Powerware comments 1

[ilpadrino]

I know that APC has a strong hold on small-medium sized companies. We've used APC but now I'm looking at consolidating the many APC units that support our servers and enabling equipment into one or two for each rack cabinet. I like what I've read about Powerware and was interested in anyone's opinion.

Specifically my requirements to start are:

3200VA for first cabinet
1100VA for second cabinet
110V-120V wall outlets, would prefer not to change to 208V
45-60 min runtime.

Thanks in advance.
Joe.

 

[josepablomir]

Powerware UPS are excellent products.
Unfortunately the maximum power you can have in the Powerware 9xxx Family (ideal for small server rooms) for 120 V models is 3000 VA not the 3200 you are looking for. Maybe 200 VA is not big deal. But be careful, the 3000 VA model requires a L5-30P receptacle (and, of course, a 30 Amps breaker in the electrical panel).
By the way, you will need also External Battery Modules (EBM) to reach the desired run-times.
May I ask you why you need two UPS? And why do you want to stay in 120 Volts?
The first question is because for your words I think you are going to install the units in 2 server racks. But does one of your racks really need 3200 VA? It is a lot of power for a server rack. If you need help estimating the power requirements of your servers let me know.
About the 120 Volts question, I don't like to plug a 30 Amps loads in a 30 Amps outlet with a 30 Amps breaker. The Powerware 9125 3000EUHW, which is hardwired allows for a much more reliable connection, and with a 20 Amps bipolar breaker and Number 10 wire you can rest more comfortable at nights. By the way, in this case, the ground, hardwired directly to the panel will present a much smaller dynamic impedance path to fault currents. And if you have overestimated the power consumption of your servers maybe one if this 3 KVA models may power both racks.
Do you want to it right? Do it "Isolated Ground" also.

Hope this help
Jose.-



_________________
Pablo Mir

http://www.pablomir.com

pm@pablomir.com

 

[ilpadrino]

Thanks for the response. I used the APC selector to determine VA. Most of the servers we have were identified on that selector. There are 13 servers, 3 of those have redundant power supplies. The second cabinet is all networking equipment, again idenitifed on APC's selector site. If it doesn't matter, we would prefer not to spend $500 or so changing the wall recepticle to 208 but I know nothing about electricity. Also if I choose the hardwired, then I have to pay an electirician anytime I would need to disconnect or install the device. Here is what Powerware has now recommended:
2 Powerware 9125 2000va + 2 EBM for runtime.
1 Powerware 9125 1500va + 1 EBM for runtime.
This totals about $5452 with shipping and 3 SNMP cards.

 

[josepablomir]

I think that something like “IT SOUNDS GOOD, THOSE ARE EXCELENT UPS” could be the appropriate response to make some kind of closure to your question. On the other hand, we don’t need people to tell us what we want to hear, but to show us some other possibilities, even if we decide to discard them.

First of all let me tell you that you don’t have to know about electricity to make the right choices; all you need is to have at hand the proper information.

If you spend $500 in an electrician to install a 208V outlet, running number 10 BX wire and replacing the breaker to properly connect the UPS that will supply power to your 13 Servers and Communications Devices’ Racks, you are making a very wise decision. How much do you spend in Anti-Virus Software for your client workstations? How much money have you invested in purchasing the Racks? How much money have you invested in deploying your IT Infrastructure, $8000, $25000, $75000, or $300000? Do you really think $500 is worth taking the slightest risk in the provision of power to your infrastructure core?

But you can think the issue from the opposite point of view: Why do I have to spend $500 in changing an outlet? Well, you are not just “changing an outlet” you are supplying 40 Amps to your Servers! Do you really want to do it from 3 common $5 electrical outlets? Do you know that many of the electrical outlets commonly founded in Server Rooms are poorly grounded (through a screw attaching the BX armor to the panel, or worst if some boxes exist)? I’ve found a lot (and I mean A LOT) of Server Room installations where the breakers do not trip fast enough when making a short circuit to ground in the outlet side. Yes, LAN Administrators, many times, knows a lot about PHP NDS, AD, PERL, or how Microsoft save the world, but nothing about Infrastructure planning. Giving proper power, grounding, noise and harmonic filtering, transient shielding, air conditioning and humidity control is, also, very important when your server room starts to grow. It is OK if you don’t know, but you have to give it proper planning.

But, let’s suppose you are in a “very tight” budgeting condition (like some other million LAN Administrators). Let’s spouse you build your servers, you use Linux, and you perform mostly all administration and maintenance by yourself. Then you can feel that an extra $500 investment is something your organization should avoid. Well, if $500 is considered “too much” money, then why don’t you choose some other lower cost Off-Line UPS? You could, also, settle for less battery run-time.

I know what you are thinking right now, but do you really think the difference between the On-Line PowerWare UPS and, for example APC Off-Line models is more important to the overall power quality performance than the difference between proper and improper power-line connection? Keep in mind you are going to drain some 40 Amps., and think again!
With Off-Line UPS you will also generate less heat so you don’t have to worry about air conditioning issues.
Don’t misunderstand my words. I prefer On-Line UPS and I like to have enough room to grow. But I don’t like to compromise other aspects of the power supply chain.

Let’s face it, you are not sure how much power you really need (I keep thinking 4000 VA inside ONE Server Rack is TOO MUCH!), and maybe you are not aware of your power line condition. If your estimation is right, the server rack alone will need more than 30 Amps. from two outlets (Let’s hope these outlets to be 20 Amps, dedicated, and with the proper breaker). If your electrical installation (panel, breakers, wiring, grounding, outlets, and any middle-connection box) is not in optimum condition this is a fault waiting to happen.

But what about if your load requires far less than the 5 KVA you are going to provide? Well, in that case you have wasted resources in the wrong direction. Maybe all you really need is a 3 KVA unit. In that case, with proper planning, you can use the resources to properly design the right solution. Maybe you can include a TVSS, or an isolated ground circuit, or both.
By the way, APC tool for estimating server power requirements is not very accurate, and worst if you have many servers together.

So, to make it clear, if your budget is reduced but you still want to do the things right the first thing you have to do is to measure the load you have (yes, if you don’t know about electricity you will need to call an electrician). With this value you can properly define how much power you will need. By the way, when the electrician performs the power measure you can ask him to test the outlets when you want to plug the UPS (condition, ground, load sharing, breaker, etc.). If you do it that way chances are you are going to save money: but for sure you are going to have a more reliable power source for your core network infrastructure.

Hope this help.

Jose.-



_________________
Pablo Mir

http://www.pablomir.com

pm@pablomir.com

 

[ilpadrino]

If selectors are not accurate, then how is it possible to determine VA need? Is there a conversion formula I can use?

For example I have 2 HP Netserver LP1000r's. From the HP documentation, 203W continuous power is required, and a maximum consumpion of 254W is listed. How do I go from this number for watts to estimate an accurate VA need?

APC's selector reads 360VA for one, 720VA for two.
Powerware does not have that HP model listed on its selector, so using their VA/A/Watts calculator I get 362VA.

It seems to me that the total can add up pretty fast. I have 13 total servers of varying power supplies.

 

[josepablomir]

The power in Watts or VA expressed in the Server Power Supply or documentation usually indicates the maximum rating the unit is able to handle. This value is usually much bigger than the real value required by the Server under normal configuration.
Unfortunately there is no formula to estimate the power requirement. If you are concerned about the exact value you have to measure it with the proper instrument (usually a True-RMS Clamp-Meter).
That's why I suggest you to call an electrician to measure the exact value (don’t forget to add some room to grow and working tolerance). And, to make a good decision, you can ask him to check your lines, outlets, electrical panel, breakers and grounding.

About the formulas, you can covert from Watts to VA. If your power supply has a maximum rating of 254 Watts it is likely to have a maximum power rating of 360 VA (assuming a power factor equal to 0.7). The “APC Selector”, like many other selectors, simply indicates the values suggested by the manufacturer, which usually are “maximum ratings”. If you dimension your UPS by adding 13 Servers Maximum Ratings you are going to over-dimension the UPS (is not a bad, but expensive).
The formula is: “Apparent Power = Real Power x Power Factor”
Apparent Power is expressed in VA (Volt Amps), and Real Power is expressed in Watts. The power factor is the Cosine of the shift angle between the Voltage that forces the Current to circulate and that Current.
The power supply of any computer has a maximum rating of real power in the DC section (the low voltage direct current which powers the electronic components inside the computer) and a maximum rating of apparent power in the AC section (the section plugged to the wall or to the UPS). Those values are related one another in a “power factor” ratio plus the thermal loss (efficiency).

Regards,

Jose.-



_________________
Pablo Mir

http://www.pablomir.com

pm@pablomir.com
NJ, (973) 699-2043

 

[getaclueeee]

Just go here, this is the only way to go:

http://www.apc.com/products/infrastruxure/index.cfm

-Bill

 

[netmanrick]

Don't forget to size the ups for INRUSH current(powering up the unit(s)).You can overload your ups.

Rick Harris
SC Dept of Motor Vehicles
Network Operations

 

[technome]

Two cents to this....
In larger installation, especially with multiple UPS units, I have an electrician run at least one extra circuit. For every server room, there should be feeds from the breaker box from the different hot legs (phases).
In a power outage, at least in New York City, the utility company strives to keep at least one of the legs hot, if possible, I assume from very local generators.

Basically, during the North East blackout, most of my commercial client had power on at least one power leg. I had servers going when most everything was out. You can not know which leg will remain powered, the reason for multiple feeds.