How to set cooling setpoint below heating setpoint

asked 2024-08-01 14:59:22 -0600

Loz95
11 ●3

updated 2024-08-01 18:24:05 -0600

Aaron Boranian

14145 ●83 ●24 http://bigladdersoftware.com/

I'm getting the following error:

DualSetPointWithDeadBand: Effective heating set-point higher than effective cooling set-point - increase deadband if using unmixed air model
**   ~~~   ** occurs in Zone=LOUNGE During Warmup, Environment=RUNPERIOD1, at Simulation time=01/01 00:00 - 00:15
**   ~~~   ** LoadToHeatingSetPoint=556.391, LoadToCoolingSetPoint=430.434
**   ~~~   ** Zone TempDepZnLd=226.72
**   ~~~   ** Zone TempIndZnLd=4607.84
**   ~~~   ** Zone Heating ThermostatSetPoint=22.78
**   ~~~   ** Zone Cooling ThermostatSetPoint=22.22

I realise this is because the cooling setpoint is lower than the heating sepoint, but the setpoints are derived from real life data where occupants have indicated this is what they use IRL. I have set the schedules so that they are not active during the same period:

Schedule:Compact,
heating_sched,
Control,
Through: 03/31,
For: AllDays,
Until: 24:00, 1,
Through: 10/20,
For: AllDays,
Until: 24:00, 0,
Through: 12/31,
For: AllDays,
Until: 24:00, 1;

 Schedule:Compact,
cooling_sched,
Control,
Through: 06/30,
For: AllDays,
Until: 24:00, 0,
Through: 09/15,
For:AllDays,
Until: 24:00, 1,
Through: 12/31,
For: AllDays,
Until: 24:00, 0;

Am I missing something?

answered 2024-08-01 19:16:16 -0600

Jamie Sullivan
276 ●10 ●5

updated 2024-08-04 16:00:21 -0600

One way of working around that could be to also schedule the setpoints - set the cooling setpoint higher when it's not supposed to be being used, and the heating setpoint lower when it's not supposed to be being used.

edit: using Dual Setpoint you should be able to do this like so:

ThermostatSetpoint:DualSetpoint,
    setpoints1,              !- Name
    Heating,                 !- Heating Setpoint Temperature Schedule Name
    Cooling;                 !- Cooling Setpoint Temperature Schedule Name

Schedule:Compact,
Heating,
,
Through: 03/31,
For: AllDays,
Until: 24:00, 22.78,
Through: 10/20,
For: AllDays,
Until: 24:00, 20,
Through: 12/31,
For: AllDays,
Until: 24:00, 22.78;

Schedule:Compact,
Cooling,
,
Through: 06/30,
For: AllDays,
Until: 24:00, 25,
Through: 09/15,
For:AllDays,
Until: 24:00, 22.22,
Through: 12/31,
For: AllDays,
Until: 24:00, 25;

Fill in setpoint values as desired. You could try to set it up to swap between single heating and single cooling, but I think that would be more complicated and not really add anything? Unless someone who knows more about the fine details of the systems says otherwise...

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Comments

Is there a way to do that using the ZoneHVAC:IdealLoadsAirSystem object? This is what my idf looks like:

``` ZoneHVAC:IdealLoadsAirSystem, Lounge_PurchasedAir, , Lounge_supply_inlet, , , 50, 13, 0.015, 0.01, NoLimit, , , NoLimit, , , heating_sched, cooling_sched, ConstantSupplyHumidityRatio, , ConstantSupplyHumidityRatio

```