CONTROL COMPONENTS

FIGURE 1. COMPONENT LOCATIONS

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AUTO RESET HIGH LIMIT

The high limit is a safety device wired in series with the ignition system. Set the high limit control to approximately 100°F above the maximum designed system temperature. If the boiler outlet water temperature should exceed the high limit setting, the main gas control valve will close but the circulating pump will continue to operate. Maximum adjustable setting is 115°C (239°F) cut-out with a 30°C (86°F) to 250°C (482°F) adjustable differential, see

Figure 2.

FIGURE 2. AUTO RESET HIGH LIMIT

THERMAL BALANCER

Figure 4 shows the internal wiring of the thermal balancer. The

device may be tested after disconnecting the four leads from their respective terminals on the unit.

1. Apply a test light to the yellow and red leads.

• The lamp should light as the contact in this circuit is normally closed when the resistor is cool.

2. Apply a light to the black and yellow leads.

• The lamp should not light as the contact in this circuit is normally open when the resistor is cool.

3. Remove the test light.

4. Apply 120 volts to the white and red leads which power the

1900 ohm resistor. After a warming period the contacts of the thermal balancer should operate.

5. Remove the test light.

6. Apply the test light as described in steps 1 and 2.

While the resistor is still warm the lamp indications should be the opposite as described previously.

INTERMITTENT IGNITION CONTROL MODULE

The Honeywell S-8600 control module contains the electronic components of the system and also serves as a control wiring system for the controls mounted on the boiler. The control module performs the following functions:

1. Checks for safe-start by sensing for a false flame condition on start-up.

2. Generates a potential of 15,000 volts for spark ignition of the pilot burner.

3. Opens the pilot valve.

4. Discontinues ignition spark when the pilot flame is established. The S-8600 control used on propane gas models provides safety lockout if the pilot fails to ignite within the pilot flame establishing period. The S-8600 control used on natural gas models continues trial for ignition until pilot flame is established.

5. After proof of pilot flame, opens then main valve.

6. On a power loss, shuts the boiler down. When power is restored it will begin a new ignition cycle.

7. On a loss of flame, shuts off main gas and starts trial for pilot ignition.

Please refer to Troubleshooting section for more information.

FIGURE 4. THERMAL BALANCER

MANUAL RESET HIGH LIMIT

This boiler is equipped with a manual reset high limit switch, located under the small cover on the side of the jacket, see

Figure 5. This device provides positive shutdown of the boiler

in the event of boiler or system malfunction. Should the surface temperature of the copper tubing heat exchanger reach 250°F

(120°C), the high limit switch will activate, the gas control valve will close, the pilot and main burners will be extinguished. If the high limit switch should shut off unit, check the following conditions:

• No water in boiler.

• Restricted water flow through the boiler.

• Improper wiring (boiler firing without circulating pump operating).

• Pump failure.

After correcting failure condition remove the protector switch cover and push the reset button. The high limit switch may be reset after the coil surface cools to 6°F (3.3°C) below the trip setting.

FIGURE 3. S-8600 INTERMITTENT IGNITION CONTROL

MODULE (IID)

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FIGURE 5. HIGH LIMIT SWITCH

PRESSURE RELIEF VALVE

An ASME rated pressure relief valve is furnished with the boiler.

A fitting for the pressure relief valve is provided in the top of the boiler. Never operate the heating elements without being certain the boiler is filled with water and a properly sized pressure relief valve is installed in the pressure relief valve opening provided.

The pressure rating of the pressure relief valve should be equal to or less than the rated pressure capacity of any component in the system including the boiler. Should the valve need to be replaced, call the toll free phone number listed on the back of this manual for further technical assistance.

Explosion Hazard

Pressure Relief Valve must comply with ASME code.

Properly sized Pressure Relief

Valve must be installed in opening provided.

Can result in overheating and excessive tank pressure.

Can cause serious injury or death.

If any pressure relief valve is replaced, the replacement valve must comply with the current editions of the ASME Boiler and

Pressure Vessel Code, Section IV or CSA B51, as applicable.

Select a pressure relief valve with a discharge NOT less than the boiler input, and a pressure rating NOT exceeding the working pressure of any component in the system.

A. O. Smith supplies a 125 psi pressure relief valve for hot water supply systems and 50 psi pressure relief valve for space heating application.

An ASME rated temperature and pressure relief valve must be installed on each and every water storage tank in a hot water supply system.

The storage tank temperature and pressure (T & P) relief valve must comply with the applicable construction provisions of the

Standard for Relief valves and Automatic Gas Shutoff Devices for Hot Water Supply Systems, Z21.22 - CSA 4.4. The T & P valve must be of the automatic reset type and not embody a single-use type of fusible plug, cartridge or linkage.

The T & P relief valve should have a maximum temperature rating of 100°C (210°F), a pressure rating NOT exceeding the lowest rated working pressure of any system component, and a discharge capacity exceeding the total input of the water boilers supplying water to the storage tank.

Locate the T & P relief valve (a) in the top of the storage tank or (b) in the side of the tank on centerline within upper 6 inches from the top of the tank. Refer to the Piping Diagrams section in Instruction Manual. Tapping shall be threaded in accordance with the latest version of the Standard for Pipe Threads, General

Purpose (inch), ANSI/ASME B.120.1.

A discharge pipe from the pressure relief valve should terminate at an adequate floor drain. Do not thread, plug, or cap the end of the drain line.

CAUTION

Water Damage Hazard

•

Pressure Relief Valve discharge pipe must terminate at adequate drain.

The Discharge Pipe:

• Shall not be smaller in size than the outlet pipe size of the valve, or have any reducing couplings or other restrictions.

• Shall not be plugged or blocked.

• Shall not be exposed to freezing temperatures.

• Shall be of material listed for hot water distribution.

• Shall be installed so as to allow complete drainage of both the pressure relief valve and the discharge pipe.

• Must terminate a maximum of six inches above a floor drain or external to the building. In cold climates, it is recommended that the discharge pipe be terminated at an adequate drain inside the building.

• Shall not have any valve or other obstruction between the pressure relief valve and the drain.

Once the boiler is installed and filled with water and the system is pressurized, manually test the operation of the pressure relief valve.

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TANK TEMPERATURE CONTROL

The water temperature in the storage tank is controlled by the

Tank Temperature Control. The sensing element is mounted inside the hot water storage tank.

Water temperature over 125°F (52°C) can cause severe burns instantly resulting in severe injury or death.

Children, the elderly and the physically or mentally disabled are at highest risk for scald injury.

Feel water before bathing or showering.

Temperature limiting devices such as mixing valves must be installed when required by codes and to ensure safe temperatures at fixtures.

The tank temperature control is adjustable from 100°F (37.7°C) to 220°F (104.4°C). It is recommended that lower water temperatures be used to avoid the risk of scalding. It is further recommended, in all cases, that the water temperature be set for the lowest temperature which satisfies the user’s hot water needs. This will also provide the most energy efficient operation of the boiler and minimize scale formation.

The boiler should be located in an area where the general public does not have access to set temperatures. Setting the water temperature at 120°F (49°C) will reduce the risk of scalds.

Some people are more likely to be permanently injured by hot water than others. These include the elderly, children, the

infirm and the physically/mentally disabled. Table 1 shows the

approximate time-to-burn relationship for normal adult skin. If anyone using hot water provided by the boiler being installed fits into one of these groups or if there is a local code or state law requiring a certain water temperature at the point of use, then special precautions must be taken. Contact a qualified service technician or qualified agency.

Use anti-scald valve(s) in the hot water system to reduce the risks of scalds at points of use such as lavatories, sinks and bathing facilities.

A change in water temperature in the storage tank lower than the

Tank Temperature Control setting will cause the sensor to close its contacts and consequently energize the boiler.

If the Tank Temperature Control is out of calibration, replace it with a new one; do not attempt to fix this control.

THERMOMETERS

Thermometers should be obtained and field installed as shown in the installation diagrams.

Thermometers are installed in the system as a means of detecting a possible liming condition in the boiler. An increase of 5°F (3°C) over the normal temperature rise through the boiler is an indication that lime is present. The term "temperature" designates the difference between the boiler inlet and outlet water temperature.

An increase of 5°F (3°C) above the recorded temperature rise may signify a liming condition in the coils or heat exchanger. Refer to Cleaning and Flushing Instructions on Page

24 for deliming instructions.

Record temperature rise at initial start-up for future reference.

DRAIN VALVE (NOT SUPPLIED)

A drain valve must be obtained and installed on each boiler and tank for draining purposes.

TABLE 1. TEMPERATURE AND TIME TO PRODUCE BURNS

Water Temperature

180°F (82°C)

170°F (77°C)

160°F (71°C)

150°F (66°C)

140°F (60°C)

130°F (54°C)

120°F (49°C)

Time to Produce 2nd & 3rd

Degree Burns on Adult Skin

Nearly instantaneous

Nearly instantaneous

About 1/2 second

About 1-1/2 seconds

Less than 5 seconds

About 30 seconds

More than 5 minutes

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