Crown Boiler TWZ175 - Manual (Page 20)

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Depending on the location of the fuel oil storage tank in relation to an oil burner, there are four types of oil piping systems
generally being used:
a) ONE-PIPE GRAVITY SYSTEM - used when a fuel oil storage tank is positioned above an oil burner fuel pump. See
Figure 15. A vertical distance from top of the tank to center line of the pump (Dimension ‘H’) over 8 feet will result in
a pump inlet pressure in excess of the 3-psi limit in NFPA-31.
b) ONE-PIPE LIFT SYSTEM (not recommended) - Used when a fuel oil storage tank is located below an oil burner fuel
pump. See Figure 16. The vertical distance from bottom of the tank to center line of the pump (Dimension ‘H’) must
not exceed that shown in the pump manufacturer’s instructions. Although all oil piping systems must be airtight, one-
pipe lift systems are particularly susceptible to nuisance lockout problems if the suction line is not completely airtight.
A two-pipe lift system is therefore recommended over a one-pipe lift system.
c) TWO-PIPE GRAVITY SYSTEM (not recommended) - Used when a fuel oil storage tank is located above an oil
burner fuel pump. See Figure 17. A vertical distance from top of the tank to center line of the pump (Dimension ‘H’)
over 8 feet will result in a pump inlet pressure in excess of the 3-psi limit in NFPA-31. This type of system should be
converted to a one-pipe gravity system, as doing so will result in lower inlet line flow and longer filter life.
d) TWO-PIPE LIFT SYSTEM - used when a fuel oil storage tank is located below an oil burner fuel pump suction port.
See Figure 18. The vertical distance from bottom of the tank to center line of the pump (Dimension ‘H’) must not
exceed that shown in the pump manufacturer’s instructions. Distance ‘H’ allowed is reduced by the number of fittings,
filters and valves installed in the line.
Once the type of system has been selected, observe the following:
1) Fuel line piping must be airtight. Do not use compression type fittings for tubing connections in fuel line piping. Use
only listed flare type fittings. Cast iron threaded fittings shall not be used.
2) Piping shall be substantially supported and protected against physical damage and corrosion where required.
3) Refer to supplied oil pump instruction manual for proper connections. On one-pipe systems, ensure that the fuel pump
return port plug is tightened securely.
4) Some fuel pumps, such as the Suntec A and B series, are supplied with a loose bypass plug which must be installed on
two-pipe systems. If such a plug is supplied, install it as shown in the pump manufacturer’s instructions. Do not install this
bypass plug on one-pipe systems as pump seal damage will result.
5) Do not use check valves, especially on gravity feed systems.
6) Do not use Teflon tape for threaded connections. Use a listed non-hardening thread sealant instead.
FIGurE 15: OnE-PIPE GraVItY sYstEM