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Hamworthy UK Commercial Office

Hamworthy Heating celebrated its 100th anniversary in June 2014. Over the past century they have consistently innovated the UK commercial boiler market and want to continue that trend.

Hamworthy is now part of Groupe Atlantic, a major European HVAC manufacturer. Its mission is “to transform prevailing energies into sustainable well-being by creating thermal comfort solutions that are ecologically efficient, accessible to all and suitable for individual needs.”

Hamworthy recently investigated how it can improve the energy efficiency of commercial office boilers by installing Hydromx® in its office in Poole, England.

The building and core of the heating system date from the 1960s and contain metals commonly found in heating systems, including steel, brass, copper and aluminium.


The Energy Saving Trust reports that “Corrosion deposits in an older central heating system can cause a significant reduction in the effectiveness of the radiators and the system as a whole – up to 15%.” And that “using an effective chemical inhibitor can reduce corrosion rates and prevent sludge and scale buildup – preventing system deterioration and maintaining efficiency. Typically it can increase boiler efficiency by about 3%.”


The building has many radiators around the perimeter of each of the three floors, and temperature control is limited to one thermostat on the third floor and thermostatic radiator valves (TRVs) on the first floor. There are no TRVs on the second or third floors.

The heating system was drained and flushed before the test and then refilled with fresh water and corrosion inhibitors; this provided an accurate baseline measurement to make a fair comparison to a “clean” system. Subsequently, 900 liters of water was replaced with a Hydromx solution and the radiators were bled within a day. There were no further changes to the building's heating system.

Hamworthy's research recorded gas consumption for two space heating boilers, one with a steel heat exchanger and the other aluminum, with a total output of 95 kW. A gas meter monitored each of the two boilers. Additional temperature data loggers ensured that internal room temperatures were consistent and comparable across the three-storey office space.

Hamworthy's engineering staff independently monitored and recorded gas consumption and internal and external temperatures to carefully compare Hydromx's performance against a baseline of water with corrosion inhibitors. Office staffing levels were consistent throughout and internal temperatures averaged 0.5°C between baseline and test periods.

The outdoor ambient temperature data used in a Heat Degree Days (HDD) analysis came from a local public weather station located a mile away. HDD measures how far the outdoor temperature is below the indoor thermal comfort temperature (1 HDD is equal to the outdoor temperature one degree lower than thermal comfort for one day).

Hamworthy measured the energy consumption (kWh) of the boilers for each degree of outdoor temperature, expressed as kWh/HDD. In this study, Hamworthy's weather-dependent consumption was 66.94 kWh/HDD with water as the system fluid and only 46.29 kWh/HDD with Hydromx – a saving of 30.9%, well above the 3% offered by chemical inhibitors alone.

“We were skeptical of Hydromx's performance claims, but the results at our offices have proven them to be true,” said Hamworthy Technical Director Bob Walsh. “A 30 percent reduction in energy consumption is a major benefit for commercial customers, and will obviously have a very significant impact on achieving CO2 reduction targets and reducing costs directly on the bottom line.”

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