Restrictor Sizing; Fitting The Flue System - Biasi Riva Combi Installation & Operation Instructions

9. Venting Cont.
The Riva is a mechanical draft, side wall vented boiler. There are two flue options available -
separate and coaxial. The coaxial option has one configuration shown on the next page. The
separate option has two possible configurations shown on the following pages.
Each exhaust option is shipped standard with 3 feet of exhaust pipe, 3 feet of intake air
is also a restrictor kit in which there are some restrictors that must be placed in exhaust breech of
fan on the top of the boiler (Fig. 9.1) according to the flue configuration used.
If additional flue piping is need for a particular application, it can be ordered separately in 3 feet
increments. Depending on the final flue pipe length, an alternative restrictor may be required. Refer
to the tables 9.1 for proper restrictor ring sizing
Figura 9.1
In general, it has to be taken in consideration that the horizontal sections of the flue pipe must have
a horizontal sloping not less than 1.5 degree (0.3 in per ft) away from the boiler. In the standard
horizontal flue kit the flue pipe is angled within the air duct therefore the air duct must be
horizontally installed. If one or more extensions have to be used they must be adequately
supported so that there is no sag in the flue pipe and a minimum fall of 1.5 degree (0.3 in per ft)
over the whole length away from the boiler is ensured.
RIVA COMBI MANUAL - REV B

9.1 Restrictor Sizing:

9.2 Fitting the flue system:

Coaxial 2.5/4.0
From 1.65 to 3.30 (ft)
From 3.30 to 8.86 (ft)
Separate 3.25/3.25
For 1. 65 and 1.65
(ft. in +out)
From 3.30 to 39.40
(ft in+out)
Table 9.1
pipe. There
Restrictor
Size
41
44
Restrictor
Size
38
41
19