Heating / cooling Detailed HVAC

mattias.jonsson · Posts: 4

Dear Design Builder,

A while ago I posted some questions on the forum regarding more than one AHU, and some other things. Andy replied and of course he was right, detailed HVAC solved most of the questions.

However, I have some more questions that I would be glad if someone could help me with. I'm attaching a file where I have built up a simple building with Detailed HVAC. The AHU is a CAV where I want a constant air temperature leaving the AHU at 17°C. Summertime the cooling coil will cool the air to that temperature, and wintertime the heating coil will heat it up to 17°C. There is also a rotating heat recovery to help, especially wintertime.
The building is then heated by radiators in the rooms.
Full fresh air will be used both during heating and cooling.

In the rooms there will then be cooling beams to lower the temperature in the rooms to summer design temperature.
My problems are as follow:

1.There are several places where I can enter the air temperature. In “Air Loop Data” I can enter both summer and winter design air inlet temperature, and these I set to 17°C.
In the zone, still under detailed HVAC, I can enter temperatures for winter and summer calculations. Is this the temperature after the cooling beam?
When I click the heating coil in the AHU I can enter an inlet/outlet temperature even there.
Which temperature is the “Master”?

On top of this I can change the temperatures in the Air Loop Setpoint Manager. Will this override the rest, or this is only used when one AHU is supporting many zones?

When running a summer design calculation I can again enter a value of the Inlet temperature. Will this affect the calculations, or will that figure be taken from the Detailed HVAC entries?

I have tried to experiment with the temperatures, but I still get a few hours per week, wintertime, where I both heat and cool the rooms at the same time. It’s mostly in the morning when the heating system is working as most…
If it’s cold in the room the radiators should heat up the room, and if it’s warm the cooling beam should cool the air, but of course I don’t want this to happen simultaneously. To prevent it I have entered the temperatures under the “Activity tab” a few degrees apart, so that cooling and heating shouldn’t happen at the same time.
I have loaded a schedule which turns off the cooling system from fall to spring, but still I get some cooling even during the winter. Any ideas how to solve this?

2.About the HVAC tab when in EDIT-mode, is that not used at all when I use the detaild HVAC, or will some entries there still apply to my model?

3.When running heating design calculations, is the heating recovery included there? I’ve read that all internal gains are excluded during design calculations and that is normal procedure also in Sweden, but normally we count on the rotating heat recovery unit to be in use.

4.The building I will simulate will have district heating. How can I simulate this? Now I have drawn a natural gas Boiler just to have a heat source.

5.Which of the airflows is the “master”? On the activity tab I can enter a airflow per person and/or area. But also in detailed HVAC I can enter airflow. Now it is set at “autosize”, but if I change this to a specific number, will this override the activity tab?

Sorry for all these questions but this is one of the final models I will run before we make the decision to buy the program, and I would like to run a full simulation where the systems are working together.

Thank you in advance!
Mattias

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