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Selecting and Setting Up Generators for Business Disaster Recovery

Posted on by GWI

The topic of generators came up in a recent management meeting about hurricane Sandy, as it is a really important component of business disaster recovery planning when you depend upon computing. We’ve since read about hospitals and other important places in NYC losing power despite their generators when they could not get fuel. Given these circumstances, I thought it would be a good time to discuss the best way to choose a generator for your business.

The diesel generator at GWI's Rockland data center.

Diesel generators, like this one at our Rockland data center, provide more stable power at capacity in a disaster recovery situation.

It’s likely the fuel shortages in New York could not have been avoided. Before college and my Internet business and when it was too cold to go lobstering with my dad, I delivered heating oil with my grandfather. Heating oil is the same fuel used by diesel generators. Concisely put; when dealing with large quantities of this fuel, the rules change due to environmental and safety risks. Smaller tanks, like those used on a normal generator or home furnace are OK. Big storage, such as used by a distributor or very large customer requires additional things like spill containment and hazmat planning. It would be difficult to store large quantities of fuel in a skyscraper safely. In the big cities, it’s usually pumped up to the generators to replenish their built in tanks. If things at ground level flood, that presents a problem if it interferes with refueling.

GWI’s “big city” data center in Portland is in a much better position. Because downtown Portland is on quite a hill, our datacenter is much too high for flooding. GWI also uses alternate datacenters so as to avoid keeping all the eggs in one basket.

All the work GWI puts into keeping things running during a disaster does little for you if your business can’t access our services. Your business may also lose money because its staff becomes unproductive without power or if sent home.  A little time spent now on business disaster recovery will save you a lot of aggravation later.


What are the options for backup generators for businesses depending on computing?

When sizing generators for our data centers, we quickly determined that it’s not a simple math-in-your-head calculation.  Here’s a summary for how I’ve calculated generator size in the past for work and home.

1. Determine peak load. Your electrical meter calculates this every month so you can be billed for this if you fit in the medium-service business category for CMP. Someone could read this from the meter, or your bill probably shows peak amount if you are in the medium-business tariff. This will be a KW figure.

2. Add a generous percentage amount for growth if you intend to increase the number of staff or IT infrastructure.

3. Adjust for engine loads.  If you are looking at propane, add 100% to that capacity estimate, as propane generators do not have as much torque as diesels and performance fluctuates as big loads are switched on. If you’re planning to use diesel add 40%. Diesel, you can run at full 100% load without much frequency fluctuation, so they don’t need as much headroom. Propane generators are slightly less expensive, so adding the capacity for propane may not make as much difference as you’d think.

For most needs, a little fluctuation in frequency or voltage isn’t a problem, but it is a real big deal for computing. Uninterruptable Power Supplies (UPS), (which you should have on your computer and networking equipment) tend to be pretty fussy, and if your generator bogs down by a few RPM or runs a little fast, the UPS won’t like that and will refuse your gift of backup electricity. Propane and gasoline generators aren’t as stable when big loads are switched on, which is why we want the extra headroom. Diesel has more torque and provides more stable power right up to the point of being overloaded.

Whatever you get, you may need a generator tech to adjust the governor when the generator is under load so that it provides the right frequency. Some UPS’s require a 1% tolerance. If you use a generator and your UPS doesn’t like it, this is probably why. An inexpensive tool to check frequency is the Kill-A-Watt; a $30 measuring instrument you plug into your electrical outlet.

Electrically, if you have 3-phase power, buy a 3-phase generator.  If you have single-phase power, buy a single-phase generator. With regard to transfer switches, there are really two types; row of switches for important small loads, or one big switch that does everything. You could spend a great deal of time and money rewiring circuits to power important loads, or you could have one big automatic transfer switch that does the whole building. While not suited to every situation, I favor the one-big-switch approach so I don’t have to worry about what’s going to work versus what is not.

4. Where will you install it? A propane generator typically is installed outdoors on a pad. A diesel can be in or outdoors. It’s possible for the diesel fuel to gel in extreme cold, so indoors would be the more conservative choice. Code for indoor generators is about the same as a boiler room.  Your generator room should have fireproof wall, vent louvers to the outdoors for big airflow in and out, a custom exhaust pipe, and sound insulation. Fuel would be stored in heating oil tank(s) plumbed to the generator or using a built in tank in the generator base. In this sense, it is simpler logistically to have an outdoor propane generator, though it’s not as efficient. Propane generators will also need a large outdoor propane tank. Outdoor generators may also need some rodent prevention as well so wires don’t get chewed or air filters occupied. Generators can also have recommended block heaters for quicker, more reliable starting in cold weather.

5. Consider big loads. If you have electric water heaters, it may make sense to convert them to on-demand propane or solar. Heating water is a big electrical load and it may not make sense to power that with a generator. For most people in Maine, air conditioning isn’t a huge concern, but for computers, it’s our second biggest load. If you have to cool or ventilate computers, a whole-building transfer switch will ensure that continues to function. As always there are benefits to conservation that go beyond the monthly power bill. If you have these sorts of big loads, there may be Efficiency Maine assistance available to allow you to more affordably update heating, air conditioning and lighting systems.

We’re not in the business of generator consulting, but do consider some of these things as you work with electrician and generator sales/maintenance businesses to determine what’s best for your business.

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