Solo Plus Instructions 1-800-782-9927 Version 12-13
Tarm Biomass · 4 Britton Lane · Lyme, NH 03768
Tarm Biomass recommends the use of an additional Termovar valve model
6440AF (TV2)
for most
installations. Without
TV2
it is possible that when a small zone is the only zone calling, a master
bathroom zone for instance, all of the heat the boiler is producing is drawn to the small zone. The re-
sult is that a 100,000 – 175,000 Btu (30-50 kW) boiler is sending all of its output to a 2,500 Btu (0.73
kW) load. The boiler could quickly reach operating temperature and shut off, which must be avoided.
TV2
solves this problem. It operates much the same way that
TV1
operates except that it is a divert-
ing valve. Port 1 of
TV2
receives water from the return manifold. Port 2 of
TV2
is connected to the
supply manifold. Port 3 of
TV2
is connected to the return to the boiler and to the thermal storage sys-
tem. When the
TV2
senses water 165 ºF (74 ºC). and above, it shunts water from Port 1 to Port 2
(back to the supply manifold). Because water returning to the boiler from the return manifold is di-
minished, the remaining flow from the boiler is forced through the heating coils in the thermal storage
system. The result is that both the zone and the thermal storage system receive hot water and the
boiler may continue to burn with a demand equal to or greater than its output. The end result is that
the heating load is always prioritized over the thermal storage system, but heat not used will be stored
in the thermal storage system for later use.
Please note the use of two opposing weighted check valves on the same pipe leading from the top of
the heating coils in the thermal storage system. Their purpose is to act as a thermal trap preventing
heated water from migrating out of the thermal storage system by convection. A ―U‖ shaped pipe trap
usually will not have a useful effect. If check valves are used, we recommend that they be cast iron
bodied universal style flow checks. They
must not
be swing type check valves, as natural gravity
flow of water will push swing check valves open.
TYPICAL CONTROL LOGIC FOR USE WITH PRESSURE TANK THERMAL STORAGE
SYSTEMS (Refer to Plumbing schematic PT1 or PT2):
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 approx. 165 ºF (74 ºC). Depending on the return water temperature at the
440A3
Termovar valve
(TV1),
water will either circulate back into the return of the boiler or will con-
tinue 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 1¼‖ 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.
Boiler Installation & Start-up > Control Logic
Page 28