12 Bottom Blowdown
Mk8 MM Manual Page | 226
12.4 Installation Guidance
The Bottom Blowdown valve must be sized appropriately for the size of the boiler and blowdown rate
required, which will be affected by the boiler pressure, size of blowdown line and blowdown line length from
the boiler to the bottom blowdown vessel. The blowdown rate that is required for that boiler will vary
according to the operating conditions, contaminants in the feed water and boiler design.
In multi-boiler systems where a bottom blowdown valve is fitted to each boiler, enabling Autoflame
sequencing in option 16 will ensure that only boiler in that loop blows down at a given time. If a blowdown
time is set the same on all the MMs in a sequencing loop, the MM with the lowest ID complete its blowdown
first, followed by the rest of the MMs, sequentially. If Autoflame sequencing is not used for multi-boiler
system requiring bottom blowdown in the UK, then valves must be interlocked; this ensures that only boiler
can be blown down at one time. Please see local code and regulation on bottom blowdown in multi-boiler
systems.
The Autoflame Bottom Blowdown Module (part number BBC70004) has a built-in, rechargeable Lithium-Ion
battery, so should a power failure to the module occurs, a Bottom Blowdown fault or MM error will be
triggered, and the servomotor will drive the blowdown valve to the closed position using battery power. The
servomotor is powered by 24VDC from the bottom blowdown module.
Note: The bottom blowdown valve must be installed along the blowdown pipeline according to local
code and regulations. It is the responsibility of the factory trained technician or engineer to configure
the bottom blowdown timings according to the specifications given by the boiler manufacturer.
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