On balance, it’s basic practice

Steve Sutton

Steve Sutton, technical manager at the Heating and Hotwater Industry Council (HHIC), says hydraulic balancing or system balancing is a simple process when commissioning a wet heating system that should be a forefront of industry efforts to increase efficiency in homes across the UK.

Put simply, balancing the system is the process of optimising the distribution of water through the property’s radiators by adjusting the lock-shield valve, equalising the pressure of the system.

Undertaking this process will ensure that the house is at the intended temperature, at minimal operating cost and optimal energy efficiency. If the water flowing through the system is not balanced, individual radiators could end up taking the bulk of the hot water flow – leaving others with a reduced flow rate.

Systems with thermostatic radiator valves could also become a noisy nuisance for homeowners if the system isn’t balanced, with water ‘streaming’ noises coming through the valves.

As the review of Part L for new build is proposing low-temperature systems for the Future Homes Standard, this issue becomes of even greater importance. With these systems working on constant low-grade heat, even distribution around the circuit is required to maintain comfort levels for the homeowner.

Equally, TRVs now feature more heavily in Part L recommendations, in line with European Energy Performance of Buildings Directive (EPDB). Here, an incorrectly balanced system may still supply hot water to the radiators that are not receiving the right amount of hot water as the TRVs operating will cut off on a hot radiator, in turn changing the pressure in the system.

As a result, maintaining temperature will be haphazard. As low-grade heating already requires a shift in usage and perception on the part of the homeowner, adding unpredictability into the mix could harm consumer confidence in the technology before it has even begun.

There is no one-reason for an unbalanced system. The amount of balancing required is dependent on the housing layout and system design, while a common cause of unbalancing is the removal of radiators for redecorating purposes, which are then refitted without rebalancing, which affects the whole system.

Consumers then try to overcome the effects of an unbalanced heating system by turning up the boiler thermostat or increasing the speed of the system pump without solving the root cause of problem.

The first step is simply to remove the air from the system by bleeding the radiators in the home. Once this has been done, the heating should be switched off to allow the radiators to cool down. The next step is manual and requires the heating engineer to turn on the central heating and make a note of the order in which the radiators warm up – the nearer to the pump, the faster the radiators tend to warm up. The heating engineer should then turn the fl ow valves, or thermostatic valves where fitted, to the fully open position and lock-shield valves on every radiator in the home by turning them anticlockwise.

This next step is straightforward. The installer can simply touch each radiator in turn to see if they heat up at the same time – if they do, the system does not need adjusting. If the engineer finds that they are not evenly warming up, then the radiator that heats up first should have its flow restricted. You can do this by closing the lock-shield valve.

The valve closure should start at 50%, with the installer monitoring the system and closing the valve further if needed, it may be necessary to close the valve by more than 80%. This will increase the fl ow rate to other radiators across the system. If some radiators remain cool, then the heating engineer should make further adjustments by restricting the hotter radiators in the system.

Previously restricted radiators should be restricted even further, while those that weren’t restricted should be restricted because they are now hot. The installer should continue to monitor the system – but it is worth noting that changes to even one radiator could affect every other radiator on the heating system. Technology has developed to the point where thermostatic radiator valves can be balanced using internal settings on the valve body.

The installer will need to select the correct setting from a ‘look up table’ for any given room and radiator size combination. Alternatively, new solutions such as circulator pumps that use an app to communicate with a smart phone or tablet and calculates the flow required for a specific radiator, and then guides the heating engineer to set the lock-shield valves correctly for each individual radiator and pipe run, ensuring accurate balancing and time saving.

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