NRP620-9 OMEPAPV20161017 (ENGLISH) REV 1
Page 10 of 42
Supplementary Central Furnace Installations
WARNING
The warm-air supply outlet of the supplementary furnace should not be connected to the
cold-air return inlet of the central furnace because a possibility exists of components of
the central furnace overheating and causing the central furnace to operate other than as
intended.
When installing the furnace as a supplementary “add-on” furnace, install the unit in a parallel air flow
configuration with the central furnace and install back draft dampers (BDD) to prevent feedback from
one furnace to the other as illustrated below.
COLD
AIR
RETURN
COLD
AIR
RETURN
WARM
AIR
SUPPLY
WARM
AIR
SUPPLY
BDD
BDD
SUPPLEMENTARY
FURNACE
CENTRAL
FURNACE
COLD
AIR
RETURN
DUCT
WARM
AIR
SUPPLY
DUCT