National Oilheat Research Alliance 15
to as a “branch header system”. When there are
multiple zones, each loop is piped parallel to
each other, but the loop itself is series piped.
Advantages
• Requires less pipe and fittings than
other systems
• Relative lower cost to install
• No special valves or fittings required
Disadvantages
• Temperature at the first heat emitter
is significantly higher than what is supplied
to the last heat emitter. Rooms at the
beginning of the loop may over-heat while
rooms at the end may under-heat. Care
should be taken when sizing and selecting
the heat emitters due to the temperature
drop of the fluid and the heat output of the
emitter with reduced temperatures.
A split series loop (Figure 2) system overcomes
some of the disadvantages of a standard
series loop by dividing the radiation into
separate zones.
These systems have either a common supply
or a common return and literally “split”
the radiation into separate zones. These two
“loops” can be on the same zone or split into
separate zones, each with its own balancing
valve, thermostat and/or zone valve/circulator.
Advantages
• Better control of temperature and thus
more comfortable than a standard series
loop.
• Smaller diameter pipe can be used due
to shorter runs.
Disadvantages
• Requires additional pipe, fittings and
components.
• Slightly more expensive to install
Figure 2