Hybrid Domestic Hot Water Retrofit
As of September 2023, 98% of British Columbia’s (BC) electricity is produced through hydroelectric generation, offering a plentiful, low-carbon energy source. However, 66% of residences in BC heat their water with gas, and domestic hot water (DHW) heating is responsible for 39% of the province’s residential GHG emissions.
Built in 1991, Fraser Pointe 1 is a 16-storey MFB in East Vancouver. The building’s original DHW system was comprised of two standard-efficiency gas-fired boilers and three 120-gallon storage tanks located on the roof of the building. In 2020, as the system was approaching the end of its service life, a BC Hydro-funded energy study was undertaken to explore options for a low-carbon replacement. A follow-up study supported by the CleanBC Custom Program was carried out in 2021 to analyze system electrification options in greater depth.
A hybrid system was chosen for the building for several reasons:
- The building’s roof did not have the structural capacity to handle the full electrification with air-source HPs without major and costly upgrades
- It offered a significant degree of operational redundancy with both HPs and gas-boilers able to function independently in required
- It offered the most cost-effective opportunity to substantially reduce emissions, with the lowest cost in terms of net present value (NPV) per tonne of CO2 reduced over the expected lifetime of the system
Lessons learned
- Avoid having multiple concurrent projects with overlapping scopes where possible, as the anticipated benefits and efficiencies are unlikely to outweigh potential conflicts and issues that arise
Key facts
| Building | Heat Pump and Source | ||
| Location | Vancouver, Canada | Number of HP | 10 |
| Construction | 1991 | Operation mode | bivalent-parallel |
| Retrofit | 2022 | Heat source | air |
| Heated area | only DHW was retrofitted | Type of system | central |
| No. of apartments | – (16 stories) | ||
| Level of insulation | good | ||
| Heating sytem | Domestic Hot Water | ||
| not covered by case study | Additional heating | gas boilers EL heating element (31kW) | |
| Storage | 5 x 450 l | ||
| Storage temperature | 60°C | ||
| Other information | |||
| Climate Zone | Cfb | ||
Summary:
A hybrid system which relied primarily on ten air-source HPs and five 450 l storage tanks, along with two-high-efficiency gas boilers to handle peak demand and provide full redundancy.
Under “normal” operation, the HPs supply 100 percent of the DHW. Should they not be able to maintain storage tank temperature at 60°C anymore, a pump is activated that pumps the water to the gas boilers.
Primary construction of the new hybrid system took place in 2022. In an effort to realize certain efficiencies, Concert Properties elected to have the building’s roof replaced at the same time. The two project teams put systems in place to facilitate communication and coordination, and took precautions, such as the installation of temporary boilers to ensure the continuous supply of hot water, to reduce the impact of the project on tenants.
Despite best efforts, the overlap created tensions and confusion between the two projects, and several complications were encountered during construction.
The new DHW system was commissioned upon installation. However, when its performance was evaluated, it was found to have a number of faults that significantly compromised its GHG savings potential. These took several months to identify and resolve.
For example, once the heat pumps were finally powered up, performance reviews of the system revealed that the majority of the building’s hot water heating load continued to be served by the boilers, with the heat pumps operating only intermittently. Ultimately, the excessive boiler operation was found to have been caused by a leftover piece of temporary programming code that had been put in place on the Building Automation System (BAS) during the interim, boiler-only operational phase, and had not been removed when the new program was written. When the temporary code was removed from the BAS, the heat pumps began carrying a greater proportion of the building’s hot water heating load, and system gas use decreased significantly.
CA004 – Fraser Pointe 1
Case study delivered by: Zero Emissions Innovation Centre (ZEIC) Fraser Pointe 1 Hybrid Domestic Hot Water Retrofit | B2E