A.O. Smith NW 37-670 - Manual (Page 11)

11
• Use a twisting, pulling action to remove elements scaled
beyond the size of the tank opening.
• Brush loose scale from elements.
• Silicates, sulfates and aluminates must be removed by
scraping or other mechanical means. Lime scale
dissolvents will not remove these types of scale which
are occasionally encountered.
5. Lime scale removal:
• Place limed ends of heating elements into UN•LIME
delimer and allow scale to dissolve. Do not permit
delimer or water to contact heating element electrical
terminals.
6. Flush cleaned ends of elements with water when deliming or
cleaning is completed.
7. Remove sediment and scale from the tank bottom through the
tank cleanout.
• The make-up water valve and boiler drain valve may be
opened to flush during the cleanout process.
8. Clean remaining gasket material from tank and element flanges.
Do not reuse original element gasket. The element gasket is Part
No. 5109.
9. Replace elements as follows:
• Put a new gasket on each element.
• Install into tank opening.
• Uniformly tighten element bolts. Torque to approximately
32 ft/lbs.
10. Connect element wiring as necessary.
11. Follow FILLING instructions to restore boiler to service.
• Check for water leaks around elements and proper
operation when boiler is filled.
• Replace insulation and cabinet panel.
CHECKLIST
Before calling for service, check the following points to see if the cause
of trouble can be identified and corrected. Reviewing this checklist
may eliminate the need of a service call and quickly restore the boiler
to service. The illustration on page 5 identifies the location of most of
the boiler components.
BE SURE TO TURN OFF THE ELECTRICITY WHEN CHECKING
EQUIPMENT.
Not enough or no heat
1. Be certain the electrical disconnect switch serving the boiler is in
the ON position. The pilot switch(es) on the cabinet front should
be on.
•
In some installations the boiler electrical service may be
limited by the power company or boiler controls. If the
boiler operates on a controlled circuit heat may be
effected.
2. Check the fuses.
• The electrical disconnect switch usually contains fuses.
• The boiler has fuses located behind the cabinet door,
see page 5 for location.
3. If the water was excessively hot, and is now cold, the high
temperature cutoff may have operated (manual reset equipped
models).
•
To reset, turn off electricity and remove the back panel
and push the reset button.
• Repeated operation of the high temperature cutoff should
be investigated by your servicer.
4. The capacity of the boiler may have been exceeded by a large
demand for heat.
•
Large demands require a recovery period to restore
water temperature.
5. Sediment or lime scale may be affecting boiler operation. Refer to
MAINTENANCE for details.
Water is too hot
1. Refer to TEMPERATURE REGULATION.
Boiler makes sounds
1. Sediment or lime scale accumulation on the elements may cause
sizzling and hissing noises when the boiler is operating.
•
The sounds are normal , however, the tank bottom and
elements should be cleaned. Refer to MAINTENANCE
for details.
2. Some of the electrical components of the boiler make sounds which
are normal.
•
Contactors will “click” or snap as the boiler starts and
stops.
• Transformers and contactors often hum.
Water leakage is suspected
1. Check to see if the drain valve is tightly closed.
2. If the outlet of the relief valve is leaking it may represent:
• Excessive water pressure or air in the system.
• Faulty relief valve.
3. Examine the flange area of the elements and tank cleanout for
gasket leakage.
•
Tighten the bolts or, if necessary, follow the WATER AND
LIME SCALE REMOVAL procedure to replace the
gaskets.
SYSTEM WATER TEST
System water test
Review SYSTEM CLEANING section, for a description of six problems
which result from loss of system chemical stability. Chemical stability
is checked by:
1. Draw off water from system. Is it dirty, discolored or odorous?
2. What is the pH of the system water? It should be neutral or slightly
alkaline.
3. Does “air” purged from system vents burn? If so, the “air” is actually
gas.
If any of the above conditions are present, all waterways should be
cleaned and the water adjusted to an alkaline condition.
If you cannot identify or correct the source of
malfunction:
1. Place the boiler electrical disconnect switch in the OFF position.
2. Close the make-up water inlet valve to the boiler.
3. Contact your servicer.