Piping - Biasi Riva Advance Combi Installation & Operation Instructions

14. Piping

All external piping components are to be supplied by the installer. The boiler, when used in
connection with a refrigeration system, must be installed so the chilled medium is piped in parallel
with the boiler with appropriate valves to prevent the chilled medium from entering the boiler. The
boiler piping system of a hot water boiler connected to heating coils located in air handling units
where they may be exposed to refrigerated air circulation must be equipped with ow control
valves or other automatic means to prevent gravity circulation of the boiler water during the cool-
ing cycle.
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 use the central
heating ow restrictor supplied with the boiler. The ow restrictor ensures that there will be
enough back pressure to make the central heating ow switch in a low head loss piping system like
primary secondary.
The ow restrictor is installed inside the pipe tail that attaches to the boiler.
Place the ow restrictor into the gasket for the central heating supply pipe
tail. Place the gasket on the pipe tail so the 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 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 circum-
stances 1 ¼" piping will be the best choice.
When the boiler is piped in this way, the
external circulator will not have any hydrau-
lic effect on the Riva Advance Combi. 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.
RIVA ADVANCE COMBI MANUAL
Boiler
Supply
System
¾"
Supply
Figure 14.1
Boiler supply
¾"
System supply
1 ¼"
Boiler
Return
Must be less than 8"
1 ¼"
Boiler Return
No more than 8"
2"
At least 16"
Figure 14.2
System
Return
System return
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