Operation of the CSX water heater in applications with building re-circulating potable water loops.
| | | | | | Solenoid | |
Pressure | | | | | Shutoff | |
Gradient | | | | | Valve | |
Monitor | | | Hi-Limit | | |
(optional) | Pressure | | |
CIP Fitting | Relief | | | | |
Valve | | | | |
Steam | | | | | Hi-Limit | |
Inlet | | | Primary | Hot Water |
| | | | | Supply |
| | | | Blending | |
| | | | Valve | | |
| | | | | | Secondary | |
| | | | | | Blending | |
| | | | | | Valve | |
| | | | | | Expansion | |
| | B | A | |
| | Tank | |
| | | | | | | |
C
CIP Fitting
Cold Water
Makeup
F&T Trap
Building Re-circulation
Condensate
Sub-cooler
(optional)
The temperature setting on the secondary blending valve determines the path water takes when returning to the CSX from the building re-circulation loop.
During periods of low demand when water returning to the CSX from the building loop is close to the required hot water supply temper- ature, water is mainly channeled through the secondary valve (path A) where it mixes with a small amount of hot water and is returned to the building.
During periods of high demand when most of the water in the return line to the CSX is makeup cold water, the cold inlet port on the secondary blending valve will narrow, forcing most of the water through paths B and C. These two paths combine at the primary blending valve where high temperature water (path C) mixes with cold makeup water (path B). The resulting interme- diate temperature water, travels to the second- ary blending valve, mixes with cold water from path A and re-enters the building potable water supply lines at the proper temperature.
High | Intermediate | Blended |
temperature | temperature | temperature |
water | water | water |
| | |
Key Components of the CSX
CSX heat exchanger - an ASME code, 316L stainless steel, shell-and-tube exchanger where potable water is heated to between 200° and 250°F depending upon supply steam pressure and hot water demand (flow rate) Primary blending valve - an all-bronze, thermostatic, fixed-temperature mixing valve where over-heated water is tempered with cold water. Hot water outlet will be approximately 20°F higher than the outlet set point of the secondary blending valve
Secondary blending valve - an all-bronze, thermostatic, fixed-temperature mixing valve located downstream of the primary blending valve and set to supply water at the required domestic hot water temperature High-temperature limits - safety devices; one located in the intermediate temperature water line and one located in the final hot water supply line. When sensing water temperature above their set points, the thermostat breaks the circuit holding the solenoid valve open.
Solenoid shutoff valve - shuts off water flow from the high-temperature side of the CSX water heater in the event of high-temperature downstream of the blending valves or a pressure equalization occurrence (if pressure gradient monitor is supplied)
Pressure relief valve - set to relieve pressures above 150 psi
Steam inlet valve (factory piped) - modulating, pressure-pilot steam valve is standard equipment when supply steam pressure is above 15 psi and optional when supply steam pressures are at or below 15 psi Pressure gradient monitor - device that monitors steam side and water side pressures. Equalization of these pressures might indicate a heat exchanger tube wall breach and, if equalization is dectected, the control breaks the circuit that keeps the solenoid shutoff valve open. (optional)
Condensate sub-cooler- additional heat exchanger used to pre-heat building re-circulating water with conden- sate and reduces condensate temperature to below 100ºF. (optional)
PVI Industries, LLC • Fort Worth, TX • (800) 784-8326 • www.pvi.com
