How many watts of power can a 3 phase 225 208y/120 produce on each leg

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BK4316

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We are installing a 3 phase 4 wire 225 208y/120 panel in a new building and there seems to be confusion between our Electrical designer and the reviewer of plans as to the load on the panel. The designer is saying we are way under the maximum wattage per leg it can provide and the reviewer is saying it is overloaded. From my readings it would be figured as: 225x208x1.73 = 80,964.00 but I am not sure if that is per leg or for all three legs combined.
Any help would be appreciated.
 
80.964 is the max KVA delivered to the load. Forget about terms like all three legs or per leg. Just confuses things.
If you are referring to the amps, you could at maximum have 225 amps "per leg" or per phase.

What is your load? That may help to define things further.
 
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powerpete69 said:
80.964 is the max KVA delivered to the load. Forget about terms like all three legs or per leg. Just confuses things.
If you are referring to the amps, you could at maximum have 225 amps "per leg" or per phase.

What is your load? That may help to define things further.
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The designer is saying the load is 132,283 total watts on the entire systems(Phase 1 - 44,096, Phase 2 - 44,136, Phase 3 - 44051)
 
I'm not sure it helps, but your power per leg would be 80.964 KVA divided by 3 = 26.988 KVA per leg. See, that doesn't help.

Perhaps there is a confusion between your connected load and your demand load. Demand load is implying that not everything is on at the same time.

TO OP, provide more much details and we can easily help you out.
 
BK4316 said:
The designer is saying the load is 132,283 total watts on the entire systems(Phase 1 - 44,096, Phase 2 - 44,136, Phase 3 - 44051)
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If that is the connected load, you may be ok. If your demand load or diversity is 50% of 132,283 watts, you might be alright. (66,141 watts)
If 132,283 is the demand load or diversified load, you are way overloaded and are going to trip the main breaker.

Which one is it? Or lets put it this way, what is your Total connected load with everything on? Is it the 132,283 number or is it a higher number?

If your plant manager feels that only half the load of this 132KW will be on all the time, then you can tell the plans examiner this information and they will have to believe it. It should already state it on the drawings. Usually its even 40% or can be 30%. That being said, if you are wrong and the demand load is higher than 50% and the breaker trips, it will be on your plant manager to pay for the upgrade. Your electrical designer can only go by the demand load that you tell him.

We typically talk in KVA than watts....but we'll save that for another time.
 
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If we do figure out that your are overloaded, not a problem. Install a 400 amp panel instead of the 225 amp panel.
There is always a solution.
 
powerpete69 said:
If that is the connected load, you may be ok. If your demand load or diversity is 50% of 132,283 watts, you might be alright. (66,141 watts)
If 132,283 is the demand load or diversified load, you are way overloaded and are going to trip the main breaker.

Which one is it? Or lets put it this way, what is your Total connected load with everything on? Is it the 132,283 number or is it a higher number?

If your plant manager feels that only half the load of this 132KW will be on all the time, then you can tell the plans examiner this information and they will have to believe it. It should already state it on the drawings. Usually its even 40% or can be 30%. That being said, if you are wrong and the demand load is higher than 50% and the breaker trips, it will be on your plant manager to pay for the upgrade. Your electrical designer can only go by the demand load that you tell him.

We typically talk in KVA than watts....but we'll save that for another time.
Click to expand...

the 132KW is the demand load with everything on, no doubt it will not all be on at the same time.
 
BK4316 said:
the 132KW is the demand load with everything on, no doubt it will not all be on at the same time.
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What you mean is the connected load.
The demand load is with the diversity of things not being on all the time.
The demand load is possibly 50% of that? Probably 40 or even 30 %.

In retrospect, a 400 amp panel probably would have been a better choice for future loads, but the 225A panel should work assuming the demand load is at the most half of the connected load.
 
powerpete69 said:
What you mean is the connected load.
The demand load is with the diversity of things not being on all the time.
The demand load is possibly 50% of that? Probably 40 or even 30 %.

In retrospect, a 400 amp panel probably would have been a better choice for future loads, but the 225A panel should work assuming the demand load is at the most half of the connected load.
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I agree, we originally ran 2 - 225 208y/120 panels from one building(it has an existing 800AMP MDP) to another separate building. Plans were approved for both but when we submitted for a single change in the plans, the actual change was accepted and then they came back and refused to approve the entire plan because of the two "feeds" so now we are trying to see if we can make one panel work without having to remove them both and putting in a new single feed. Big headache.
 
electrofelon said:
132KW is way more than a 225 amp panel can handle. You can't take some demand percentage off of that, that's not how it works.
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Interesting prospective.
We have done it that way for decades. The building department has never rejected the "demand load". In fact we make a chart that shows the connected load with the demand load (50% of connected load for example). We then plop that chart right on the permit set, usually on the single line.
Gets passed by building permit and works great in the field.

Should an AHJ reject such a thing, then it is what it is. I have yet to see that rejection.
 
BK4316 said:
I agree, we originally ran 2 - 225 208y/120 panels from one building(it has an existing 800AMP MDP) to another separate building. Plans were approved for both but when we submitted for a single change in the plans, the actual change was accepted and then they came back and refused to approve the entire plan because of the two "feeds" so now we are trying to see if we can make one panel work without having to remove them both and putting in a new single feed. Big headache.
Click to expand...
Again, if need be, run a 400 amp breaker, 500 MCM wire and a 400 amp panel.
 
powerpete69 said:
Interesting prospective.
We have done it that way for decades. The building department has never rejected the "demand load". In fact we make a chart that shows the connected load with the demand load (50% of connected load for example). We then plop that chart right on the permit set, usually on the single line.
Gets passed by building permit and works great in the field.

Should an AHJ reject such a thing, then it is what it is. I have yet to see that rejection.
Click to expand...
How do you come up with that demand load and/or what part of 220 is it in?
 
IMO What powerpete is describing is the diversified load. I usually reserve the term demand load for a load calculation based on NEC demand factors or calculations. I try not to size things based on diversified load because I don’t believe it’s approved by NEC in most cases.

An exception would be optional standby by generators , I take a closer look at the loads and operations of the building to get a better idea of what the actual load may be to determine a diversified load.

I do agree that if it’s seems reasonable and delivered professionally that a plans examiner will except it. I have recently started adding a “Power Management load summary” to some larger electric vehicle charging station sites that have the delivered power to each station limited due to how long the cars will be charging and I do size the service based on this number. I think the NEC is catching up to this principle and will have it covered soon but I don’t think as of right now I’m sizing these services with an approved NEC method.
 
Not sure if I follow the question! How are your served loads? There must be some demand factor you can lean on, IMO.
 
Just curious, is there anywhere in the code that explicitly says that a switchgear, MDP or power panel has to be designed around the idea of the connected load being lower than 80% of the Main Breaker?
 
electrofelon said:
No, unless the load is continuous.
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Perhaps that is why we can get away with it.
I personally prefer to design to the connected load, just because it gives plenty of room for future loads or sub panels.
But it is not always feasible especially when adding loads to existing panels or when you get into enormous amp situations.

Every examiner we have worked with has always wanted to know the load calculation whether it is a new or existing panel. We add the load chart with the connected and demand load and demand load percentage. On the single lines, right by the main breaker or MLO, we also put the connected amps, percentage of diversity and the diversity amps to add information as well.

Another good example is one of those older folks assisted living homes with the 208V MDP's. If you do a connected load on every PTAC, Refrigerator, Microwave, you get huge amps. Then add in the connected load of the entire main kitchen...etc. Obviously, these loads will not be on all at the same time. Some of these assisted living homes can have over a 5,000 amp connected load at 208V which is simply too big when you know the thing is going to happily run at 1,500 amps all day long. The plan examiners seem to take this into account especially when the drawings look professional.
 
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