Piping; Primary-Secondary Piping; Riva Combi Manual - Rev B - Biasi Riva Combi Installation & Operation 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
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"
32
tail 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"

RIVA COMBI MANUAL - REV B

System return