The Heatstore Unvented Mains Pressure Water Heater is a purpose-designed unvented hot water storage cylinder available in capacities of 100, 120, 150, 170, 210, 250, and 300 litres, offered in both direct and indirect models. It is designed to provide a continuous supply of hot water at mains pressure, ensuring consistent flow rates even when multiple outlets are in use.
Function Description:
The Heatstore HSU unit features a stainless steel inner vessel for excellent corrosion resistance, encased in resilient thermoplastic mouldings and plastic-coated steel sheet. It is insulated with CFC-free polyurethane foam to meet European heat loss requirements. The system includes all necessary safety and control devices, pre-adjusted for connection to the cold water mains.
Direct models are equipped with one or two 3kW immersion heaters (depending on capacity) for heating water directly. Indirect models utilize a primary heating coil connected to a central heating system boiler, with an additional 3kW immersion heater for backup or supplementary heating.
The system incorporates a Cold Water Combination Valve, which includes a pressure reducer, strainer, expansion valve, and check valve, to manage mains water pressure and prevent backflow. An expansion vessel accommodates water expansion during heating, maintaining system pressure. Safety is further enhanced by a factory-fitted Temperature/Pressure Relief Valve.
Important Technical Specifications:
- Capacities: 100, 120, 150, 170, 210, 250, 300 litres.
- Maximum Water Supply Pressure to PRV: 16.0 bar.
- Operating Pressure of Unit: 3.5 bar.
- Expansion Vessel Charge Pressure: 3.5 bar.
- Expansion Valve Setting: 6.0 bar.
- Max. Primary Working Pressure (Indirects only): 3.0 bar.
- Opening Temperature of T&P Relief Valve: 90°C.
- Opening Pressure of T&P Relief Valve: 10 bar.
- Pipe Fittings: All pipe fittings are 22mm compression fittings, threaded 3/4" BSP male parallel.
- Recommended Cold Water Supply: 22mm pipe, minimum 1.5 bar pressure and 20 litres per minute flowrate.
- Electrical Supply (Direct Models): HSUDC100 has one 3kW immersion heater. Other direct models have two 3kW immersion heaters. 250 and 300 litre units have an additional boss for an optional third immersion heater. All units must be earthed and protected by a suitable fuse and double pole isolating switch.
- Electrical Supply (Indirect Models): All indirect units are fitted with a 3kW immersion heater and a combined thermostat and thermal cut-out. Must be earthed and protected by a suitable fuse and double pole isolating switch.
- Standing Heat Losses (at 20°C ambient, 65°C water): Ranging from 1.14 kWh/24h (100L) to 2.72 kWh/24h (300L).
- Heating Times (15 to 65°C, 70% recovery time):
- HSUDC100 (3kW input): 2h 08m (1h 17m recovery).
- HSUDC150 (6kW input): 1h 33m (1h 08m recovery).
- HSUDC210 (6kW input): 2h 21m (1h 51m recovery).
- HSUIC100 (indirect): 21m (15m recovery).
- HSUIC150 (indirect): 24m (20m recovery).
- HSUIC210 (indirect): 32m (29m recovery).
Usage Features:
- Siting: Must be installed vertically on a level base capable of supporting the full weight of the unit. Should be sited to minimize dead leg distances and avoid extreme cold temperatures.
- Discharge Pipework: Safety valve discharge pipes (D1 from valve to tundish, D2 from tundish to safe termination point) must be installed with a minimum fall of 1:200, terminating visibly and safely. D2 pipe size must be at least one size larger than the nominal outlet size of the safety device, with specific sizing guidelines based on length and number of elbows.
- Secondary Circulation: Can be connected to the Heatstore HSU via a swept tee joint into the cold feed. Requires a 15mm secondary return pipe with a check valve and a WRAS approved bronze circulation pump. Not recommended for direct electric units on Off Peak electricity tariffs.
- Temperature Controls: Adjustable thermostats for both direct immersion heaters and indirect heating sources, typically factory set to 55-60°C (approx. graduation 4). Adjustment range is 10-70°C.
- Operational Faults: A fault-finding chart is provided to identify and rectify common issues such as no hot water flow, cold water from taps, or water discharge from safety valves.
Maintenance Features:
- Annual Maintenance: Recommended to be performed by a competent installer annually, coinciding with boiler maintenance.
- Safety Valve Operation Check: Periodically inspect and manually open the Temperature/Pressure Relief Valve and Expansion Valve for a few seconds to ensure free discharge and correct reseating.
- Strainer Cleaning: Turn off cold water supply, boiler, and immersion heaters. Depressurize the system. Remove the Pressure Reducing Valve cartridge to access and clean the strainer mesh.
- Immersion Heater Descaling/Replacement: Requires draining the unit and turning off water/electrical supply. Immersion heaters can be removed using the supplied key spanner. Scale should be carefully removed from elements, and sealing surfaces must be clean. New gaskets should be fitted if necessary.
- Expansion Vessel Charge Pressure Check: Periodically check and recharge the expansion vessel to 3.5 bar using a tyre pressure gauge and pump. Intermittent discharge from the Expansion Valve indicates reduced air volume.
- Benchmark™ Log Book: An "Installation, Commissioning and Service Record Log Book" is supplied to document installation, commissioning, and subsequent service/maintenance operations. This log book should be completed by the installer and countersigned by the customer.
The Heatstore HSU is guaranteed against faulty materials and manufacture for 10 years (5 years for expansion vessel, 2 years for valves, fittings, and electrical parts), provided it is installed and maintained according to instructions and relevant regulations. It is not guaranteed against frost damage or excessive scale build-up in the inner container/immersion heater(s). The product is manufactured from recyclable materials, and insulation is CFC/HCFC free.
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