7
heater. This problem is a direct result of the back
flow preventer . . . . . not the heating system. An
expansion tank may need to be installed to solve this
problem. Most water heaters are now labeled with
this information.
Multiple water heaters:
When sizing requirements
call for more than one water heater per air handler,
water heaters may be connected together according
to the water heater manufacturer’s instructions. (See
figure 10 page 9)
Anti-scald valve:
A water heater is designed to
produce hot water. Hot water represents a serious
safety hazard due to the potential of scalding. The
temperature of water normally required to provide
space heating (135 to 140 degrees) may be hotter
than certain codes allow for domestic hot water. An
“anti-scald valve” can be installed in the hot water
piping that would allow the domestic water to be sup-
plied at a lower temperature than the space heating
water. These can be obtained locally and should be
installed according to the manufacturer’s installation
instructions. (See figure 12)
START - UP PROCEDURE
(Heating cycle)
1. Open the main shut - off valve to the water heater
and the two shut - off valves to and from the air
handler or hot water coil.
2. Fill the water heater. Open a hot water faucet
somewhere in the house while filling the water
heater in order to vent the air. When the tank is
full and all the air is purged, close the faucet.
3. Ignite the water heater according to the manu-
facturer’s instructions and allow it to come up to
temperature (about 45 minutes).
DO NOT IGNITE
THE WATER HEATER WITHOUT WATER IN
THE TANK!
4. Purge the air handler’s hot water coil and lines: The
following procedure allows the use of city water
pressure to purge the air handler hot water coil and
lines even when the air handler is located higher
than the water heater. Once the air is completely
removed upon start - up, the circulating pump
will circulate the required amount of hot water
through the heating loop.
Note:
It may require purging several gallons of water
so either have a bucket available or connect a gar-
den hose to the purge valve and route to a drain.
Close valve number 2 and open valve number 3
(See figure 7). Next , open the air purge valve
located either on the flow control module or inside
the air handler. When all the air is purged, close
valve number 3 and open valve number 2. When
all the air is purged, open both valves and close
the air purge valve.
5. On Grundfos pumps, vent the air from the pump
chamber by loosening the large screw plug on
top of the pump motor until water appears. Then
retighten the plug.
6. Switch the room thermostat to “heat” and set it high
enough to energize the fan motor and pump. It
may be necessary to “feel” the pump to determine
if it is operating. If the pump is operating properly
and the water temperature in the water heater has
reached the set point, the hot water line going into
the air handler will begin to get hot. If the pump
is running but hot water is not circulating, refer to
"troubleshooting”.
7. Adjust the water heater thermostat so that the water
entering the hot water coil is 135 to 140 degrees
with the system energized and operating long
enough for all temperatures to stabilize.
