Power and PDU
 

I'm 'helping' with a dc move and evaluating power options...and I know very little about power/volts/amps (but more than most in the group).

We are looking to run most everything on 110 V, but that would be expensive in terms of the extra power runs vs low utilization of the racks. Is it possible (what product?) to convert a 1 - 30A/208V circuit to something like 1 60A/110V or 2-30A/110V or 3 - 20A/110V? They all use the same power, right?

thanks

Is it possible? Sure. Do you want to spend money and rack space on installing transformers in each of your racks? Sounds like a losing proposition to me.

You could get three phase branch circuits and PDUs. That will reduce the number of cables and probably save you on installation costs, but you'll still have the same amount of current-bearing conductors (but less neutral and ground conductors) as if you provisioned individual 110VAC circuits. I believe both APC and BayTech make three phase managed PDUs.

From what i understand about the power... I would say, Use a UPS that takes in 220V and puts out 110V That should solve your problems on that part

why not use 208V?
Less heat and use less power.
I can't think of very many machines that will not run 208V, will everything being produced with switching power supplies.

Actually the new thing for future data centers is 48V PDU providing power to all machines in the rack.
Only need 2 PDU's per RACK!! Less heat.

Just my 2 cents worth.

Keith

Thanks for the comments and help.

The colo's prices are $200/month for 110V and $250/month for 208V. Taking 2 - 110's is $400/month vs splitting a 208 into two is still $250. So a $150/month savings by splitting the 208V.

My understanding on heat is that a server is going to put out the same heat no matter what Volt you send it. 5 AMPs x 110V = 2.5 Amps x 220V = 550 Watts

Does anyone know of a product that would convert to 208 into two 110?

Building power comes in three basic varieties:
480Y/277V,
208Y/120V,
240Delta/120V
120/24)V, 1 Phase.

480Y/277V - Typical for large building
208Y/120V - Typical for small buildings
240Delta/120V - Not used that much any more except in older areas
120/24)V, 1 Phase - Residential and some small office buildings.

There isn't any such animal as 110V or 220V, but don't worry about that as everyone know what you are talking about.

To keep this short. I'm going to assume a 208Y/120V panelboard (aka load center, fuse box) voltage.

This is a 4 wire service. Three hots and one neutral.


The voltage between and tow hots is 208V. Between any Hot and neutral is 120V.

For a typical 20A, 120V receptacle circuit a contractor would run a Hot a Neutral and a Ground.

For a typical 20A, 240V receptacle circuit a contractor would run two Hots and a Ground (sometime a neutral is run as well).

Most people run either of the two circuits above and use IT equipment with autosensing power selection (very coomon today - but check the power supply if you change).


Some Manufactures provide a plug strip in their cabinets (HP calls them PDUs although thats not a correct electrical term) where the run the three hots a neutral and a ground and tehn connect one third of teh receptacle to each hot and the common neutral. Note that the three hots are 120 degrees out of sync so they can use a common neutral and the currents don't mathematicall add up (ie 20 + 20 +20 is not equal to 60).

The output of a UPS might be more limited especially it its small.

An electricain shoudl be able to give you a reasonable cost for changing a circuit from 120 to 240v or the otehr way around. Keep in mind the plugs/receptacles will be different so you will need new plug strips, cord, etc. Get a couple of prices.

It will be probably be a lot more difficult to increase the amperage.

There are large products that do this, however, if you want something to put into your cabinet you could make one using a transformer, two circuit breakers, and two power strips.
The transformer would be something like http://www.outbackpower.com/pdfs_man...structions.pdf Note that there is also an optional fan cooling unit.

Then get an electrical distribution box at Home Depot and install the breakers, knockouts to connect to the power strips, and transformer.

I STRONGLY recommend that you do NOT do this. Pay the extra monthly for the two 120 V power strips

CORRECTION -- if the 208V is two hots and a neutral and a ground, you do not NEED the transformer.
Just connect the two hots to each circuit breaker and then to the power strips.
The only reason to add the transformer is to reduce harmonics that may be on the line.

Again, I STRONGLY recommend that you do NOT do this. Pay the extra monthly for the two 120 V power strips
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