Site Visit - Measuring Post Install Performance

Travelodge Stonehouse – Demand-Led Sizing of Amicus AquaStore

Sector:

Travelodge Stonehouse | Amicus AquaStore

The technical outcome

Two Amicus AquaStore LAAS8-455-12 units were selected to meet a calculated 2,000 litre, two-hour peak. Their combined output is 2,112 litres at a 50°C temperature rise. After 1,518 operating hours per unit, recorded immersion use remained limited, indicating that the heat pumps supplied most of the hot water demand. Below is an insight into the survey conducted and the findings recorded on site.

Project at a glance

Application	Design basis	Selected plant	Operating result
40-bedroom hotel	2,000 litres over each 120-minute peak	2 × Amicus AquaStore LAAS8-455-12	Predominantly heat pump operation

For a hotel, domestic hot water is a guest-critical service. The design must cover concentrated periods of demand, provide sufficient recovery and work within the available plant room conditions. At Travelodge Stonehouse, the engineering review process started with the demand profile and followed it through to model selection, ventilation review and the verification of installed performance.

The challenge: design around the peak

The Stonehouse working example is based on a 40-bedroom hotel. The demand assessment allows 25 litres per person, with two people per room, and assumes two daily peak periods of 120 minutes. This produces a required volume of 2,000 litres during each peak.

Design input	Value used
Hotel size	40 bedrooms
Hot water allowance	25 litres per person
Occupancy basis	2 people per room
Peak profile	2 peaks per day, each lasting 120 minutes
Required hot water per peak	2,000 litres

This demand-led approach is important because storage capacity alone does not describe how the system will perform. The design also needs to account for usable draw-off and the volume recovered while demand continues.

Selecting the AquaStore operating strategy

Amicus AquaStore offers three operating modes. The appropriate mode depends on the hot water profile, the required recovery rate and the plant room conditions. Efficiency mode should normally be the starting point. Where peak demand cannot be met consistently in Efficiency mode, Hybrid mode provides additional recovery support without moving fully to electric-only operation.

Mode	How it operates	Best suited to
Efficiency	The heat pump does most of the water heating. In low demand conditions, the upper immersion is not used and the lower immersion operates only if ambient temperature falls below 7°C.	Projects prioritising maximum efficiency where demand can be met mainly by heat pump operation.
Hybrid	The heat pump remains the primary heat source, while the immersion elements can support recovery when demand exceeds a predetermined level.	Higher-demand periods requiring faster recovery while retaining heat pump operation as the primary heat source.
Electric	The unit operates as a conventional electric water heater using the immersion elements to heat the stored water.	Applications requiring electric-only operation, including winter operation where cold air discharge needs to be avoided.

Sizing the solution

The selected model was the LAAS8-455-12. Although the nominal storage capacity is 445 litres, the calculation uses 80% of storage for first-hour draw-off. This provides a realistic allowance for usable volume during peak demand and combines that stored volume with ongoing heat pump recovery.

Sizing point	Single-unit output	Technical interpretation
First-hour draw-off at 50°C temperature rise	706 litres	Usable storage plus heat pump recovery.
Second hour at 50°C temperature rise	350 litres in Hybrid mode	Additional recovery during the extended peak.
Two-hour peak production at 50°C temperature rise	1,056 litres per unit	Two units cover the 2,000 litre design peak.

Capacity check

1,056 litres per unit × 2 units = 2,112 litres over two hours

Design requirement: 2,000 litres over two hours | Redundancy margin: 112 litres

Two LAAS8-455-12 units were therefore selected. At a 50°C temperature rise, their combined two-hour output exceeds the calculated peak requirement while retaining a straightforward two-unit arrangement.

Plant room and ventilation review

The plant room was assessed as part of the application design, not as a separate installation detail. The room measured 4.4 m × 3.5 m × 2.5 m, giving a volume of 38.5 m³. Ventilation was provided through a louvred door with two openings, each measuring 380 mm × 384 mm.

Plant room parameter	Recorded value
Room dimensions	4.4 m × 3.5 m × 2.5 m
Room volume	38.5 m³
Ventilation arrangement	Louvred plant room door
Louvred openings	2 × 380 mm × 384 mm

Installed performance validates the design

The most useful test of the sizing exercise is the operating data from the installed system. Both units had recorded 1,518 operating hours at a 60°C set point, with a plant room ambient temperature of 21°C. Both units were operating in Hybrid mode.

Unit	Installed hours	Upper immersion	Lower immersion
AquaStore 1	1,518 hours	6 hours = 0.4% of insalled hours	8 hours = 0.5% of insalled hours
AquaStore 2	1,518 hours	9 hours = 0.6% of insalled hours	14 hours =0.9% of insalled hours

Across both units, total recorded operation was 3,036 unit-hours. Combined immersion run time was 15 hours for the upper elements and 22 hours for the lower elements. The figures indicate that most of the hot water demand was produced by the heat pumps, with the immersion elements providing limited support. As a percentage breakdown, the upper and lower elements accounted for just 2.4% of the total operating time, demonstrating the exceptional energy efficiency of the installation.

This is the purpose of the Hybrid setting in this application. The heat pump remains the primary source of heat, while the immersion elements are available to support recovery when required. The recorded data therefore provides practical evidence that the selected mode is giving the installation resilience without making direct electric heating the normal source of hot water.

Technical conclusion

The Travelodge Stonehouse installation demonstrates a complete application process: establish the peak demand, assess usable storage and recovery, select the operating strategy, confirm plant room conditions and then review actual operating data.

The calculated requirement was 2,000 litres over each two-hour peak period.

Two LAAS8-455-12 units provide a combined 2,112 litres over two hours at a 50°C temperature rise.

Hybrid mode balances heat pump-led operation with additional recovery support when required.

After 1,518 operating hours per unit, immersion run time remained limited, indicating that the heat pumps were meeting most of the demand.

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