The IndoorTemperature goes too low after modifying the setPoints in BuildingProgram

ArchVittorio · July 16, 2023, 11:49pm

Setpoints are strange!

Greetings to Everyone. Here’s a problem about the setpoint. The indoor temperature were unexpectedly low, having comparison and study, the problem is within the _HB ProgramType component.

1. Customizing the Setpoint.

I’ve changed the Setpoint with new schedules.
Notice that my setpoints are being more leninet:

The default Cooling_sch is 6:00-18:00——24°；18:00-6:00——29.5°;
Whereas mine is workingHour——26°; unoccupiedHour——36°.

And also I turned off all the heating during summer.

2. Simulate with Modified Program.

I run the simulation /only in SUMMER-TIME, I gained the data and I can read the IndoorTemperature.

The Indoor_Temperature is between 12-15 degree. That is unrational!

Meanwhile, the Heating demand is considerably low, which can be ignored.

3. Simulate with Original Program.

I unplugged this wire(from _HB setpoint to _HB program Type), so that the setpoints will be back to the base programe as the default.

I simulate again, and I can get the result:

The IndoorTemperature is between 16-22°, which seems like more rational to me.

The heating demand during summer is back, unexpectedly.

4. Honeybee Setpoint Component.

Because I have to set both setpoints simutlaneously, so I can’t use the single varible method to figure out which one, the cooling_sch or heating_sch is causing the malfunction. Or even worse, both are detrimental.

5. Summerizing the problem.

According to common sense, indoor temperatures in summer should not be maintained within the range of 12-15 degrees. It’s July 21st after all. Moreover, the base program is generating summer heating, which is also an error. Why are these abnormal values appearing? If the indoor temperature is really that low, there would be no need for air conditioning, and the CoolingDemand should be 0.
So what cause this deflection?

ArchVittorio · July 17, 2023, 8:55am

With the modified, the Heating demand is considerably low, which can be ignored.

ArchVittorio · July 17, 2023, 10:19am

I unplugged this wire(from _HB setpoint to _HB program Type), so that the setpoints will be back to the base programe as the default.

ArchVittorio · July 17, 2023, 10:20am

The IndoorTemperature is between 16-22°, which seems like more rational to me.

ArchVittorio · July 17, 2023, 10:21am

The heating demand during summer is back, unexpectedly.

ArchVittorio · July 19, 2023, 11:32pm

Newly Study:

A single variable method study:

By deconstruct the base program plug it back the the customized setpoint, I can test the heating or cooling schedule individually.

The outcome:

Only if I use the original heating_sch of the base program, the indoor temperature will return to normal values (16-22).
With this heating_sch, I would have a large energy consumption in summer, even larger than the cooling demand. (In this case it’s double larger.)
If I use the modified heating_sch, the temperature never rises. Even it’s in hottest hours of the hottest days, it still ranges between 12-15. Although the temperature is low, the cooling system is running hard.
Whichever cooling schedule I used, original or basic, the cooling demand is about 209888 kW·h, they’re only different within 20 kW·h.
The cooling system is working 24/7. Throughout the whole analysis period, there’re only 4 hour it’s out of running. Unexpectedly.

2 conclusions(or assumptions):

The rooms depend on heating system to get to a normal temperature. If I turn it off in summer, it runs every 7:00 in every morning, and then turns off at 8:00, then the room stay cold.
The cooling system is running 24/7, that’s why the indoor temperature is shockingly low.

Some Hypothesis

TOO MUCH INSULATION: My study is retrofitting the old building. So I’m attaching new insulation to the original mass, resulting in its having 2 layers for insulation. Maybe the thermal performance is too well so the out door high dry bulb temperature won’t affect alot inside.
A WRONG TYPE of HVAC: Now I’m using “_HB All-Air HVAC” with the type “PVAV with gas boiler reheat.” My cooling setpoint is 26, but it’s running all the hours! Is the “all-air system” needs to run all the hours? So maybe i should change to another system?
SETTING of HVAC GOES WRONG: Now my setting of hvac component are all default. The only thing related to it is the setpoint. Should I plug other control to it, i.e. economizer /vintage /sensible_hr… If these control can make it runs only in the needed hours, that the problem will be solved.

ArchVittorio · July 19, 2023, 11:33pm

My HVAC system be like:

ArchVittorio · July 20, 2023, 2:28pm

Here’s the simulation file from grasshopper. All the simulated geometries are packed up inside, so we don’t need a rhinoceros model to support it.
All the key toggles are falseStart, so you can open it freely.

Note that: all the process I’m not sure, refereing to my assumptions above, are grouped and painted in red color.

MingboPeng · July 21, 2023, 12:36am

Hi @ArchVittorio, I checked your model. It seems your air flow rate for ventilation isn’t set correctly. The unit for flow/person is m3/s-person, I guess your “7” is for ACH, right?