We have a 150 kva UPS system that is logging from 107 up to 129 kva. The IT guys want to know how much more they can add before we have a problem. We are in the planning stage of upgrading our system but that will take time, they want to know what happens when we hit 150. Any ideas on how to explain the problem we already have.
UPS Load
- Thread starter cordial98
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Re: UPS Load
I assume you have a dual conversion UPS. In my company we limit the load to 80%. But the problem you will experience is once you hit the limit your inverters will shut down to protect themselves from overload.
The other problem you could experience is if you should loose station AC power is the battery reserve time drops to a few minutes. And if the batteries have any kind of problems, if they are VRLA they likely do, then the system is likely to crash in the event of AC power failure.
I assume you have a dual conversion UPS. In my company we limit the load to 80%. But the problem you will experience is once you hit the limit your inverters will shut down to protect themselves from overload.
The other problem you could experience is if you should loose station AC power is the battery reserve time drops to a few minutes. And if the batteries have any kind of problems, if they are VRLA they likely do, then the system is likely to crash in the event of AC power failure.
Re: UPS Load
At some point of 150KVA or above, the Inverter's will shut down assuming this is a dual conversion UPS (rectifier-DC-inverter). Every manufacture has a set point between 100-to-110%. What does the generator have to do with anything? The generator only goes on-line in the event of commercial AC power loss or test.
At some point of 150KVA or above, the Inverter's will shut down assuming this is a dual conversion UPS (rectifier-DC-inverter). Every manufacture has a set point between 100-to-110%. What does the generator have to do with anything? The generator only goes on-line in the event of commercial AC power loss or test.
wanderer20001us
Senior Member
Re: UPS Load
Just an Example:
MGE EPS 6000 UPS
125% of rated load for 10 minutes
150% of rated load for 1 minute
212% current limit for By-pass shutdown
Keep in mind 80% loading should be maximum loading. Also remember a 150kVA unit is rated 120kW and assumes an 80%pf. Know your true load, not just the kVA. Most IT equipment will run very close to unity power factor from what I've experienced.
Just an Example:
MGE EPS 6000 UPS
125% of rated load for 10 minutes
150% of rated load for 1 minute
212% current limit for By-pass shutdown
Keep in mind 80% loading should be maximum loading. Also remember a 150kVA unit is rated 120kW and assumes an 80%pf. Know your true load, not just the kVA. Most IT equipment will run very close to unity power factor from what I've experienced.
brian john
Senior Member
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Re: UPS Load
I myself have never overloaded a UPS, but I have been involved in serval projects where customers did this.
1. Overheating from 103%load and cooling was not adequate through the UPS. system went to bypass no one paid attention and during a utility anomaly they lost the load.
2. System loaded to 100% (or close) system was going to bypass due to loads that would come on line at certain times (printers).
3. And as mentioned battery back up time calculated at 80% at 100 percent and older batteries with a numerous outages the system crashed.
Pushing the limits will work but I would have a plan in effect for access to a PC for emailing your resume out.
How about smaller UPS systems till such time the existing system is upgraded?
I myself have never overloaded a UPS, but I have been involved in serval projects where customers did this.
1. Overheating from 103%load and cooling was not adequate through the UPS. system went to bypass no one paid attention and during a utility anomaly they lost the load.
2. System loaded to 100% (or close) system was going to bypass due to loads that would come on line at certain times (printers).
3. And as mentioned battery back up time calculated at 80% at 100 percent and older batteries with a numerous outages the system crashed.
Pushing the limits will work but I would have a plan in effect for access to a PC for emailing your resume out.
How about smaller UPS systems till such time the existing system is upgraded?
Re: UPS Load
cordial98, here is something you might want to implement in the future. Most of the larger UPS have programmable alarm set points, system load being one of them.
When a UPS is initially installed set the system load alarm to 60-to-70%. When this point is reached, it is time to plan for expansion; we kick off a EWR to cover it.
Then set the alarm point for 80%. When this point is reached, freeze the system and do not allow any more loads to be added until the expansion is completed.
Another very important step is battery PM. Most UPS use VRLA batteries which are very prone to failure and only have a life span of 5-to-10 years under ideal operating condition, which are rarely ever met. Ambient are and pilot cell Temperature?s need to be monitored around the clock with a recording device. Terminal torque needs inspected every month or two, float charge monitored, and most importantly a load test performed once a year.
Flooded batteries are much more reliable and need less maintenance, but they still need ambient air temperature monitored, terminal torque inspection, and float current monitored.
Good Luck, Dereck
cordial98, here is something you might want to implement in the future. Most of the larger UPS have programmable alarm set points, system load being one of them.
When a UPS is initially installed set the system load alarm to 60-to-70%. When this point is reached, it is time to plan for expansion; we kick off a EWR to cover it.
Then set the alarm point for 80%. When this point is reached, freeze the system and do not allow any more loads to be added until the expansion is completed.
Another very important step is battery PM. Most UPS use VRLA batteries which are very prone to failure and only have a life span of 5-to-10 years under ideal operating condition, which are rarely ever met. Ambient are and pilot cell Temperature?s need to be monitored around the clock with a recording device. Terminal torque needs inspected every month or two, float charge monitored, and most importantly a load test performed once a year.
Flooded batteries are much more reliable and need less maintenance, but they still need ambient air temperature monitored, terminal torque inspection, and float current monitored.
Good Luck, Dereck
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