UPS Upgrade

[electronext]

Im new here in the forum, and i've learned a lot of things by simply reading all posted threads. So, Thank you.
Can you guys help me on this. We need to upgrade our data center 30KVA UPS to 30KVA SMART UPS VT. this model include an automatic maintenance bypass panel. i attached here the existing electrical plan together with our proposed plan. my question is,
1. can we connect the existing 33KVA AVR before the new 30KVA UPS at the same 100AT lines?
2. Does the AVR consume as much current as the UPS?
3. Will there be any problem if an AVR is connected before the UPS? I mean, the redundancy on voltage regulation? We want to place the AVR before the UPS mainly because, at bypass mode (normal line) we still want the input supply to be regulated.

Any help will be much appreciated.

 

[rbulsara]

Why do you need an AVR, if you have an UPS? Someone is selling you something you do not need.

Rafiq Bulsara

http://www.srengineersct.com

 

[ScottyUK]

If you already have the regulator then I see no harm in keeping it although I'd be tempted to put it in the bypass supply only and feed the rectifier directly unless the supply is very weak and prone to wild fluctuations.

If you intend to regulate the mains to the UPS then the regulator appears to be marginally sized if you're expecting it to supply the UPS, plus its losses, and also the power required for recharging the battery following a power outage.


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If we learn from our mistakes I'm getting a great education!

 

[electronext]

We already have the AVR sir. Will the AVR act as a load? and if we connect the 33kva avr before the 30KVA UPS to 100AT lines, can the breaker sustain the current draw?

 

[alehman]

The AVR will not add much load - just it's internal losses. I agree that it seems unnecessary and it could interact unpredictably with the UPS rectifier input.

The 100A breaker is more than enough for 30kVA of load. Check with the UPS and AVR manufacturers for recommended breaker size.

If you must comply with the NEC, the 100A main breaker in your panel is too large. It should be 90A maximum for protection of the 45kVA transformer.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[waross]

Your bypass panel is missing one circuit breaker. I agree, following an outage, your 30 KVA UPS will be supplying the load and recharging the batteries and may draw more than the 33 KVA AVR can supply. I support the suggestion of installing the AVR in the bypass line only. That is between the bypass circuit breakers.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[electronext]

Thanks for all the reply. Really appreciated guys. I attached here the UPS & Automatic maintenance bypass panel connections. Im confused where we can connect the AVR in bypass mode? Without them connected at the same line? Because we eliminated all transfer switches since we will replace them with the automatic maintenance bypass panel.

 

[ScottyUK]

Sorry, I was assuming a single UPS, not a modular system. Most larger UPS designs have separate inputs to the rectifier and the bypass, but it doesn't look like an option on that design.


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If we learn from our mistakes I'm getting a great education!

 

[raithrovers1]

Scotty UK is correct. You orginal system had two sets of input terminals on the UPS. One for the rectifier supply and one for the bypass supply. On your original system you used the same supply for these from the 45kva isolating transformer through CB's.
Your new system may have the ability to be wired like this but you will have to check with APC.
The AVR is on the bypass line to protect the load from any fluctuations while the system is running in bypass either for maintenance or due to an inverter failure.
There is no real benefit from putting an AVR on the rectifier input supply and is only adding something to this supply that may fail.

UPS engineer

http://www.calibrepower.co.uk