PB Heat DE User Manual download pdf (Page 27)

B. CONTROL DESCRIPTIONS

See Figure 6.1 in Section 6 (Electrical) for locations of

these devices.

1. FLAME ROLL-OUT SAFETY SHUT-OFF SWITCH

(FLAME ROLL-OUT SWITCH) – A thermally

activated switch located between the first burner

from the left and the manifold bracket. The flame

roll-out safety shut-off switch will sense excessive

temperature caused by continued flame roll-out and

shut down main burner gas. This is a non-recycling

switch that must be replaced once it has been

activated and the cause of the roll-out eliminated.

2. PRESSURE SWITCH – A pressure sensing device

that is located in the jacket vestibule. This control

senses a suction pressure when fan is energized on a

call for heat. Switch contacts close allowing control

circuit to energize ignition system.

3. LIMIT (AQUASTAT) – A thermally activated,

manually adjustable switch located on the left side of

the boiler, towards the top and rear. The temperature

sensing element is placed in the supply and will shut

down main burner gas if the supply water exceeds

the preset temperature limit. This is a recycling switch

that will automatically reset when the supply water

falls below the preset temperature.

4. LOW WATER CUT-OFF (FOR GRAVITY SYSTEMS

OR HOT WATER BOILERS INSTALLED ABOVE

RADIATION LEVEL) – A level-sensing device (float

or probe) located in supply piping near the boiler. If

water level in the system drops below the control’s

position, it will shut down main burner gas. The

control will automatically reset once the water level

rises above its position.

C. ADJUSTMENT OF GAS PRESSURE

REGULATOR

1. Connect a manometer to 1/8 N.P.T. tapping on gas

manifold, set manifold pressure as follows for various

gases.

a. Natural Gas . . . . . . . . . .3.5″ W.C. (0.9 kPa)

b. LP Gas . . . . . . . . . . . . .10.0″ W.C. (2.5 kPa)

2. To adjust gas pressure, turn adjusting screw of gas

pressure regulator counterclockwise to decrease

pressure, clockwise to increase pressure. Refer to

Figure 7.2 for location of gas pressure regulator.

Replace the cap screw when adjustment is complete.

3. In no case should the final manifold pressure vary

more than ±0.3 inches water column (0.07 kPa)

from the above specified pressures. Any necessary

major changes in the flow should be made by

changing the size of the burner orifice spuds.

4. When adjustment is complete, turn off boiler, gas

flow and electricity to boiler. Remove manometer

connection from valve and plug tapping with plug

provided. Turn utilities back on and resume

checkout.

D. CHECKING BURNER INPUT

1. Refer to rating label mounted on the jacket top panel

to obtain the rated BTU per hour input. In no case

shall the input to the boiler exceed the value shown

on the rating label.

2. Check input by use of the following formula

(PB Heat suggests reading meter for 2 Cu.Ft.

[0.0566 cubic meter]):

U.S. Customary Units:

Input (BTU/Hr.)= 3600 x F x H

Where:

3600 – Seconds per hour

F – Cubic Feet of Gas Registered on Meter

H – Heat Value of Gas in BTU/Cubic Feet

T – Time in Seconds the Meter is Read

SI Metric Units

Input (kW)= 3600 x F x H

T x 3.6

Where:

3600 – Seconds per hour

3.6 – Megajoule (MJ) per kilowatt hour (kwhr)

F – Cubic Meters of Gas Registered on Meter

H – Heating Value of Gas in MJ/Cubic Meter

T – Time in Seconds the Meter is Read

3. As an alternative, use Table 7.1a and 7.1b. Use the

heating value provided by gas supplier. Use a

stopwatch to record the time it takes for 2 cubic feet

(0.0566 cubic meter) of gas to pass through the

meter. Read across and down to determine rate.

START-UP PROCEDURES

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PB Heat DE User Manual Page 27

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