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A5. 3-way Multiple Boiler RTC in Primary/Secondary – Heating and DHW using Indirect Water Heater on Primary Loop;
Using Sequencer with & 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) The Outdoor Sensor (S4) and the Mix Supply Sensor (S3) are required when the Outdoor Reset feature is selected. An appropriate sequencer must also
be selected. The mix sensor must be installed 10 pipe diameters downstream of the system pump, in the primary loop. The mix sensor must be secured
to the surface of the pipe using a wire tie or similar device.
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 valves, V1 & V2, must be no greater than 11 linear feet of pipe from the Return Sensors, S1 & S2.
7) There shall be a MINIMUM of 4 linear feet of pipe between the By-pass Mix Points, M1 & M2, and the Return Sensors, S1 & S2.
8) The balancing valves in the boiler return lines, V3, 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.