Chromalox Boiler PQ402 6 User Manual

SERVICE MANUAL  
4
CES  
(Supersedes PQ402-5)  
PQ402-6  
161-049460-001  
FEBRUARY, 1999  
Chromalox Electric  
Steam Boilers  
The troubleshooting of Chromalox electric boilers can best be  
placed into five major areas. These areas are: (1) fusing (2) con-  
tacts, elements and voltages (3) pressure control (4) low water cut-  
off (5) water feed mechanism.  
of the Installation and Operating Instructions for  
your specific Chromalox Electric Steam Boiler.  
For convenience, we have outlined a brief description of typical  
malfunctions and the area that should be explored in order to make  
the proper correction. This is followed by a detailed analysis of the  
five areas listed above.  
WARNING: Hazard of Electric Shock and Thermal  
Burns. These troubleshooting checks should only  
be performed by qualified personnel after review  
TYPICAL MALFUNCTIONS & PROPER CORRECTION  
3. For boiler without motor and pump assembly: check pressure  
of water supply to insure that it is consistently a minimum of  
10 psi greater than the desired boiler operating pressure.  
4. Check water inlet check valve.  
5. For boiler with motor and pump assembly: check mercury  
tubes in the Low Water Control.  
6. A. Check motor and pump for binding and over  
heating. If caught in time, this can be observed  
by a humming sound. Replace if defective.  
Boiler does not heat:  
1. Check power fusing.  
2. Examine control circuit fuse.  
3. Reset button on the Low Water Control must be depressed (for  
states requiring a reset button).  
4. Float valve in the Low Water Control is not functioning prop-  
erly.  
5. Elements and/or contactors faulty.  
6. Mercury tube in Low Water Control has cracked and mercury  
has escaped.  
B. Check for defective solenoid valve.  
C. Make sure pump is running with correct rotation.  
D. Check impeller adjustment on turbine type pumps.  
Boiler takes too long to reach operating pressure or  
does not maintain desired pressure:  
Boiler appears to be leaking from beneath the jacket:  
1. Check amperage on each supply leg of power harness. Reading  
should correspond to a rating of not less than 10% of rated boil-  
er amperage.  
1. Check boiler fittings for looseness; tighten as required.  
2. Check boiler fittings for cracks; replace as necessary.  
3. Examine heating elements around boiler flange.  
If considerable difference exists:  
A. Available voltage is insufficient for boiler needs.  
B. Heating element failure has occurred.  
C. Fibre carrier in contactor requires replacement. On multi  
contactor units, check contactors and coils to determine if  
one is defective.  
IMPORTANT: Leaking is a hazard, correct to prevent further  
damage to other components.  
Boiler overflows:  
2. Check to determine whether boiler selected is underrated for  
the application.  
3. Additional Equipment added after initial installation, thus  
undersizing boiler.  
4. Steam piping not insulated.  
1. Float valve on the Low Water Control is stuck in the down  
position.  
2. Solenoid valve is not operating.  
3. Check for defective mercury tube on the Low Water Control if  
boiler has a motor and pump assembly.  
Boiler continuously blows power fuses:  
Pressure increases beyond the preset limits causing  
safety valve to blow:  
1. External fusing is not sized properly. Correct sizing is next size  
larger than boiler rating.  
2. Check lines between element and contactors with an ammeter  
for uniform readings.  
3. Check for evidence of charring which indicates loose connec-  
tions.  
4. A short circuit exists in the boiler.  
1. Check bellows in the pressure control.  
2. Check for clogged syphon tube.  
3. Contactor points have fused.  
4. Check pressure control setting against safety valve rating.  
Manual reset button needs constant resetting (for  
states requiring reset buttons only):  
Boiler does not fill with water automatically or does not  
maintain constant pressure:  
1. Check water supply line for closed valves.  
2. Check power fusing.  
1. Boiler is not level; relocate if necessary.  
© 2010 Chromalox, Inc.  
 
CONTACTOR FAILS TO ENERGIZE  
If the contactor fails to energize, check for blown fuses in  
the control circuit. If the fuses are not blown, check the contac-  
tor holding coil. The holding coil can be checked by jumpering  
Terminal L1 of the line and Terminal No. 4 (coil lead) on the  
contactor. See Figure 1.  
A. If the contactor fails to energize, then the coil is defective.  
B. If the contactor energizes, it is an indication of failure in  
either the Pressure Control or in the McDonnell-Miller three  
wire mercury switch.  
Figure 1  
Since the Pressure Control and the three wire mercury switch  
are wired in series, they can be checked one at a time by placing  
a jumper across each control. If the mercury switch or Pressure  
Control fail to energize, check the McDonnell-Miller controls by  
jumpering Terminals 5 and 6. See Figure 2.  
At this point, the contactor should energize unless there is an  
open wire in the control circuit.  
Figure 2 — Low Water Cut-Off Junction Box  
PRESSURE CONTROL — Malfunctions in the pressure control  
can be mechanical or electrical.  
Pressure  
Control  
Setting  
The bellows should be removed and the small orifice at the  
bottom cleaned out. The bellows must be replaced if it is punc-  
tured. The syphon tubing should also be cleaned by steam while  
the control is removed; it will be necessary to join the two loose  
leads in order to activate the boiler. See Figure 3.  
Differential  
Control  
Setting  
The electrical controls should be checked by referring to the  
Contactors, Elements and Voltages section.  
Bellows  
NOTE: If control is purchased locally, remove #8-32 orifice  
screw.  
Syphon  
Tube  
Figure 3 — Pressure Control  
 
LOW WATER CUT-OFF — Like the pressure control, difficul-  
ties can be broken down into the mechanical and electrical  
groups.  
assure that it is properly seated. If the valve seat is scarred or  
defective, the entire valve seat must be replaced. Also, if the float  
valve is in the down or “off” position, it may be punctured or  
encrusted with dirt and the unit must be disassembled.  
The mechanical difficulties can be corrected on the high pres-  
sure 100 psig motor and pump units in the following manner:  
1. Remove the cover and test the free movement of the float  
valve. If the float valve is in the off or down position, then the  
float is either punctured or dirt and sediment is encrusted in the  
float chamber. Both of these problems will involve disassem-  
bly of the float chamber.  
2. Check the electrical contacts to determine if they are defective.  
Defective mercury tube contacts will cause the boiler to fill high-  
er than normal. This occurrence will require replacement of the  
mercury tube.  
On all McDonnell-Miller cut-offs, restrictions in the equalizer  
column can cause burnt out elements. The cause will appear to be  
a low water condition. Regular blowdown procedures on the  
equalizer column as well as the boiler will prevent this occur-  
rence. Correction of the problem can be made by both removing  
the plug from the side of the column and opening the Low Water  
Cut-Off blowdown valves. A snake should be used to clean the  
vertical and horizontal columns.  
The electrical trouble shooting should be checked by referring  
to the Contactors, Elements and Voltages section.  
On low pressure feed units, the mechanical test is best made  
by cleaning the valve seat beneath the float valve linkage to  
WATER FEED MECHANISMS — A common problem in this  
area is boiler flooding, which may be caused by a defective float  
or solenoid.  
A defective check valve can cause the pump motor to run  
continuously or cause loss of water pressure. If the pipe between  
the check valve and the water supply is hot, boiler water is back-  
ing up through the check valve and the check valve must be  
replaced. A defective check valve can also prevent water from  
entering the boiler.  
The Low Water Cut-Off must be disassembled to check the  
float valve. The solenoid can be isolated by disconnecting the  
union after the solenoid and energizing and de-energizing the  
solenoid. If water comes out continuously or does not come out  
at all, then the solenoid is defective.  
The coupling between the motor and pump may be loose; the  
entire pump must be replaced if the coupling is excessively worn.  
Limited Warranty:  
Please refer to the Chromalox limited warranty applicable to this product at  
2150 N. RULON WHITE BLVD., OGDEN, UT 84404  
Phone: 1-800-368-2493  
 

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