Start up, Prior to start up, Initial start up – John Wood Commercial - 300-400K BTU User Manual

Page 49: Fire or explosion hazard

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prior to start up

Installation and start up of this water heater requires abilities

and skills equivalent to that of a licensed tradesman in the field

involved, see Qualifications on page 6.
Do not place the water heater in operation if any part has been

under water. Immediately call a qualified service technician to

inspect the water heater and to replace any part of the control

system and any gas control which has been under water.
Light the water heater in accordance with the Lighting and

Operation Instruction label on the water heater and in this manual

beginning on page 52.
The water heaters covered by this manual are equipped with

an electronic control system (see page 41) which automatically

sequences the Combustion blower, pre and post purging of

the combustion chamber, the Hot Surface Igniter, the 24 VAC

gas Valve, Main burner ignition, and flame sensing. The control

system will lock out after three unsuccessful ignition attempts.
before attempting start up, thoroughly study and familiarize

yourself with the exact Sequence Of Operation, see the written

Sequence Of Operation on page 49 and the Sequence Of

Operation Flow Chart on page 55.
be certain that the water heater is full of water, that air is purged

from the gas and water lines and that there are no leaks in the

gas and water lines. Ensure all inlet water valves are open.
filling the water heater
Follow these steps to fill the water heater prior to start up.
1. Close the heater drain valve.
2. Open a nearby hot water faucet to permit the air in the system

to escape.

3. Fully open the cold water inlet valve allowing the piping and

water heater to fill with water.

4. Close the hot water faucet opened in Step 2 as water starts

to flow.

supply gas line purging

Fire or Explosion Hazard

Read instruction manual before

installing, using or servicing

water heater.

To avoid risk of fire or explosion purge discharge must not

enter into confined areas or spaces where ignition can occur.
The area must be well ventilated and all sources of ignition

must be deactivated or removed.

Gas line purging is required with new piping or systems in

which air has entered.

Use only the gas shown on the water heater rating label.
Keep ignition sources away from faucets after extended

periods of non-use.

1. Close the Main gas Shutoff Valve, see Figure 52 on page

36.

2. Purge all air from the supply gas line up to the water heater’s

Main gas Shutoff Valve.

3. When all air has been purged from the supply gas line,

tighten all supply gas line connections.

4. Check for gas leaks, see gas Line Leak Testing on page 37,

and repair any leaks found.

initial start up

reQuired test eQuipment

• Two u-tube manometers, recommended ranges; 0-14” W.C.

(0-3.5 kPa) and 0-35” W.C. (0-8.7 kPa) or pressure gauges.

• Two digital manometers can be used in place of u-tube

manometers or pressure gauges. recommended ranges;

-14.00 to +14.00” W.C. (0-3.5 kPa) resolution 0.01” W.C.

and 0-35” W.C. (0-8.7 kPa) resolution 0.10” W.C.

note:

All test equipment must be acclimated to ambient

temperature before calibration and use.
preparation
1. using the control system menus, change the Operating Set

Point to the lowest temperature setting, see Operating Set

Point And Differential Adjustment on page 44.

2. Turn the water heater’s on/off switch to the “off” position.
3. Close the Main gas Shut Off Valve, see Figure 52 on page 36.
4. Push in the gas control knob slightly and turn to the

“off”position, see Figure 56 on page 50.

5. Wait five (5) minutes for any residual gas to clear.
6. Connect one manometer (higher range) to an available test

port on the supply gas line at the water heater. There is a

1/8" NPT Tee fitting and pipe nipple installed for the Low gas

Pressure switch on the inlet side of the 24 VAC gas Valve

with a 1/8" NPT plug for this purpose. For AJWSH130 400

Natural gas model, connect the manometer to the supply gas

pressure test port, see Figure 57 on page 51.

7. Connect one manometer (lower range) to the manifold gas

pressure tap at the outlet of the 24 VAC Gas Valve, see

Figure 56 on page 50 for location.

8. Open the Main gas Shutoff Valve.
9. Measure and record the supply gas pressure, this is a “static”