TW2000 WOOD–FIRED BOILER – INSTRUCTION MANUAL
TW2000 12 Jan-08
2.6 PLUMBING CONNECTIONS
There are only two differences between the installation of any conventional hot water heating
system and those using a Kerr TW2000 boiler – the safety override zone valve, and the blow-
down extinguishing system. A circulator of at least 5-G.P.M. capacity must be used in a system
using the Kerr TW2000 boiler to assure circulation of water. Also the recommended expansion
tank size for the TW2000 is a 12” Dia. X 36”.
The normally open zone valve must be installed to allow a free flow of water in a power off
situation. Kerr recommends that the valve be placed as shown in Fig. TW-1 or Fig. TW- 4. The
override zone valve should be on the loop supplying the living area on the main floor level (i.e.
kitchen – living room). The override loop for the safety shall have at least 30 ft. of radiation
above the wood boiler. Do not use basement loop for the safety override loop, as this will not
provide gravity flow in a power out situation. This override loop must be capable of dissipating
at least 10% of the estimated heat output of the Kerr TW2000 boiler in the event that the
circulation is reduced because of electrical power failure. The safety by-pass dump zone shall
NOT run through any plastic piping. A deliberate manual action shall be required to make the
override loop inoperative.
The blow-down extinguishing system is installed to control the fire in case overheating causes
excessive pressure in the pressure vessel. The relief valve, included, is threaded into the top
of the pressure vessel and copper pipe is installed from its exhaust to the flange above the
loading door on the firebox.
In addition to its ability to heat the home, this boiler is provided with a domestic coil position. A
copper coil may be purchased with your boiler or added at a later date. It may be utilized as a
single water heater or in conjunction with an oil, gas or electric heater.
2.6.1 FREE STANDING
Free Standing installation requires additional components, which are not included in the
TW2000 boiler kit. Check wiring diagrams TW – 5 and TW – 6 for additional required
components.
In the freestanding, or stand-alone system, the Kerr TW2000 boiler is the sole source of
central heating. In this system connect the piping as you would for any conventional hydronic
heating system (using zone valves, circulator zoning, or single zone flow check system). The
boiler must not be installed as a gravity system, as the controls are not designed for this type
of operation. When installing the Kerr TW2000 boiler as a stand-alone system, the boiler may
be wired in two ways. For the Stand-Alone wiring diagram, Fig. TW-5 a triple function
aquastat and an additional transformer must be purchased separately and installed in
place of the dual aquastat supplied with the boiler. An alternative Stand-Alone Wiring diagram,
Fig. TW-6 is shown, but an additional relay and housing must be purchased separately
and wired using high voltage wire only (using 120v wire on 24v coil also). The only
special piping needed is the connection of the special safety by-pass zone valve and blow
down system as described above. For plumbing details see Fig. TW-4.
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