220.44 – Handbook Commentary

[charlie b]

I am supporting the design for a large hotel. The calculated service load is very close to pushing us up from a 5000 amp board to the next standard size of 6000 amps, and we really don’t want to go there.

Table 220.42 (applicable to lighting loads) gives us more generous demand factors than does Table 220.44 (applicable to receptacle loads). The Handbook Commentary that follows article 220.44 says that we can combine the receptacle load with the lighting load, and use the demand factors of Table 220.42. (Actually, the Commentary points us to Table 220.12, but I think that is a typo.) I don’t quite see that in the words of the article.

For receptacle load in non-dwelling units, I have always used the “100% of the first 10K and 50% of the rest” rule. Can I take the 50/40/30 rule that applies to hotel lighting loads, and use to for the receptacles as well? If so, can I take the further step of adding the lighting to the receptacles, before applying the 50/40/30 rule? For this project, it would give us another 200 amps of margin below the 5000 amp service size.

 

[petersonra]

hmmm

220.44 Receptacle Loads — Other Than Dwelling
Units. Receptacle loads calculated in accordance with
220.14(H) and (I) shall be permitted to be made subject to
the demand factors given in Table 220.42 or Table 220.44.

220.14 Other Loads — All Occupancies.
****
(H) Fixed Multioutlet Assemblies. Fixed multioutlet assemblies
used in other than dwelling units or the guest
rooms or guest suites of hotels or motels shall be calculated
in accordance with (H)(1) or (H)(2). For the purposes of
this section, the calculation shall be permitted to be based
on the portion that contains receptacle outlets.

So, I would suggest you can only use the provision you want for other then dwelling rooms.


However, take a close look at 220.14 (J)

(J) Dwelling Occupancies. In one-family, two-family, and
multifamily dwellings and in guest rooms or guest suites of
hotels and motels, the outlets specified in (J)(1), (J)(2), and
(J)(3) are included in the general lighting load calculations
of 220.12. No additional load calculations shall be required
for such outlets.

Does that mean what it appears to mean at first glance?

 

[charlie b]

Thanks, Bob. But I don't think we are dealing with 220.14(H), "fixed multioutlet assemblies." To me, that brings to mind a picture of a lab bench with a receptacle every two feet within a surface raceway. I think instead that we are dealing with 220.14(I), and 180 VA per duplex receptacle.

Regarding 220.14(J), we are not calculating the lighting load using the 2 VA per square foot allowance. Rather, we are adding up the actual ratings of the luminaires, using a panel schedule Excel file that does the math for us. So I don't think I can take advantage of this article.

 

[steve66]

I am supporting the design for a large hotel. The calculated service load is very close to pushing us up from a 5000 amp board to the next standard size of 6000 amps, and we really don’t want to go there.

Table 220.42 (applicable to lighting loads) gives us more generous demand factors than does Table 220.44 (applicable to receptacle loads). The Handbook Commentary that follows article 220.44 says that we can combine the receptacle load with the lighting load, and use the demand factors of Table 220.42. (Actually, the Commentary points us to Table 220.12, but I think that is a typo.) I don’t quite see that in the words of the article.

For receptacle load in non-dwelling units, I have always used the “100% of the first 10K and 50% of the rest” rule. Can I take the 50/40/30 rule that applies to hotel lighting loads, and use to for the receptacles as well? If so, can I take the further step of adding the lighting to the receptacles, before applying the 50/40/30 rule? For this project, it would give us another 200 amps of margin below the 5000 amp service size.

Yes, that's the way I understand it.

As far as seeing it in the words of the article, look at 220.12(J). It says all general use outlets are included in the lighting load calculation of 220.12. No additional load shall be required for such outlets.

 

[steve66]

Regarding 220.14(J), we are not calculating the lighting load using the 2 VA per square foot allowance. Rather, we are adding up the actual ratings of the luminaires, using a panel schedule Excel file that does the math for us. So I don't think I can take advantage of this article.

Try using the 2VA /SF (which includes the guest room receptacle loads), and apply the demand factors in Table 220.42. That gives you a 30% demand factor for a large percentage of your load.

 

[charlie b]

I appreciate the input, but I don't think I am making my issue clear. I don't think 220.12 is a player anymore. At the start of a project, I might assign 2VA/SF as the lighting load, and I know I won't have to separately account for general purpose receptacles. But we are way past that point. The design is essentially done. I know exactly how many light fixtures of which types will be installed, and I therefore know that load. How that number relates to 2VA/SF is no longer important. I must provide a branch panel that is rated to handle the amount of lights I have placed on that panel, not the amount of VA associated with the area that that panel serves. I must provide a service that is rated to handle the total load that I have designed to be installed, not the amount of VA associated with the total area of the building. The service load has been calculated by taking the connected VA for each circuit at the branch panel level, adding up the circuit loads to get the BP loads, adding up the branch panel loads to get the distribution panel loads, and adding up the distribution panel loads to get the service load. At each of those panels (i.e., branch, DP, and service), I can apply demand factors to the load connected to that panel (including load connected to all its downstream panels), to get the calculated load for that panel.

For this specific project, I don't need to get fancy at the BP or DP level. But I am asking whether, at least at the service panel, I can take all the loads that had been classified as receptacles, and all the loads that had been classified as lighting, add the two together, and then apply the 50/40/30 demand factors of Table 220.42. What I am doing now is to apply the 50/40/30 only to the loads classified as lighting. I am applying the 50% of loads over 10K rule to loads classified as receptacles. If I can apply the 50/40/30 rule to receptacles, I can save 200 amps on the calculated service size.

 

[augie47]

Please take any Art 220 comment I make with a grain of salt, but it seems to me the receptacle outlets associated with the dwelling units (guest rooms/guest suites) would be subject to 220.42 and all others to 220.44.

 

[Smart $]

.... I don't think 220.12 is a player anymore. ...

The simple answer is, if you are not calculating lighting load per 220.12, your calculation is not NEC compliant. The only time you can use connected load in your calculation is when it exceeds 220.12 value, or if your project qualifies under the exception for energy codes.

When your calculation is compliant with 220.12, through 220.14(J) the general use receptacles of hotel rooms are included in the lighting load.

220.42 and its table have no bearing on the matter, as all the calculation criteria must be met prior to getting to that stage of the calculation.

 

[Sahib]

The intent of code to apply 2VA/sq.ft even when you know actual loads is to provide spare capacity. Have you included spare circuits or provisìon for it in your design Charlie?

 

[steve66]

For this specific project, I don't need to get fancy at the BP or DP level. But I am asking whether, at least at the service panel, I can take all the loads that had been classified as receptacles, and all the loads that had been classified as lighting, add the two together, and then apply the 50/40/30 demand factors of Table 220.42. What I am doing now is to apply the 50/40/30 only to the loads classified as lighting. I am applying the 50% of loads over 10K rule to loads classified as receptacles. If I can apply the 50/40/30 rule to receptacles, I can save 200 amps on the calculated service size.

Yes, for all the guest room receptacles per 220.12 J.

Please take any Art 220 comment I make with a grain of salt, but it seems to me the receptacle outlets associated with the dwelling units (guest rooms/guest suites) would be subject to 220.42 and all others to 220.44.

That's exactly how I see it too.

 

[Strathead]

The simple answer is, if you are not calculating lighting load per 220.12, your calculation is not NEC compliant. The only time you can use connected load in your calculation is when it exceeds 220.12 value, or if your project qualifies under the exception for energy codes.

When your calculation is compliant with 220.12, through 220.14(J) the general use receptacles of hotel rooms are included in the lighting load.

220.42 and its table have no bearing on the matter, as all the calculation criteria must be met prior to getting to that stage of the calculation.

Thank you. that is what I was thinking but then felt I was too lazy to verify before making a fool of myself.

 

[charlie b]

The simple answer is, if you are not calculating lighting load per 220.12, your calculation is not NEC compliant. The only time you can use connected load in your calculation is when it exceeds 220.12 value, or if your project qualifies under the exception for energy codes.

The total area of the hotel is just over 200,000 SF. At 2 VA/SF, that gives a lighting load of 400 KVA. The total connected lighting load, per the panel schedule, is 585 KVA. The receptacle load is over 800 KVA. I can't size the service on the basis of the 2VA/SF.

 

[Strathead]

The total area of the hotel is just over 200,000 SF. At 2 VA/SF, that gives a lighting load of 400 KVA. The total connected lighting load, per the panel schedule, is 585 KVA. The receptacle load is over 800 KVA. I can't size the service on the basis of the 2VA/SF.

Only if you "know" the connected load is 585KVA. go to sleep tonight, forget that this was the job you spent way too much time on adding up every light fixture, and use the 2VA per square foot that the code allows when you don't do the calculations. You wouldn't be asking if you didn't believe the amperage you want to use is adequate. Sometimes the minimums calculated by the NEC are over and sometimes they are WAY over, but never are they even close to being under in my experience. I have seen an 800 amp calculated load, never peak higher than 225 amps and average 180.

 

[charlie b]

. . . forget that this was the job you spent way too much time on adding up every light fixture. . . .

I didn't spend any time at all doing that. The 114 tabs in the Excel file we used for the panel schedules did that task for us. One of our designers typed in the load on each circuit, when the circuit was assigned to a specific set of lights. But that was not too arduous, as there were a limited number of room types, and much of the circuit assignment work was repetitive.

We all know that the actual load will be far lower than the calculated load. But I still need to size the equipment on the basis of the service load calculation.

 

[Smart $]

The total area of the hotel is just over 200,000 SF. At 2 VA/SF, that gives a lighting load of 400 KVA. The total connected lighting load, per the panel schedule, is 585 KVA. The receptacle load is over 800 KVA. I can't size the service on the basis of the 2VA/SF.

Why not?

Do you feel every connected light and receptacle (at calculated value) will be energized concurrently at some point in time?

Code permits you to go to any value greater than 2VA/ft²... But when your connected load is greater than the 220.12 minimum, Code does not actually require you to use the connected load value.

So make your lighting load 585kVA and "absorb" the 800kVA receptacle load in that value... or increase it to any value you want. You are only obligated to make the general lighting load 400kVA and you can justify (irrationally) up to 1385kVA. Pick a number in between that you are comfortable with and go with it... :happyyes:

 

[steve66]

I agree with Charlie - If you know the total connected load of the light fixtures exceeds the 2 VA/sf, you have to use the total connected load. The handbook even says so in the commentary for 200.12(D). (I know - the handbook isn't code, but the authors tend to know their stuff.)

I'm not saying it makes any sense - if you have 1.99 VA/sf of total connected load, you are still allowed to use 2 VA/sf, with a demand factor of 30% for everything over 100KVA. So table 220.42 allows you to install a service sized for less than the capacity of the connected load if you are under 2 VA/sf. But if you are over 2 VA/sf, you have to size everything for the total connected load.

2 VA/sf is way over the energy code limit, but that's a whole different issue.

I can only assume the connected lighting load is so high due to a lot of fixtures that accept standard incandescent lamps. It also seems very probably compact fluorescent or LED lamps will be installed in these fixtures. Maybe current limiters or something similar would help, or maybe you can use the new exception in the 2014 code if you meter the lighting load and set off an alarm when some maintenance guy goes around and replaces all the LED lamps with 100W incandescent lamps.

One more point: I still think you can take advantage of table 220.42 for the guest room receptacles, even if you don't use it for the lighting.

 

[Strathead]

I agree with Charlie - If you know the total connected load of the light fixtures exceeds the 2 VA/sf, you have to use the total connected load. The handbook even says so in the commentary for 200.12(D). (I know - the handbook isn't code, but the authors tend to know their stuff.)

I'm not saying it makes any sense - if you have 1.99 VA/sf of total connected load, you are still allowed to use 2 VA/sf, with a demand factor of 30% for everything over 100KVA. So table 220.42 allows you to install a service sized for less than the capacity of the connected load if you are under 2 VA/sf. But if you are over 2 VA/sf, you have to size everything for the total connected load.

2 VA/sf is way over the energy code limit, but that's a whole different issue.

I can only assume the connected lighting load is so high due to a lot of fixtures that accept standard incandescent lamps. It also seems very probably compact fluorescent or LED lamps will be installed in these fixtures. Maybe current limiters or something similar would help, or maybe you can use the new exception in the 2014 code if you meter the lighting load and set off an alarm when some maintenance guy goes around and replaces all the LED lamps with 100W incandescent lamps.

One more point: I still think you can take advantage of table 220.42 for the guest room receptacles, even if you don't use it for the lighting.

Where in the code does it say you have say you have to use the higher load. I just looked and this is what I found...220.12 requires you to use the table 220.12 as the minimum load for specified occupancies. There is a informational note which holds no requirement to be followed that says the loads specified may not be sufficient. Table 220.12 in conjunction with 220.14J tells you to use 2va per square foot for all the lighting and that all of the general use outlets in the guest rooms don't need to be additionally calculated. So as far as I am concerned the square footage as spelled out in the code, covers all the lighting, on the inside of the building, period. It also covers all the receptacles in the rooms unless there is on that is marked, something like, "coffee pot" or "microwave" and that is it.

So Charlie, it depends how the information was entered in the spreadsheet, whether is spit out a valid number. I suspect it didn't. And even if it did, the lighting doesn't need to be figured as connected load. Nothing that I found in the code says it does.

 

[steve66]

Where in the code does it say you have say you have to use the higher load. I just looked and this is what I found...220.12 requires you to use the table 220.12 as the minimum load for specified occupancies. There is a informational note which holds no requirement to be followed that says the loads specified may not be sufficient. Table 220.12 in conjunction with 220.14J tells you to use 2va per square foot for all the lighting and that all of the general use outlets in the guest rooms don't need to be additionally calculated. So as far as I am concerned the square footage as spelled out in the code, covers all the lighting, on the inside of the building, period. It also covers all the receptacles in the rooms unless there is on that is marked, something like, "coffee pot" or "microwave" and that is it.

So Charlie, it depends how the information was entered in the spreadsheet, whether is spit out a valid number. I suspect it didn't. And even if it did, the lighting doesn't need to be figured as connected load. Nothing that I found in the code says it does.

Handbook commentary from 220.12(D) : In general, no additional calculation is required for luminaries (recessed and surface mounted) installed in or on a dwelling unit, because the load of such luminaires is covered in the 3 va sf calculation specified by table 220.12. Where the rating of the luminaires installed for general lighting exceeds the minimum load provided for in table 220.12, the minimum general lighting load for that premises must be based on the installed luminaires. Distinguishing between the luminaires installed for general lighting versus those installed for accent, specialty, or display lighting is much easier to delineate in commercial (particularly mercantile) occupancies.

I've never thought about it until just now, but it doesn't appear table 220.12 was ever intended to include display or accent lighting.

 

[Smart $]

.... So table 220.42 allows you to install a service sized for less than the capacity of the connected load if you are under 2 VA/sf. But if you are over 2 VA/sf, you have to size everything for the total connected load.
...
One more point: I still think you can take advantage of table 220.42 for the guest room receptacles, even if you don't use it for the lighting.

Table 220.42 applies to the general lighting load no matter how it is calculated under 220.12... except under the energy code exception.

Handbook commentary from 220.12(D) : In general, no additional calculation is required for luminaries (recessed and surface mounted) installed in or on a dwelling unit, because the load of such luminaires is covered in the 3 va sf calculation specified by table 220.12. Where the rating of the luminaires installed for general lighting exceeds the minimum load provided for in table 220.12, the minimum general lighting load for that premises must be based on the installed luminaires. Distinguishing between the luminaires installed for general lighting versus those installed for accent, specialty, or display lighting is much easier to delineate in commercial (particularly mercantile) occupancies.

I've never thought about it until just now, but it doesn't appear table 220.12 was ever intended to include display or accent lighting.

Based on the installed luminaires is not saying it must be exactly the connected load.

The only time you can't use 220.42 for general lighting is under the energy code exception of 220.12.

 

[steve66]

Table 220.42 applies to the general lighting load no matter how it is calculated under 220.12... except under the energy code exception.

I read it again, and I agree. Table 220.42 applies to the general lighting load, regardless if its calculated from the connected load, or the table 220.12. That makes more sense.

So how does one calculate the guest room receptacle load when you are using the total connected lighting load? If we were using table 220.12, we wouldn't have to count them at all per 220.12 (J).

But we are using the total connected lighting load, not table 220.12. It seems like we should have to add something for the guest room receptacles. I

t sounds like Charlie is using 180VA per duplex, and in that case it seems like he can definitely use the demand factors in table 220.42.