Homemade Hydronic Heating System
My homemade hydronic heating system was born out of a desire to expand my approach to frugal living to include a better way to heat my home than simply using a wood stove insert in the living room fireplace and one in the kitchen.
The basic idea is to capture heat that would otherwise be sent up the flue. Stack gases must remain high to prevent buildup of creosote, but there is plenty of heat to be extracted from the average wood stove to make it worthwhile for me to give it a try - after some long and hard thinking.
Let's look at the benefits and drawbacks of homemade hydronic heating to see if this might be something good to consider. The benefits include:
- Maximizing the utilization of heat from a wood stove.
- Creating an inexpensive system with readily available materials.
- Making "scavenged heat" available for multiple applications.
- It's an involved project that is difficult because routing water to wood stove locations isn't normally done.
- Incorporating a water-to-air heat exchanger into the furnace air intake can be complicated and expensive.
- There is a risk of water damage if the system leaks.
- It's largely an experimental project, with lots of precautions and testing required.
The collector portion of the homemade hydronic heating system is a set of homemade heat exchangers in and on the large fireplace insert in the living room. They are made from black iron pipe. They heat water that is pumped through them as part of a closed-loop system.
The heated water is passed through a water-to-air heat exchanger (coil) located in an auxiliary air plenum attached to the furnace cold air return where heat is given up to intake air when the furnace blower is running. A damper in the cold air return allows the furnace to draw air from the upstairs cold air returns as one would normally expect, or from the auxiliary air plenum where the water-to-air heat exchanger is located.
After passing through the furnace air plenum heat exchanger, the heated water is routed through baseboard heaters located in the hall and bedrooms, and then returns to the suction side of the system pump.
The heart of the homemade hydronic heating system is located directly below the fireplace insert in the basement and consists of a pump, air ejector, hot water filter, pressure relief valve and several manually operated ball valves that allow for system fill and flush.
A pressure gauge is mounted on the pressure side of the pump, and two remote temperature sensors are used to monitor the stove inlet and outlet temperatures.
The homemade hydronic heating system also contains a hot water system expansion tank and dielectric unions that isolate the iron piping of the pumping system and stove heat exchangers from the remainder of the system that is plumbed with copper and Pex plastic piping.
Last but not least, a backup source of power is provided to the pump so it can be quickly switched over in the event of an outage of normal household power. This keeps water moving within the system, thus preventing still water from flashing to steam inside the fireplace insert heat exchangers.
This homemade hydronic heating system is setup to operate in three modes, all manually controlled using ball valves. Three system configurations allow heating the:
- furnace water-to-air heat exchanger only
- baseboard heaters only
- furnace heat exchanger first and then baseboard heaters
The normal configuration for the system is as described in number 3 above. This allows excess heat to be drawn off of the system by simply running the furnace on the recirculation mode. Otherwise, the system provides steady heat to the baseboard heaters by simply maintaining a constant recirculation of the system.
Performance of the homemade hydronic heating system is dependent upon four basic factors: the strength of the wood fire; the effectiveness of the fireplace insert heat exchangers; the type of applications drawing off heat; and, the number of applications drawing off heat.
With four internal heat exchangers and one external heat exchanger on the fireplace insert, the ability to draw heat off of the wood fire is good. Output water temperature in the system can easily reach 160 degree F with a good strong fire, even when dumping heat to the 5 baseboard heaters in the bedrooms and hall.
When using the baseboard heaters alone, temperature differential across the fireplace insert heat exchangers is about 10 degrees F. When using the water-to-air heat exchanger in the auxiliary air plenum with the furnace running on recirculation (no heat) mode, the temperature differential across the fireplace insert heat exchangers is about 30 degrees F, and floor register output from the furnace air system is more than 100 degrees F.
No amount of fire in the fireplace insert can keep the output water temperature of the system above 120 when the furnace is placed in the recirculation mode. This speaks to the effectiveness of the 160,000 BTU water-to-air heat exchanger in the auxiliary air plenum of the furnace.
Looking to the Future
After gaining a bit more experience with the system, "bells and whistles" will be added to provide automated control of the homemade hydronic heating system. In addition, a "thermal battery" for overnight operation will be added, more baseboard heaters will be incorporated, a domestic hot water application will be added, and the backup power source for the pump will be automated.
These additional modifications will improve the convenience and effectiveness of this system that is used for about 4 months out of the year.
Done with Homemade Hydronic Heating, back to Alternative Energy Sources