Why do we need online UPS configuration

[Anonymous user]

Hey Forum
I have been out of the game a for while and have been brought in to look at a troublesome critical electrical supply circuit.

Firstly though I am curious about why we need to configure a UPS in online mode, I have been told these are using the UPS power all the time instead of coming up when the mains fails (i.e. standby mode).

Back in the day I had my server room AS400s hooked up to a UPS which was in standby mode, I never had issues with a power up delay causing the AS400s to suffer from brown outs. Believe me this UPS would have to click on and operate 20 times a day at least. It took a lot of detective work and we found that the sari shop downstairs (on the same electrical feeder) had a big Daikin AC unit that would drop the voltage and click on our UPS every time the compressor ran. I loved those days in Sri Lanka.

So whats wrong with UPS in standby mode? Is it just a fad because the technology is now cheaper? I need to know because I may need to suggest a UPS in standby mode to satisfy the issue we have with this system.

TIA

Multivits

[Anonymous user]

Thanks Voidstar

The issue is that the UPS has failed for a second time. I have the replacement ready to be installed. Our facility in brand new and this particulat circuit was a late add on and we knew virtually nothing about until I had to step in and start by drawing it all out.

The primary need for the circuit is to provide mains power to critical equipment during our transition form mains to our onsite gas fired gen sets. Normally our gen sets run it grid parrallel import mode (because we utilise waste exhaust heat for chilled and hot water services, but that another story).

But if the grid fails we can switch into complete island mode and run from the gen sets. The problem is that we need a source of electrical power to keep the auto gas shut off valves open (or the gens set stop, catch 22), the BMS system up (so that it can control the load shed and the controlled re-powering sequencing of the main DBs around the facility) and to power the motorised contactors (which bring on each main electrical panel).

Firstly we don't know exactly what else is connected to the UPS (I am planning to trace the cabling and draw it and label it). When we know we can calculate actual up time based upon current load.

The UPS feeds through a FG Wilson auto transfer switch, the UPS is connected as the "mains" input. The "gen" input to the transfer switch is a regular feed from an adjacnet panel. When the UPS fails the transfer switch goes to "gen" mode (which is really just mains).

I don't like this set up because to me it is flawed if the online UPS fails (like it now has). I have been trying to figure out a way of putting a second UPS in standby mode on the "gen" input the the transfer switch but it starts getting tricky to cover all scenarios. I have attached the circuit drawingh as we currently know it.

Are there similar appliactions and circuits that we can use or if anyone has a good idea to give us at least one level of redundancy.


TIA
Multivits

[voidstar_apc]

>
I don't like this set up because to me it is flawed if the online UPS fails (like it now has). I have been trying to figure out a way of putting a second UPS in standby mode on the "gen" input the the transfer switch but it starts getting tricky to cover all scenarios. I have attached the circuit drawingh as we currently know it.
>

I'll bet. The APC solution is to use a redundant UPS like Symmetra. Two advantages of Symmetra over having two separate UPSes:
- Two UPSes means you're buying twice the power, twice the batteries, etc. Symmetra uses an extra power module and extra batteries to get redundancy.
- If the UPS is hardwired, an electrician is needed to replace a failed UPS. Symmetra modules are user-swappable.

[BillP]

in addition to a modular and redundant UPS, you could also look into a service bypass panel which will give you a wrap around bypass. this means that if you need to take a UPS out of operation for any reason, you can use the wrap around bypass to bypass the UPS without taking your load down.

[here is a user manual for some of the service bypass panels|http://www.apcmedia.com/salestools/SCON-7Q3JQ2_R0_EN.pdf]

[Anonymous user]

Thanks "Picked a Winner"

Yes there is already a Service Bypass Panel (on the CCT diagram it is included in the UPS box).

We can also take the UPS out of service because of the feed into the transfer switch.

But my real concern is about supporting our essentials during the generators start up and shed if we have a failed UPS. As stated the generators can not start in a blackout situation unless the UPS is up to supply the gas auto shut off valve (and others).

TIA

Multivits

[Anonymous user · Accepted solution]

Hey Forum
I have been out of the game a for while and have been brought in to look at a troublesome critical electrical supply circuit.

Firstly though I am curious about why we need to configure a UPS in online mode, I have been told these are using the UPS power all the time instead of coming up when the mains fails (i.e. standby mode).

Back in the day I had my server room AS400s hooked up to a UPS which was in standby mode, I never had issues with a power up delay causing the AS400s to suffer from brown outs. Believe me this UPS would have to click on and operate 20 times a day at least. It took a lot of detective work and we found that the sari shop downstairs (on the same electrical feeder) had a big Daikin AC unit that would drop the voltage and click on our UPS every time the compressor ran. I loved those days in Sri Lanka.

So whats wrong with UPS in standby mode? Is it just a fad because the technology is now cheaper? I need to know because I may need to suggest a UPS in standby mode to satisfy the issue we have with this system.

TIA

Multivits