Parking BTUs with Buffer Tanks (Part 1 & 2)
In this two-part interview, Moe Hirsch goes deep and wide on buffer tanks and strategies for “parking” BTUs in hydronic systems.
When we use boilers, we want to use a heat sink to “park” BTUs in a buffer tank so that we can temporarily store extra heat and avoid short cycling through load matching. However, few boilers have an actual buffer tank; many systems have a means of creating a buffer, though. Buffer tanks are good for parking BTUs in systems with zones and microzones that require varied heating needs. The amount of BTUs you store depends on the temperature difference between the beginning and end of the tank and the water quantity.
Systems with a high domestic hot water load can also benefit from a buffer tank. You can pipe the domestic hot water tank as its own zone and step down the rest of the structure. However, there will be some standby losses for a tradeoff greater capacity. You also cannot use the buffer tank as an air eliminator or separator; they work only for BTU parking.
Contrary to popular belief, buffer tanks do NOT prevent flue gas condensation. If the buffer tank reaches 120-130 degrees, then it may prevent flue gas condensation via the flywheel effect. Flue gas condensation on boiler systems has to do with excess air, combustion, and run cycle length.
Moe and Bryan also discuss:
- Pressure tanks
- Variable frequency drives
- Getting extra BTUs
- Snowmelt systems and Combi-boilers
- Two-pipe and four-pipe configurations
- Creating and positioning buffer tanks
- Hydraulic and air separation
- Reverse indirect water heaters
- Parking BTUs in concrete
- Water storage temperature
- Using a biomass boiler as a backup
- Stratification: tall tanks vs. wide tanks
- Cycle times and mathematical formulas
- Outdoor reset targets
- Boiler startup conditions
- Manual reset high limit
Check out Moe's website HERE.
Learn more about Refrigeration Technologies HERE.