Using SANCO2 HPWH for Hot Water & Space Heating
When you are building a high efficiency home, it makes sense to squeeze all the performance you can from your mechanical systems. Premium HRVs/ERVs are already designed to operate at their highest efficiency to reclaim the heat energy in your home, but what about the systems producing that heat? One of the more popular methods for heating a high efficiency home is through radiant heating using hot water. The SANCO2 water heaters we carry make a great option for achieving this purpose and can pull double duty for radiant heating and domestic water heating. The best application for this combination system (often referred to as a Combi System) is with radiant floor heating. This provides consistent and efficient “floor up” heating for the home, and many homeowners really enjoy the feel of this design. With this system you can heat all of your house, or just supplement a few rooms.
Why Radiant Floor Heating
Radiant floor heating makes your home more comfortable in many ways. For one, it doesn’t make any noise since there is no blowing air like with forced air systems. This means less dust and allergens get stirred up. With a radiant floor, warmth rises evenly from the ground up, making the temperature gradient in your room more even. Radiant floors don’t use “hot” water, typically only seeing temperatures in the 80F-120F range. Opting for the lower end of this is the optimal choice for use with SANCO2 systems. With the SANCO2 heat pumps, keeping return temps to the heat pump low is an important factor for efficient heat pump operation.
SANCO2 heat pumps offer some of the highest COPs of any heat pump water heater, and one of the crucial requirements for this is having low input temps. Since they are designed to raise main supply water from ~50F to 145F in a single pass, higher input temperatures will reduce this efficiency, which is why radiant floor with its low temperature usage is the best radiant option to pair with SANCO2.
Configured in a Combi set up such as this, a single SANCO2 heat pump design is capable of meeting heat load demands of up to ~8,000 BTU/h, while reserving the rest of its heating capacity for domestic hot water delivery. This system should see an annual average COP of ~4 with 80F return water to the system. It is important with this set up to note that efficiency is required that domestic hot water usage be greater than 25 gallons per day. SANCO2 heat pumps are also capable of providing hot water at very low ambient temperatures, down to -25F. Combi systems should ideally be designed and used in climates with a design winter temperature 22F, which will ensure you don’t see a reduction in radiant floor heat output on the days when it matters most. Larger heat loads may be supplemented with a second heat pump or auxiliary heat, but they latter must be carefully designed so as to not interfere with the heat pump’s efficiency.
How to Configure SANCO2 Combi Systems
Configuring a radiant system with a SANCO2 heat pump is achieved through good planning and the use of some key pieces of equipment. The basic list consists of one SANCO2 Heat Pump, at least one 83-gallon tank, two water circulation pumps, a heat exchanger, temperature sensors and controls (packaged as “TACO X-Pump Block, which is the only one approved for warranty), expansion tank, relief valve, and various check valves.
A minimum tank size of 83 gallons is required to ensure proper tank stratification of hot and cold water as this is important to proper and efficient operation of the SANCO2 system.
The TACO X-Pump block is a water-to-water heat exchanger and is used to separate the potable water from the radiant heat loop water. This is required by code to keep the water in your heating loop from contaminating general use water in the SANCO2 system. It essentially consists of a stack of plates with dedicated flow channels to allow heat from your water tank to be transferred to the radiant loop without touching one another.
YOU CAN LEARN MORE ABOUT CONFIGURING A SANCO2 COMBI SYstem at our SMALL PLANET UNIVERSITY COURSE on THINKIFIC
When considering adding a SANCO2 combi system to your home, it is only recommended for high efficiency homes. With a high efficiency home, lower heat loads are more achievable thanks to better thermal design and highly insulated walls and windows. Lower heat loads are better suited for pairing with a SANCO2 combi system because of the relatively low heating temperature of radiant floor heating and the recovery time and duty cycle of SANCO2 systems when you take domestic hot water consumption into account.
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By using SANCO2 in a combi system, energy usage for home heating can be greatly reduced. In one case study done in Nevada City there was a ~ 50% reduction in KWH used during heating season. Its easy to see why this combi system is desirable for high efficiency homes, especially when the overall goal is to save on energy spending over time. Small Planet Supply carries SANCO2 heat pumps and tanks, as well as TACO X-Pump Blocks and other TACO products useful for combi installation.
SANCO2 Combi System Frequently Asked Questions
+ Can the SANCO2 be used as a combination domestic hot water and radiant heating system (Combi) for my house?
Certainly. To meet the heating load with a single heat pump, your heating load must be less than 10,000btu/hr and SANC02 recommends you use at least 25 Gal of domestic hot water per day to maintain tank stratification and efficiency.
+ How do I know that the heating demand is acceptable?
A heat load calculation by the radiant floor installer or engineer or the Passive House consultant would give you that number (taking into account actual insulation values and air tightness of the house) . Small Planet Supply can help with a quick feasibility study as well. Further, this heating load needs to be met with a low temperature system (e.g., radiant floor), in order for the heat pump to work efficiently. The SANCO2 heat pump combi system is NOT suitable for high-temperature heating systems, such hydronic baseboards, or so-called radiators.
+ Can I simply pull hot water from the tank and feed it into the radiant floor tubing?
You should not, as potable water should not be sent through the space heating system. A packaged heat exchanger with integrated circulation pumps called the Taco XPump Block is available in both our USA and Canada warehouses ; https://www.tacocomfort.com/product/x-pump-block/) does the job gracefully.
+ Will I run out of hot water when I'm taking my shower?
In fact, a minimum of 25 gal per day of hot water consumption is required for the combi system to work efficiently. You are unlikely to run out of hot water if the water temperature returning from the radiant floor does not exceed 80-100°F and the heating demand stays below the limit mentioned above.
The SANCO2 Combi system is configured using a SANCO2 heat pump water heater. To learn more about SANCO2 heat pump water heaters, click here.
SANC02 Combi Questions? Phone Consultation Appointments are Available
Have some questions about the SANC02 system and want to feel like you’ll have enough time to have them all answered? We’re offering complimentary consultations with one of our specialists. You can schedule it using the button below.
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