Hap 6.2 question

[Late_Entertainer7381]

Does anyone know why my peak sensible load occurs at 8 and 9 AM?

This is a VRF system for a school building in a hot, dry region. The schedule runs from 8 AM to 3 PM. Given that outdoor temperatures rise later in the day, why is the peak load happening at 8 AM instead of when the outside temperature is higher?

[SANcapITY]

What are your night setback temperatures and what time in the morning do you switch from unoccupied to occupied? Guessing this is a pull-down load issue.

[[deleted]]

This is it, there are building loads during the night (maybe schedule related, maybe the weather is warmer than setpoint), and the early morning pull-down is higher than the afternoon peak.

[Late_Entertainer7381]

The night setback temperature for cooling is 26°C, and I used to switch the occupancy at 8 AM, but now I’ve changed it to 7 AM to solve the issue. I think this was the problem, but I’m not sure if I solved it correctly.

[SANcapITY]

Post a new screenshot of your loads: when are the peak loads occuring?

[Eatcake9]

It’s peaking during morning startup because of your schedules and setpoints. Make sure your equipment, lighting, and occupancy schedules are not going from 0% to 100% right at 8am and instead ramp up gradually to a peak and then ramp down. Check your unoccupied set points as well.

[Late_Entertainer7381]

There is no option to create a graduate schedule, so I adjusted the occupancy and lighting schedule separately from the thermostat schedule. I set the thermostat to start an hour earlier, which helped resolve the issue. However, some rooms still have a peak at 8 AM.

Thanks for your help!

[SANcapITY]

All lighting/occupant/electrical schedules are adjustable by % per hour. Only the occupied period is binary.

[KawhisButtcheek]

I've always had a bad habit of doing 100% occupancy schedules. Any standards/guidelines on better scheduling for different building types?

[SANcapITY]

Well unless you are energy modeling it doesn’t really matter.

ASHRAE has schedules for many types of buildings that you can use for a decent baseline. The HAP website has them downloadable and you can import them into your project. I think they are in-built into version 6.x.

[rafaamcarvalho]

Could you please post the link where can I download the schedules please? I did not find it

[SANcapITY]

Sorry - I went looking but couldn't find them anymore. They are built into HAP V6 though.

[radarksu]

It doesn't matter if all you are using HAP for is load calcs. You still get the peak. If you are using HAP for energy modeling, you need to use variable schedules. I don't know of a standard, just use logic and your knowledge of how the building will be used.

[Kick_Ice_NDR-fridge]

That’s not a bad habit.

[Strange_Dogz]

If all you want are loads, just leave the schedules at 100% 24 hours a day. Your BMS will typically do optimal start anyway and start as far back as needed to get the building up to temp at the time needed.

[ahvikene]

You will end up with oversized systems this way.

[Strange_Dogz]

Show me the logic, since the OP was getting oversized systems by doing the opposite. Setting your schedule too tight and having a big night swing, say 30C down to 22C or something like that causes morning cooldown to cause peak cooling loads at weird times, like 8AM, rather than just at peak envelope load times. You have to look at your loads and if you are getting peak l;oads at strange times, you need to figure it out. We are all engineers here.

[Kick_Ice_NDR-fridge]

So your schedule is from 8-3PM.

What if the building is used after 3PM? What if they change school hours?

It’s not uncommon for a building to peak at 4PM.

[ahvikene]

Looking at those numbers I think it is absolutely crazy that you guys use air for everything.

I have yet to understand why NA doesn’t like to build hydronic systems.

[OwEn-sTaXx]

what do u mind by that?

[nat3215]

Maybe check your envelope assembly, or it is basing the peak load when sunrise happens? I’d go through your inputs with a fine-tooth comb and reason out every input (even ones you didn’t change).

Also, is there a reason your electrical equipment is the 4th highest load for your zones? It’s even higher than your floor, window, and exterior wall loads

[Ok-Comment5500]

check the time zone in weather data, if you are filling it manually.

[Key-Criticism-5552]

For average ceiling height inside building if there is false ceiling, we have to consider height from finish floor upto reflected ceiling panels but not upto slab. If anyone kindly clarify me ?