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FIGURE 2
SCHEMATIC TANKLESS HEATER PIPING
5. TEMPERING OF HOT WATER
Installation of an automatic mixing valve will
lengthen the delivery of the available hot water by mixing
some cold water with the hot. This prevents excessive
and possibly scalding hot water. Higher temperature hot
water is possible by piping the hot water from the heater
prior to entering the mixing valve. The mixing valve
should be "trapped" by installing it below the cold water
inlet to heater to prevent lime formation in the valve.
6. FLUSHING THE BOILER
All water contains some sediment which settles on
the inside of the coil. Consequently, the heater should
be periodically backwashed. This is accomplished by
installing hose bibs as illustrated and allowing water at
city pressure to run into hosebib A, through the heater,
and out hosebib B until the discharge is clear. The tees
in which the hosebibs are located should be the same
size as heater connections to minimize pressure drop.
7. HARD WATER
May be applicable to some city and particularly well
water. Have your water analyzed by a qualified water
treatment specialist to determine if a water softener,
conditioner or filtration is required. Treated water will
ensure longer tankless heater life and performance
and is also beneficial to all the piping and fixtures in
the building.
8. FUEL SUPPLY PIPING
For information regarding gas supply line piping
schematic and sizing, drip leg, gas pressure regulator,
oil supply line piping schematic and sizing, oil pump,
and oil filter, please refer to the BURNER
INSTALLATION AND OPERATION MANUAL.
9. RELIEF VALVES
Boiler relief valves are normally shipped loose and
have been properly sized for your boiler. The aggregate
capacity of the relief valves (as stamped on the valve
rating plates), must meet or exceed the minimum
required relieving capacity as stamped on the boiler
rating plate.
Install the valve(s) in the fittings supplied on the top
of the boiler using appropriate pipe dope. In some cases,
reducing bushings are required to adapt the relief valve
inlet to the boiler fitting. When required, the bushings are
supplied by Burnham. Using the bushings is NOT a code
violation. Always install the relief valves in the vertical
position with no intervening valve.
Pipe the relief valve to a safe point of discharge, with
same pipe size as the valve outlet connection – never
reduce. The discharge piping shall be arranged as short
as possible, and properly supported to prevent stresses
on the relief valve. Never install a valve or plug on the
relief valve outlet piping.
A method of gravity drain must be employed in the
discharge pipe at or near each relief valve and where
condensate may collect. Where a vertical discharge pipe
is used, a drip pan elbow is highly recommended.
10. BOTTOM BLOWDOWN PIPING
See suggested piping schematics for bottom
blowdown piping. The bottom blowdown connection on
the boiler has been properly sized according to ASME
Code. DO NOT reduce the blowdown piping size from
the boiler connection to the point of discharge. Do not
use galvanized pipe or fittings.
Valve ratings:
For ASME Section IV low pressure steam (15 psig)
and water boilers, the valve pressure rating shall meet
or exceed the boiler MAWP rating, as stamped on the
boiler, but in no case less than 30 psig. The minimum
temperature rating of the valves shall be 250F.
13
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