25
4 - FUNCTION OVERVIEW
Key to fi gures 4-1:
1 - Air inlet
2 - Flue exhaust
4 - Sealing chamber
6 - High limit supply temperature switch
7 - Supply temperature sensor
8 - Water pressure sensor
9 - Flue gas temperature sensor
10 - High limit fl ue gas temperature fuse
12 - Premix burner
13 - Ignition electrodes
14 - ignitor
15 - Return temperature sensor
16 - Modulating PWM fan
17 - Back fl ue preventer
20 - Gas valve
22 - Detection electrode
24 - CRV Stainless steel heat exchanger
25 - Water supply
26 - Water return
27 - Gas inlet
28 - Blocked fl ue pressure switch
29 - Condensing blocked drain switch
30 - Condensing drain
31 - Condensate Siphon
36 - Condensate neutralizer box
37 - ASME Safety relief valve (ASME Safety
P-T relief valve when is water heater)
Figure 4-1 - Hydronic functional schematic for models 199