Callback form submitted successfully. You will recieve call soon.
There are two common types of water heaters used in residential applications today – vented and unvented. While vented hot water heaters are perhaps the more common of the two, unvented water heaters are quite popular. They provide good flow rates at taps and appliances, and require less installation space than conventional gravity systems (vented hot water heaters).
Also unlike conventional gravity hot water systems, unvented water heaters do not have a feed and expansion tank located above them, and there is no need for a vent pipe. In a gravity system, the vent pipe is open to the atmosphere and prevents unwanted pressure build-up within the system. The key difference between the two types of systems is the fact that unvented boilers are sealed. This is also why installation of these systems is strictly controlled by part G3 of the building regulations.
It should also be noted that direct unvented water cylinders require the skills of a plumber qualified to work on unvented heaters and a part “P“ registered electrician, as their function requires both skill sets. At EasyFlow, we have both qualified plumbers and electricians to handle these situations.
Unlike gravity systems, unvented water heaters rely on the pressure and flow of water from the mains for their own water pressure and flow. If the incoming water pressure and flow is insubstantial, installing an unvented water heater will not alleviate the problem.
In an unvented system, the incoming mains water first passes through a stop cock, line strainer, a pressure reduction valve and a check valve before it enters the water cylinder. The pressure reduction valve would typically reduce incoming water pressure to three bars. Water can be heated directly by immersion heaters in the case of direct electric systems, or indirectly by a boiler, a primary circuit and a heating coil.
As the water temperature rises, so does the volume of water in the cylinder. Heated water is now trapped between the closed hot water taps at the point of exit and the single check valve at the point of entry. As the water expands, the pressure within the cylinder increases beyond the initial three bars of pressure. The expansion is taken up by an expansion vessel, or in the case of a MegaFlo, an expansion bubble within the water cylinder itself. The expansion vessel contains a flexible membrane and is charged to a similar pressure as the static pressure of the tank.
Water stops expanding when the heat source is removed. In a direct system, the immersion heater-mounted thermostats would keep the water temperature below 65 degrees centigrade. Unvented water cylinders are highly insulated, so they require heating only once per day to provide enough heated water to supply household needs for a full 24-hour period.
Obviously, if the thermostat mounted to the immersion heater failed, the water would continue to be heated beyond the 65-degree point. As a result, expansion would continue increasing, and pressure would build within the cylinder. Apart from the risk of scalding, the real danger occurs when the temperature passes 100 degrees centigrade. At this point, there is a significant risk that water would transform to steam, which could then expand 1600 times the volume of water and cause an explosion. This is where the safety devices built into unvented water heaters come into play and prevent the risk of dangerous situations.
The first level of defence is an overheat cut-out. If the temperature passes 85 degrees, the overheat thermostat would activate and eliminate the danger. The overheat thermostat must be manually reset, though, and this should be done in conjunction with a safety inspection.
If the overheat thermostat were to fail, a temperature and pressure relief valve would activate at 95 degrees. The valve opens, allowing hot water to exit the tank safely via a discharge pipe and tundish, connected to the drain. In turn, this allows cold water to flow into the tank and further reduce the temperature.
Additionally, there is another expansion valve set to six bars, which opens if the pressure within the cylinder rises above the safety threshold.
While very different from gravity systems, unvented water heaters are efficient and easy to use provided you understand how they operate and how to set the controls. The section above outlined how unvented water heaters function, and now it’s time to discuss how to get the best operation out of your water heater.
Most direct unvented water heaters have two immersion heaters. One is located at the bottom of the water cylinder itself. The second is located about halfway up the cylinder. If your unit only has a single immersion heater, it will be located at the bottom of the cylinder. The lower unit is always the primary heating element. If you own an Economy 7 or similar supply, the main immersion heater will operate during “economy supply hours“, which are typically after midnight, and will heat water for up to seven hours (or the number of hours specified in the model designation). If you do not own an economy electrical supply, you can operate the main immersion heater at any time of day or night. The main heating element should always be fitted with a time control to avoid costly electricity bills. Use this to your advantage, while tailoring the heating schedule to your specific usage needs.
While the lower heating element is called the “main“, the second heating element (if so equipped) is called the boost. This heating element can be operated at all times, day or night, even with economy supplies. Again, this element can be controlled with a timer to ensure maximum hot water availability on your schedule.
As mentioned, the second heating element located midway up the cylinder is called a “boost“. Generally speaking, you should turn it off and leave it off until it is needed. The lower heating element should provide more than an adequate supply for your hot water needs. Economy 7 users will have a timed function on the supply. Other users will have to set the amount of time they wish to heat the water on the time clock. Six hours of heating should be sufficient in most instances, and it is best to heat the water from midnight until 6:00 AM.
The boost heating element is used to “top up“ the water temperature within the cylinder outside of the times mentioned above. It’s an important feature for temporary higher usage needs. For instance, a number of people may have just showered and another would like to shower, but the water is not hot enough. Using the upper boost immersion heater for an hour would ensure enough hot water for this.
It is important to note that the interior of your water cylinder is not segmented – it is a single open cylinder. However, because of the shape, heated water is stratified into layers with colder water at the bottom and hot water at the top. As hot water is drawn from the top of the cylinder, it is replaced by colder water from the bottom. The more hot water being used, the more cold water will fill the cylinder. Using the boost immersion heater applies heat to the already warm (but not completely hot) section of the cylinder.
In most unvented water heaters, both the main heater and the boost heater are rated at 3 kW. In some water heaters, they are identical, such as the Santon Premier Plus. However, in some systems, they differ, with the lower heating element being curved and elongated.
At EasyFlow, we guarantee the work we undertake for you, but we will not guarantee manufacturers’ parts. Manufacturers generally offer a 12-month warranty on parts, which we pass on to our customers. Note that some manufacturers do not offer a warranty on a new part that has been installed on an old water heater.
A number of manufacturers produce unvented boilers. These include:
Each manufacturer produces cylinders designed to operate reliably under the increased stresses produced by high temperatures and pressures. Call EasyFlow today for more information on repairs or annual maintenance on your existing unvented water heater, or to discuss the installation of a new unvented water heater.
Most unvented water cylinders require annual maintenance, as specified by the manufacturer. In addition, the service record should be signed and dated by the professional servicing the unit. At EasyFlow, we operate an annual service register to make this simple to remember. We send reminder cards close to the annual service due date, and then follow up with a reminder phone call to book the service appointment with a plumber. We also provide you with a service logbook if your installation/service logbook provided by the original installer has been misplaced. Your service history is also kept on file at our office should that information be required. Call EasyFlow today at 0800 433 4043 and sign up for annual unvented water heater service – we’re proud to serve all of Manchester, Liverpool, Chester and Leeds areas.
If you need assistance with any hot water heater repairs, to schedule hot water heater maintenance, or to install a new hot water heater, call EasyFlow at 0800 433 4043
Our maintenance plans are designed to ensure our customers enjoy peace of mind, and constant hot water. We keep your hot water flowing while minimising your costs and eliminating stress. Let our experts identify and correct water heater faults, while you enjoy low monthly payments.
Just a word of thanks for the emergency support and repair carried out this week. Once again the work was carried out expertly, without leaving any mess and with great courtesy. Well done and thanks again for the support in our hour of need, much appreciated. Regards
BRH, Manchester
10th January, 2022
No Hot Water
Really appreciated the immediate answer when I phoned on Tuesday, which was a Public Holiday, about a significant leak in our pressurised hot water system. Really appreciated the quick call back to discuss the emergency situation and for the repair carried out by him on Tuesday this week. Once again the work was carried out expertly, without leaving any mess and with great courtesy. An excellent service. Well done and thanks again for the excellent support in our hour of need; much appreciated.
Brian, Styal Road Wilmslow
28th December, 2021
Maintenance Plan
After a few years of struggling to get adequate hot water our landlord finally brought in the right people for the job. Chris our engineer was superb, after a brief chat with myself he diagnosed & repaired the issue in under two hours. Excellent service & very professional. Thanks to you we now have plenty of hot water 24/7.
Chris Sheridan, Manchester
23th March, 2021
Blending Valve Replacement
After having a bad experience with a Company pretending to be local who pretty much ripped me off, I was glad to find Easy Flow were local and the service from start to finish was excellent. Got a call back within ten minutes and was promised someone would be round to review that evening and then complete the job a couple of days later if needed. Chris, who attended texted me to give me an ETA and arrived when promised, masked up and Covid friendly. Really nice guy who told me the problem and was looking at his diary and decided to stay and complete the job then, so stayed on a Friday evening for almost two hours, leaving at 7.30, ensuring the job was done... Could not recommend highly enough...
Terry Garnett , Salford
15th January, 2021
No Hot Water
Very efficient and thorough - thanks again.
Danny Benson, Castlefield
10th August, 2020
Annual Service
EasyFlow installed a new thermal store water heater in our flat in Manchester city centre. Throughout the whole process, from the initial inspection, the quick turnaround in providing a quote through to full installation, we were extremely pleased with the service provided and would highly recommend to anyone in need of a heating specialist.
Matt and Alice, Manchester, UK
17th May, 2020
Installation
Engineer was prompt, very thorough, I had asked for service and repair. This was done swiftly and his knowledge of the product instilled confidence in his work. Quick, clean and good job well done. I shall be booking an annual service next year.
Beverley Venyige , West Yorkshire
30th March, 2020
Annual Service