To determine whether commercial heat pumps can be used for commercial DHW generation, Pete Seddon and Sean Ehlen of the Rinnai Tech Team examine their potential within DHW hot water generation.
The phrase used for commercial hot water generation is "domestic hot water" which clearly can be deceptive and therefore needs to be defined. Domestic hot water, or DHW, could be easily defined as hot water used exclusively for homes and other domestic properties. The term "DHW heating" refers to the use of hot water for both residential and business DHW needs.
Reducing CO2 emissions is the primary goal of international policy, with climate change occupying a prominent position. One important sector where CO2 emissions are thought to need to be reduced is the heating industry. This raises a number of concerns about emerging technology and the uses of DHW heating in the commercial sector. Consequently, we answer the commonly asked question, "Can Commercial Heat Pump technology be used for commercial DHW?"
By using best practice design principles, a property's energy requirements for commercial heating can be reduced. Ensuring the thermal efficiency of the property is at the correct levels will result in reduced energy consumption for commercial heating. Commercial DHW heating, however, is unaffected by this notion because the demand for ablutions is going to continue in a constant usage pattern within the building envelope.
It is common for residential and commercial buildings with DHW facilities to be powered by a gas-fired device, such as a gas-fired storage water heater, continuous flow water heater or indirect boilers and cylinders. The potential for naturally occurring bacteria to proliferate is one of the issues with commercial DHW production. If the DHW is not generated to the correct temperatures and stored correctly, harmful bacteria may grow within the system. Reducing storage capacities or using appliances that reach temperatures above 60 degrees Celsius are the simplest ways to combat bacterial growth.
By following these best practice techniques, the system will be well placed to ensure that bacteria are either rapidly destroyed by elevated temperatures or do not have the chance to develop within the cylinder or wider system. Swift temperature elevation is one of the main reasons why combustion appliances are favourable for reducing bacteria proliferation.
For as long as gaseous fuels like hydrogen and rDME are unavailable, gas appliances will still run on fossil fuels until they are replaced. Thus, commercial heat pump technology can be especially important for the decarbonisation of homes and businesses as this technology is readily available.
Can commercial DHW be used with commercial heat pumps?
Whether they are commercial air source heat pumps or commercial ground source heat pumps, commercial heat pump technology can be applied to commercial DHW. However, there are some criteria to be aware of.
1. Temperature requirements: To transfer and store heat, commercial heat pumps need a tank. Because of the possible growth of bacteria in the water, a temperature control regime will be necessary.
2. Control of legionella: ACOP L8 and Building Regulations stipulate that stored water.
must be maintained at 60 degrees Celsius. This temperature guarantees a decrease in
the growth of Legionella.
3. Hot water: At 55˚ C, Legionella bacteria would be eliminated. To further inhibit the
growth of Legionella bacteria, there are further steps we can take in the system.
design.
4. Oversizing - Prevent oversizing on storage and make sure the water held within the system is used at least once or twice per day. For commercial Heat Pumps with a maximum limit of 55˚ C we could look at including immersions within the cylinder. These immersions could be programmed to operate daily at 60˚ C or above, thus killing the bacteria. This process would be classed as a pasteurisation cycle.
In conclusion, commercial heat pumps can supply commercial DHW. However, designers must be considerate of the design parameters above. Performance requirements to ensure optimum system performance is also a major consideration.
For support on heat pump design and gaining an understanding of measuring full system efficiency using SPF (Seasonal performance factors) visit our training page at https://www.rinnai-uk.co.uk/training/cibse-cpd-training-enrolment
