Any generator experts in the house?

[41magsnub]

I was tasked with redneck engineering a generator backup for our "data center".  Data center is a strong word, it is 8 servers plus random network equipment and an IP PBX.  Within these servers we have our internal domain controller/exchange box, a citrix box, 2 servers for a company we rent rack space to, and our public web environment on a couple of servers.  The company we rent rack space to is our accounting firm where they are distributed all over the country and access quickbooks and whatnot via citrix.  We trade rack space and maintenance for the servers for doing our bookkeeping.  It works out quite well but they are asking for more uptime in the event of a power outage during the business day.

Currently it is all comfortably run off of 2 APC Smart UPS 3000XL units.  However, the power around here is rough since neither the city or power company is trimming trees and the squirrels like to kamikaze the transformers about every other month or so.  When it goes down it tends to be down for a couple of hours.  We have complained but it does not seem to matter.

I've done some basic load calculations and a 7500 or 10000 Watt generator would run the network and one of the AC units which would be good enough.  However, my boss and I disagree on a couple of things.  He thinks he can just get any cheap generator (< $1000) of sufficient size and run the UPS units off of it once the wiring and transfer switch in place. 

I think that is all well and good from a structure standpoint, but one of the cheap generators made for power tools and a welder is going to have too much of a frequency variation and will cause the UPS units to think the power is too rough and stay on battery.  I think we need to spend a lot more on the generator, one made for residential or commercial applications that has some sort of regulation to clean up the power.

Am I right on this?

What I would rather do is build a much larger UPS system using deep cycle batteries, shooting for several hours rather than screwing around with the generator.

[AZRedhawk44]

What I would rather do is build a much larger UPS system using deep cycle batteries, shooting for several hours rather than screwing around with the generator.

This will work.  As long as your goal is no more than 2-3 hours, that is. 

10k watts @ 2 hours run time on 110AC is 20,000 watt-hours, and 180 amps.  You need to be able to provide 180 amps in your battery well and not completely deplete your batteries.  Typical battery discharge should be no more than 25%, so you need 800 to 1000 amps in your battery well for 2 hours of server up-time.

You could wire a charge controller into a 1000 amp battery well, take your main feed for the datacenter power into the charge controller, then hang your servers off of a 12K-watt AC inverter.

Of course... you need it to be redundant.  Lose the AC inverter and your system is offline.

[Nick1911]

I've known someone who ran a UPS off a generator with no issues.

To my knowledge, generators have true sine wave output, not nasty waveforms like inverters typically put out.

At any rate, the computer gear should chug along quite nicely even off quite dirty power.  Switch mode power supplies are cool like that, in my experience.

[41magsnub]

The main reason I am paranoid is several years ago as an experiment I hooked up a small APC smart ups to our 5000 Watt generator at my cabin to try to charge the battery on a laptop.  The UPS definitely did not like it.

[mgdavis]

I have no personal experience, but it is my understanding that Honda generators are pretty much the only consumer grade ones that are suitable for running computers.

[Fly320s]

Do those small generators have self-start capability?  You don't want to hand-start that thing every time.

Is it gas powered?  Natural gas? Propane (LPG)?  Where are you going to install it?  Vent the exhaust. Store the fuel?  Do building codes or fire codes address this?

Do you forecast your power needs to increase?  If so, how long until you outgrow the small generator?

[41magsnub]

Do those small generators have self-start capability?  You don't want to hand-start that thing every time.

Is it gas powered?  Natural gas? Propane (LPG)?  Where are you going to install it?  Vent the exhaust. Store the fuel?  Do building codes or fire codes address this?

Do you forecast your power needs to increase?  If so, how long until you outgrow the small generator?

I see the power needs decreasing slightly as we move more towards virtualization.  There are also redundant servers I can shutdown that do not need to run during an outage to reduce the load if it comes to that.  All we want to run are the servers, if the power is out most of us have laptops with batteries good for at least 3 hours.  If the outage lasts longer than that so be it, at least the servers and hosting is still up.  We get about an hour out of the UPS units right now. 

When I said redneck engineering I meant it, the idea is to have a portable gas powered generator to wheel outside and plug into the exterior wall.  Wiring would be preinstalled to just plug the generator into the wall outside that leads to the transfer switch.  Once it is started then hit the manual transfer switch.

I'm deferring on the building code question to the owner.  Fuel storage should not be a real problem, it would just be a couple of plastic gas cans.  We might need to put in a fire proof cabinet or whatever for that which would not be a big deal.  The generator would be outside when running so exhaust venting is not an issue.

When we discussed this a couple of years ago I suggested moving our server operations to a proper data center in one of the bank buildings a few blocks away that has all this stuff set up, just keep the internal LAN equipment here.

[RevDisk]

I've done some basic load calculations and a 7500 or 10000 Watt generator would run the network and one of the AC units which would be good enough.  However, my boss and I disagree on a couple of things.  He thinks he can just get any cheap generator (< $1000) of sufficient size and run the UPS units off of it once the wiring and transfer switch in place. 

I think that is all well and good from a structure standpoint, but one of the cheap generators made for power tools and a welder is going to have too much of a frequency variation and will cause the UPS units to think the power is too rough and stay on battery.  I think we need to spend a lot more on the generator, one made for residential or commercial applications that has some sort of regulation to clean up the power.

Am I right on this?

What I would rather do is build a much larger UPS system using deep cycle batteries, shooting for several hours rather than screwing around with the generator.

I'd recommend a 15kw generator, but I always prefer to overspec my power needs.  Or get two smaller generators and the kit necessary to load balance them.  I'd recommend going this route if you think you could do it right.

If you wanted to go with the UPS, it could get expensive unless you jury rig it while I don't exactly recommend.  I don't have my energy calc app handy... Actually I usually cheat and just give the specs to my APC rep.  Poor guy, I occasionally give him nasty requests. "I need two dozen beefy UPS's DELIVERED in 18 hours.  - (click click) Uhm.  Closest ones are in Chicago...  - So?  - #*%@$$, I hate you.  - Good.  17 hours, 58 minutes.  Better get moving."

A decent enterprise UPS's should be able to handle nasty variance.  Or just get a really decent warranty.  Just mention it to your rep and see how badly they cringe.

[Hawkmoon]

I think that is all well and good from a structure standpoint, but one of the cheap generators made for power tools and a welder is going to have too much of a frequency variation and will cause the UPS units to think the power is too rough and stay on battery.  I think we need to spend a lot more on the generator, one made for residential or commercial applications that has some sort of regulation to clean up the power.

Am I right on this?

I don't think so. Any generator you can buy is going to put out power that's clean enough for normal household use, and that's clean enough for the UPSs to "see" correct line voltage and run in A/C mode, just filtering the power. Don't make things more complicated than they are.

When I said redneck engineering I meant it, the idea is to have a portable gas powered generator to wheel outside and plug into the exterior wall.  Wiring would be preinstalled to just plug the generator into the wall outside that leads to the transfer switch.  Once it is started then hit the manual transfer switch.

No. First the transfer switch, then you connect/start the generator. There are several reasons for this, but the legal one is you don't want to fry anyone who might be working on the line. Second reason is, if you start/connect the generator first, you will be trying to power your whole street/neighborhood/town until you pull the switch.

How big was that generator again?

[41magsnub]

I don't think so. Any generator you can buy is going to put out power that's clean enough for normal household use, and that's clean enough for the UPSs to "see" correct line voltage and run in A/C mode, just filtering the power. Don't make things more complicated than they are.

No. First the transfer switch, then you connect/start the generator. There are several reasons for this, but the legal one is you don't want to fry anyone who might be working on the line. Second reason is, if you start/connect the generator first, you will be trying to power your whole street/neighborhood/town until you pull the switch.

How big was that generator again?

good point on the transfer switch thing. 

My main paranoia about the existing UPS units not working with it is we are really trying to do this on the cheap as a manual method to make things work when the power is out.  There was no intention of buying new UPS units, just a used cheap generator, transfer switch, and the wiring.  I have a 5000 watt Coleman generator we bought for power tools when replacing the roof at my cabin.  The one time I tried to connect an APC Smart UPS to it the APC unit freaked out and would not come on when connected to power.  I don't have a way to test this at all prior to making the investment and seeing if it all works.

I'm also concerned that we are not going to get all that great of advice from the electrician, he is the owners currently unemployed electrician brother in law.  Besides, he won't know crap about this anyway having just done small commercial and residential projects.

[Leatherneck]

I have a 5kw Honda and it starts well every time and runs my home PC sets through a basic UPS very well. But I'm with AZR: go for a unit designed to be standby power: Generac and many others make whole-house standby units that run off propane or NG and self-start. They're designed for longer-term use and don't require refueling every 10-15 hours. They typically cost under $$4,000, depending on size. Use existing UPS units and have plenty of power to boot for lights, A/C, frig, stove, etc.

TC

[never_retreat]

This should do the trick for you.
http://cgi.ebay.com/Caterpillar-1500-KW-Diesel-Generator-Only-350-Hours_W0QQitemZ230401223620QQcmdZViewItemQQptZBI_Generators?hash=item35a4fbabc4

[guns and more]

To do it right you should have a diesel generator capable of handling the AC also..................but

Sounds like your boss doesn't want to go all out.

I recommend the Honda 3000 SI. We run our fiber systems off of them at work (in the field) and they are reliable as a crowbar.
Start with a key, run 12 hrs on a tank, and are QUIET.

[Hawkmoon]

I don't have a way to test this at all prior to making the investment and seeing if it all works.

Sure you do. Take one of your UPSs home and plug it into your Coleman generator.

I have a 6,000 watt (or so) "Brand X" generator for storm power at home, and my computers are on APC Back-UPS units. They coexist just fine with the generator.

[cassandra and sara's daddy]

i recommend dual fuel  propane doesn't get stale  runs cleaner

http://www.propanecarbs.com/dualfuelconversion.html

[RocketMan]

A generator with good frequency regulation is imperative.  If the generator output frequency drifts much off 60Hz, say below 57 or above 63, a decent UPS will reject it and not switch back to line mode.  If your UPS is not sensitive to frequency variation, you don't have a good one.
A good UPS does more than watch for voltage abnormalities.

[Firethorn]

No. First the transfer switch, then you connect/start the generator. There are several reasons for this, but the legal one is you don't want to fry anyone who might be working on the line. Second reason is, if you start/connect the generator first, you will be trying to power your whole street/neighborhood/town until you pull the switch.

Not the manual transfer switches I've used.  They're Line->Off->Generator.

The military one I used you had to flip the main breaker off, move a sliding metal lockout plate to allow you to throw the breaker for the generator.

You want to start the generator BEFORE you hook it up, let it stabilize.

What we did for our NCC/server farm (using a big milspec diesel generator, mind you):

Start the generator.  Get it stabilized(took some fiddling, the poor thing was a bit worn out)
Flip EVERY breaker off.  Power was already out or going to go out.  All equipment is on their UPSes.
Move the lockout plate, flip the generator supply breaker on.
Using a priority list, flip on each breaker, one by one, stabilizing the generator again each time.  Did I mention that the generator's automatic control equipment was a bit broke?
Once everything was on generator, detail a couple airmen to run out every 15 minutes or so to rebalance the generator.  (Load didn't vary much at that point, so it didn't vary much).

Rebalancing the generator:  Work 3 knobs to keep the generator producing power at 240V@60Hz.

A generator with good frequency regulation is imperative.  If the generator output frequency drifts much off 60Hz, say below 57 or above 63, a decent UPS will reject it and not switch back to line mode.  If your UPS is not sensitive to frequency variation, you don't have a good one.
A good UPS does more than watch for voltage abnormalities.

Hah!  If you have a *REALLY* good UPS, it'll fix that problem for you.   

For computer supplies, especially modern switchmode ones, as long as the frequency is between 48 and 63 or so, you're good to go.  In which case having an oversensitive UPS is actually a bad thing.

[Gewehr98]

A generator with good frequency regulation is imperative.  If the generator output frequency drifts much off 60Hz, say below 57 or above 63, a decent UPS will reject it and not switch back to line mode.  If your UPS is not sensitive to frequency variation, you don't have a good one.
A good UPS does more than watch for voltage abnormalities.

And a better UPS can make clean power from garbage input.  They just cost more, because they're making 60Hz true-sine output power 100% of the time.  My PowerWare and MGE UPS units do that already, you just have to look for that type of internal UPS operation.  "Line Interactive" and "True UPS" mode units are a lot more forgiving of their input power waveforms.

My 3,000 watt Generac portable ain't the cleanest on the output, but it'll feed an ancient APC 800RT UPS and run several computers no problem.  I know, it's what I did for 3 weeks straight during the Florida hurricane season of 2004 as they attempted to restore the power grid.  I've even run the computers directly off the Generac, just to see how tolerant the computer power supplies are.  Switched-mode computer power supplies can accept some pretty crappy input power and still keep on ticking! Heck, they're creating their own square waves to feed the internal transformers...

Note that some higher-end inverters will also produce true-sine output.  I have a 2,000 watt Xantrex ProSine inverter attached to a batch of TelCo batteries, and it's rock-solid.  The rack is charged via those leftover VW/Audi dashtop solar panels, but provides a nice amount of capacity before I have to fire up the Generac. Here's the earliest incarnation, with just 6 batteries at the time:

[Desertdog]

A situation like this the best fuel is NG, if available with little or no cost.  Next best is Propane.  More cost for tank and piping.

With NG or Propane no fear of anybody stealing the fuel and the fuels do not sour, sludge up, or get condensation in them.  Since they should be piped in, reduces the possiblity of the generator it self walking off.

Gasoline and Diesel both has a tendency to go bad if not left in storage for a long time.

[RocketMan]

You look like you're having way more fun than should be allowed with that setup, Gewehr98.  That is pretty sweet.  I'm jealous.