Fun practice Service Load Calc.

[Dsg319]

I would bet it is near impossible to write one of these books and not have a mistake here or there.

Yep I’m sure somebody can find one in any book no matter the author.

I used Ray Holders material for both of my test, along with Mikes.

 

[kevin]

I think the neutral calc is incorrect. It is using the water heater as 120v load. Although it doesn't state 120 or 240 one usually assumes 240v on the water heater so no neutral load there. I stand by 230 amps for the neutral until I find another of my mistakes.

Did you apply 220.61(B)(1)? I agree with 230 amps for the neutral (as a starting point), but took the first 200 at 70 percent, the remainder (30 amps) at 70 percent and ended up with a final value of 221 amps for neutral.

 

[Dennis Alwon]

The 230 amps for the neutral included 70% for the range and dryer neutral in my calc

Lighting and Receptacles		16,125
Appliances		8,775
Dryers		15,750
Cooking Equipment		14,448
A/C versus Heat
Total Demand Volt-Amperes		55,098
Total Demand Amperes		230

 

[kevin]

The 230 amps for the neutral included 70% for the range and dryer neutral in my calc

Lighting and Receptacles		16,125
Appliances		8,775
Dryers		15,750
Cooking Equipment		14,448
A/C versus Heat
Total Demand Volt-Amperes		55,098
Total Demand Amperes		230

I fully agree with your calculations. Bright minds think alike! However, I think that we are entitled to use 220.61(B) to further reduce the 230 amps.
See Informative Annex D, Example D4(A). At the very end, the "Minimum Size Main Feeders (or Service Conductors) Required" are calculated using a "Further Demand Factor". It appears that the 70% Permitted Reductions of 220.61(B) apply to (the previously reduced) 70 % of the range neutral.
That's my read FWIW.

 

[Konen]

I fully agree with your calculations. Bright minds think alike! However, I think that we are entitled to use 220.61(B) to further reduce the 230 amps.
See Informative Annex D, Example D4(A). At the very end, the "Minimum Size Main Feeders (or Service Conductors) Required" are calculated using a "Further Demand Factor". It appears that the 70% Permitted Reductions of 220.61(B) apply to (the previously reduced) 70 % of the range neutral.
That's my read FWIW.

 

[Konen]

Question for all you Load Calculation Masters.

On the topic of motors:
430.24 Says:
"Conductors supplying several motors, or a motor(s) and other load(s), shall have the ampacity not less than the sum of each of the following:
(1) 125% of the FLC rating of the highest rated motor, as determined by 430.6(A)
(2) Sum of the FLC rating of all other motors in the group, as determined by 430.6(A)
(3) 100% of the noncontinuous nonmotor load
(4) 125%% of the continuous nonmotor load"

Now when sizing the Service conductors for let's say:

(1) 480v, 2hp, 3ø-2,827VA
(1) 480v, 5hp, 3ø-6,319VA
(1) 480v, 10hp, 3ø-11,639VA

I would do 125% of 11,639VA=14,549VA
14,549VA+6,319+2,827VA=23,695VA

Now would this calculation change if one of those motors was rated for continuous use?

 

[kevin]

Question for all you Load Calculation Masters.

On the topic of motors:
430.24 Says:
"Conductors supplying several motors, or a motor(s) and other load(s), shall have the ampacity not less than the sum of each of the following:
(1) 125% of the FLC rating of the highest rated motor, as determined by 430.6(A)
(2) Sum of the FLC rating of all other motors in the group, as determined by 430.6(A)
(3) 100% of the noncontinuous nonmotor load
(4) 125%% of the continuous nonmotor load"

Now when sizing the Service conductors for let's say:

(1) 480v, 2hp, 3ø-2,827VA
(1) 480v, 5hp, 3ø-6,319VA
(1) 480v, 10hp, 3ø-11,639VA

I would do 125% of 11,639VA=14,549VA
14,549VA+6,319+2,827VA=23,695VA

Now would this calculation change if one of those motors was rated for continuous use?

No change if the 10 HP motor were the only continuous load.
Add 25% of the VA of either or both of the other two motors if any of them were continuous.

 

[Konen]

No change if the 10 HP motor were the only continuous load.
Add 25% of the VA of either or both of the other two motors if any of them were continuous.

Awesome thank you, that was one of the big questions I had, I'm trying to get in touch with PSI to reschedule my Major load calculations exam but they changed all there numbers

 

[Dennis Alwon]

I guess I never realized there was a

I fully agree with your calculations. Bright minds think alike! However, I think that we are entitled to use 220.61(B) to further reduce the 230 amps.
See Informative Annex D, Example D4(A). At the very end, the "Minimum Size Main Feeders (or Service Conductors) Required" are calculated using a "Further Demand Factor". It appears that the 70% Permitted Reductions of 220.61(B) apply to (the previously reduced) 70 % of the range neutral.
That's my read FWIW.

I never realized there was another 70%-- my bad. If I looked further on the spreadsheet I would have seen it. This is a Mike Holt spreadsheet that I just total screwed up because I never used it. I used the single family one. Mike got 221 also. Thanks to both of you.

 

[NAjxBUEEdA7PoKoX7vD2]

I tested my multifamily load calc spreadsheet with the example in this thread a couple of days ago. I have since reworked my dryer logic and the appliance count as applied to the service. I am now on the issue of selecting cooking B or C. Could it be different for the feeder and for the service?

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The heading for Table 220.55 reads: (Column C to be used in all cases except as otherwise permitted in Note 3.)

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Note 3. Over 13∕4 kW through 83∕4 kW. In lieu of the method provided in Column C, it shall be permissible to add the nameplate ratings of all household cooking appliances rated more than 13∕4 kW but not more than 83∕4 kW and multiply the sum by the demand factors specified in Column A or Column B for the given number of appliances. Where the rating of cooking appliances falls under both Column A and Column B, the demand factors for each column shall be applied to the appliances for that column, and the results added together.

---

The 2017 Handbook commentary:

The values in Column C are applicable to installations where all
ranges in the group have the same rating. Note 1 applies where the
ranges are rated greater than 12 kilowatts and Note 2 applies where the
ranges in a group have different ratings. Column C must be used unless
Note 3 is applicable. Notes 3 and 4 cover installations where the circuit
supplies multiple cooking components, which are combined and
treated as a single range.

Table Note 3. For a group installation of ranges with ratings between
13⁄4 kilowatts through 83⁄4 kilowatts, the ratings are permitted to be added
together for determining a demand factor. Ranges rated below 31⁄2 kilowatts
should be grouped independently of those rated 31⁄2 kilowatts and
above. The appropriate column (A or B) is used rather than Column C.
Calculation Example
Determine the maximum demand for 4 ranges rated at 4.5 kW, 5 kW,
5 kW, and 8.5 kW, respectively.
Solution
Step 1. Combine ratings into single value: 4.5 kW + 5 kW + 5 kW +
8.5 kW = 23 kW
Step 2. Determine demand factor: 50% (Column B, 4 ranges)
Step 3. Calculate the maximum demand: 23 kW × 50% = 11.5 kW

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Here is a chart of the difference between Column C and Column B at 1 to 75 units.

 

[Konen]

I tested my multifamily load calc spreadsheet with the example in this thread a couple of days ago. I have since reworked my dryer logic and the appliance count as applied to the service. I am now on the issue of selecting cooking B or C. Could it be different for the feeder and for the service?

---

The heading for Table 220.55 reads: (Column C to be used in all cases except as otherwise permitted in Note 3.)

---

Note 3. Over 13∕4 kW through 83∕4 kW. In lieu of the method provided in Column C, it shall be permissible to add the nameplate ratings of all household cooking appliances rated more than 13∕4 kW but not more than 83∕4 kW and multiply the sum by the demand factors specified in Column A or Column B for the given number of appliances. Where the rating of cooking appliances falls under both Column A and Column B, the demand factors for each column shall be applied to the appliances for that column, and the results added together.

---

The 2017 Handbook commentary:

The values in Column C are applicable to installations where all
ranges in the group have the same rating. Note 1 applies where the
ranges are rated greater than 12 kilowatts and Note 2 applies where the
ranges in a group have different ratings. Column C must be used unless
Note 3 is applicable. Notes 3 and 4 cover installations where the circuit
supplies multiple cooking components, which are combined and
treated as a single range.

Table Note 3. For a group installation of ranges with ratings between
13⁄4 kilowatts through 83⁄4 kilowatts, the ratings are permitted to be added
together for determining a demand factor. Ranges rated below 31⁄2 kilowatts
should be grouped independently of those rated 31⁄2 kilowatts and
above. The appropriate column (A or B) is used rather than Column C.
Calculation Example
Determine the maximum demand for 4 ranges rated at 4.5 kW, 5 kW,
5 kW, and 8.5 kW, respectively.
Solution
Step 1. Combine ratings into single value: 4.5 kW + 5 kW + 5 kW +
8.5 kW = 23 kW
Step 2. Determine demand factor: 50% (Column B, 4 ranges)
Step 3. Calculate the maximum demand: 23 kW × 50% = 11.5 kW

---

Here is a chart of the difference between Column C and Column B at 1 to 75 units.

I've noticed in this book they tend to lean towards column C because as far as I have seen it lowers the demand load

 

[TheWantonElectrician]

I'm having trouble understanding why in Konen's Multi-Family Standard Calculation example Column B's 0.43 demand factor (corresponding to 6 units) is used, as opposed to Column C's 20kVA maximum demand. In the Annex D4(b), the value from column C is used (20 ranges = 35,000VA). Does it have to do with using the standard method vs optional (or multifamily optional)?

 

[Little Bill]

I'm having trouble understanding why in Konen's Multi-Family Standard Calculation example Column B's 0.43 demand factor (corresponding to 6 units) is used, as opposed to Column C's 20kVA maximum demand. In the Annex D4(b), the value from column C is used (20 ranges = 35,000VA). Does it have to do with using the standard method vs optional (or multifamily optional)?

Welcome to the Forum!
Would you please go into your profile and add your occupation?

 

[Dennis Alwon]

I'm having trouble understanding why in Konen's Multi-Family Standard Calculation example Column B's 0.43 demand factor (corresponding to 6 units) is used, as opposed to Column C's 20kVA maximum demand. In the Annex D4(b), the value from column C is used (20 ranges = 35,000VA). Does it have to do with using the standard method vs optional (or multifamily optional)?

Any range up to 12kw can use col.B so I suspect that the .43 factor ends up less than the 21,000 from col c

 

[TheWantonElectrician]

Hence the change from positive to negative in NAjxBUEEdA7PoKoX7vD2's chart as more appliances are added. Thanks!

 

[Little Bill]

Hence the change from positive to negative in NAjxBUEEdA7PoKoX7vD2's chart as more appliances are added. Thanks!

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