Radiantec
INDIRECT SYSTEM INSTALLATION
INSTALLATION SUPPLEMENT
240
The indirect system uses a heat exchanger to separate the heating fluid from the domestic hot water. An advantage is that an antifreeze solution may be added to the heating fluid, and snow melting can be added to the system.
Some code administrators may require the heat exchanger. A disadvantage is that the cooling benefit is eliminated. Also, with the addition of a heat exchanger, cost and complexity are increased.
Indirect systems can be used when antifreeze must be added to the heating fluid, or when codes mandate this separation.
Indirect System
APPLICATIONS
1. Allows for the use of a domestic water heater as the source for heating and domestic hot water in locations where separation of the two is required.
2. Allows for the use of two different types of fluids in each part of the system (anti-freeze for snowmelt and water in the heater, for example).
3. Provides absolute protection from oxygen diffusion in boiler applications.
A heat exchanger is a device that exchanges the heat from one fluid to another without mixing the fluids.
A Radiantec heat exchanger is a stack of stainless steel plates that are stamped together so that they form chambers between them. Domestic hot water flows through half of the chambers and the heat- ing fluid flows through the other half.
Heat from the domestic water heater is exchanged to the heating system fluid without mixing the fluids.
OPERATION
When heat is called for by a thermostat, the heater pump comes on and water flows from the water heater through one side of the heat exchanger, heating it up in the process. At the same time, the zone pump comes on and causes water (or anti-freeze) to flow through the other side of the heat exchanger to pick up the heat and then travels through the heating zone. When the thermostat in the zone is satisfied, it shuts the pumps off.
INSTALL THE HEATING SIDE OF THE SYSTEM
The heating side of the indirect system is a “Closed” type system, and these systems are described in another supplement titled Install a ‘Closed” type heating system. Please refer to this supplement for this part of the installation.
INSTALL THE DOMESTIC SIDE OF THE SYSTEM MOUNT THE HEAT EXCHANGER
It is convenient to make a mounting frame for the heat exchanger out of framing lumber (in this case, 2×4’s). It is desirable to insulate the pipes and heat exchanger for efficiency. Wood has better insulating properties than a metal hanger.
MOUNT THE PUMP
Mount the pump so that draws water from the heating outlet of the tank (closer to the top), passes it through the heat exchanger, and then goes into the heating inlet of the tank (closer to the bottom).
Mount Pump
Please refer to the “Closed” heating system supplement for information on installing Zone Distribution Manifolds.
COMPLETE THE LOOP
Complete the piping between the heat exchanger, the pump and the tank. Do not add any extra valves or flow control valves.
PREVENT STAGNATION OF THE POTABLE WATER DURING THE NON-HEATING PERIODS
This design element allows a small amount of water to go back and forth between the loop and the tank by “gravity” (the differences in the buoyancy of warm water and cold water). This small amount of water flow will help to pre- vent stagnation of the potable water in the loop during non-heating periods.
INSULATE FOR EFFICIENCY
The small amount of hot water that will pass back and forth between the water heater and the heat exchanger means that the loop should be well insulated for efficiency.
Copyright 2003, Robert J. Starr
Revised on 1/12/04