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Unvented hot water cylinders

Unvented hot water cylinders store water supplied directly from the incoming water mains. It is heated by an electrical heating element or from a boiler. The incoming mains pressure/flow rate should ideally be 2-3 bar with a flow rate of approximately 25 litres per minute, giving the cylinder the ability to deliver excellent flow rates to several outlets (taps or showers) simultaneously. Another benefit of these higher flow rates and increased pressure is that taps and showers at the top of a building in a loft space or similar can benefit from excellent showers without the need for pumps. It also gives a dry loft scenario which makes systems less subject to freezing up in the winter.

Types of unvented hot water cylinders

There are basically two types of unvented cylinders available:-

Bubble Top: This cylinder employs a bubble of air at the top of the cylinder, enclosed by a membrane, which as the heated water expands compresses the air thus making room for expansion.

External Expansion Vessel: This type of cylinder uses a separate expansion vessel to accept the increased volume of hot water as it expands. It should be noted that should the incoming water main pressure be less than ideal a new water main supply to the property would probably be the answer. The flow rate to the house would be improved (due to the larger bore of the new main supply) even if the pressure could not be increased. This work can be “moled under the ground” to avoid any major disruption. We can arrange this for you.

A working display of an unvented hot water cylinder is available to view in our showroom.

Please ring Natalie or Kim for further information or for a more “technical” chat Alan of Peter would be pleased to meet you in our showroom at a time convenient for yourself.

Requirements: There are two documents that must be met if it is to comply, The Building Regulations and The Water Supply Regulations. Unvented hot water system installation is classified as a “controlled service” and regulation G3 of the building regulations applies. The local building authority must be notified before the installation takes place unless the proposed installer has the necessary qualifications. We at Alan D Scoffield hold all the required documents to carry out these works.

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