Manuals and technical information
What the Mini Store does
The Heat Geek Mini Store provides hot water where a conventional cylinder is difficult to fit. Cupboards rarely get bigger when you need them to.
Heating water fills the shell; mains water passes through a coil and comes out hot. I have worked with the Mini Store and like it because it solves a real space problem.
The separate Heat Geek Super Cylinder stores domestic hot water, with heating water passing through its coils. Our guide covers its sizes and connections.
It can also solve a safety discharge-pipe problem. Its domestic hot-water coil holds less than 15 litres; the larger shell contains heating-system water. The Mini Store's design avoids a conventional unvented cylinder's dedicated discharge arrangement. That matters on vented-to-unvented upgrades, where we can struggle to find a suitable route for the safety pipe.
Mini Store sizes and dimensions
Dimensions and filled weights from the v1.4 manual, page 11. Allow additional room for pipework, valves, brackets and access.
| Model | Heating-water volume | Height | Diameter | Filled weight, excluding brackets |
|---|---|---|---|---|
| XS | 60 L | 635 mm | 475 mm | 84 kg |
| Mini Store | 80 L | 830 mm | 475 mm | 111 kg |
| FAT | 110 L | 830 mm | 550 mm | 145 kg |
| Tall | 110 L | 1100 mm | 475 mm | 149 kg |
| XL | 130 L | 1000 mm | 550 mm | 172 kg |
XS height discrepancy: the manual says 635 mm; Newark's webpage says 625 mm. Confirm the supplied height before planning a tight fit.
FAT and Tall hold the same volume in different shapes. Newark recommends choosing the largest Mini Store that fits, allowing a lower operating temperature for the required hot-water demand.
View the original dimensions and weight table
Connections and fitting
| Item | v1.4 specification |
|---|---|
| Heat-source flow and return | 1-inch female BSP |
| Mains inlet and hot outlet | ¾-inch female BSP |
| Sensor pocket | 10 mm, fitted at low level |
| Mains coil pressure | 4 bar maximum; supplied pressure reducer preset to 3 bar |
| Heating-water shell | 1.5 bar recommended set pressure; 6 bar maximum working pressure |
- Horizontal mounting: use the manual's supports and vent/drain arrangement. Primary connections must stay in the upper half, preferably facing upwards. Check the full supported load.
- Safety protection: appropriate temperature and pressure protection still applies below 15 litres (Approved Document G, paragraph 3.19). Follow the Mini Store installation requirements; the sealed heating circuit still needs its own pressure-relief and expansion protection.
- Expansion: do not assume an expansion vessel is never needed. Page 5 specifies cold-pipe expansion accommodation or a 2 L vessel on non-isolatable DHW pipework where that accommodation is insufficient.
- Pipe insulation: insulate adjoining pipework and seal joints for at least 1 m from the store.
View connection, orientation and bracket drawings
How long will the shower stay hot?
One manufacturer example: 55°C store, 6 L/min shower, 6 kW heat input.
| Model | Listed shower duration |
|---|---|
| XS | 9 minutes |
| Mini Store | 13.5 minutes |
| FAT / Tall | 20 minutes |
| XL | 24 minutes |
Manual, page 13. Assumes a 40°C shower, 13°C incoming mains and 2.5-minute heat-delivery delay. These are manufacturer figures, not guaranteed shower times for your house.
Use the heat pump's delivered hot-water output, rather than relying on its nominal kW label. Colder mains, higher flow and slower heat delivery change the result.
What our customers have said
Mini Store FAT 110 L with a 5 kW Vaillant aroTHERM
Fitted below a worktop. The customer says it is great for showers, but needs the Mini Store set to 55°C to fill a hot bath.
Mini Store XL 130 L with a 5 kW Vaillant aroTHERM
The customer is delighted with theirs and reports great hot-water pressure and shower performance. Based on their experience, they recommend going for the biggest Mini Store.
Controls worth checking
- Hysteresis: the temperature drop before reheating starts. The manual suggests around 3°C.
- DHW power mode: limiting heat-pump output can shorten the available shower.
- Response time: check how long useful heat takes to reach the store, including restart delays and defrost interruptions.
- Sensor position: v1.4 moved it lower for quicker response. Older connection layouts and videos differ.
Commission using measured shower flow, successive showers and the household's bath requirements. Higher storage temperatures can extend delivery, with an efficiency trade-off.
What the reviews show
Urban Plumbers' August 2024 test uses the 60 L XS with a 5 kW Vaillant. He reports a 10-minute-41-second usable shower at roughly 5 L/min, a 55°C store and 27°C outdoors.
Heat Geek's June 2024 demonstration uses the 110 L FAT with a 7 kW Vaillant. Adam reports 45 minutes at 8.5 L/min, a 40°C shower and 60°C store. These are different setups and conditions; neither result is a winter guarantee.
Winter owner reports include a FAT owner happy with successive showers but unable to fill a deep hot bath, and a Tall owner disappointed by efficiency and winter delivery. Both installations predate v1.4. They show why sizing and commissioning matter; they are not a verdict on every Mini Store.
Frequently asked questions
Does it have an immersion heater?
The v1.4 manual specifies no immersion boss. Confirm how the proposed system will provide backup hot water if the heat pump is unavailable.
Can I heat it only on cheap-rate electricity?
You can schedule heating, but stored heat alone provides less flexibility than a larger cylinder. Newark recommends keeping reheating available; a shower outside the schedule may run out before the next heating period.
How much does a Mini Store cost?
Use Newark's price guide for the vessel. An installed quote also needs the pipework, valves, supports, controls and any backup provision. Confirm VAT and delivery when comparing prices.
Check the available space and hot-water demand
For a Lincolnshire heat-pump installation, send us the cupboard dimensions and your shower or bath requirements.