8
Suction Vacuum Test.
A fuel pump suction vacuum test should be performed. See the fuel
pump manufacturers literature for details. The suction vacuum must be limited to ensure that
there is adequate pump lift. This problem becomes proportionately larger with underground
tanks. If the following procedures are followed, burner related problems will be minimized:
a) Connect vacuum gauge to fuel pump. Suction vacuum must not exceed 10 inches of mer-
cury for single stage pumps and 15 inches for two stage pumps. It is preferable to stay
below these limitations.
b) When the suction line is tight and properly installed the pump will hold its vacuum for a
minimum of 60 minutes after shutdown.
c) Installation of a check valve in the suction line of a two pipe system is advisable under all
circumstances. Be sure the check valve fittings are airtight.
11) Connect the electric supply to the boiler as indicated on the wiring diagram. The wiring
must be instal
l
ed in accordance with the National Electrical Code and any other state and
local codes and the following requirements.
a) Internal wiring is completed at the factory on packaged boilers. External wiring must
conform with the National Electric Code and local codes.
b) Field connections should be protected with a 15 amp fuse.
c) A separate, fused disconnect switch should be installed and located near the unit so
that power can be shut-off for servicing, unless already equipped.
d) Install the room thermostat (not provided) on an inside wall away from cold drafts,
windows or heat from fireplaces, appliances or sunlight. Set the heat anticipator in
accordance with the manufacturer’s instructions. Connect the thermostat leads to the
“TT” terminals on the circulator control.
C. Operational Sequence
1) TDX-WC equipped with tankless coil are equipped with a combination aquastat control
which has high and low limits to be set at 180° F and 160° F respectively by the installer.
These settings are nominal and may be adjusted for the particular installation conditions.
A 20° F difference between high and low limit is recommended. The control prioritizes
domestic hot water heating as explained below.
a) When room temperature falls below thermostat setting, thermostat calls for heat start
ing the burner and circulating pump. The burner and pump continue to operate until
room heating requirements are satisfied (thermostat setting is reached), or until boiler
water temperature reaches the high limit control temperature setting. If the high limit
control temperature setting is reached, the burner shuts off and the circulating pump
continues to operate until the room heating requirements are satisfied. If the thermo-
stat continues to call for heat after the boiler water temperature has dropped to
approximately 10 degrees below the temperature setting of the high limit control, the
oil burner will start again and the circulating pump will continue to run.
b. The boiler water temperature is normally maintained at 160°F around the tankless coil
by the operating control so that an abundance of hot water is available. If the boiler
water temperature should fall approximately 10 °F below the operating control low