Hydronic Heating - the basics
I use hydronic heating to help heat my home in the winter. Simply stated, it's home heating using hot water instead of hot air.
Think of it as a variation on steam heat. Instead of piping steam throughout the house, we pipe hot water.
My system is homemade, so it's inexpensive and somewhat experimental, but it works just fine. As I gain experience and insight, I'll improve the system for effectiveness.
A fair bit of research was required to learn about how heating with water works, so let me share what I've learned through research and experimentation.
How it Works
Essentially, a hydronic heating system uses hot water for various heating applications in and around the house. It's old technology that has seen recent improvements that add efficiency as well as effectiveness.
Typically, a special hot water tank is used to heat up water that is then circulated through a main header. Off of the header are several zone valves that are thermostatically controlled. When there is a demand for heat in a certain area of the house, the zone valve opens and its associated pump operates to supply hot water to the area.
Most systems employ baseboard heaters that release heat along the baseboards in a room. Some systems run piping under the floorboards and concrete foundation to heat living areas from the floor up.
Hydronic heating systems can also provide warmth for tile floors in bathrooms, towel bars, and hot water to small water-to-air heat exchangers with fans that provide miniature forced air heating for specific areas in the house.
It's common for hydronic heating systems to use a single high efficiency water heater to provide heat for the house as well as heat for domestic hot water.
Hydronic Heating Components
In addition to the main water heater tank, systems will typically have:
- circulating pumps that distribute water through the system
- zone control vales that open to heat specific areas
- temperature sensors to monitor and automatically operate the system
- tempering valves that allow water of different temperatures to mix in order to maintain a desired temperature
- piping for distribution and heat exchange
- accessories like towel bar heaters
- flat plate or shell heat exchangers that convert hydronic heating to domestic hot water
- controllers that operate the system based on user settings and sensor input
- monitoring systems that provide data on system status and operating history
When dealing with heated water, there are a few considerations that might go unnoticed for those of us who are most familiar with forced air heat. Consider that:
- Water will corrode metal parts in the system.
- Leaks in the system can damage portions of the house.
- Heat exchange piping embedded in concrete and tile floors is very difficult to alter, repair or replace.
- Water expands as it's heated, and so pressure build up must be dealt with.
- Water freezes in cold weather unless it's heated periodically, kept circulating or mixed with anti-freeze.
Also note that hydronic systems aren't instant on and off. They are systems designed for slow and steady release of heat. Therefore, it must be operated continuously in cold weather in order to keep up with the demand placed on it.
In addition, heating with water counts on the principle that heat rises. Therefore, elements of the system that are designed to give off heat are placed low in areas that require heating.
Hydronic systems also make use of the concept of "thermal mass" to keep things warm. Warm concrete, wood flooring and water tends to stay warm and give off heat slowly. Generally, the longer it takes to heat something up, the longer it retains that energy and the slower it releases it.
Done with Hydronic Heating, back to Alternative Energy Sources