Hotel HVAC load calculation NEC 2014 (CEC- 2017)

[Sierrasparky]

I am wondering if I am calculating a hotel HVAC load correctly?

I assume you take the heating or the cooling load which ever is greater.

In this case the heating load is actually greater because it is all resistant heat.

There are 75 rooms and each quest room has a 3kw electric heater.
According to :

220.51 Fixed Electric Space Heating. Fixed electric
space-heating loads shall be calculated at 100 percent of
the total connected load. However, in no case shall a feeder
or service load current rating be less than the rating of the
largest branch circuit supplied.

I take it this means that the electric heating load calculation is in added on top of all other loads or reductions.

OR is this type of load lumped into the entire load and then subjected to the various reductions as in Table 220.42

 

[david luchini]

I take it this means that the electric heating load calculation is in added on top of all other loads or reductions.

Yes

 

[Sierrasparky]

So Table 220.42 is only for general lighting loads.

How close would you run a service size to a calculated load.

If you have a 800 amp service would you feel comfortable with a 795 amp calculation?

Some hotels see 100 % occupancy for weeks others just a day or 2.

 

[jumper]

So Table 220.42 is only for general lighting loads.

How close would you run a service size to a calculated load.

If you have a 800 amp service would you feel comfortable with a 795 amp calculation?

Some hotels see 100 % occupancy for weeks others just a day or 2.

I have no problem with a 795A NEC calculated load on a 800A service....

unless the customer happens to expect future expansion. Design issue. Not a safety issue.

 

[Cow]

I have no problem with a 795A NEC calculated load on a 800A service....

unless the customer happens to expect future expansion. Design issue. Not a safety issue.

We did an 800 amp service with a 795 amp load about 3 years ago. Not ideal, but we couldn't wait for a SWBD and metering cabinet to be built, because the customer started the process so late. A CT can and 800 amp perch are readily available, so we went with it.

I wouldn't hesitate to do it again if I was comfortable with the load diversity, I might also be inclined to price out 1000 amp gear and offer an upgraded price to the customer at the same time.

In your case, to have all 3kw heaters on at exactly the same time, would be pretty rare. I'd have to think some would be cycling on and off with the stat even if every room was occupied in the middle of winter.

 

[Open Neutral]

In your case, to have all 3kw heaters on at exactly the same time, would be pretty rare. I'd have to think some would be cycling on and off with the stat even if every room was occupied in the middle of winter.

I clearly remember a Xmas eve in the dark about 80% of the time. See it was Dade County, there was a freeze and everyone's resistive heat was nailed on trying to keep up. FPL was used to summer loads, but as they later admitted, compressors cycle but resistive heat just latched on, period. Ergo rolling blackouts much of the night.

But hey, they had a near-perfect PF; Mr. KiloVAR was nowhere to be found that night.

 

[Sierrasparky]

I clearly remember a Xmas eve in the dark about 80% of the time. See it was Dade County, there was a freeze and everyone's resistive heat was nailed on trying to keep up. FPL was used to summer loads, but as they later admitted, compressors cycle but resistive heat just latched on, period. Ergo rolling blackouts much of the night.

But hey, they had a near-perfect PF; Mr. KiloVAR was nowhere to be found that night.

hum :?

now I am not feeling so warm and fuzzy about running so close to the max.

 

[Strathead]

I have no problem with a 795A NEC calculated load on a 800A service....

unless the customer happens to expect future expansion. Design issue. Not a safety issue.

Even then, a simple 30 day load monitoring or even better full history from smart utility data usually available will likely allow all the future expansion one would need.

 

[Cow]

hum :?

now I am not feeling so warm and fuzzy about running so close to the max.

If this is something existing, we call the utility and ask them for a load sheet or at a minimum have them verify peak demand for us.

If they're not able to do that for some reason, or if we're only trying figure the load on one particular feeder we will install our Fluke logger with a 15 minutes averaging sample rate and let it run. Of course, in your instance with heating being a heavier load than AC, that'd mean you'd need to do this in the dead of winter to get maximum results.

 

[jumper]

Even then, a simple 30 day load monitoring or even better full history from smart utility data usually available will likely allow all the future expansion one would need.

:happyyes:

That is why I specifically said a NEC calculated load.

Real load gonna plenty smaller.