A.O. Smith VF VB 500, Instruction Manual

Page: 10 / 52

10
The Discharge Pipe:
• Shall not be smaller in size than the outlet pipe size of the valve, or
have any reducing couplings or other restrictions.
• Shall not be plugged or blocked.
• Shall not be exposed to freezing temperatures.
• Shall be of material listed for hot water distribution.
• Shall be installed so as to allow complete drainage of both the relief
valve and the discharge pipe.
• Must terminate a maximum of six inches above a floor drain or
external to the building. In cold climates, it is recommended that the
discharge pipe be terminated at an adequate drain inside the building.
• Shall not have any valve or other obstruction between the relief valve
and the drain.
Once the boiler is installed and filled with water and the system
is pressurized, manually test the operation of the pressure relief
valve. See the maintenance section of this manual for instructions.
Your local code authority may have other specific safety relief
valve requirements not covered below. If any pressure relief valve
is re placed, the replace ment valve must com ply with the current
version of the ASME Boiler and Pressure Vessel Code, Section
IV (“HEATING BOILERS”).
VW HOT WATER SUPPLY BOILERS, are shipped with a 125 psi
(860kPa) pressure relief valve that must be in stalled in the water
out let as near to the boil er as possi ble.
This ASME-rated valve has a discharge capacity that exceeds maximum
boiler input rating and a pres sure rating that does not exceed maximum
working pres sure shown on boiler rating plate. In addition, a CSA
design-certified and ASME-rated tempera ture and pressure (T&P)
relief valve must be installed on each and every water storage tank
in hot water supply system. The T&P relief valve must comply with
appli cable construction provisions of Standard for Relief Valves for
Hot Water Supply Systems , ANSI Z21.22 or CSA 4.4. T&P re lief valve
must be of automatic reset type and not embody a single-use type
fusible plug, cartridge or linkage.
T&P relief valve should have a temperature rating of 210°F (99°C),
a pressure rating not exceeding lowest rated working pressure of
any system compo nent, and a discharge capacity exceeding total
input of water boilers supply ing water to 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 14 and 15. The tapping should be threaded in
accordance with the current edition of the Standard for Pipe Threads,
General Purpose (inch), ANSI/A SME B1.20.1. The location of, or in-
tended location for, the T&P relief valve should be readily accessible for
servicing or replacement.
VB HOT WATER HEATING BOILERS, are shipped with a 50 psi
(345kPa) pressure relief valve. This relief valve must be in stalled
in the water outlet as near to the boiler as possi ble.
GENERAL
REQUIRED ABILITY
INSTALLATION OR SERVICE OF THIS BOILER REQUIRES
ABILITY EQUIVALENT TO THAT OF A LICENSED TRADES MAN
IN THE FIELD INVOLVED. PLUMBING, AIR SUPPLY, VENTING,
GAS SUPPLY, AND ELECTRICAL WORK ARE RE QUIRED.
LOCATION
When installing the boiler, consideration must be given to proper
location. The location selected should provide ade quate air supply
and be as centralized with the piping system as possible.
If the boiler is installed above radia tion 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 opera tion 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 oper ate with a
positive vent pressure and with a vent gas tempera ture less than
120°F (49°C) above its dew point. Category IV appli ances are
often termed “High Effi ciency” appliances.