Stuck on Load Calcs, Electrical Administrator Test WA

[User1728]

Hi everyone. I'm trying to pass the load calculation portion of my Electrical Administrator Test for Washington State. I have already passed the RCW/WAC and NEC portions. Today I took my test and missed it by one question (6/10). If anyone is able to answer some of the questions I have I would really appreciate it.
First off to calculate a duplex dwelling unit in the optional method my understanding is we treat it as an optional method triplex building (so we do a multifamily building calc the optional method). "SimplyElectrical" has a video on YouTube which I was using as a reference. During the test I did it this way and I wasn't getting the correct answer.
Secondly, I am doing a calc for a single commercial building, that has one single service entrance, but is split into two manufacturing facilities. At first I tried calculating the first facility and then the second and adding them together, but that didn't work. Then I tried calculating it all together since it's all on one service but that didn't work either.
I'm not exactly sure which ones I missed after that but I think it might have been a standard duplex dwelling unit and possibly a motor calc.
For the standard duplex dwelling unit I just did a standard single family dwelling unit but as I was going through it I multiplied everything by two before I applied demand factors. I learned to do it this way but I have seen it done other ways as well. Am I supposed to multiply it by 2 as I am going through AFTER the demand factors? Do I do a standard single calc and just multiply by 2 at the end?
I would appreciate any feedback on this and I will respond to any questions. This is my first time posting here, I tried not to go to indepth on the questions since I read somewhere it is a violation. Thank you all, I will not give up on this.

 

[TealHeals]

Oooooh - I remember a mixed commercial building question on my WA administrator exam.
For the standard duplex dwelling, I multiplied the loads by 2 before applying the demand factors. I would be curious to check the numbers on a standard calc for one - then multiplying it by 2 at the end. I don't think that would necessarily work because the 4 or more fixed appliances are counted across both units.
Good luck on your re-take. At least you won't have to slog through the other sections when you sit down with those calcs again.

 

[User1728]

Hmm, okay that's what I did for standard duplex, I will keep practicing that. Any idea on how to do the other two I mentioned? Do you know of anything I can use to practice; workbooks, YouTube videos, etc.

 

[TealHeals]

I'm not sure I got the mixed commercial one right - despite doing it the way I was taught and triple-checking my numbers. So I don't want to give you bad information. I did separate calcs based on the usage and then added up my final answers.
I really liked the Tom Henry's test prep book for the motors refresher.

 

[tortuga]

Hi everyone. I'm trying to pass the load calculation portion of my Electrical Administrator Test .../...
First off to calculate a duplex dwelling unit in the optional method my understanding is we treat it as an optional method triplex building (so we do a multifamily building calc the optional method).

Here is a duplex calc to chew on sorry its a bit long;
The next 5 questions will be based on the following scenario:
A 2000 sq ft home is being converted into a duplex.
Unit A (Existing Home, Remodeled):
The existing home will be gutted and rewired to current Code minimums. It will be reduced to 1400 sq ft and designated Unit A. The kitchen will include:

• a 1200 W dishwasher,
• a 1/3 HP 115 V garbage disposal motor load, and
• an 11 kW range.

Existing loads to remain include:

• a 240 V, 5500 W electric resistance water heater,
• two 240 V, 1.5 kW electric resistance heaters, and
• a 2-ton, 240 V ductless heat pump system.

When the heat-pump loads fan and compressor nameplate ratings ( FLA / RLA) are manually summed, the total is 19.2 A.
The nameplate also lists an MCA of 24.0 A and a MOP of 25 A.
Additional equipment includes:

• a laundry room with a washer and dryer (the dryer has a 22.5 A, 120/240 V nameplate), and
• an outdoor 7.2 kW EVSE.

The electric space heaters are individually controlled in the bedrooms and are expected to operate at the same time as the heat pump during the heating season.

Unit B (New Dwelling Unit):
The new dwelling unit will include 600 sq ft of existing space and a 400 sq ft addition.

Unit B will have:

• a 9.7 kW induction range,
• a 9 A, 120 V dishwasher,
• a 240 V, 4.5 kW electric resistance water heater, and
• a 240 V heat pump with a manually summed nameplate rating of 12.2 A,

The unit also includes a full laundry area with a 5 kW dryer, and a outdoor 7.2 kW EVSE.

Question 1
If the duplex is served by a 120/240V service the calculated load rounded to the nearest amp using the optional method in 220.85:
A) 237A
B) 320A
C) 240A
D) 243A

Spoiler: Answer

Unit​	Description​	VA​	QTY​	VA Extended​	AMPS​
Both​	Total SQFT​	3​	2400​	7200​	​
A​	Range​	11000​	1​	11000​	​
A​	EVSE​	7200​	1​	7200​	​
A​	Dryer​	5400​	1​	5400​	​
A​	Heatpump​	4608​	1​	4608​	​
A​	Water Heater​	5500​	1​	5500​	​
A​	Heaters​	1500​	2​	3000​	​
A​	Kitchen App​	1500​	2​	3000​	​
A​	Laundry​	1500​	1​	1500​	​
A​	Dishwasher​	1200​	1​	1200​	​
A​	Disposal 1/3HP​	864​	1​	864​	​
B​	Range​	9700​	1​	9700​	​
B​	EVSE​	7200​	1​	7200​	​
B​	Dryer​	5000​	1​	5000​	​
B​	Heatpump​	2928​	1​	2928​	​
B​	Water Heater​	4500​	1​	4500​	​
B​	Kitchen App​	1500​	2​	3000​	​
B​	Laundry​	1500​	1​	1500​	​
B​	Dishwasher​	1080​	1​	1080​	​
​	Sum of loads for both units​	​	​	85380​	​
​	​	​	​	​	​
​	Multiply sum of both by 1.5 to create 3 equal units​	128070​	​
​	​	​	​	​	​
​	Demand Factors for 3 units:​	​	45.00%​	​	​
​	Multiply By demand factor for three units​	​	​	57631.5​	240​

Note this is the same as a 67.5% demand factor for two units in table 220.84