The most frustrating thing about the Major Calculations portion of the test is deciding which way to do the calculation. I have studied 2 reference manuals and Annex D of the NEC and still fail Laser Grade's version. Does anybody publish a reference (in English) that would help prepare a person to pass the WA Administrators test???
WA. Administrators
- Thread starter solson
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- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
If I may ask, what do you mean by "which way to do the calcs"? Do you mean the standard method and the optional method? If they don't tell you which to use, then do them both, and give the lower of the two answers as your answer.
CALCS
CALCS
I think I am allowing the vagueness of the questions confuse me. However, if they ask for standard calc on a duplex with 1 set of service conductors, do I combine all the loads as if it were a single family residence? If so, can I total the small appliances and apply 75% demand factor? If there is no dryer included in the residental calc am I to assume no 1500va laundry outlet? I could sit there and do all possible scenarios on each question but I would run out of time. The test proctors will not tell me which ones I missed so I never know if I picked the correct calc. I guess at $50 a throw its a valuable education.
CALCS
I think I am allowing the vagueness of the questions confuse me. However, if they ask for standard calc on a duplex with 1 set of service conductors, do I combine all the loads as if it were a single family residence? If so, can I total the small appliances and apply 75% demand factor? If there is no dryer included in the residental calc am I to assume no 1500va laundry outlet? I could sit there and do all possible scenarios on each question but I would run out of time. The test proctors will not tell me which ones I missed so I never know if I picked the correct calc. I guess at $50 a throw its a valuable education.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
What I tried to say is that if they do not tell you to use the standard method, then you should try both the standard and the optional, and use the lower of the two answers. But I suspect they will tell you which method to use.
If you are talking about a duplex, and if that means the utility supplies power to a pair of meters and each meter supplies power to a different half of the duplex, then you need to make sure you know whether the question is asking about the SERVICE to the building, or the FEEDER to a single unit. It sounds like the question you described is asking about the service to both units. In that case, you count all loads, and apply demand factors, treating it like a single building.
For example, you need to include 1500 VA for each of 2 SA circuits for each of 2 dwelling units. That counts as 6000 VA. Then you add the VA/sq.ft. for the total square feet in both units, and add 3000 VA to account for the laundry circuits for two units. Then you apply the demand factor for the total VA.
So, yes, if there are two fixed in place appliances in each unit, for a total of four, you do get to use a demand factor of 75% for this item.
As to whether or not to count laundry circuits, even if they don't give you the VA for a dryer, you still have to count 1500 VA for the laundry. That is to make sure the home can accommodate a washing machine and a gas dryer. If there is no load given in the problem for a dryer, then assume it is a gas dryer, and that its load is counted as part of the 3VA/sq.ft. The only time you get to omit the 1500 VA laundry circuit is if the problem explicitly states that there will be no laundry permitted in the building.
One final note, if they are asking about the feeder to one unit, you don't get to use demand factors that take into account the loads in the other unit. For example, if there are only two fixed-in-place appliances in each unit, then you get to use the 75% demand factor for the service to both units, but not for the feeder to a single unit.
If you are talking about a duplex, and if that means the utility supplies power to a pair of meters and each meter supplies power to a different half of the duplex, then you need to make sure you know whether the question is asking about the SERVICE to the building, or the FEEDER to a single unit. It sounds like the question you described is asking about the service to both units. In that case, you count all loads, and apply demand factors, treating it like a single building.
For example, you need to include 1500 VA for each of 2 SA circuits for each of 2 dwelling units. That counts as 6000 VA. Then you add the VA/sq.ft. for the total square feet in both units, and add 3000 VA to account for the laundry circuits for two units. Then you apply the demand factor for the total VA.
So, yes, if there are two fixed in place appliances in each unit, for a total of four, you do get to use a demand factor of 75% for this item.
As to whether or not to count laundry circuits, even if they don't give you the VA for a dryer, you still have to count 1500 VA for the laundry. That is to make sure the home can accommodate a washing machine and a gas dryer. If there is no load given in the problem for a dryer, then assume it is a gas dryer, and that its load is counted as part of the 3VA/sq.ft. The only time you get to omit the 1500 VA laundry circuit is if the problem explicitly states that there will be no laundry permitted in the building.
One final note, if they are asking about the feeder to one unit, you don't get to use demand factors that take into account the loads in the other unit. For example, if there are only two fixed-in-place appliances in each unit, then you get to use the 75% demand factor for the service to both units, but not for the feeder to a single unit.
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