and it seems to make sense to use some of the 24 on the spare AP7953... The problem is that the DC only give us 1 32A commando which is used by the live AP7953.

So... is it possible for us to power the other AP7953 via one of the 16A sockets on the live one? I mean, does such an adapter exist that would convert the IEC C19 socket to an IEC 309 socket so that we can plug the other unit into it?

I appreciate that obviously we would need to be careful about the current draw on this as it would be limited to 16A (32A PDU) but really we're only talking about using 5/6 of the sockets on the 2nd PDU (probably with no more than around 1A on each).


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doodlepop_apc
Crewman
Crewman
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Re: Possible to chain multiple PDUs together?

This was originally posted on APC forums on 12/9/2008


AP9899 looks like the closest we might be able to get to this (for some reason I hadn't managed to find that). I think the problem is that the PDU has a 32A commando on it though, so instead of "309-16A" it would need to be "309-32A" ... as far as I'm aware they're different sizes.

BUT I highly doubt that there's such a wire which takes a 16A input (male) to a 32A output (female) socket as in general it makes very little sense. Also the logic behind this was that we could save ourselves a few £ by using the existing hardware, but really the AP9899 seems a similar price to a basic unswitched PDU bar (i.e. with just a few sockets) so whatever sense it might've made at the time I asked the question, I guess the point is that it can be done cheaper / similar cost anyway - and in a much cleaner fashion.

That's aside from any electrical regulations which may (or not) apply.

Thanks for help/comments anyway though.

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5 Replies 5
mtroha_apc
Lieutenant JG
Lieutenant JG
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Re: Possible to chain multiple PDUs together?

This was originally posted on APC forums on 12/9/2008


Doodle,

Wow, didn't see the cost of that cable when I found it! Guess its true, just dumping a basic PDU into the mix would be cleaner and just as cost effective as the other.

Glad we could at least provide some insight for you!

-Mike

Cap1_apc
Lt. Commander
Lt. Commander
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Re: Possible to chain multiple PDUs together?

This was originally posted on APC forums on 11/19/2008


I'd highly recommend against this.

What you are suggesting will most likely breach several electrical codes. Will it work? Maybe...

I'd also almost guarantee that the metering functionality wouldn't work as advertised. Basically, not such a good idea.

Best bet is to have an electrician properly pull you another 32amp circuit.

doodlepop_apc
Crewman
Crewman
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Re: Possible to chain multiple PDUs together?

This was originally posted on APC forums on 11/19/2008


I would be surprised re. electrical codes since it is feeding a 16A supply to a 32A commando (not the other way around) so what can be against code about it? As for the metering... honestly I see no reason why it wouldn't work, as the voltage will remain as expected by the unit. Providing the current drawn stays within the limitations of the 16A socket the whole thing connects to I don't see anything unsafe or functionally crippling - but I'm willing for someone to point out the lack of understanding I have on these points...

Please don't misunderstand: I'm not simply stating that I'm right "it must obviously work" etc. as if I knew the answer I wouldn't have asked the question. However, I'm hoping for an answer backed by facts that I can digest and understand rather than just guesses (which I can make, right or wrong).

The extra 32A circuit is out of the question as the datacentre would want to charge another £x00/month for that. The alternative to the plan of chaining the PDUs would be to buy horizontal power bars, but it seems a bit silly spending £x00 on one of those when we already have a switched PDU spare? I'd like to take that option with unlimited funds, but unfortunately financial restrictions apply.

mtroha_apc
Lieutenant JG
Lieutenant JG
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Re: Possible to chain multiple PDUs together?

This was originally posted on APC forums on 12/8/2008


Doodlepop,

I too am not entirely sure whether this will work fully or not. I do agree with your reasoning, that theoretically you will be able to get output power via the outlets of the daisy chained PDU.

I have found some IEC C19/C20 to IEC 309 power cords which might assist you with this process. SKU's for those are AP9899 and AP9876.

You will have to keep in mind, not only can the second PDU not exceed the 16A capacity of the power cord used as well as the 16A capacity of the outlet bank that the second PDU is plugged into on the first PDU. This data will have to be carefully monitored by yourself to ensure none of the limits are exceeded.

With all this being said, this would not be a support means of using the rPDU's and if you have any problems, APC Support would in fact instruct you that this is not support and each PDU's requires it's own dedicated circuit. If you are going to do this, proceed with caution and knowing that this would void any warranties on the PDU's as it is an unsupported process. I would also recommend metering the outlets prior to plugging anything in to ensure nothing abnormal is happening to the power with the daisy chained connections you want to make.

Again, I don't forsee any huge problems, and am unaware of whether it would violate any local electical codes for you. I just want you to understand that APC doesn't test our products in this configuration, so we really can't vouch for how it would work or assist you in support if you encounter problems.

-Mike

doodlepop_apc
Crewman
Crewman
0 Likes
0
126

Re: Possible to chain multiple PDUs together?

This was originally posted on APC forums on 12/9/2008


AP9899 looks like the closest we might be able to get to this (for some reason I hadn't managed to find that). I think the problem is that the PDU has a 32A commando on it though, so instead of "309-16A" it would need to be "309-32A" ... as far as I'm aware they're different sizes.

BUT I highly doubt that there's such a wire which takes a 16A input (male) to a 32A output (female) socket as in general it makes very little sense. Also the logic behind this was that we could save ourselves a few £ by using the existing hardware, but really the AP9899 seems a similar price to a basic unswitched PDU bar (i.e. with just a few sockets) so whatever sense it might've made at the time I asked the question, I guess the point is that it can be done cheaper / similar cost anyway - and in a much cleaner fashion.

That's aside from any electrical regulations which may (or not) apply.

Thanks for help/comments anyway though.