additional loads, service upgrade

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flyingjon

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The original plan to upgrade a service is now under further review. :eek: A customer will be adding an immense spa/endless pool unit outside. 11KW/240V of electric heat, 40A/240V pumps for endless pool, and 50A/240V for the hydro-spa heat/pump. Do I figure this at continuous duty 125%, or just 100%. Or should a duty cycle be considered?Either way 140 amps of additional load is making me consider a 300 amp/ 240V service (install a 400 amp meter base capable of double lugging to create 2 taps for 150amp panelboards)
 
Re: additional loads, service upgrade

The largest motor is counted at 125%, and it?s good bet that one of the new pumps would qualify. But as to the required service size, I think you are into 220.31(A). Depending on how much of the ?heat/pump? is heat and how much is pump, and which motor gets the 25% add on, you are installing on the order of 35,000 watts of load. But only 8,000 watts of that needs to be counted at 100%. Figuring the remainder at 40% gives you about 18,800 new watts, or just under 80 new amps. How does that fit in with the existing service?

You can also use one year?s worth of maximum load data, if you can get it, or perform a 30 day load study, per 220.35. If you can show the owner right now that the new load would be too much for the existing service, then you will have no problems convincing them to upgrade to 300 amps.
 
Re: additional loads, service upgrade

On Mike Holts Home Site under Free Stuff there is a nice Residential Load Caculator that can assist you in this caculation
 
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