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A4. 3-way RTC in Primary/Secondary – Heating and DHW using Indirect Water Heater on Primary Loop; without Outdoor
Reset (MECHANICAL)
NOTES:
1) Install the boiler as indicated above for systems where return temperatures may be less than 135F and heating/DHW with an indirect water heater.
2) This arrangement is NOT recommended for outdoor reset applications. The reset temperature will constantly change DHW water performance.
3) The by-pass piping, diverting valve and boiler circulator must be sized using the sizing charts found in Appendix B.
4) A domestic hot water priority could be used provided the diversion from the heating system loop does not impact the system heater’s performance.
5) Closely spaced tees must connect the branch to the larger header. The Tee centerlines must be no greater than 4 times the larger header pipe diameter.
6) The diverting valve, V1, must be no greater than 11 linear feet of pipe from the Return Sensor, S1.
7) There shall be a MINIMUM of 4 linear feet of pipe between the By-pass Mix Point, M1, and the Return Sensor, S1.
8) The balancing valve in the boiler return line, V2, may be necessary in low head by-pass loop applications.
9) The indirect heater aquastat (A1) is a normally closed switch. Circuit breaks on temperature rise.
10) Expansion tanks, air scoops and other components left out for clarity.
11) Observe all applicable plumbing and electrical codes.
This diagram is for reference only. The installer or designer is responsible for the proper selection and design of the
system.