HVAC Contractors in 87123

Pressurised cylinders were introduced to the UK market as long ago as the 1980s. They are often referred to as unvented cylinders and are proving to be highly popular. Their popularity is evident both in the domestic market and the professional space with plumbing and heating engineers. In 2007 unvented systems accounted for around 50% of the installed systems for the first time.

Compare this with pressurized systems which use the pressure of the mains system to provide hot water at convenient pressure levels. As the name suggests, pressurized systems sustain the incoming pressure of the cold water mains (normally around 2-3 bar in most residential areas in the UK). By keeping the system sealed, the hot water is pumped out to the user at the same flow as the cold water that comes out of the cold water tap.

However, pressurized systems, as the name suggests, are effectively passing the incoming pressure of the mains cold water system into the hot water system. A typical residential area in the UK would have a mains cold water pressure of around 2-3 bar. By keeping the system sealed, unvented systems can sustain this pressure within the hot water loop, providing sufficient pressure in the shower, kitchen or wherever else it is need in the house.

It is important to point out that the system is sealed and hence pressurized. As such it requires special training for correct design and installation. Since water expands upon heating it creates a few additional issues to account for. Unlike traditional systems where the header tank can take any expansion of the hot water, in sealed systems the technology has been designed to address this using a few checks and safety equipment along the hot water loop.

An additional safety mechanism is the pressure and temperature relief valve. The PT valve is a mechanical instrument that is designed to open whenever the temperature or the pressure exceeds a preset level, thus creating a potential hazard. When the temperature or pressure becomes too high, the PT valve opens up, discharging excess water into the drain (normally through a tundish), and in doing so reduces the temperature and pressure.

Another safety measure is the temperature and pressure relief valve. The PT valve is a simple yet smart mechanical valve which senses whether the temperature or the pressure within the cylinder is too high (or is breaching a preset level). At that point the valve opens up to let the extra steam out into the drain, thus immediately reducing the temperature, the pressure and the volume of water in the system.

The safety checks and valves ensure a safe and reliable hot water system. The Cold water enters the system at mains pressure, keeping the system (which is sealed) at a constant pressure throughout. The water heats up within the cylinder and is then delivered to the user (still at mains pressure). As the hot water is drawn to the user (normally from the top of the cylinder), fresh cold water enters the cylinder (normally from the bottom) to replenish the levels and sustain the pressure.

Unvented cylinders normally fall into one of two main categories - direct and indirect:

* Direct cylinders - typically using an electrical immersion heater to heat the water. In this arrangement the electrical unit is immersed in the water within the cylinder and is hence heating the water directly. Typical heating units come with a capacity of 2.5 to 3.6kW.

* In-direct cylinders - this set up is based on a heat exchanger. Since the water inside the tank is heated by another medium using the heat exchanger, it is considered to be done indirectly. Typically a boiler is used to heat up water which is then pumped through the heat exchanger where the heat is transferred to the water inside the cylinder.

Over the last two decades unvented systems have carved a strong position in the plumbing and heating arena. Since strong competition is expected to drive prices down and availability up, unvented systems have a bright future in the UK.

HVAC Contractors in 87123

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Tal Potishman, editor of Heating Central, writes articles on home heating, plumbers, Kensington boiler, underfloor heating and solar thermal. He specializes in helping save money by advising on efficient heating.

HVAC Contractors in 87123: 87123 Heating

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