North Star M157594AF.1 Owner's Manual page 44

Descale heating coil
Inlet
Inspect heating coil
and desoot as
needed
Maintenance & Repair
Descale coil tubing annually or more frequently as needed.
In hard water areas, scale can build up inside the heating coil tubing. Scale
deposits will decrease the output pressure and temperature of heated spray,
and may eventually clog water flow through the heating coil.
Descale the coil tubing at least annually and more frequently if you detect a
decrease in output pressure or temperature.
To descale the coil:
1) Mix a commercial coil cleaner in a 5-gallon bucket and elevate the
bucket so it is higher than the unloader.
2) Attach the high-pressure hose(s) to the high-pressure water outlet on the
machine. Do not hook up the spray gun.
3) Place the other end of the high-pressure hose(s) in the 5-gallon bucket.
4) Attach a shorter length of garden hose to the garden hose inlet on the
pump.
5) Prime the pump by filling the hose with water, then placing the end of
the hose in the bucket.
6) Run the pressure washer in cold mode for 1 to 3 hours, recirculating the
cleaning solution. CAUTION: Do not run the burner.
7) Dispose of the cleaning solution where it is not harmful to animals or the
environment.
8) Flush with fresh water and clean the inlet strainer when finished.
Inspect and desoot coil annually.
Most coils never require desooting. However, poor grades of fuel oil or
inadequate combustion air will cause heavy soot build-up on the outside
Outlet
Figure 18
44