.BuildSysPro.Systems.HVAC.Production.HeatPump.FixedSpeed.Examples.MozartMultizoneHeatingSystem

Information

Hypothesis and equations

Example of the MozartMultizone model with a heating system including an air-to-water heating pump and 4 hot water radiators (one per room except for two rooms for simplification).

There is only one water loop (the heat pump and the four radiators are in series).

The production (heat pump) and the emission part (hot water radiators) of the heating system have their own control strategy:

• all-or-nothing regulation at thea heat pump with an hysteresis of +/- 2°C around 50°C
• proportionnal integral control for the hot water radiator.

The setting of a PI controller needs two values:

• the gain k assessing the proptionnal band between the controled value (radiator mass flow rate => heating power) and the mesured value (room temperature). Here the raditor must be off (=0) when the room temperature is two degree above the setpoint and fully opened (=1) when the temperature is two degree below it. The gain is worth to 0,25 (=(1-0)/(2+2°C)).
• the integrator time constant Ti assessing the duration after which the integral part has an higher weight then the proportional part. This duration must be consistent with the inertia of the system. Here the thermal mass of a room could be assessed in first order to 20 minutes (the needed time you consider for an usual HVAC systems to reach a new setpoint). If the intagrator time constant is too short, the system will go up and down or diverge. In the default setting of this model, it could seem the case for many heating periods. But the up and down is not due to the radiator PI controler but due to the all-or-nothing control of the heat pump.

Bibliography

none

Instructions for use

The heat pump parameter PumpOperation is set to "Independant control" because its all-or-none control is on the water temperature outlet and so the water pump has to run all the time to let the heat pump know the heating needs at the emittors (here the hot water radiators).

Known limits / Use precautions

none

Validations

Validated model - Hubert BLERVAQUE 03/2021

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Licensed by EDF under a 3-clause BSD-license
Copyright © EDF 2009 - 2023
BuildSysPro version 3.6.0
Author : Hubert BLERVAQUE [prestation externe] (03/2021)
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