Piping - QHT Riva Installation, Operation And Service Instructions

14. Piping

All external piping components are to be supplied by the installer. It is very important to
use a Primary Secondary piping scheme when an external circulator will be used. Also,
when the boiler is piped in a primary secondary manner, it is necessary to us the central
heating flow restrictor supplied with the boiler. The flow restrictor ensures that there will
be enough back pressure to make the central heating flow switch in a low head loss piping
system like primary secondary.
Installation of flow restrictor: The flow restrictor is installed inside the pipe tail
There are two methods for accomplishing a Primary Secondary piping system. The first is
to use two closely spaced tees for the boiler supply and return. An example is shown
below in Figure 14.1. The run legs should be sized so that there is no excessive head
loss on the external circulator that is installed. In most circumstances 1 ¼" piping will be
the best choice. When the boiler is piped in this way, the external circulator will not have
any hydraulic effect on the Riva boiler. This is essential to ensure that the flow switch will
operate properly.
The second method is a hydraulic separator. Hydraulic separators are available commercially;
however you can also construct your own. An example of a hydraulic separator is given in Figure
14.2. It is important that the separator be at least 2" in size to ensure proper performance.
1 ¼"
RIVA HEAT ONLY MANUAL - REV B
that attaches to the boiler. Place the flow restrictor
into the gasket for the central heating supply pipe
tail. Place the gasket on the pipe tail so the flow
restrictor seats into the pipe tail. Then install the
pipe tail onto the boiler.
Boiler supply
No more than 8"
¾"
System supply
At least 16"
Boiler Return
2"
System return
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