Taco i Series Instruction Sheet

Instruction Sheet
102-145
® i Series - Outdoor Reset (iSeries-R)
2-Way and 3-Way i Series Mixing Valves
SUPERSEDES: New EFFECTIVE: August 1, 2003
Plant ID# 001-1025
The iSeries-R is a microprocessor-based valve designed to regulate the supply water temperature to a heating system by modulating
the position of an iSeries Mixing Valve. The iSeries-R operates the valve to provide outdoor reset to the heating system. A boiler sensor
installed on the return line to the boiler is used to protect the boiler against flue gas condensation.
Outdoor Reset
In order to properly control a hot water heating system, the heat supplied to the build-
ing must equal the heat lost by the building.
• The heat supplied to the building is directly proportional to the temperature of the
water and the surface area of the heating element. The higher the temperature of the
water flowing through the heating terminal, the higher the heat output.
• The heat lost from a building is dependent on the outdoor temperature. As the out-
door temperature drops, the building heat loss increases.
These two facts lead to the concept of outdoor reset which increases the supply
water temperature as the outdoor temperature drops. Using this approach, the heat
lost from the building is matched by the heat provided by the terminal units, therefore
providing more comfort and energy savings.
Reset Ratio
The Reset Ratio sets the relationship between outdoor temperature and supply
water temperature. It determines the amount the supply water temperature is raised
for every 1 degree outdoor temperature drop. For example, if a Reset Ratio of 1.2
is selected, the supply water temperature is increased by 1.2 degrees of every 1
degree of outdoor temperature drop.
2-Way / 3-Way Mixing
An iSeries Mixing Valve may be used to mix the hot boiler water temperature with the cooler return water temperature from the system
loop. The position of the iSeries Mixing Valve is modulated in order to inject different rates of hot water into the cool system return water.
This allows for virtually any water temperature to be supplied to the heating system. When deciding between a 2-way or 3-way valve,
maximum flow rates must be considered. See the charts on page 2 before selecting style of valve / piping.
Most boilers cannot operate at low temperatures, therefore the iSeries-R can be modulated back in order to prevent the boiler from
operating at cold temperatures, by installing the boiler return sensor.
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