Solo Plus Instructions 1-800-782-9927 Version 12-13
Tarm Biomass · 4 Britton Lane · Lyme, NH 03768
3.4.10 Control Logic
TYPICAL CONTROL LOGIC FOR USE WITH BLADDER LINED COIL-TYPE THERMAL
STORAGE SYSTEMS (Refer to Plumbing Diagram STSS1 or STSS2):
The process begins when a fire is lit in the boiler and the boiler’s control is reset. Water within the
boiler begins to warm. Hot water from the boiler will begin to circulate to the heating system when the
water temperature reaches approximately 165 ºF (74 ºC). Depending on the return water temperature
at the
4440A3
Termovar valve
(TV1),
water will either circulate back into the return of the boiler or
will continue on to the supply manifold.
TV1
is a three way thermostatic tempering valve. Port 3, which is the return to the boiler, always
stays open. Port 1 remains open until it senses 165 ºF (74 ºC) water. At temperatures above 165 ºF
(74 ºC), Port 1 on
TV1
begins to close and Port 2 begins to open. Port 2 is fully open when the return
water reaches 172 ºF (78 ºC).
The thermostatic element in the Termovar prevents cold water returning to the boiler until the boiler
reaches operating temperature. The Termovar then gradually opens, blending hot boiler supply water
with the cold return water. Once system temperature equalizes, the Termovar opens fully to allow full
flow to and from the heating load (the house and/or a heat storage system). Please note: The balancing
valve shown as a 1 ¼‖ ball valve upstream from port 1 is essential. Start with this valve closed ½ way
and adjust more open or closed as necessary. Never fully close or fully open this valve. For custom-
ers who have chosen the LOADING UNIT TERMOVAR
4832S
the balancing valve is built in and
balances automatically.
Assuming that
TV1
is hot, the water being circulated by C3 is now heading for the supply manifold.
If no zones are calling for heat the Honeywell
V8043F1101
zone valve
(ZV1)
will remain closed. All
of the hot supply water being moved by
C3
must travel through the heating coils in the thermal stor-
age system moving from top to bottom and then back through Port 2 of the Termovar and back to the
boiler.
Tarm Biomass recommends the use of the
BLTCONTROL
(available through Tarm Biomass) where
the Solo Plus boiler is used with another backup boiler.
BLTCONTROL
is a three position control
that allows switching between wood only, wood with automatic back-up, or back-up only, by control-
ling the operation of the back-up auxiliary boiler.
BLTCONTROL
takes input from a zone relay con-
trol and determines based on thermal storage system temperature or second stage thermostat reading,
whether to pull heat from the thermal storage system or the back up auxiliary boiler.
BLTCON-
TROL
simply integrates the Solo Plus boiler and thermal storage system with an existing fossil fuel
heating system.
If at any point while the boiler is in operation, a zone calls for heat,
ZV-1
opens and circulator
C1
is
energized. Heat flows directly from the boiler to the supply manifold. If the boiler has burned
through its wood and has cooled, Port 2 of the
TV1
valve will close and
C3
will stop. Flow through
the boiler will cease. Once the boiler is eliminated from the plumbing circuit, any zone that calls must
pull heat through the thermal storage system. Return water passes into the bottom of the heating coils
and exits the top of the coils, re-heated by the thermal storage system, and moves to the supply mani-
fold. If however, upon a call for heat, the temperature in the thermal storage system is below the aq-
uastat (HONEYWELL
L4008A
or equivalent) set point,
C1
will cease operation and
ZV-1
will close.
The back up boiler will be energized through the switch control to meet the heat demand.
Boiler Installation & Start-up > Control Logic
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