Safety Connections And Pressure Testing; Pressure Relief Valve; Boiler Pressure Test; Low Water Cut-Off (Lwco) - Viessmann VD2-320 Installation Instructions Manual

Connections

Safety Connections and Pressure Testing

Pressure relief valve

Do not install any valve(s) between the pressure relief
valve and the boiler. When installing a discharge pipe from
relief valve to drain, adhere to the following excerpt from
the ASME Boiler and Pressure Vessel Code:
1. When a discharge pipe is used, its internal cross-
sectional area shall be not less than the full area
of the valve outlet or of the total of the valve
outlets discharging thereinto and shall be as
short and straight as possible and so arranged
as to avoid undue stress on the valve or valves.
When an elbow is placed on a safety or safety relief
valve discharge pipe, it shall be located close to the
valve outlet.

Boiler Pressure Test

The boiler must be leak tested and hydrostatically
pressure tested with a maximum of 120 psig (827 kPa)
and a minimum of 110 psig (689 kPa) before being
connected to piping or an electrical power supply and
placed in operation.
1. Install supply and return headers complete with
pressure gage, temperature gage, air vent, low
water cut-off, boiler drain valve and bypass pump.
Pipe up to isolation valves. Close isolation valves.
2. Install temporary caps on the nipples for mounting
the pressure relief valve and expansion tank.
3. Connect hose to boiler drain valve and fill boiler
slowly until pressure gage indicates max. 120 psig
(827 kPa).

Low Water Cut-off (LWCO)

26
Vitorond 200, VD2 Series 320 to 1080 Installation
2. The discharge from safety or safety relief valves
shall be so arranged that there will be no danger
of scalding attendants. When the safety or safety
relief valve discharge is piped away from the
boiler to the point of discharge, there shall be
provisions made for properly draining the pipe.
The size and arrangement of the discharge pipe shall
be such that any pressure that may exist or develop
will not reduce the relieving capacity of the relieving
devices that are required to protect the boiler.
4. Maintain pressure for 30 minutes. During time of
pressure testing, do not leave boiler unattended.
5. Inspect all push nipples and pipe connections with
flashlight for leaks. Place a piece of paper under the
cast iron block to catch any minor leaks from the
bottom push nipples.
6. After 30 minutes, release water pressure from
boiler by opening drain valve slowly, remove caps
and install pressure relief valve and expansion tank
immediately.
After boiler has passed pressure test, proceed with
installation.
If boiler is installed above radiation level, a low water
cut-off device of approved type (standard equipment)
must be installed in all instances. The approved low
water cut-off device must be installed by the mechanical
contractor where required by local codes.
Viessmann recommends the use of a LWCO in all
instances.