ffh-top diagramnew

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.