220.84 Single Feeder

[court]

I have a multifamily project that requires some of the larger units to be fed via (2) 200A meters that will be totalized via the utility company. Our interpretation, and we would argue that, this would still qualify as a 'single feeder' even though it's technically (2) 200A feeders to a single unit but it's their service that is totalized into one. I understand one of the stipulations of 220.84 is that no dwelling unit is supplied by more than one feeder so I wanted to see what others thought.

 

[Tulsa Electrician]

Are you doing a calculation.

 

[court]

yes, this would be for calculation purposes.

 

[pipe_bender]

So you want to call two separate 200A feeders one feeder?

 

[court]

So you want to call two separate 200A feeders one feeder?

We understand the code in English language reads that way. We also understand the resistance to calling this one feeder as I mentioned it is technically two. However, it's not like it's being fed from another buildings service or something like that in which we would understand why 220.84 would not be allowed. This is still coming from (1) building service and (1) meter stack serving each grouping of floors, the (2) meters would be totalized making it effectively (1) service on the utility side per unit.

 

[Elect117]

The demand factor allows for diversity in loading and was designed by making assumptions. By having two feeders to the same dwelling unit, you won't have the same loads on each feeder. Therefore changing the applicable load diversity and demand factors. Arguably, you will be less, but, if done incorrectly, you could be applying a demand factor to loads that you shouldn't. For example, sq ft. lighting and general use receptacles are divided to both meters? one meter? How many units are you counting? 1 unit or 2 units? Is the heater or A/C the largest load or are they feed from different feeders? What about the SABCs and laundry circuits? Are they divided between the two feeders?

You don't plan on using this to size the wire for the services / feeders correct? That would also provide a averaged number where you could be loading one feeder higher than the other and end up with one of them being overloaded. Though, that is very unlikely with a 200A feeder.

I find it hard to argue that it is a single feeder, since you are very aware that they are from two different services, meters, and mains.

I personally, would not design it that way, but to each their own. What is the loading on these apartments that need two 200A meters?

 

[court]

The demand factor allows for diversity in loading and was designed by making assumptions. By having two feeders to the same dwelling unit, you won't have the same loads on each feeder. Therefore changing the applicable load diversity and demand factors. Arguably, you will be less, but, if done incorrectly, you could be applying a demand factor to loads that you shouldn't. For example, sq ft. lighting and general use receptacles are divided to both meters? one meter? How many units are you counting? 1 unit or 2 units? Is the heater or A/C the largest load or are they feed from different feeders? What about the SABCs and laundry circuits? Are they divided between the two feeders?

You don't plan on using this to size the wire for the services / feeders correct? That would also provide a averaged number where you could be loading one feeder higher than the other and end up with one of them being overloaded. Though, that is very unlikely with a 200A feeder.

I find it hard to argue that it is a single feeder, since you are very aware that they are from two different services, meters, and mains.

I personally, would not design it that way, but to each their own. What is the loading on these apartments that need two 200A meters?

Understand your points. To be fair, we are NOT using 220.84 for the individual unit calculation as that would yield no diversities using that method. However, 220.84 would be applied to the meter stacks serving these units (ranging from 23-30 units per meter stack). We are counting these are one unit with the wattage per square foot based on 220.42 and counting all appliances, hvac, etc. at 100% like we typically would using 220.84. These units range from 2500 sq ft to 20000 sq ft and they are not typical dwelling units. Luxury units with all the bells and whistles.

 

[Rock86]

Understand your points. To be fair, we are NOT using 220.84 for the individual unit calculation as that would yield no diversities using that method. However, 220.84 would be applied to the meter stacks serving these units (ranging from 23-30 units per meter stack). We are counting these are one unit with the wattage per square foot based on 220.42 and counting all appliances, hvac, etc. at 100% like we typically would using 220.84. These units range from 2500 sq ft to 20000 sq ft and they are not typical dwelling units. Luxury units with all the bells and whistles.

Are you following Section 220 all the way? a 20,000 sqft units would be an incredible load but it should still go on one meter, your best bet would be make it a 3phase system to reduce your feeder size if you are larger than a 400A at 240V-1ph. Also, youre not saving any money running (2) separate feeders to one dwelling unit and the tenant will end up paying two separate service charges... I don't even know if the utility company would allow that.

What are you getting for a total load and a load per unit?

 

[court]

Are you following Section 220 all the way? a 20,000 sqft units would be an incredible load but it should still go on one meter, your best bet would be make it a 3phase system to reduce your feeder size if you are larger than a 400A at 240V-1ph. Also, youre not saving any money running (2) separate feeders to one dwelling unit and the tenant will end up paying two separate service charges... I don't even know if the utility company would allow that.

What are you getting for a total load and a load per unit?

The load has been calculated at 3-phase already for the units, still yielding a 400A service for the larger units. They will not pay two separate service charges as I stated they would be totalized by the utility company. The highest load at 3-phase for the larger units is around 325A.

 

[Elect117]

Then I would not include them in the demand factor calculation for the multimeter stack.

I would add them to the service calculation separately.

For example, 25 units, 5 units are fed by two meters.

20 units with DF from 220.84 + standard method for the remaining 5 units.

 

[Rock86]

The load has been calculated at 3-phase already for the units, still yielding a 400A service for the larger units. They will not pay two separate service charges as I stated they would be totalized by the utility company. The highest load at 3-phase for the larger units is around 325A.

So it is a primary metered system? saying "totalized" doesn't clear things up.

 

[Elect117]

So it is a primary metered system? saying "totalized" doesn't clear things up.

They totalize it in the billing software.

Meter 1 + meter 2 = Meter 3, customer pays the bill for meter 3.

 

[Rock86]

They totalize it in the billing software.

Meter 1 + meter 2 = Meter 3, customer pays the bill for meter 3.

Is that a California thing? We deal with plenty of multi meter stacks, and primary meters. Never seen a dwelling unit permitted to have more than one meter.

 

[Elect117]

Is that a California thing? We deal with plenty of multi meter stacks, and primary meters. Never seen a dwelling unit permitted to have more than one meter.

Maybe it is a California thing? I also, haven't see any utility do it for providing a residential dwelling unit with more than one meter.

But I have heard of totalizing for primary meter services where there is a redundant or back-up service or where a facility has multiple services (usually multiple 2000A to 5000A services) at the same voltage.

 

[tortuga]

220.84 deals with calculating a single feeder or service load for one service or feeder that supplies three or more units 220.84 (A) says you need to meet condition 1 that 'No dwelling unit is supplied by more than one feeder' I don't see how two feeders would be considered one.

 

[Tulsa Electrician]

Since there is two feeders feeding a single dwelling. I would say you could not use the 83% rule as well. Not that you mentioned it. Just something to consider if exhisting feeders or new.

Gets me thinking about when you have two meters on a single dwelling. One for EV and one for the rest. Can not use the 83% rule.
Maybe an exception for 29 code.

 

[wwhitney]

Say we have a service supplying feeders A and B. And say feeder A supplies feeders 1 through 5, and feeder B supplies feeders 6 through 10. Each numbered feeder supplies all the loads associated to a similarly numbered dwelling unit, and nothing else. [If there are house loads, the service also supplies feeder C for them, but I will ignore that.]

In this configuration, clearly 220.84 applies to the service and to feeders A and B. Now let's replace feeder 1 with feeders 1A and 1B, both of which go to dwelling unit 1. What currents have changed? Only the current on feeder 1 has changed, getting split between feeders 1A and 1B. None of the currents on the service conductors, on feeders A and B, or on feeders 2 through 10 have changed.

Therefore there is no technical basis for this splitting of feeder 1 into feeders 1A and 1B to affect the allowable load calculation methods for the service or for feeders A and B. So I conclude that what 220.84(A)(1) should mean is that "Every dwelling unit supplied by the feeder or service has all of its associated loads supplied by the feeder or service."

I'm just arguing on the technical merits, without comment on whether the actual wording of 220.84(A)(1) can be stretched to the above meaning. Although if it can, I am in favor of doing so.

Cheers, Wayne

 

[Elect117]

Say we have a service supplying feeders A and B. And say feeder A supplies feeders 1 through 5, and feeder B supplies feeders 6 through 10. Each numbered feeder supplies all the loads associated to a similarly numbered dwelling unit, and nothing else. [If there are house loads, the service also supplies feeder C for them, but I will ignore that.]

In this configuration, clearly 220.84 applies to the service and to feeders A and B. Now let's replace feeder 1 with feeders 1A and 1B, both of which go to dwelling unit 1. What currents have changed? Only the current on feeder 1 has changed, getting split between feeders 1A and 1B. None of the currents on the service conductors, on feeders A and B, or on feeders 2 through 10 have changed.

Therefore there is no technical basis for this splitting of feeder 1 into feeders 1A and 1B to affect the allowable load calculation methods for the service or for feeders A and B. So I conclude that what 220.84(A)(1) should mean is that "Every dwelling unit supplied by the feeder or service has all of its associated loads supplied by the feeder or service."

I'm just arguing on the technical merits, without comment on whether the actual wording of 220.84(A)(1) can be stretched to the above meaning. Although if it can, I am in favor of doing so.

Cheers, Wayne

I think the issue is with applying table 220.84.

They don't specify the demand factor as feeders or services, they apply it as dwelling units. Their assumption is that all of the loads would be in each dwelling unit's individual feeder or service. Thus developing a safe, reliable, and repeatable demand factor.

I don't disagree with what you are saying.

I think the code applies limits to the use of demand factors to limit the possible incorrect outcomes. The same logic can be applied if all the units have a gas range or don't have space heating / Air conditioning circuits. Those factors wouldn't effect the demand factors for the service right?

But they are requirements to use table 220.84.

 

[court]

Is that a California thing? We deal with plenty of multi meter stacks, and primary meters. Never seen a dwelling unit permitted to have more than one meter.

What Elect117 said. It is the sum of (2) meters and the owner/tenant paying for the combined total. It is allowed in California by certain utilities within reason.

 

[wwhitney]

They don't specify the demand factor as feeders or services, they apply it as dwelling units. Their assumption is that all of the loads would be in each dwelling unit's individual feeder or service. Thus developing a safe, reliable, and repeatable demand factor.

Right, you want to be sure that if you are taking credit for the dwelling unit by including it in the count for the determining the demand factor, that you have included all of the dwelling unit loads. That is the point of 220.84(A)(1).

The current text does that just by saying that each dwelling unit has only one feeder. So if you're counting part of the loads, you must be counting all the loads, because there's only one feeder that can be supplying the loads.

But that's unnecessarily specific. If you have multiple feeders to the dwelling unit, as long as the feeder/service you are calculating supplies all of those feeders, what does it matter? Not all.

The same logic can be applied if all the units have a gas range or don't have space heating / Air conditioning circuits. Those factors wouldn't effect the demand factors for the service right?

Sure they would. Different types of loads would have different likelihoods of concurrent use across multiple units. So the values in Table 220.84 are blended values reflecting the current weighted expected maximum concurrent use of all the loads. Remove large loads like electric ranges or HVAC from all the units, and run the sorts of load studies that you'd need to run to determine the values in Table 220.84, and you'll find different demand factors are appropriate.

Cheers, Wayne