Current draw on MCC's and G650's

[Axelman]

I need to spec a UPS for an installation where we have a mixture of one MCC cabinet with 5 carriers plus 6 x G650's.
The MCC cabinet is existing and is a 48VDC and I know that G650's can be powered by 48VDC as well.
I need to find out what the load will be of fully loaded carriers. I did find some figures but they look obscenely high:

G650 - 13.9 Amps x 6 = 83.4 Amps
MCC - 58.3 Amps

A total of 141.7 Amps!!! If these figures are true, then the client will need his own nuclear power plant on site!

Can someone confirm / deny these figures? As usual, Avaya documentation is not the best.

Thanks in advance....

 

[phonesrus]

You must realize that these are maximum current ratings, if every phone on every carrier and all trunks were in use, and the system was recharging internal batteries, all of which is a virtual impossibility. Find an electrican with a clamp-on amp meter and have them check the average current draw during your busiest hours at the breaker box, or some other accessible point. Then calculate your load and required run time for a more realistic figure.

 

[Axelman]

Thanks mate.

I do realise that this is 'worst case scenario' but what figure shall one use to calculate a realistic scenario?
I don't have the option to measure the load at the moment because it would mean a power outage while I do this and the site is a call centre for emergency services (critical).

I was hoping that someone had some realistic specs out there....

 

[phonesrus]

If you have an electrican with a clamp on ampmeter it does not have to break the circuit, it is inductively coupled. You only need access to the hot lead (+) to get a reading.
Apart from that, a reasonable factor would be 33 to 35% on the high side and 15% on the low side. It entirely depends on the maximum number of active users and call volume at any given time and the amount of hold over that you want. May I take it that this is a non USA installation, based on the 48 volt mains?
If you havn't done so you might check the web sites for a couple of UPS vendors, I have seen charts there for various applications, which might give you some insight.

Are the 650's in different locations or co-located with the MCC. If they are co-located, and this is an emergency services facility then a UPS and back-up generating unit would be a more realistic scenario. But, I am second guessing you probably.

 

[Axelman]

I never realised that the load can be measured without breaking the circuit. If so, I can probably get a sparky (Electrician) to check it.
You're correct, this is an Australian installation. I might have a talk to one of the local UPS suppliers as well.

 

[nohuhu]

Axelman,

http://www.powerware.com/avaya/

, there's an ups calculator tool available.

 

[4merAvaya]

You stated that this is a -48 volt system. Typically, there are load meters installed in the charging/control panel. That should provide the actual current draw now. You can't use an amprobe on a DC circuit. Don't forget, that the amperage on a -48 volt system will be substancially higher than a commercially powered system.

Kevin

 

[Axelman]

Ouch! If thats the case, I'm back to square one:
There is a load meter on the front and the existing system draws 31 Amps. But we are changing it to retain one of the three MCC cabs and replacing the other two with 6 x G650 gateways. Hence the need to find specs.