29
C. 3WOOD
Boiler
with circulator
Piped in Parallel with Oil/Gas Boiler
In the traditional American baseboard, hydronic system, the heating temperature in the house or zone is controlled by circulating
or not circulating water of a fairly high and relatively constant temperature to radiation. The thermostat used in such a system is a
simple switch to a relay which turns the circulator on and off. The vast majority of American heating systems use cast iron
boilers which have internal tankless coils for producing domestic hot water. The parallel piping arrangement is the correct
application for maintaining temperature in the oil/gas boiler with wood heated hot water as well as heating the radiation in the
house. Since the specifics of such a system will vary from installation to installation, the following procedure provides an
example of one specific installation which can be used as a model for actual situations.
1. Insure that the existing system has flow checks or electric zone valves in the supply lines to the various heating zones, and that the
Space heat and DHW circulators are mounted on the return line going back to the Oil/Gas boiler. If not, they must be installed in
these locations.
2. Remove the existing radiation supply and return lines from the oil or gas-fired boiler. Install pipe tees on the supply and returns
from nipples coming out of the existing oil/gas boiler.
NOTE
: Occasionally, extra supply and return taps are available on oil/gas
boilers. These plugs may be removed and used to run the lines between boilers. Re-install the supply and return lines.
3. Install a tee with a 1”branch coming out of the supply tapping of the
3WOOD
boiler
for the dump zone.
4. Then install another tee with a ¾” branch for the Aquastat for the
3WOOD
boiler’s
circulator. Install the Honeywell L4006B
into the branch of the tee using the 3/4 “ immersion well.
Caution: Be careful to maintain a 12” minimum clearance between the
flue pipe and the
3WOOD
boiler aquastat.
5. Pipe from this tee down to the return tee or tapping on the existing oil/gas boiler.
Note: By adding the gallonage from the addition of the
3WOOD
boiler,
an expansion tank should be added or the existing
tank should be increased in capacity.
6. Install a tee with a 1” branch coming out of the return tapping of the
3WOOD
boiler for the dump zone.
7. Install piping, flow check and circulator from
3WOOD
boiler
to the supply tee installed on the oil/gas boiler.
Note: Aquastat settings for the existing oil/gas boiler should be as follows:
High Limit – 165F
Low Limit - 150F
Circulator - 140F
But these settings can be raised if the
3WOOD
boiler isn’t fired for extended
periods of time.
