Pressure and Temperature Control
Variable flow rates to terminal units require a variable speed pump, resulting in varying pressures at different points of a communal heating system. A detailed explanation of this can be found in ‘Energy Efficient Pumping Systems’ (BSRIA BG 12/2011).
This Design Guide is the result of a research project conducted by BSRIA in association with a project steering group of 8 companies, one of which was SAV Systems UK Ltd.
It should be noted that 2-port valves (such as thermostatic radiator valves) are not designed for variable system pressures. By themselves, 2-port valves would be unable to control water temperature effectively at the terminal units, which is a common problem in many multi-residential buildings.
The answer is to combine differential pressure control valves (DPCVs) with temperature control valves in heating and hot water circuits, to enable the two-port control valves to operate as designed. The DPCVs respond dynamically to peaks and troughs in pressure throughout the day, maintaining constant pressure differential and enabling consistent performance at the terminal units.
System Bypasses/idling flow rates:
Bypass flows should be avoided, to prevent return temperatures from terminal units from rising under part-load conditions. If bypasses are necessary, they need to be carefully controlled to keep bypass flow to the minimum acceptable.
Good system balancing is critical. Poor commissioning risks undermining the overall energy efficiency of a building, especially if system return temperatures from the terminal units are left higher than necessary. Unwanted bypass flows can also lead to increasing pump energy to prevent the less favoured circuits from being starved.
SAV have put together a CIBSE-accredited CPD Seminar, which explores the main issues arising from a 70/40 approach to design. The agenda for this is given under the CPD Seminars tab further along this website. The 70/40 method can be expected to have far-reaching implications, and discussions which are a normal part of each Seminar will sharpen your insight into developments in this field.
If you would like to explore the potential offered by the 70/40 method to any building services project, please feel free to provide some information via the Contact Us page, or by phone / e-mail. We would then assess how best to develop the ideas further, either by CPD Seminar, round table discussion, site visit or other communication.
We look forward to hearing from you.
Please contact SAV Systems using the details below or by going to the Contact Us page.
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