RIVA PLUS COMBI MANUAL
31
Piping
14.
All external piping components are to be supplied by the installer. It is very important to use a Pri-
mary 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 fl ow restrictor
supplied with the boiler. The fl ow restrictor ensures that there will be enough back pressure to
make the central heating fl ow switch in a low head loss piping system like primary secondary.
Installation of fl ow restrictor: The fl ow restrictor is installed inside the pipe tail
that attaches to the boiler. Place the fl ow restrictor
into the gasket for the central heating supply pipe tail.
Place the gasket on the pipe tail so the fl ow restrictor
seats into the pipe tail. Then install the pipe tail onto
the boiler.
There are two methods for accomplishing a Primary Secondary piping system. The fi rst 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 Plus Combi. This is essential to ensure that the fl ow switch will operate properly.
Figure 14.1
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.
Figure 14.2
Must be less than 8"
Boiler
Return
Boiler
Supply
System
Return
System
Supply
1 ¼”
¾”
2"
No more than 8"
At least 16"
1 ¼”
¾”
System supply
System return
Boiler supply
Boiler Return
