Mains Pressure
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If..
Then this page is designed to inform you of the options
available, and any important concepts that should be understood.
The information is not specific to our products, but generic in nature
(where possible), and covers just about everything. Is your Mains Suitable? First off, it is important to know than any mains fed system (i.e. without stored cold water) is limited by the amount of water that the pipework into the property can provide. The higher the mains water pressure the more water will be available, however the size and length of pipework is also important. This is because when water flows, pressure is lost in the pipes and fittings. Even with a high mains water pressure, a long length of small bore supply pipework can 'use up' the available pressure, resulting in poor flow rates. In existing properties, the water supply can often be gauged best by opening up cold taps that are connected to the mains. These will usually include an outside tap or kitchen tap. As you open up more than one tap, the ability of each tap to keep flowing is an indication of the water available. Your local water supplier should be able to assist in testing pressures and flow rates properly. It may be a good idea to check pipework within the property, as you may find that the supply into the property is in fact excellent, however is fitted with a small bore isolating valve, or a run of smaller bore pipe, either of which would greatly limit the water getting through to taps. If the mains supply pipework is unable to provide the peak water requirements then there are only a few options:
In a few installations, the desired peak water demand is higher than the local water authorities can provide. On these occasions, cold water storage is the only option, and pumps have to be used to boost pressures and flow rates to taps. That said, most properties have more than adequate water
supplies, and mains fed hot water system become an option. Low Cost Options Do not overlook the cheapest options - it is not always necessary to upgrade the entire hot water system to improve a shower. The simplest way to boost water pressure is with a pump. These fall into three categories:
In addition to pumps, Venturi showers are often an economical solution. These are shower units that use the pressure of the cold mains supply to 'drag' the hot into the shower at higher flow rates. Where there is reasonable mains pressure to the cold tap, these systems can provide superb performance showers at a very low cost. More info... Pump Sets A pump set is made up of TWO booster pumps, a cold water tank, an accumulator vessel, and controls. They are used where the mains water supply cannot be made large enough to feed multiple outlets at once, but the client still demands to do so. Two pumps are used to provide duty / assist operation, with both pumps only running together at maximum load. The use of two pumps also allows water to still be provided should one pump fail - this is very important. The cold water tank must be sized to provide both hot and cold supplies at maximum use, although a large ball-valve in the cold tank is used to maximise the input from the mains. The accumulator is basically a pressure vessel that stores a certain volume of high pressure water, and prevents the pumps from having to run when someone is only brushing there teeth. The larger the accumulator, the more water can be drawn without the pumps operating, and also helps reduce wear on the pumps, although 60 litres is a typical size. The controls provide the duty / assist operation using pressure switches, but will also alternate which pump comes on first to even out wear, and provide pump over-ride and protection. Pump sets generate as much water, and pressure as you can specify. They are very effective when used in conjunction with Heat Bank thermal stores to provide hot water, as this will preserve the higher pressures and flow of hot water to outlets. Combination Boilers You may be considering a combination boiler, where there is no need for a hot water cylinder at all. Before going down this route, be aware that combination boilers can only supply one tap at a time, and as such are simply not an option on installations where showering is not to be affected by the opening of a second outlet. There is a very good reason for using a hot water cylinder of any type - domestic sized boilers, or electric heaters, cannot generate heat quickly enough to feed multiple outlets. To achieve this, the boiler's heat output has to be stored, in a hot water store, to be used up quickly when required. One other point to be aware of with regard to combination boilers is that should one break down, the property will be without both hot water and heating until the boiler can be fixed. When a hot water store is used, there is always the facility for electric backup, allowing hot water to be obtained (be it in reduced amounts) while waiting for the boiler to be fixed. That said, in one bedroom flats, with only one or two occupants and space is at a premium, then combination boilers are usually the best choice.
Terminology & Technology: The Modern Store The next item is often only a point of terminology. Most people make the mistake of assuming all mains hot water cylinders are pressurised, or unvented. This is not the case, as modern thermal store systems use an un-pressurised (vented) hot water store, whilst still providing pressurised hot water to taps. It may seem a small point, however the differences are fundamental. Unvented hot water cylinders contain a large amount of hot water at high pressure - not too high as the cylinder has a limit. This water goes to the taps, and the cylinder fills with water from the mains. A thermal store contains a large amount of hot water at no pressure. The heat stored in this water is transferred to the mains water flowing to taps, which is kept separated at full mains pressure. Both do the same job, providing pressurised hot water, although a thermal store can provide much higher pressures, and has many other advantages. Unvented cylinders, unlike thermal stores, will require:
The only situation where it is necessary to use an unvented cylinder in place of a thermal store is when the store cannot be heated above 65°C. Where the only heat source is solar panels or a geo-thermal source then an unvented cylinder may perform better. Where the store is to be heated by a gas or oil boiler, or by electric elements, thermal stores will perform better. Although DPS sell a complete range of unvented cylinders (see DPS Amazon), the Heat Bank thermal stores, and most notable the Pandora Heat Banks, represent the most modern technology and are the best choice in 99 out of 100 contracts involving mains fed stores. Another warning regarding terminology is when talking about the primary (or boiler/heating) system. This is usually separate from the hot water storage - in the sense that the water in each does not mix. The primary system is usually pressurised, and so the term 'pressurised system' takes on a third possible meaning! Be careful to distinguish between the domestic water supplies, the water in the hot water store, and the water in the boiler system.
GX Fully Integrated Thermal Store Systems - Vented Primary Systems Only Other than the Pandora, the most notable type of thermal store DPS manufacture is the GX range for vented boiler systems. These differ from the Pandora in that the water in a GX store is the same water as the boiler and radiators - there is no heat transfer coil used to separate the store water from the typically higher pressure heating water. GX stores make use of a feed and expansion tank and can only be used on vented boiler systems. The feed and expansion (F&E) tank is usually recognised as the smaller of the two tanks in your loft, and requires an overflow pipe because it is fitted with a ball valve. It is used to fill the boiler, central heating, and the GX store with water, and allow for expansion / contraction of this water as it heats up and cools. The GX stores are designed to be a fast recovery system, allowing a smaller sized store to be used. The following table summarises their advantages and disadvantages over the standard Pandora Heat Banks (or unvented systems).
Electric Systems Where your system is electrically heated, and there is no gas/oil boiler, then the latest Electric Pandora Heat Banks provide the simplest type of system to date - and the best performing. These systems do not require a specially trained installer. They only have two pipework connections - cold in and hot out - no discharge pipes. Mains pressure up to 6 bar, and a standard system will run a bath and two showers simultaneously. No maintenance other than adding one litre of inhibitor every 5 years. These systems are our biggest selling product, as they are used a great deal in modern new-build flats. The current trend towards greater hot water demands, combined with the drive for 'fit-and-forget' systems, puts the Electric Pandora well in front of all other systems. Another trend in new-build is for quick-fit systems, and also to make the task of installation as simple as possible. The Pandoras reflect this, having all components factory fitted, set, wired, and tested. Power cables and controls are usually provided, making wiring very quick. It is important to check out the type of electricity tariff available to you, as the controls you need will reflect this. Get the controls or the tariff wrong, and you may find yourself heating all your hot water on peak-rate electricity when you could easily have the system set to run entirely on cheap-rate! Don't panic, just ask your electricity supplier for your options regarding tariffs for electric hot water storage. Most properties without a gas/oil boiler provide central heating with wall-mounted storage heaters. It is also possible to run radiators or under-floor heating off a Heat Bank. These systems are referred to as the Heat Bank 2000 range.
Summary Table
*1 F&E Tank may be built into top of store, or at high
level in top floor cupboard, but must be higher than all radiators.
Pandora Heat Bank Thermal Stores:
GX Heat Bank Thermal Stores: Unvented Cylinders: Tank Fed Systems:
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