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.
http://www.cnmonline.co.uk/Unvented-Water-Heaters-c-173.html

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 on CNM Online Ltd have ‘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.