Yea but it’s existing and there are a lot of loads, you just simply can’t get every load there is. Do we just go by rule of thumbs?
No you do a load calculation lol. That’s why we charge by the hour right ?? Or you could put a logging meter on it for a month or two
Think he is asking for an existing service, when should you inform POCO that you are adding significant amount of load that they may want to consider whether or not they need to increase transformer size. Just because you might have plenty of service conductor doesn't mean they have a transformer that can actually supply that much for extended periods of time. They tend to size transformers for actual demand conditions.
No engineer I know has ever done a calculation to check if load is adequate, they just simply did estimations
It depends on many factors. First you need to know what the demand history looks like and then figure what the future demand will look like.
A lot of the time you don't even need to calculate existing, contact the POCO and get demand history from them. May need to get the customer to authorize this before they will give it to you.
If I’m adding like 200kw, of course I would ask utilities if service is adequate, but if it’s 15kw, I’m not quite sure. I just don’t know where the line crosses
If adding 15 kW to a dwelling service chances are you contact POCO. If you adding 15 kW to something already served by a 1.5mVA transformer, you may not even be close to needing to contact them about it.
Very clearly that’s not what he asked. And either way still need to do a load calculation to tell the poco the intended load. And if they didn’t install a transformer for the current capacity that’s on them
What if it’s a residential apartment building?
I've had many situations where service was fairly oversized for the initial load, but when adding some significant load the POCO needed to increase transformer size, but the service was able to handle the additional load.
POCO's seldom install a transformer for current capacity unless maybe a larger commercial/industrial facility that is loaded to that capacity.
I wouldn't bother with a load calc, they are pretty much worthless and besides the POCO doesn't necessarily serve with the capacity of the service size.
I'll bet the POCO throws those stupid NEC load calcs in the garbage - they probably find them more worthless than I do
15 kVA is only 18 A at 480 V 3 phase. I would not worry all that much about adding such a minor load.
