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Old 01-13-2005, 11:10 PM
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Default RFP for POWER

It's been my experience that most colo providers offering space by the rack include some power connection for each rack bundled in with the offer.

It's generally not enough if you intend to fill the rack. They offer it this way because price seams to be king; quote the minimum provisions so you can get a prospects attention and the add on the options. If they quoted it all in the base package, no one would give them a second look.

My suggestions is to include in your RFP a statement of what you want and this will depend on the equipment that you expect to be installing.

You will need to add the load up and determine how many circuits that you need and what voltages you need. A circuit can only support 80% of its rating, so a 20A circuit can only carry 16Amps.

When calculating your load you need to add up the 208V loads and the 120V loads separately. Also a few simple formulae might be helpful as different manufacturers state their equipment data in different terms.

VA = Amps * Volts
Watts = Amps * Volts * PF

PF on new equipment is usually 0.9 or better.

Its not uncommon to add up the nameplate ratings on existing installations and find out that a 20A circuit is carrying 30 Amps. The nameplate loads that they manufacturer qoutes are usuall substantially overstated. I'd be careful about trying to factor this in unless you have a lot of experience with a brand, model and configuration of the equipment that you are installing.

If your equipment has dual (redundant) power supplies then you will need to request circuits from different sources for maximum availability. Keep in mind that in this confiuration, should one power circuit fail, then all the load will dump to the other. So you can only load the circuit to 50% or 8A or you will create a cascading failure. This may be obvious but it's amazing how many "professionals" in the field miss this.

Heres the rub: a number of colo providers are charging by the amp ($6/amp+/-). If I'm using redundant circuits then I'm paying double even though I'm not using any more resources or energy then a single circuit provides. This translates into a big cost for me and a lot of profit for the colo provider. Colo is still a great deal for the one or two cabinet user. If you are going to lease a lot of space or have a lot of racks then you need to negotiate a better deal.

Hope that this is helpful.

Ken Baudry
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