Another Table 220.55 question

[Grouch1980]

I've searched thru several threads on this one, but couldn't find an answer.

Regarding Notes 1 and 2 for Table 220.55, how come the notes only mention 'ranges'. For example, Note 1 says "Over 12 kW through 27 kW ranges all of same rating." Note 2 says "Over 8-3/4 kW through 27 kW ranges of unequal ratings"

How come these notes don't mention individual ovens or cooktops? If you look at examples, they include ovens and cooktops. It's differentiated in the title of the table, but not in these 2 notes. OR is it the intent of the word 'ranges' to include individual ovens and cooktops? I know a range is a combination cooktop and oven, but why is it differentiated in the title of the table, and not these notes?

 

[wwhitney]

How come these notes don't mention individual ovens or cooktops?

Because Note 3 covers those. So if you have an oven or cooktop above 12 kW, looks like you don't get to use any demand factor for those appliances.

Cheers, Wayne

 

[Grouch1980]

But in this thread: https://forums.mikeholt.com/threads...sing-column-c-after-using-column-b-c.2559362/

A 6 kW cooktop is used in the example, and column C is applied, note 2. The 6 kW cooktop is brought up to 12 kW, to comply with Note 2.

What I'm getting at is that a cooktop was used with note #2. Yes note 2 only mentions 'ranges.'

 

[wwhitney]

But in this thread: https://forums.mikeholt.com/threads/table-220-55-–-demand-factors-for-household-electric-ranges-using-column-c-after-using-column-b-c.2559362/

A 6 kW cooktop is used in the example, and column C is applied, note 2. The 6 kW cooktop is brought up to 12 kW, to comply with Note 2.

No. Whenever you have N cooking appliances, all of which are at most 12 kW, of any type, you can just ignore all the notes and Columns A and B and just use the Column C number for that number of cooking appliances. That's what the very lengthy title of Table 220.55 tells you.

You only need to look at the Notes and Columns A and B if (a) you have ranges above 12 kW (see Notes 1 and 2) or (b) you have some cooking appliances below 8.75 kW and you want to see if the alternative method listed in Note 3, which utilizes Columns A and B, gives you a lower answer.

So Note 2 plays no part in the answer in the thread you referenced. It's just a straight lookup in Column C, 2 cooking appliances, each no more than 12 kW.

Cheers, Wayne

 

[Grouch1980]

No. Whenever you have N cooking appliances, all of which are at most 12 kW, of any type, you can just ignore all the notes and Columns A and B and just use the Column C number for that number of cooking appliances. That's what the very lengthy title of Table 220.55 tells you.

That I follow.

You only need to look at the Notes and Columns A and B if (a) you have ranges above 12 kW (see Notes 1 and 2) or (b) you have some cooking appliances below 8.75 kW and you want to see if the alternative method listed in Note 3, which utilizes Columns A and B, gives you a lower answer.

I follow that too.

So Note 2 plays no part in the answer in the thread you referenced. It's just a straight lookup in Column C, 2 cooking appliances, each no more than 12 kW.

Cheers, Wayne

But look at Post #12 in the thread. A 6 kW cooktop is being converted to 12 kW, using Note 2. If Note 2 only mentions 'ranges'... how come a cooktop was applied?

 

[wwhitney]

But look at Post #12 in the thread. A 6 kW cooktop is being converted to 12 kW, using Note 2.

I don't agree with that statement from Post #12 of that thread. We can delete all the notes and Columns A and B, and then just based on table heading and Column C say " How many appliances? 2. Are they all 12 kW or less? Yes. Then the answer is 11 kW." There's no need to "promote" the cooktop to 12 kW, just to note that 6 kW <= 12 kW.

Now it is interesting to note that the answer doesn't depend on the exact rating of the two cooking appliances, 2 cooking appliances in Column C means 11 kW, whether the two appliances are 12 kW each or 2 kW each. Of course, in the latter case you are clearly better off using the optional method of Note 3 instead of the default method of Column C.

In other words, you only need Note 2 if one or more of the cooking appliances, but not all of them, is over 12 kW, and the appliances over 12 kW are all ranges. As without Note 2, you wouldn't be able to use the Table in that case.

Cheers, Wayne

 

[Grouch1980]

I don't agree with that statement from Post #12 of that thread. We can delete all the notes and Columns A and B, and then just based on table heading and Column C say " How many appliances? 2. Are they all 12 kW or less? Yes. Then the answer is 11 kW." There's no need to "promote" the cooktop to 12 kW, just to note that 6 kW <= 12 kW.

I follow.

Now it is interesting to note that the answer doesn't depend on the exact rating of the two cooking appliances, 2 cooking appliances in Column C means 11 kW, whether the two appliances are 12 kW each or 2 kW each. Of course, in the latter case you are clearly better off using the optional method of Note 3 instead of the default method of Column C.

I follow.

In other words, you only need Note 2 if one or more of the cooking appliances, but not all of them, is over 12 kW, and the appliances over 12 kW are all ranges. As without Note 2, you wouldn't be able to use the Table in that case.

Cheers, Wayne

So Note 1 and Note 2 is strictly for ranges. If I have a cooktop, or an oven, Note 1 and Note 2 don't apply. Do I have that correct?

 

[wwhitney]

So Note 1 and Note 2 is strictly for ranges. If I have a cooktop, or an oven, Note 1 and Note 2 don't apply. Do I have that correct?

Certainly that's what the text of Note 1 and Note 2 say, they use the word "range" rather than "household cooking appliance" as in Note 3.

However, it seems to me that Notes 1-3 give comparatively overly conservative answers in several cases:

Example 1(a): 3.5 kW + 8.75 kW gives (0.75*3.5 + 0.65*8.75) = 8.31 kW
Example 1(b): 3.5 kW + 9 kW gives 11 kW

Example 2(a) 6 kW range + 14 kW range gives 11 * 1.05 = 11.55 kW
Example 2(b) 6 kW cooktop + 14 kW range gives (0.8*6 + 8*1.1) = 13.6 kW

Cheers, Wayne

 

[Grouch1980]

Is this correct? 10 kW oven + 11 kW range + 15 kW range gives (8 (for the oven, column C, no notes apply) + 12.1 (for the 2 ranges, note 2)) = 20.1 kW

 

[Grouch1980]

Example 2(b) 6 kW cooktop + 14 kW range gives (0.8*6 + 8*1.1) = 13.6 kW

Don't you have to use though column C OR columns A & B? This is a mix of column B and column C.

I swear, I will never understand this table fully. The authors were too ambitious in combining everything into one table. It should be partitioned into several tables to avoid confusion.

 

[wwhitney]

Is this correct? 10 kW oven + 11 kW range + 15 kW range gives (8 (for the oven, column C, no notes apply) + 12.1 (for the 2 ranges, note 2)) = 20.1 kW

I agree. But I also think that there's no good reason for this code section to treat that combination differently from 10 kW range + 11 kW range + 15 kW range.

Don't you have to use though column C OR columns A & B? This is a mix of column B and column C.

Well, with the above mix of appliances, you split them into two groups, and applied the table separately to each group, and added the results. When doing that, each application of the table is separate, so one application can use column C, the other columns A&B.

Cheers, Wayne

 

[Grouch1980]

Example 2(b) 6 kW cooktop + 14 kW range gives (0.8*6 + 8*1.1) = 13.6 kW

I assume another way to calculate this is to apply column C to the 6kw cooktop… 8kw, and then add 8*1.1 = 16.8kw.

Is this correct? But we would use the 13.6kw answer since it is lower.

 

[wwhitney]

I assume another way to calculate this is to apply column C to the 6kw cooktop… 8kw, and then add 8*1.1 = 16.8kw.

Is this correct? But we would use the 13.6kw answer since it is lower.

Yes on both.

These examples show that Table 220.55 adequately covers the case of many household cooking appliances of not more than 8.75 kW; many household cooking appliances between 8.75 KW and 12 kW; and many ranges. But it seems a bit unreasonable when mixing those categories.

At a minimum, I think there should be a Note 3.5 that says "with N household cooking appliances not more than 8.75 kW and M ranges, you can use the row M value from column C (as adjusted per Notes 1 and 2 if necessary) for the ranges along with the row N+M values from columns A and B (as per Note 3) for the household cooking appliances."

But we don't have that. Moreover, IIRC the examples in Annex D all carefully avoid these mixed cases.

Cheers, Wayne

 

[Grouch1980]

Moreover, IIRC the examples in Annex D all carefully avoid these mixed cases.

Yessss!!! They give you clean examples. Avoiding the difficult ones. Annex D provides no help.

Thanks for the help.

 

[Grouch1980]

Is this correct? 10 kW oven + 11 kW range + 15 kW range gives (8 (for the oven, column C, no notes apply) + 12.1 (for the 2 ranges, note 2)) = 20.1 kW

I have another way of looking at my example… is this correct also?

11 kW demand for the 10 kW oven and 11 kW range.. using row 2 of column C.

And for the 15 kW range… using note 2 gives you 9.2 kW.

11 kW + 9.2 kW gives you 20.2 kW.

However, I would use 20.1 kW from my original way in Post #9 since it is a lower value (although a minor difference).

 

[NAjxBUEEdA7PoKoX7vD2]

See the last post on this page:

https://forums.mikeholt.com/threads/combined-apartments-and-article-220.2565817/#post-2729121

and the first post on this page:

https://forums.mikeholt.com/threads/article-220-load-calculation-question.2565539/

This topic is not worth nitpicking. Article 220 needs to be rewritten so it includes Excel formulas. I can assure you that the graph of demand increase with the number of units is not actually a sawtooth. In some places at least, Article 220 lacks wisdom and credibility. It is poorly written.