| Abstract | Drain Water Heat Recovery (DWHR) units are heat exchangers designed for recovering thermal energy from warm water that travels down shower drains. There are numerous challenges this technology faces for broader application in Canada, which span from misleading terminology to inapplicable building codes and rated conditions. Semantically, the phrase drain water heat recovery is misleading when referring to these heat exchangers, as their operation is not applicable to black water in drains, nor is it applicable to fixtures that do not have concurrent water draw and drainage (e.g. clothes or dishwashers). In terms of building codes across different Canadian jurisdictions, none have incorporated the latest CSA (Canadian Standards Association) standard covering the performance of DWHR heat exchangers, namely CSA B55.1-20, which was published in 2020. This is a significant oversight, as CSA B55.1-20 incorporates near-horizontal DWHR heat exchangers into the rating procedure; prior to this (i.e. CSA B55.1-15), horizontal designs could not be rated nor certified in Canada. The consequences of outdated codes in this case are as follows: • Local codes such as Ontario’s SB-12, refer to an outdated version of the CSA standard, which only allows for installation of vertical DWHR heat exchangers. • Local codes such as Ontario’s SB-12, include minimum efficiency requirements for DWHR heat exchangers; however, these minimums are based on vertical units, and a market-sweep of commercially available products revealed that out of over 50 products, only 3 are of horizontal design while meeting the minimum requirements. In terms of realistic installations for DWHR heat exchangers, neither local building codes nor CSA B55.1 account for plumbing configurations where heat exchangers get installed. The thermal performance for a DWHR heat exchanger is a strong function of flow rates passing through it, and these flow rates are influenced by the plumbing configuration in the dwelling. The rated effectiveness value that is determined through the CSA standard is only applicable to one particular plumbing configuration, while neglecting all other possibilities. As summarized, DWHR technology is facing challenges on multiple fronts, which have collectively barred optimal utilization of the technology in Canada. Building codes often promote the adoption of efficient technologies by granting points; however, it is important to tackle the identified issues beforehand to ensure these points are awarded appropriately. Failure to address these issues could lead to inconsistencies and potential misuse of the point system. |
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