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16

teMperature controls

The  boilers  covered  in  this  instruction  manual  are  equipped  with 

(adjustable) thermostat or step control to regulate water temperature 

and other controls to provide safety features. See the wiring diagrams 

on  page  13  &  14  and/or  literature  included  with  this  manual  for 

additional information.

Hot  water  temperatures  required  for  automatic  dishwasher  and 

laundry use can cause scald burns resulting in serious personal injury 

and/or death. The temperature at which injury occurs varies with the 

person’s age and duration of exposure. The slower response time 

of children, the elderly or disabled persons increases the hazards to 

them. Never allow small children to use a hot water tap or draw their 

own bath water. Never leave a child or disabled person unattended 

in a bathtub or shower. The boiler should be located in an area where 

the general public does not have access to set temperatures.

Figure 1. shows the approximate time-to-burn relationship for normal 

adult skin.

Water Temperature

Time to Produce 2nd & 3rd 

Degree Burns on Adult Skin

180°F (82°C)

160°F (82°C)

150°F (82°C)

140°F (82°C)

130°F (82°C)

120°F (82°C)

80°F (82°C)

Nearly Instantaneous

About 1/2 second

About 1-1/2 seconds

Less than 5 seconds

About 30 seconds

More than 5 minutes

- - - - - - - - - - - - - - - - -

fIGure 1.

•  Additional  instructional  literature  is  provided  with  the  boiler  for 

adjusting this control.

Always close and lock the cabinet door after making a temperature 

adjustment. Turn on electricity.

draInInG

The boiler must be drained if it is to be shut down and exposed to 

freezing  temperatures.  Maintenance  and  service  procedures  may 

also require draining the boiler.

1. Turn off the electrical disconnect switch.

2. Open a nearby outlet until the water is no longer hot and close the 

make-up water valve and system valves as necessary.

3. Open a nearby outlet to vent the parts of the system being drained.

4. Open the boiler drain valve.

5. If  the  boiler  is  being  drained  for  an  extended  shutdown,  it  is 

suggested the drain valve be left open during this period.

  •  Follow FILLING instructions to restore boiler to service.

Summary of Contents for NW 37-670

Page 1: ...ep for future reference COMMERCIAL ELECTRIC BOILERS Thank you for buying this energy efficient boiler from us We appreciate your confidence in our products MODELS NW 37 670 INSTALLATION OPERATION SERV...

Page 2: ...the type of hazard what can happen if you do not follow the safety message and how to avoid the risk of injury The California Safe Drinking Water and Toxic Enforcement Act requires the Governor of Ca...

Page 3: ...ay also cause erratic control system operation on ELECTRONIC CONTROL models This boiler must be connected to a grounded metal permanent wiring system or an equipment grounding conductor must be run wi...

Page 4: ...hen standing in water When replacing fuses always use the correct size for the circuit See page 12 through 14 The principal components of the heater are identified on page 8 The model and rating plate...

Page 5: ...4 4 4 3 3 3 3 1 1 1 1 NW NW NW NW NW 96 96 96 96 96 330K 390K 420K 450K 480K 36 36 36 36 36 38 38 38 38 38 16 16 16 16 16 69 1 2 69 1 2 69 1 2 69 1 2 69 1 2 17 17 17 17 17 1 1 2 1 1 2 1 1 2 1 1 2 1 1...

Page 6: ...1800K 1860K 1980K 2100K 66 66 66 66 56 56 56 56 28 28 28 28 90 1 2 90 1 2 90 1 2 90 1 2 25 1 2 25 1 2 25 1 2 25 1 2 2 1 2 2 1 2 2 1 2 2 1 2 30 30 30 30 33 33 33 33 7 3 4 7 3 4 7 3 4 7 3 4 8 8 8 8 2 2...

Page 7: ...60 2 90 4 90 6 60 1501 1668 1299 1443 648 720 792 864 542 602 663 723 NW NW NW NW NW NW NW 220 220 220 220 220 220 220 780K 840K 900K 960K 1020K 1080K 1140K 2 662 140 2 866 920 3 071 700 3 276 480 3 4...

Page 8: ...8 FEATURES AND COMPONENTS ACTUAL CONFIGURATION MAY VARY...

Page 9: ...the area adjacent to the boiler or to lower floors of the structure 3 The discharge opening of the temperature and pressure relief valve should always be piped to an open drain 4 Close to the point o...

Page 10: ...ut being certain the boiler is filled with water and a properly sized pressure relief valve is installed in the relief valve opening provided The pressure rating of the relief valve should be equal to...

Page 11: ...ng increase in water pressure due to thermal expansion Thermal expansion can cause premature tank failure leakage This type of failure is not covered under the limited warranty Thermal expansion can a...

Page 12: ...th this computation the next higher standard rating or setting should be selected Boiler Circuits The boiler s electrical components are pictured and identified on page 8 The model and rating plate il...

Page 13: ...TH THERMOSTAT NOTE S 1 IF A MANUAL RESET HLMT IS USED THE SECOND AUTO RESET HLMT SWITCH IS NOT USED STD WIRING OPTIONAL OR FIELD WIRING AS REQ D NOTE S 1 IF A MANUAL RESET HLMT IS USED THE SECOND AUTO...

Page 14: ...ON LIGHT 1 OFF ON 2200 2 OFF ON 135 3 OFF ON 4 20MA 4 OFF ON 0 10VDC 5 DS PROP 6 PROG UN 7 OFF VER 8 SEC MN 1 DELAY 1 2 DELAY 2 3 DELAY 3 4 1 5 2 6 4 7 5 8 16 THE ABOVE DIP SWITCH SETTINGS ARE AN EXAM...

Page 15: ...y be in the control circuit in addition to the automatic high limit previously described The control has an adjustable range of 110 F to 290 F and activates and locks on a temperature increase When th...

Page 16: ...proximate time to burn relationship for normal adult skin Water Temperature Time to Produce 2nd 3rd Degree Burns on Adult Skin 180 F 82 C 160 F 82 C 150 F 82 C 140 F 82 C 130 F 82 C 120 F 82 C 80 F 82...

Page 17: ...dential pipe dope thread cutting oil solder flux dirt and other foreign materials breakdown to form gas This is indicated by a continuing need for purging even through the system is closed 2 Pump seal...

Page 18: ...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...

Page 19: ...ges for forwarding the new tank or replacement part from the nearest distributor and returning the claimed defective tank or part to such distributor c All cost necessary or incidental for any materia...

Page 20: ...A DIVISION OF A O SMITH CORPORATION RENTON WASHINGTON Technical Support 800 527 1953 Parts Department 800 433 2515 www hotwater com...

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