Heating system with first and second heating devices and bypass line

A heating system for heating a fluid received at an inlet, the system comprising:

• (a) a first heating device disposed in a first heated line branched from the inlet, wherein a first flow of the fluid through the first heated line is configured to be modulated by a first valve;
• (b) a second heating device disposed in a second heated line branched from the inlet, wherein a second flow of the fluid through the second heated line is configured to be modulated by a second valve;
• and
• (c) a bypass line and a third valve disposed in the bypass line branched from the inlet, wherein a third flow through the bypass line is configured to be modulated by said third valve,
• wherein the first heating device comprises a burner and a coil-tube heat exchanger, the coil-tube heat exchanger is disposed in a forced-air path driven by a blower, the fluid is configured to be heated by forced-air of the forced-air path through the coil-tube heat exchanger and optionally heated by the burner,
• wherein the second heating device comprises a thermal storage tank including a heat storage substance selected from water or a phase-change material (PCM), the thermal storage tank thermally coupled to a heat pump such that, in a space-cooling mode of the heat pump, heat removed from a conditioned space is stored in the thermal storage tank for later delivery to the fluid via the second heated line, and
• wherein a controller is configured to cooperatively modulate the first, second, and third valves based on an outlet-temperature setpoint of the fluid so that the temperature of the fluid received at an inlet is modified by selectively mixing flows from the first heated line, the second heated line, and the bypass line.