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AQUA PLUS indirect-fired water heaters — Product Manual
Recirculation
(continued)
Components
Circulator (Figure 6, item 1)
1. Little flow is required to maintain a temperature
in the piping.
2. Size of circulator depends on minimum flow re-
quirements of the tempering valve.
3. Minimum flow rates of the tempering valve must
be maintained.
Aquastat (Figure 6, item 2)
1. Used to control the on-off position of the circula-
tor. Aquastat is set 5° to 10° lower than mixed water
outlet of the mixing valve (#7).
2. The circulator cannot run continuously as bypass
through the mixing valve will eventually allow the
temperature on the piping to climb to the water
heater temperature during draw periods.
Check valves (Figure 6, items 3–6)
1. Assure the flow of water in one direction.
2. Each check valve functions as follows:
a. #3 and #4 prevent bypass in the event of pres-
sure drop.
b. #5 prevents thermal siphoning of hot water to
the cold water supply.
c. #6 prevents flow of cold water to the tempered
water supply. A draw of tempered water will
not result in flow of cold water into the return
loop.
Operation
1. During period of normal use (fixtures on) — Cir-
culator is off. There is no flow through #6, there is
flow through #5 equal to the flow at the fixtures,
there is flow through #3 and/or #4 equal to flow
at fixture.
2. When all fixtures are off — Circulator is off. There is
no flow through #3, #4, #5 or #6. Water temperature
in piping is cooling.
3. When temperature at aquastat #2 falls 10° below
temperature to be maintained — Circulator is on.
There is flow through #6 equal to the minimum
required by the mixing valve, flow through #3 and
#4 equals the flow of the circulator. There is no
flow through #5.
4. Aquastat reaches temperature — Circulator is off.
There is no flow through #3, #4, #5 or #6.
Figure 6 Recirculation piping
Potential problems
1. Missing check valves #3 or #4 — Extreme pressure drop can cause
reverse flow of water; hot to cold supply or cold to hot supply.
2. Missing check valve #5 — Hot water can migrate from the water heater
back through the cold water supply.
3. Missing check valve #6 — Cold water can be forced back through the
tempered water supply when a fixture is opened.
4. No aquastat #2 — Circulator runs continuously. Small amount of
water will pass through mixing valve. Eventually all hot water is flow-
ing through valve. Recirculated water through cold port, hot water
through hot port.
5. Circulator too small — Mixing valve performance erratic.
Part number GL-E223-ADOC 0311
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