ZERO PRESSURE, FIXED SUPPLY TEMP – PRIMARY SECONDARY PUMPING:
A primary-secondary pumping scenario involves two pumps: The primary pump circulates water between the GARN unit and the heat distribution piping; the secondary pump circulates water through the heat distribution piping.
Advantages
Disadvantages
The main advantage of this type of system is that it can be directly connected to an existing zero pressure heating system. Temperature and flow can be controlled independently. Primary loop pump only needs to be sized from the primary loop piping. Secondary loop pump only needs to be sized for secondary loop piping. No mixing valve required. No expansion tank required.
Cannot connect to a pressurized system. If pumping to a level higher than the level of the GARN unit, the system will drain back to the GARN which could prevent many pipes from remaining “ wetted ” .
24
Hydronic System Design Manual ©DECTRA CORPORATION - March 2013
Made with FlippingBook - professional solution for displaying marketing and sales documents online