Hot Water Storage
Adding hot water storage in a project
Hot water storage is selected in the Heat pump task. When you first enter the Heat pump task, after selecting a heat pump you will be shown a list of recommended hot water storage options.
If you initially did not include hot water in the project, navigate to the Heat pump task, on the left below the 'Heat pump load' section you will see the 'Hot Water Storage' section. Click the pencil icon to add hot water storage.
Selecting a hot water option
When selecting a hot water storage option, you can select from the recommendations or scroll through the options on the left to pick from the pre-plummed, standard, pre-plummed slimline, slimline and horizontal cylinder options. Cylinders that are incompatible with the selected heat pump say 'incompatible with selected heat pump' in red text.
When you have an option selected, to the top right you will see spec information and bottom right Midsummer stock information. Where your account is connected to Midsummer, you will also see your specific pricing.
Hot water recommendations
Recommendations are based on compatibility with the heat pump and sized on the number of bedrooms and occupants (allowing for 45ℓ per occupant). Adjust the number of bedrooms/occupants and click Recommend to get updated recommendations
System details and DHW calculations
Once you've selected a hot water storage option, you can see the option selected in the Hot Water Storage section of the Heat pump task. Here you will see all the specifications and the following:
- Cylinder re-heat time (min)
- Domestic hot water (DHW) energy demand (kWh/year)
- Vdraw/Mix down volume (ℓ)
- Legionella Purge Demand (kWh/year)
Editing hot water storage options
You will also have the following options to the top right of the Hot Water Storage section:
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Pencil: edit selection |
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Cog: edit hot water storage settings |
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Bin: remove hot water storage |
Hot water storage settings
Clicking the cog will show you a variety of options that you can edit:
- DHW Storage Temperature (°C)
- Difference between flow temperature while providing hot water and storage temperature (°C)
- Flow Temperature while providing hot water (°C)
- Draw Water Temperature (°C)
- Supply Water Temperature (°C)
- Pipework Efficiency (%)
- Water used per person per day (ℓ)
Under 'Legionella', you then have the following options
- Legionella purge required (Yes/No)
- Legionella purge frequency (Weekly/Daily)
- Legionella heat source (Immersion/Heat pump)
- Legionella purge temperature (°C)



