nick panaro
Member
what is the difference between a U.P.S. system and emergency backup power?
backup power
- Thread starter nick panaro
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- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
A UPS (Uninterruptable Power Supply) has a built in battery that provides power to the loads for a limited amount of time. It takes AC power from the utility source, converts it to DC, then an inverter changes it back to AC. The battery is connected in the middle part of that chain, so that the battery can give its energy to the loads (via the inverter) when the utility source is lost.
The word ?emergency? is often misused, especially by persons who are not members of the electrical profession. To us, it refers to a specific set of equipment intended to supply power to a specific set of loads, and it is governed by NEC article 700. A load can only be supplied by an ?emergency source? if some governmental agency says that that load is a emergency load. The most common emergency load is egress lighting, and it is the building codes that says that that load must be supplied by an emergency source. The rules require that that particular load must be energized no more than 10 seconds after loss of the utility source, and must be maintained for at least 90 minutes.
Welcome to the forum.
The word ?emergency? is often misused, especially by persons who are not members of the electrical profession. To us, it refers to a specific set of equipment intended to supply power to a specific set of loads, and it is governed by NEC article 700. A load can only be supplied by an ?emergency source? if some governmental agency says that that load is a emergency load. The most common emergency load is egress lighting, and it is the building codes that says that that load must be supplied by an emergency source. The rules require that that particular load must be energized no more than 10 seconds after loss of the utility source, and must be maintained for at least 90 minutes.
Welcome to the forum.
- Location
- Massachusetts
There is some crossover between the two but in general,
A UPS is ready to go all the time, if the utilty fails the UPS picks up the load so fast that computers stay online and no outage is seen.However UPSs usually have short run times, they can only carry the load as long as their batteries last or whatever other source they use.
On the other hand emergency backup power usually means a source that is available but there will be some down time between utility loss and the back up source coming on line. These other sources are typically generators but could be fuel cells or another service from the utility etc.
We must be careful to use NEC terminology here, the word 'Emergency' has a specific meaning when talking about back up power. To the NEC a generator that backs up things like egress lighting, exit signs, fire alarm systems is part of an "emergency system" and has very strict rules about how they can be installed. Those rules are in Article 700
The generator at someones home for back up, or a generator that backs up a data center is not an 'emergency generator" it would be a Optional Standby generator as covered by article 702 with less restrictive rules.
A UPS is ready to go all the time, if the utilty fails the UPS picks up the load so fast that computers stay online and no outage is seen.However UPSs usually have short run times, they can only carry the load as long as their batteries last or whatever other source they use.
On the other hand emergency backup power usually means a source that is available but there will be some down time between utility loss and the back up source coming on line. These other sources are typically generators but could be fuel cells or another service from the utility etc.
We must be careful to use NEC terminology here, the word 'Emergency' has a specific meaning when talking about back up power. To the NEC a generator that backs up things like egress lighting, exit signs, fire alarm systems is part of an "emergency system" and has very strict rules about how they can be installed. Those rules are in Article 700
The generator at someones home for back up, or a generator that backs up a data center is not an 'emergency generator" it would be a Optional Standby generator as covered by article 702 with less restrictive rules.
Last edited:
- Location
- Massachusetts
Wow, I think Charlie and I agree, I just type slower. 
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Wow, I think Charlie and I agree, I just type slower.
ya but you posted the second post so fast you tied your first post time, imagine if you were a little faster, you would have posted ahead of yourself
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Don't worry. I won't let it become a habit.
dbuckley
Senior Member
- Location
- Canterbury, New Zealand
With many larger UPS systems ("online" or "dual conversion") the UPS is holding the load (almost) all the time, and thus it doesn't need to "pick up" the load, it already has it.
There's a lot of detail beneath that simple statement waiting to catch the unwary, however
And as to another point mentioned earlier - not all UPS systems use batteries, some use a mechanical flywheel on something akin to a motor/generator set to maintain the output.
- Location
- Massachusetts
I know, I would say that describes most of the ones we install. I was trying to keep it basic, there are almost countless different probabilities.
I service a location that has grid interactive solar, a cogen fuel cell that also provides back up during utility failure, a dual conversion UPS for selected electronics and the typical EBUs for lighting ...what is back up, what is emergency and what is 'normal' power gets kind of blurred.
Another site we service has utility, generator, cogen fuel cell, UPS and large battery banks as the 'emergency' supply.
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