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OPERATION
CEMLINE® Feed Forward Water Heaters can supply domestic hot water
with a temperature range set point of 105 to 180 deg F using low
pressure steam (2-15 psig). Models are available for flow rates
from 15 to 120 gallons per minute.
The CEMLINE Feed Forward Instantaneous Water Heaters (FFH) use a pressure
sensing blending valve to mix overheated hot water with cold water to
make hot domestic water. Cold water is passed through the tubes of the
heat exchanger while 2 to 15 psig steam is piped to the shell of the
heat exchanger which overheats the water in the tubes. A differential
pressure sensing head then blends the cold water with the over heated
hot water to deliver domestic hot water at a stable temperature with
an adjustable range of 105 to 180°F. FFH water heaters are not recommended
for water with hardness over 140 parts per million. If water hardness
exceeds 140 ppm either put a water softener in the system or use CEMLINE
SEH series water heater.
The varying pressures from above and below the diaphragm of the blending
valve are used to balance the differential pressure sensing head. A
sensing line is run from the cold water supply to the top of the blending
valve applying pressure downward on the diaphragm of the blending valve.
The blended water’s pressure is applied upward upon the diaphragm of
the valve from below. When the pressure on the diaphragm is even, the
valve is closed and hot water is not sent out to the system.
When a demand rises in the system for hot water, the pressure of the
blended water decreases. As the blended hot water’s pressure
drops, the pressure on the diaphragm from the cold water becomes greater
than the pressure of overheated hot water on the diaphragm. The greater
pressure of the cold water pushes the diaphragm down, which pushes the
stem of the blending valve down, thus opening the hot water ports on
the valve allowing more overheated hot water to blend and be sent out
as hot water into the system.
When the demand for hot water stops, the pressure of the blended hot
water increases equaling that of the cold water, thus raising the diaphragm
and the stem of the blending valve which closes off the opened hot water
ports and stops the blending of hot water.
The valve allows for automatic proportioning of the hot and cold water
thereby maintaining the desired set temperature even during conditions
of uneven flow. The water is blended quickly,which prevent any lags
in response to demand.
The blending valve is safe and will shut-off in situations of loss of
cold water pressure. Should the movement of the blending valve be restricted
by foreign debris carried in the water,a yielding spring arrangement
allows the diaphragm and stem to move up,uncovering a heat damper in
the characterized blending valve. This damper allows cold water to enter
the blended mix,eliminating the possibility of over-heating or scalding.
Moving the adjustment rod on the stem of the blending valve easily sets
the temperature of the FFH allowing for an easy startup of the unit.
The domestic hot water temperature range is 105 to 180°F.
CEMLINE FFH units can be completely packaged allowing the customer to
receive a water heater that only requires connections to be made to
the cold water inlet,hot water outlet,steam in,and condensate out. This
is the ideal way to install an FFH heater as it reduces piping times
at the job site.
STANDARD
EQUIPMENT
Pressure Sensing blending valve
FFH heaters use a differential pressure sensing blending valve that blends cold water with the over heated hot water to deliver domestic hot water at a stable temperature with an adjustable range of 105°F
to 180°F
Helical Wound Coil
The helical
wound coil is designed to provide the maximum heat transfer from the
low pressure steam (2-15 psig) on the shell side to the water locating
within the tubes. The standard coil material is copper, however the
coil is available in 90:10 copper nickel, and admiralty brass. The coil
has a pressure rating of 150 psig
Ductile Iron Vessel
The ductile iron vessel has 2-15 psig saturated steam. The
vessel is rated at 75 psig working pressure.
Structural I-beam support Skid Base
CEMLINE
heaters are mounted on structural I-Beam support skids designed as
a permanent base. This skid is pre-engineered to allow correct support
for the heater.
Water Pressure Gauge
CEMLINE
packaged heaters are supplied with a large, easily readable pressure
gauge.
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OPTIONAL
EQUIPMENT
Recirculation Kit
A recirculation kit is REQUIRED if the water in the system
is recirculated to the unit. The recirculation kit allows for
the passing of recirculated hot water, which prevents overheated
water leaving the FFH heater.
Packaged Unit
Completely
packaged and skidded unit. The only connections to be made are
the cold water inlet, hot water outlet, steam in, and condensate
out.
Upstream Pressure reducing Valve
In some installations, the steam pressure supplied will
be above 15 psig. In these instances, CEMLINE can provide
a pilot operated pressure reducing valve (PRV) to be piped
upstream of the FFH that will reduce the steam going to
the unit 15 psig.
Insulation Cover
The
insulation cover is placed over the top of the heat exchanger
to prevent heat loss of the heat exchanger. This high quality
insulation is an extremely reliable means of minimizing heat loss.
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RECIRCULATION
KIT
A recirculation kit is REQUIRED if the water
in the system is being recirculated. Temperature control problems
will occur if the recirculation kit is not used in a recirculating
system.
Temperature control problems will occur if a recirculation
kit is not installed in a recirculated system. The problem, recirculated water returning to the heater hot, is experienced during times of little or no hot water usage. The movement of the water through the system
will cause the blending valve to sense a pressure drop and cause the valve
to open and heat the hot water hotter. Eventually, the water in the system
will become dangerously hot. Therefore, when recirculating water, it is
essential that a recirculation kit be supplied. The recirculation kit
allows for the proper mixing of hot and cold water into the system through
the use of a balancing valve and a 3-way thermostatic valve. The mixing
valve allows for the diverting of hot water away from the heater if the
system temperature is already at the heaters set point. For safety purposes
the mixing valve is non-adjustable, preventing accidental changes in the
hot water system temperature thus preventing any over-temperature situations.
See the operation schematic below.
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