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System design
What impact does the type of building project have on boiler choice?
In refurbishment projects, the existing commercial heating system design dictates what can or can’t be done. The replacement of pipework and other heating components may not be practical due to time constraints, costs and building regulations. A good example of such is our Corpus Christi case study.
Boiler compatibility can also be an issue, especially when the old heating system is ‘dirty’ from years of use. However, via methods such as hydraulic separation between primary (new boiler) and secondary (old pipework) circuit, this problem can be bypassed, an example is Hull & East Yorkshire Centre for the Deaf. In comparison, new builds allow more freedom when it comes to heating design, but are subject to stricter building regulations, such as Part L, e.g. in relation to carbon emissions.
Why is it important to correctly size a domestic hot water system?
Accurately sizing hot water systems helps to ensure the system meets demand in the most effective way. If correctly sized, a domestic hot water system should run more efficiently, resulting in reduced heat up and recovery times, with no risk of hot water running out. It should also result in reduced energy use, and a lower carbon footprint. Hamworthy Heating offer a selection of CIBSE approved Continuous Development (CPD) modules on ‘Domestic Hot Water (DHW) Best Practise’. For more information visit HERE.
What guides and methods are currently used for sizing domestic hot water systems?
At Hamworthy Heating, our engineers use the most up to date version of sizing standards from official bodies to size hot water systems. These include:
CIBSE Guide G:2014 Public Health Engineering
IOP Plumbing Services Design Guide
British Standards BS 8558:2015
What is an unvented hot water system?
An unvented hot water system has no cold water feed tank but rather has a sealed (unvented) hot water cylinder fed directly from the cold water mains and uses mains pressure. The unvented cylinder maintains a steady pressure from an incoming water supply. Unvented systems are ‘sealed/closed’ systems and so require additional ancillary equipment, such as an expansion vessel to manage the changes in pressure within the system as the water within heats up, and a pressure reducing valve to regulate the pressure of the incoming cold water.
What are the benefits of an unvented system?
Unvented systems save space because they don’t need a separate cold water tank and the associated pipework that links it across the system. They therefore have a greater capacity for large commercial or residential properties to deliver hot water across complex designs and longer pipe runs. They also usually have stronger water pressure than tank fed systems as the pressure comes from the mains feed, and water outlets like taps and showers give a better performance. There is far less risk of unvented systems freezing in winter and they are less likely to become contaminated – something that can happen with vented systems due to the use of an open tank.
Can the Purewell Variheat boiler run on an open vented system?
Yes. The Purewell Variheat boiler is able to operate on an open vented heating system.
We would advise compliance with minimum pressure requirements at boiler, reference guidance note INDG436 (Health and Safety Executive).
Open vent and cold feed pipes must be installed correctly and in compliance with BS6644. You can refer to the installer guide for detailed information on Open Vent and Cold Feed pipes.
However, Hamworthy recommends the use of sealed heating systems, where possible.
If you want to know the difference between a sealed system and open vented system, find out more here.
Does the Ensbury boiler need shunt pumps & a minimum flow rate?
The Ensbury boilers do not require back end protection pumps.
There is no minimum flow rate required with these boilers for purposes of cooling, however minimum flow rates need to be maintained to maintain energy output.
Can the Wessex ModuMax boiler run on an open vented system?
Yes. The Wessex ModuMax boiler is able to operate on an open vented heating system.
We would advise compliance with minimum pressure requirements at boiler, reference guidance note INDG436 (Health and Safety Executive).
Open vent and cold feed pipes must be installed correctly and in compliance with BS6644. You can refer to the installer guide for detailed information on Open Vent and Cold Feed pipes.
However, Hamworthy recommends the use of sealed heating systems, where possible.
If you want to know the difference between a sealed system and open vented system, find out more here.
What are the options when a heat pump might not suit retrofit specification?
While the installation of heat pumps will play a large part in helping the Government achieve its net zero target – air source heat pumps (ASHPs) can fit almost anywhere: retrofit or new build, domestic or industrial and commercial, mixed-use developments – but what about the opportunity in buildings that are not ready to rely completely on low carbon heating systems?