# Sizing UPS and?

Status
Not open for further replies.

#### girl

##### Member
how to determine what size UPS I should buy if the load is :
six data (computer) units will be pluged in and each unit is:
30 Amps, 208 Volts (canadian way) which means 2 phases or one phase if we are talking USA way?

again: 6 units 30 amps EACH,
208 volts (two phase-two hot wires)

Do I add those 6+30= 180 amps, or?
Does it mean I need 200Amp UPS?

sorry guys but I really don't have a clue how to do it.

thank you all

#### iwire

##### Moderator
Staff member
30 amps does not sound like the load it sounds like the breaker or receptacle size. How did you come up with 30?

#### tonykarr

##### Member
Maximum UPS size would be .8x30 = 24A x208 = approx 5 KVA x 6 = 30 KVA. Usually the actual load of this type of equipment does not exceed 40-50% or the input circuit breaker, so 30 KVA would a good size.

#### girl

##### Member
30 amps does not sound like the load it sounds like the breaker or receptacle size. How did you come up with 30?
I did think amps are load? that is true we say 30 amps breaker or receptacle size, but also don't we say if we are measuring something with Amprobe and it reads 30Amps isn't it load?, I don't know? thanks.

#### girl

##### Member
Maximum UPS size would be .8x30 = 24A x208 = approx 5 KVA x 6 = 30 KVA. Usually the actual load of this type of equipment does not exceed 40-50% or the input circuit breaker, so 30 KVA would a good size.
I feel bad but I have to ask you more: for 30 KVA what size circuit breaker should be on the main panel so I can turn it ON/OFF?
Two pole, 208V, ...Amps?

*****Main panel is rated: 120/208 Volts, 200Amps. There are some other 1 pole and 2 pole breakers already on the panel for some other circuits (receptacles).

Thank you very, very much.

#### tonykarr

##### Member
For a 3 phase panel you will need 125A 3 poles C.B. (subfeed). You may be able to get by with 100A 3 poles but it may trip if the UPS is close to fully loaded after an extended power outage.

30,000/1.73/208 = 83A maximum current, plus you will need to add approx 10%-25% (depending on the UPS setting) for battery re-charge.

I don't think 30KVA UPS are available in single phase.

#### girl

##### Member
For a 3 phase panel you will need 125A 3 poles C.B. (subfeed). You may be able to get by with 100A 3 poles but it may trip if the UPS is close to fully loaded after an extended power outage.

30,000/1.73/208 = 83A maximum current, plus you will need to add approx 10%-25% (depending on the UPS setting) for battery re-charge.

I don't think 30KVA UPS are available in single phase.
tony, first of all I have to Thank you you very much for your help.

I would like to ask you a bit more: if I buy that 3 phase (pole) 125A subfeed, then what would be the size of the circuit breaker inside that panel: the same or a bit less, like is 100A circuit breaker ok?

Thank you from the bottom of my heart.

#### tonykarr

##### Member
What I meant by subfeed circuit breaker is that you will need to install this 125A CB within your 200A panel if it can accommodate it. Usually, you can't install CB larger than 100A in a distribution panel unless you either order the panel with a "subfeed" CB (larger than 100A) or rework the existing panel if legally possible.
It sounds like there are a lot of issues you need to address before you do proper planning, such as:
2. Are the loads 120 volts, 208/1 or and 208/3, or combination of all?
3. Are some of the proposed loads/circuits redundant? In other words, do the actual equipment requires two inputs (with dual power supplies)? New critical equipment such as servers do have dual power supplies.
4. What is the existing load on the existing 200A panel?
Is it single or 3 phase? Can it handle the proposed loads or you need to bring another feeder?

Based on what you find above, you can size the correct UPS and associated feeders, circuit breakers and distribution.

#### girl

##### Member
What I meant by subfeed circuit breaker is that you will need to install this 125A CB within your 200A panel if it can accommodate it. Usually, you can't install CB larger than 100A in a distribution panel unless you either order the panel with a "subfeed" CB (larger than 100A) or rework the existing panel if legally possible.
It sounds like there are a lot of issues you need to address before you do proper planning, such as: