Section 3. Operation; Controls Location - Natco VW Installation And Operating Instructions Manual

2K. Two-Temperature System
See Figure 16 and Figure 17 for piping
schematic. This system is designed to maintain
the tempered water circulating loop at the desired
temperature during idle periods as well as when
there is a demand for hot water. It is
recommended for general purpose water supply
including shower and bathing applications.
water at 180F is available directly from the tank.
Section 3
Operation
3A. Controls - General
1. Electronic Ignition Controls:
a. Intermittent Ignition:
Pilots are automatically lit when the operating
aquastat calls for heat (System #4 and #9)
Manual
Pilot
Valve
Manual
Main Gas
Valve
Safety
Gas
Valve
Rating Plate
Ignition Control
Operating
Gas Valve
Figure 18 – Controls Location
The unit performs its own safety check and
opens the main valves only after the pilot is
proven to be lit. Whenever the pilot flame is
interrupted, the main gas valve closes within
8/10 of a second.
b. Electronically Supervised Standing Pilot
System (System #16):
When pilot flame fails, the ignition control
module responds in less than 0.8 seconds
and provides 100% safety shutdown.
2. Operating Controls:
a. Electrically Operating Controls:
Single, two-stage, four-stage or modulating
aquastats are provided in models VW, PW
and IW heaters to control the desired service
water tempera-ture. The temperature
sensing bulb is located either in the heater
inlet or outlet header.
b. Modu-snap Valves:
These valves are furnished in addition to the
main electric gas valve (standard on model
Flow
Switch
Hi-Limit
17
Pressure
Relief
Valve
In
Out
Transformer
Terminal Strip
Operating
Control
(Aquastat)