WA. Master test question help (two dwelling units)

[JHansen]

This question has been asked similarly before, I need help with exactly how to solve it.

Below is an exact test question I faced with the Washington State Master Exam--- Major Calculations.

Using the optional method, calculate the total load on the service for a duplex with the following information.
1900 sq. feet
3K Water Heater
11 amp dishwasher
5 amp disposal
9K Range
3 AC's each 21 amps at 240 V
1 20K Heater

My problem is how to use the optional method for two units instead of three.

When I solve the VA for one unit, do I then multiply it by 3 and use Table 220.84 demand factor percentage for 3 units (which is 45%)?

There were 2 questions similar to the above. Using the optional method to solve a duplex.

I got a 60% which means I missed 4 questions

 

[Dave_B]

duplex

duplex

When I solve the VA for one unit, do I then multiply it by 3 and use Table 220.84 demand factor percentage for 3 units


a duplex is 2 unitshttp://forums.mikeholt.com/images/smilies/wink.gif

 

[charlie b]

When I solve the VA for one unit, do I then multiply it by 3 and use Table 220.84 demand factor percentage for 3 units (which is 45%)?

That is how I interpret 220.85.

 

[ray cyr]

The way I read this is, first do a standard or general calc (under part 3) for a 2 unit multifamily dwelling, then do an optional calc for an identical 3 unit multifamily dwelling (under part 4) and then compare the two values and choose the lesser.
Is this correct? or do I need to reread it?
Ray

 

[charlie b]

Sort of. You don't have to do the standard method. It would be to your advantage (or actually, the owner's advantage), but it is not necessary. That is because 220.84 allows you to use its method (i.e., pretending you have a 3-unit building), if that method gives you a lower answer than you get in Part III.

But if you get a lower answer from the Part III (Standard) method, you still get to use the optional method. You can always use the method that gives the higher result. So if you just use the 220.84 method, and never discover that the Part III method's answer would have been lower, you are still legal.