Continuous Duty Loads and Service Calculations

[cdcengineer]

I have always calculated commercial lighting as a continuous duty load for branch circuit and overcurrent protection sizing. I have also considered it to be continuous duty when calculating commercial services.

Today, an associate is arguing that it is not required to be multiplied by 125% for service calculations.

In looking at NEC 220, I can't argue with him. Anyone have input here? I have hit all continuous duty loads with 125% for load calcs for a long time. If I've been wrong, at least it's been an error on the conservative side.

Thx for any input and happy 4th to all

 

[Little Bill]

I have always calculated commercial lighting as a continuous duty load for branch circuit and overcurrent protection sizing. I have also considered it to be continuous duty when calculating commercial services.

Today, an associate is arguing that it is not required to be multiplied by 125% for service calculations.

In looking at NEC 220, I can't argue with him. Anyone have input here? I have hit all continuous duty loads with 125% for load calcs for a long time. If I've been wrong, at least it's been an error on the conservative side.

Thx for any input and happy 4th to all

You might want to look at 215.3 or 230.90 for OCPD for feeders or services.
Look at 215.2 and 230.42 for feeder or service conductors.
Happy 4th to you too!:thumbsup:

 

[Smart $]

Based on Annex D examples, the extra 25% applies for other than dwellings. To back this up, see examples D3 and D3(a) and compare those calculations to the dwelling examples.

 

[Little Bill]

Based on Annex D examples, the extra 25% applies for other than dwellings. To back this up, see examples D3 and D3(a) and compare those calculations to the dwelling examples.

That is what I used to back up my thoughts. I didn't include the examples. I wanted to see what the OP (or anyone) concluded from the references I posted.

 

[Smart $]

That is what I used to back up my thoughts. I didn't include the examples. I wanted to see what the OP (or anyone) concluded from the references I posted.

After reconsideration, I probably overstated the extra 25% applies to other than dwelling. Refer to occupancy types in Table 220.42. The thing is, where demand factoring applies, that is saying even if there are continuous lighting loads, they will not all be on at the same time. The footnote even rescinds demand factoring where lighting loads will all be on at the same time for hospitals and hotel/apartment occupancies.

When we consider the Annex D examples, we must also take into consideration that where dwelling calculations are shown, it is likely assumed that there are no continuous lighting loads. And on the other side of the coin, the D3 and D3(a) examples likely assume all lighting loads to be continuous. It is just easier than separating continuous and non-continuous...

 

[cdcengineer]

Thanks to all for the responses. I knew I wasn't crazy. Sometimes you know the answer, but can't back it up. That was the case on a Friday right before the holiday. It seems the longer you work at something, the harder it gets to remember all the references it takes to support the knowledge.

Thx again

 

[iwire]

It is worth looking into the definition of continuous load.

Continuous Load. A load where the maximum current is
expected to continue for 3 hours or more.

That being the case a single circuit supplying only the lighting on the sales floor of a store would be a continuous load.

But on the other hand a circuit supplying some open area lighting in an office building that also supplies a number of offices with motion sensors would not be (IMO) continuous load as the 'maximum' load would not be expected for 3 hours.