Lifebreath 4TONDHW(T) - Manual (Page 6)

Call for Space Heating Only
Operation
When the thermostat calls for heat, the
circulation pump is activated and hot water is
drawn from the top of the water heater through
the air handler, and then returned to the water
heater. There should be at least a 20˚F (11˚C)
temperature drop between the hot water
supplied to the air handler and the returning
water temperature. If the temperature drop is
less then 20˚F (11˚C) two things may happen:
1. Mixing of warm return water with the hot
water within the water heater (no tank
stratification), which will result in a lower hot
water supply temperature.
2. A water heater thermostat temperature
differential (between on and off) is approximately
18˚F (10˚C). Therefore, if the return water is not
cool enough, it may not activate the water heater
thermostat, which causes the burner to operate.
All of the water in the water heater will be cooled
before the burner begins to operate. This may
cause large swings in the delivered hot water
temperature, causing poor space heating
performance, fluctuating domestic water
temperatures and effectively reducing the supply
of domestic hot water.
Call for Domestic Hot Water and
Space Heating Operation
When both return water from the space heating
loop and new cold water (replacing domestic
water being used) enters the water heater, the
mixed entering water is cool enough to activate
the thermostat quickly. In this situation, the water
heater must be capable of satisfying the
combined need for hot water (domestic hot water
and space heating) at the same time.
Air System
A circulation fan draws cool house air at approx.
70˚F (21˚C) from the return ductwork, forces
it through the water coil where it is heated, and
then distributes it to the various rooms of the
house through the supply ductwork.
Water Piping
The Piping and fittings used to connect the water
heater and air handler must be sized to handle
the volume of hot water required by the air
handler within the pressure limitations of the
circulation pump. All piping, fittings solders, and
fluxes must be acceptable for use with domestic
hot water.
Note: Chemicals (such as boiler system additives)
cannot be added to the system because water passing
through the heating loop re-enters the domestic
water systems.
Circulation Pump
The circulation pump is factory installed within
the air handler. The water flow rate will vary
depending on the pumps performance and
the head pressure (resistance) of the complete
heating loop system.
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