To supply the volume of water required for a bath tub requires lots of current for an electric instant water heater to be effective. In most UK households your current breaker box would not have the capacity for the extra demand that is required to supply a bath tub quickly enough. The average bath tub capacity in the UK is somewhere between 40 and 60 gallons, this is equal to >182 to 272ltrs. However the majority of people will only fill the bath tub half way up or even less in most cases, especially if they have a water meter fitted! Therefore the average water required for a bath tub is somewhere in-between 45 and 90litres depending on the user! The average hot water flow rates for a typical shower unit rated at >8.5kW will supply roughly >2-3 litres of hot water per minute. Therefore if you were to fill a bath tub using just a “shower type” instant water heater this would take >20 to 30 minutes to achieve a suitable bathing level. The main advantages of instant water heaters are that they are much smaller and easier to fit and they can be installed in smaller cupboard spaces than a stored water heater. Instant water heaters provide hot water on demand, thus heating the water as and when required, making them more economical than a conventional stored water tank. The down side for instant water heaters is they are limited with their flow rates and the fluctuations of the cold water temperatures during the winter months. The problem with “low power” instant water heaters if they are to be used for a bath tub is that by the time the water is at a desired level the majority of the heated water will have been lost to the bathroom. For any instant water heater to satisfy a bath with enough hot water the power of the instant water heater therefore has to increase to enable it supply enough hot water very quickly within a short period of time before the water cools down. The only way to achieve this is by installing a Three Phase Instantaneous water heater capable of supplying multiple sinks at the same time, or a bath! Three phase water heaters are ideal for gyms, hairdresser salon, schools, work places or even washroom toilet blocks that supply 6-8 hand basins at the same time. Three phase units have the capacity to run multiple outlets from the same power supply at the same time. A typical three phase water heater required to fill a bath would have an output of 27kW. However the majority of households in the UK do not have a three phase power supply. The majority of people in the UK have single phase power supplies and unfortunately there are no single phase instant water heaters that will supply enough hot water quickly enough to satisfy the bath tub. The DHE 27kW is a three phase instant water heater and would be capable of supplying enough hot water for six hand wash basins simultaneously or multiple showers or one bath. The DHE27 would struggle to do more than one application at the same time – e.g. whilst running a bath, if hot water is called for at the sink or shower, it may affect the bath tub supply. Please see link to the DHE27 three phase instant water heater, http://www.cnmonline.co.uk/Stiebel-Eltron-Instantaneous-Water-Heater-27kW-pr-33339.html
If you require an electric water heater to serve a residential property we would generally recommend a storage type water heater. Storage type water heaters hold a specific volume of water at a suitable temperature available for you to use while ever the heater is switched on. As you draw water off, the heater tops itself back up and brings the water back to temperature again. These types of water heater are available in a range of different sizes. In order to serve all of the hot water outlets in a residential property, you would generally require 80L- 100L of water. Different manufacturers make storage type water heaters and all of the dimensions and technical information is listed on the individual product descriptions. For details of our current range of storage type water heaters, please click on the link below. Water Heater
There are several different choices available for hand washbasins. You may choose to go for a small storage type water heater- these are available in both under sink and over sink models. Choosing a storage type water heater will guarantee you a specific volume of water at a suitable temperature whilst the heater is switched on. If however you are likely to run off the whole contents of the water heater at once, you would have to wait while the heater filled itself back up and re-heated for more hot water.
Another option for hand washbasins are instant water heaters. Instant water heaters do not store water; they simply heat the water as it passes through the heater. This type of water heater can save on running costs as they only use electricity when the hot water is required. Instant water heaters are available in a range of kW ratings, and the general rule of thumb is that the more powerful the water heater is, the better ‘flow-rate’ and the more consistent performance you will get. Instant water heaters can be a good option if you have a washroom that is used heavily over a short time, i.e. at staff lunch breaks where a small storage water heater might run out of hot water.
An average kitchen sink will usually take between 10L and 15L of water to fill it up so we would generally lean towards a storage type of water heater. This type of water heater allows you to store a particular volume of water at a suitable temperature (some heaters have thermostats on the front to allow you to specify a temperature) that can be delivered quite quickly. You could choose to have an instant water heater, but to get the water to a similar temperature you would need to choose one of the more powerful models, and the water would probably run slower out of the instant type models.
When deciding which type of water heater to use for your bath, sink or hand wash basin it is important to understand the difference between vented and un vented.
An unvented water heater has a water cylinder that stores hot water and delivers it at mains pressure. Unvented water heaters do not rely on gravity for the supply of hot water so they can be installed virtually anywhere under or over sink, cupboard space. The main advantage is that you can get a power shower hot water supply without the expensive and noise of a power pump. The bath, sink or hand basin fills faster and smaller bore pipe-work can be used. This also means you don't have gallons of cold water stood in the loft space merrily producing bacteria for you to bath in. Unvented water heaters can also be used with standard, mixer and auto sensor taps. The disadvantages of unvented water heaters is that it can be a BOMB if not installed correctly and for this reason all installers of unvented cylinders MUST be registered for such work. To accommodate for the expansion of water which occurs when the water is heated in the cylinder, a diaphragm pressure vessel should be used on the cold feed water supply connection seek professional advice. Requires mains pressure to work efficiently and if you lose the mains water supply then you have no back up!
Vented water heaters are designed to vent the expansion naturally through special vented taps or through the main hot water supply spout. If the water heater is classed as being vented, then it can be either an under or over sink water heater. The under sink water heater will need special vented taps for it to work safely. The over sink water heaters are usually pre-fitted with a swivel spout. If the vented water heater is an over sink unit then it will have a spout supplied at the front, this means the expanded water will vent via the special taps or spout. The advantages of this type of water heater are that there is no need for a diaphragm pressure vessel fitting in the cold water pipe-work. They are energy efficient and very reliable water heaters that generally have longer warranties with them. The disadvantages are that special expensive taps may be required if the unit is for under-sink use. Requires mains pressure to work efficiently and if you lose the mains water supply then you have no back up!
Put simply an unvented system is one that is NOT vented to the atmosphere, and a vented system is one that IS
Water heaters do differ in their complexity. Some of the catering water heaters do not need any installation at all, you simply plug them in and stand them on the counter top, while some of the un-vented water heaters require installation by qualified plumbers with a special licence, so it is difficult to answer yes or no. As a general rule, if you are unfamiliar with the product and are not qualified to install the product, we would advise you to seek professional advice.
Some water heaters have optional accessories, which may or may not be required, depending on how you are installing the heaters. All of the water heaters ‘technical information’ downloads explaining how the water heaters are to be installed. Some water heaters will require special vented taps, and others will require expansion vessels so it is important that you read through the technical information beforehand. If you are not a qualified plumber, or if you are not sure about what it is that you need, we would advise you to print off the information and consult the qualified person you will be using to install your water heater. Alternatively, you can click here to contact our support team and we can try and find out more information for you.
If your water heater develops a fault within the warranty period it is usually best to contact the manufacturer, as some are able to arrange for service engineers to visit you and look at the heater. All manufacturers operate differently, but they will be the best people to advise you how to proceed. Please visit our Faulty Item section for more information.
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