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8 Connecting the DHW pipe
• Installation and service must be performed by a
qualified plumber.
• In the Commonwealth of Massachusetts, this
product must be installed by a licensed plumber
or gas fitter in accordance with the Massachusetts
Plumbing and Fuel Gas Code 248 CMR Sections
2.00 and 5.00.
• Observe all applicable codes.
• Components used in domestic piping must meet
requirements in NSF/ANSI 61 Drinking Water
System Components.
8.1 Installation
8.1.1 Guidelines
Installation location
• If the Combi Boiler is installed in a closed water
supply system, such as one having a backflow
preventer on the DHW cold water supply line,
means shall be provided to control thermal
expansion. Contact the water supplier or a
local plumbing inspector on how to control this
situation.
• If installing the Combi Boiler on a roof:
If the Combi Boiler is installed on a roof to supply
hot water to the levels below, make sure that
the water pressure supplied to the Combi Boiler
does not drop below 29 psi. It may be necessary
to install a pump system to ensure that the water
pressure is maintained at this level or to decrease
the flow rate by adjusting the water fixture.
Check the pressure before putting the Combi
Boiler into operation.
Failure to supply the proper pressure to the
Combi Boiler may result in noisy operation,
shorter lifetime of the Combi Boiler, and may
cause the Combi Boiler to shut down frequently.
Potable water
• DHW Piping and components connected to the
Combi Boiler shall be suitable for use with potable
water.
• Toxic chemicals, such as those used for boiler
treatment, shall not be introduced into the
potable water.
• A Combi Boiler used to supply potable water
may not be connected to any heating system or
components previously used with a nonpotable
water heating appliance.
Pressure Relief Valve
• A pressure relief valve must be installed near the
DHW outlet that is rated in accordance with and
complying with either The Standard for Relief
40
Connecting the DHW pipe
Valves and Automatic Shutoff Devices for Hot
Water Supply Systems, ANSI Z21.22, or The ANSI/
ASME Boiler and Pressure Vessel Code, Section IV
(Heating Boilers).
• A pressure relief valve must be capable of an
hourly Btu rated temperature steam discharge
capacity of 199,900 Btu/h.
Multiple valves may be used.
The pressure relief capacity in DHW must not
exceed 150 psi. (The pressure relief capacity on
the heating pressure relief valve connection must
not exceed 30 psig.)
• Do not install a shutoff valve between a relief
valve and the Combi Boiler.
The relief valve must be installed such that the
discharge will be conducted to a suitable place for
disposal when relief occurs.
• No reducing coupling or other restriction may be
installed in the discharge line.
The discharge line must be installed to allow
complete drainage of both the valve and the line.
• If this Combi Boiler is installed with a separate
storage vessel, the separate vessel must have its
own temperature and pressure relief valve.
• Temperature and pressure relief valve must also
comply with The Standard for Relief Valves and
Automatic Gas Shutoff Devices for Hot Water
Supply Systems, ANSI Z21.22 (in the U.S. only).
• A temperature relief valve is not required, but
if one is used, do not install the valve with the
probe directly in the flow of water.
This may cause unwarranted discharge of the
valve.
• When the system requires water for space
heating at temperatures higher than required for
other uses, a means such as a mixing valve shall
be installed to temper the water for those uses in
order to reduce scald hazard potential.
Connnecting water supply
• Flush water through the pipe to clean out metal
powder, sand and dirt before connecting it.
• Use a union coupling or flexible pipe for
connecting the pipes to reduce the force applied
to the piping.
NOTE • Do not use piping with a diameter
smaller than the coupling.
• Avoid using joints as much as
possible to keep the piping simple.
• Avoid piping in which an air holdup
can occur.
Cold water supply
• Be sure to check the water pressure.
- In order for the client to use the Combi Boiler
comfortably, 15 to 150 psi* (103.4 to 1034 kPa)
of pressure is needed from the water supply.
* Recommended 30 psi for maximum
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