residental load calculation

[fjm]

can someone help me load calculate this residence existing 150amp panel all electric house, think it's no more the 1000sqft. just by looking at the photo alone I'm coming out with 190 plus amps. I must not be doing this right. my plan was to add tandems and open two pole for a mini spilt now I'm wondering if the service can take it.

 

[GoldDigger]

A correct load calculation follows one of the two procedures set out in detail in the NEC.
It does not consist of adding up the breaker ratings.

 

[jumper]

can someone help me load calculate this residence existing 150amp panel all electric house, think it's no more the 1000sqft. just by looking at the photo alone I'm coming out with 190 plus amps. I must not be doing this right. my plan was to add tandems and open two pole for a mini spilt now I'm wondering if the service can take it.

Adding up breakers is incorrect.

You need to do a proper load calculation according to article 220.

Annex D in the back has examples that may help you familiarize yourself with the process.

 

[fjm]

I understand, I gave it a shot with breaker ratings and sq ft. isn't possible to get close with whats given in the photo and sqft 5000w dryer, 4500 HW, 9600w range, 1500w Laundry,3000w 2 S.A,1000sqft=3000va.and i fig the heat by 240x20=4800x3=14400x.8=11520. well pump?thats in there too, DW ? maybe

 

[jumper]

Did you look at the article and examples I cited?

 

[Dennis Alwon]

Without doing a calculation I am going to tell you that you are fine. I would be very surprised if you were even close to 125 amps

 

[Dennis Alwon]

I don't understand the heat-- I used 14,400kw and I came out with 140 amps but I added dishwasher , microwave and other stuff. I used a large well pump but that heat is awfully high for a 1000 sq, ft house- probably closer to 10,000 or 8,000 va,

With the heat at 10kw the service would work at 125 amps because the calculated load would be 118 amps

 

[fjm]

then I'm doing something really wrong. cause I'm coming up with 196a, gotta try it again what do you think of the baseboard heat calculation I'm using

 

[Dennis Alwon]

then I'm doing something really wrong. cause I'm coming up with 196a, gotta try it again what do you think of the baseboard heat calculation I'm using

I have no idea what you did there. How many units are they and what wattage are they? Are they separately controlled thermostatically?

 

[fjm]

yeah its a three bedroom little house 1000sq is a generous guess. HO wants a 1.5 ton minisplit. I did my load calculation over. GL 4575,dry 5000,range 9600, dw 900, hw 3375,micro1000, and well pump 3000va. total 22,875+4575=27,450 how much should I add for heat 100% of load.

 

[Ponchik]

View attachment 14357

I tried to attach a blank load calculation that I use on regular bases. Try it and see let me know how it works.

 

[Iron_Ben]

If this service is metered by a "smart" meter, actual load history may be readily available via the serving utility's website. We completed a changeout of all our meters (about 300,000) to smart three years ago. Some utilities were ahead of us and some behind. There's conflicting info out there, but I think by now, the US is at about 50% smart, maybe a little more.

 

[ActionDave]

then I'm doing something really wrong. cause I'm coming up with 196a, gotta try it again what do you think of the baseboard heat calculation I'm using

Did you take Jumper's advice. The annex is immensely helpful.

 

[kwired]

I understand, I gave it a shot with breaker ratings and sq ft. isn't possible to get close with whats given in the photo and sqft 5000w dryer, 4500 HW, 9600w range, 1500w Laundry,3000w 2 S.A,1000sqft=3000va.and i fig the heat by 240x20=4800x3=14400x.8=11520. well pump?thats in there too, DW ? maybe

What are individual unit ratings of the heaters? Looks like you just took three 20 amp circuits and assumed they all were loaded to 80%.

 

[fjm]

What are individual unit ratings of the heaters? Looks like you just took three 20 amp circuits and assumed they all were loaded to 80%.

I did. I never saw the baseboard heaters in each room, or how the circuit was separated.

 

[fjm]

Did you take Jumper's advice. The annex is immensely helpful.

I did the load calculation with the annex as per the advice and it did help me out, definitely refreshed my memory.

 

[iwire]

I understand, I gave it a shot with breaker ratings

Forget the breaker ratings, the breaker ratings have nothing to do with a load calculation at all.

Pick up a code book and look at 250.87.

 

[cpinetree]

Does the heat load even matter if you are adding a mini-split? or does the mini-split have heat also?
If no heat in the mini-split, the ac load and the mini split are going to be much less than the existing heat load.
I'm in Florida so mini splits with heat are very rare here.
Just curious

 

[GoldDigger]

Does the heat load even matter if you are adding a mini-split? or does the mini-split have heat also?
If no heat in the mini-split, the ac load and the mini split are going to be much less than the existing heat load.
I'm in Florida so mini splits with heat are very rare here.
Just curious

It is entirely common for a mini-split to be a heat pump, although without backup resistive heat. That could then be a concurrent load with other heating in the residence.

 

[cpinetree]

Does the heat load even matter if you are adding a mini-split? or does the mini-split have heat also?
If no heat in the mini-split, the ac load and the mini split are going to be much less than the existing heat load.
I'm in Florida so mini splits with heat are very rare here.
Just curious

It is entirely common for a mini-split to be a heat pump, although without backup resistive heat. That could then be a concurrent load with other heating in the residence.

Entirely possible yes, but what about this one?
Here in Florida we have wired exactly 1 with heat and well over 50 without.
I was just bringing it up as a question to the original poster.