MEPworx – Adding and setting up Heat Interface Units (HIUs)

By David Wren

In line with the CIBSE Code of Practice, CP1-2020, Heat Networks have been incorporated via placement of HIUs within the Piping program. This enables diversified flow rates for both the Heating and Hot Water to be sized, without the need to access the Public Health program.

This allows the option of using the CIBSE Code of Practice 1 (CP1) suggested heat losses, without detailed modelling or accurately detailed room heat losses, which are grouped into Zones from the Building and Energy programs. Similar options are available for Hot Water considerations.

Looking at the dialog for Inserting or Editing an HIU, the first two tabs for the HIU Details and the Electrical Details are fairly standard. The Further Details tab is where the HIU’s performance characteristics are set up.

The information and data-field descriptions below are extracts from the in-program Help (F1).

HIU's Further details

Hot Water
Hot Water Peak - The Hot Water Peak Flow rate can be entered in a number of ways, depending upon the level of details known.

• Entered - This enables alternate calculated data to be manually entered and it will override suggested values.
• Single outlet - Use this option if the HIU is serving a single hot water item as opposed to a bathroom. The suggested Hot Water (HW Output) load is 23.4 kW and does not include a heating component.
• 1 bathroom - The COP Hot Water (HW Output) loads are 36.7 kW.
• 2 bathroom - The COP Hot Water (HW Output) loads are 41.8 kW.
• 3 bathroom - The COP Hot Water (HW Output) loads are 43.5 kW.

Dwelling Served - Usually, a single HIU serves a single dwelling.

Space Heating
Source/Zone

• Entered - This allows overriding the calculated and suggested heating Output requirements with manually entered data.
• From CoP - Selecting this option will populate Output with the following:
1 bathroom. CoP stipulated Heating loads are 2.0 kW
2 bathroom. CoP stipulated Heating loads are 2.5 kW
3 bathroom. CoP stipulated Heating loads are 3.0 kW
• Zone - This allows each apartment Heat Losses, that should be grouped together from the Building and Energy Programs by allocating all rooms to the same dwelling zone.

Connection Point Use this to determine the 'z' position of the heating and hot water connection points.
This is typically the opposite of the connections supplying the HIUs.

When sizing the landlord's pipework from the central plant room, using the formula given in the graph below, the central heating diversity never falls below 0.63.

We have modelled the schematic example from CP1 Appendix D (shown below) in Piping, using CIBSE CP1 Annex D.CYC.

This file can be found in Example Projects, from the Projects tab on the MEPworx front screen.

For additional guidance, please also refer to the Help Videos. These can be found in the Help tab on the MEPworx front screen. Select the Piping section and # 12 - Heat Interface Units (HIUs).

Please refer to the CIBSE Code of Practice 1 (CP1) for further guidance regarding this subject.