Single dwelling load calculation

[Copperclad]

Hi All!
I have a customer that is bent on replacing his traditional water heater with a tankless model.
This thing is 24kw! Ive done many "insta hot" installs over the years, but this is my first in a residence.
The first thing I did was a load calculation on the dwelling. Please someone check my math, I feel this can not be right.

1700 sq ft livable space 1700 X 3 = 5100w
(2) small appliance ckts@1500 ea= 3000w
(1) additional sm. app. ckt@1500= 1500w
(1) laundry ckt@1500 ea. 1500w
lighting sub total 11,100w

1st 3000w @ 100% 3000w
remainder from 3001 to 120,000@35% 6000w
remainder over 120,000 n/a

total lighting load 9000w

appliance load
(1) disp @ 600 600w
(1) micro @ 1500 1500w
(1) d/w @ 1200 1200w
(1) food center@600 600w

appliance sub total 3900w

3900@ 75% (4 or more units)
total appliance load 2229w

(1) electric clothes dryer @ 5000 5000w
(1) proposed water htr @ 24000 24000w
(1) range @ 8000 8000w

(1) electric heat @10000 X 1.25 12,500w
supplementary heat (space htr) 1500w

(1) pool pump @1200X 1.25 1500w


(2) wood saws in shop @ 3700 ea 7400w


Ok now, Please correct if Im wrong guys,

9000 lighting
2229 appliance

 

[Copperclad]

sorry for the lengthy post

sorry for the lengthy post

Sorry guys for the lengthy post. I came up with a total
70,000w / 240 = 291 amps!~?
Is even close to being right?

Any advise will be appreciated.

 

[conmgt]

I don't think you need to add both saw in the shop at 100%. What is the horsepower?
The chances that both saws would be on at the same time AND bogged down to draw full current is unlikely.

The DHW is 100A on its own.

 

[suemarkp]

I'd give the Optional calculation a try, as you can apply a 40% factor to the water heater. Space heating does not have to be 125% for the Optional calc, nor do I think it has to be for the standard either.

I think too many people over rate the benefit of a tankless water heater, and there are negatives if you exceed the flow rate or the controls aren't very good. The losses in a well insulated tank are not that much. It takes a lot of energy to heat water. I'd suggest a heat pump water heater instead as that should be the cheapest way to heat water with electricity.

 

[Smart $]

...

1700 sq ft livable space 1700 X 3 = 5100w
(2) small appliance ckts@1500 ea= 3000w
(1) additional sm. app. ckt@1500= 1500w
(1) laundry ckt@1500 ea. 1500w
lighting sub total 11,100w

1st 3000w @ 100% 3000w
remainder from 3001 to 120,000@35% 6000w
remainder over 120,000 n/a

total lighting load 9000w

...

That's all the further I got before major discrepancy...

It's 8,100 ? 35% = 2,835VA, not 6,000VA

Total Lighting Load Demand = 5,835VA