A.O. Smith VB/VW-500 - Manual (Page 10)

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location. A drain line must not contain any valves between the
boiler and the relief valve, or the relief valve and the drain exit. In
addition, there should not be any restrictions in a drain line nor
should it be routed through areas where freezing conditions might
occur. Do not thread or cap the drain line exit. Restricting or
blocking a drain line will defeat the purpose of the safety relief
valve and may create an unsafe condition. Install a drain line
with a downward slope such that it will naturally drain itself.
Your local code authority may have other specific safety relief
valve requirements not covered below. If any pressure relief valve
is replaced, the replacement valve must comply with the current
version of the ASME Boiler and Pressure Vessel Code, Section
IV (“HEATING BOILERS”).
Select a relief valve with a discharge rating NOT LESS than the
boiler input, and a set pressure NOT EXCEEDING the working
pressure of any component in the system.
FOR VW HOT WATER SUPPLY BOILERS, the units are shipped
with a 125 psi (860kPa) pressure relief valve that must be installed
in the water outlet as near to the boiler as possible.
This ASME-rated valve has a discharge capacity that exceeds the
maximum boiler input rating and a pressure rating that does not
exceed the maximum working pressure shown on the boiler rating plate.
In addition, a CSA design-certified and ASME-rated temperature
and pressure (T&P) relief valve must be installed on each and
every water storage tank in the hot water supply system. The T&P
relief valve must comply with the applicable construction provisions
of the Standard for Relief Valves and Automatic Gas Shutoff
Devices for Hot Water Supply Systems, ANSI Z21.22 or CAN/
CSA-B149.1-00, or current edition. The T&P relief valve must be
of the automatic reset type and not embody a single-use type
fusible plug, cartridge or linkage.
The T&P relief valve should have a temperature rating of 210°F
(99°C), a pressure rating NOT exceeding the lowest rated working
pressure of any system component, and a discharge capacity
exceeding the total input of the water boilers supplying water to the
storage tank.
Locate the T&P relief valve (a) in the top of the tank, or (b) in the side
of the tank on a centerline within the upper 6 inches (152mm) of the
top of the tank, see Figures 13 and 14. The tapping shall be threaded
in accordance with the current edition of the Standard for Pipe Threads,
General Purpose (inch), ANSI/ASME B1.20.1. The location of, or
intended location for, the T&P relief valve shall be readily accessible
for servicing or replacement.
FOR VB HOT WATER HEATING BOILERS, the units are shipped
with a 50 psi (345kPa) pressure relief valve. This relief valve must
be installed in the water outlet as near to the boiler as possible.
GENERAL
REQUIRED ABILITY
INSTALLATION OR SERVICE OF THIS BOILER REQUIRES
ABILITY EQUIVALENT TO THAT OF A LICENSED TRADESMAN
IN THE FIELD INVOLVED. PLUMBING, AIR SUPPLY, VENTING,
GAS SUPPLY, AND ELECTRICAL WORK ARE REQUIRED.
LOCATION
When installing the boiler, consideration must be given to proper
location. The location selected should provide adequate air supply
and be as centralized with the piping system as possible.
If the boiler is installed above radiation level, a Low Water Cutoff
Device must be installed in the boiler outlet at the time of installation.
PANELS AND COVERS
All panels and covers (e.g. control and junction box covers;
front, side and rear panels of boiler, see Figure 8) MUST be in
place after service and/or before operation of the boiler. This
will ensure that all gas ignition components will be protected
from water.
The VF is a low-pressure boiler (Category IV) to be used as either
hot water supply (domestic/commercial water heating) or hot water
heating (hydronic) application. Category IV boilers operate with a
positive vent pressure and with a vent gas temperature less than
120°F (49°C) above its dew point. Category IV appliances are
often termed “High Efficiency” appliances.