Pool Boiler

The boiler is a natural gas fired 1,200,000 BTW/hr RBI LW1200. Details are contained in RBI drawing #42-2112 (not published on the Wiki as it may be considered RBI proprietary).

Interlocks prevent the boiler from operating when the water level is too low, sufficient water flow is not present or the air pressure differential (as generated by the blower motors) is insufficient. Redundant over-temperature lock-outs (including those added by FFSC maintenance) prevent operation in the event that the temperature rises beyond a threshold.

Operation

Details to follow.

Adjustments

Details to follow.

Maintenance

Regular inspections are mandated by the state and the insurance company. These inspections occur every three years. Prior to the official inspection, a Steam/Hot Water ASME CSD-1 form must be completed by a qualified technician. This form contains details about the boiler (identified by the state license and serial numbers), identifying key controls, their set-points and operation test results. Any issues found during the technician's inspection must be remedied before the document becomes acceptable as proof of compliance per Rule 27 of the State of Michigan Boiler Code.

Two copies of the CSD-1 should be kept by FFSC. One placed in a room near the boiler, another in a central filing location.

Recirculation Valve

Adjustments to the recirculation valve require extreme care, especially when the main pump is operating. The butterfly valve has a tendency to pull itself closed rapidly if the operator is not careful. Such a rapid change in flow and pressure may cause significant damage to the system.

When adjusting the recirculation valve, use the following precautions:

• Ideally, turn off the main pump before adjusting.
• If the main pump cannot be stopped, use two hands and extreme care in moving the valve position. Ensure the valve is locked into a notch before releasing the lever.
• Adjust the position by no more than 1-2 notches in the open or closed direction. Observe changing in the operating parameters (i.e. boiler manifold temperature) before making additional adjustments.

Troubleshooting

First, always ensure that the breaker and GFCI are not tripped, and that the power switch on the side of the unit is turned on.

If the boiler does not fire in response to a call for heat, the issue is likely related to an interlock or the ignition system. Verify that the low water sensor is reset; it can be tripped by air infiltration when the pump is stopped. Ensure that the pump is operating. Verify that the covers are securely fastened; a loose cover leaks air and may not close the air pressure switches. Finally, check for the presence of spark and/or pilot light. This is visible via a small window on the lower-left of the unit.

The automation system may provide some additional insight regarding a boiler fault state via the PLC Display. In the topics below, additional faults and possible remedies are explored.

Low Air Pressure

The Low Air Pressure switch closes when the positive air pressure differential formed in the combustion chamber meets a minimum threshold. Assuming the blower is operating, insufficient air pressure may be the result of:

• Excessive air leakage. Tighten enclosure bolts and an adequate seal is present. Sometimes, pushing on the boiler's combustion chamber enclosure panel may be enough to force marginal pressure over the threshold.
• Improper airflow adjustments. Consult a qualified technician; blower airflow may need to be adjusted.
• A failed air pressure switch, or an electrical issue. Repair may be necessary.

This fault may be identified by the boiler status indicated the LCD on the automation system PLC.

Natural Gas Odor

A natural gas odor may be observed when the flame sense module (FSM) has opened the pilot valve, but no spark is present. The pilot gas is flowing but has not ignited. In this case, it is likely that the ignition transformer has failed.

Turn off the boiler and contact a qualified technician.

Low Temperature Fault

A boiler controller Low Temperature Fault is often caused by one of the following:

• The recirculation valve is not in the optimal position and should be adjusted. Reasons the valve may need adjustment include:
  • A significant change in pool temperature. Early season operation (where the pool is significantly lower than 80 °F) will require the valve to be closed further.
  • A significant change in operating flow rate.
• The recirculation pump may not be operating. Verify that the pump is operating properly.

Theory of Operation

The operation sequence below is based upon the procedure described in the LCD Series manual, with adaptations per the installation wiring.

Stage 0: Water Level OK

The low-water cut-out disconnects power from the 75 VA control transformer in the boiler. This prevents boiler operation when a low water situation is encountered.

Stage A: Demand for Heat

A demand for heat occurs when all of the following conditions are met:

1. The boiler temperature controller low operator relay contact is closed, indicating that no faults are active.
2. The measured temperature (via the pool temperature controller) has dropped to the heat threshold, which closes the relay contact.
3. The normally-closed Boiler Disable relay contact (part of the pool automation system) is closed (relay not activated), permitting boiler operation (no fault observed).

NOTE: These three interlocks align with the LOW OPERATOR temperature switch from #11 to #13, REMOTE OPERATOR OPTION function from #13 to #14 and ENABLE RELAY OPTION from #14 to #15 in RBI drawing 42-2112. Connections at terminals #13 and #14 are no longer made within the boiler housing.

If all three interlocks are satisfied:

1. The automation system relay CR2110 is energized, which activates PLC input X10.

Stage B: Temperature and Water Flow OK

The temperature and water flow are deemed OK when:

1. The High Temp latching switch is not closed (in the Honeywell L4006E, with a reset pushbutton located on the front side of the boiler). This is a normally-closed switch; the switch is closed when the high-temperature latch is not set.
2. The Water Flow switch is closed, indicating that sufficient flow in the loop is present.

NOTE: These two interlocks align with the HIGH TEMP temperature switch from #15 to #17 and WATER FLOW switch from #18 to #21. JUMPER F is in place; the low-water cut-off interlock is located earlier in the chain.

If the High Temp interlock is satisfied:

1. The boiler time-delay relay TD4 (blower delay post-purge) is engaged, which immediately energizes contactor C1, turning on the boiler loop circulation pump. Activation of the pump should result in closure of the Water Flow switch.

If both the High Temp and Water Flow interlocks are satisfied:

1. The boiler time-delay relay TD3 (pump delay post-purge) is engaged, which immediately energizes contactor C2, turning on the blower motors (low speed).
2. The automation system relay CR2111 is energized, which activates PLC input X11.

Stage C: Low Air Pressure OK

The low air pressure switch closes in response to sufficient positive pressure in the combustion chamber.

Once the Low Air Pressure interlock is satisfied:

1. The boiler time-delay relay TD1 (blower delay pre-purge) is engaged.

NOTE: This interlock aligns with the LOW AIR PRESS switch from #22 to TD1 pin #1.

Once the TD1 delay has elapsed:

1. The flame sense module (FSM) is powered, which opens the pilot gas valve. Relay R7 is engaged, which powers the spark generator transformer.
2. The automation system relay CR2112 is energized, which activates PLC input X12.

NOTE: Flame fail/lockout is not considered here. The present flame sense module (FSM), or "intermittent pilot ignition" module, does not include alarm contacts (UTEC 1003-638A). The specified module, a UTEC 1003-61A is unavailable on the market at this time. The alarm contacts are required to engage R1, the flame fail/lockout relay. This is problematic, as it would allow the ignition transformer to spark indefinitely, eventually resulting in component failure. As a work-around, the automation system provides a monitored lockout function via the Boiler Disable relay.

Stage D: Main Gas Valve On

The main gas valve (also referred to as the "main valve" or MV) turns on (becomes active) when the flame sense module (FSM) confirms the presence of the pilot flame.

Once this has occurred:

1. Relay R8 is energized to disable the spark generator transformer.
2. The MAIN GAS indicator on the boiler is illuminated.
3. The automation system relay CR2113 is energized, which activates PLC input X13.
4. The relay in the pool temperature controller is energized, which provides confirmation that a request for heat has been satisfied.
5. The boiler temperature controller main valve active input (relay) is energized.

Stage E: Stage 2 Active

Description pending.

Summary of Control Interlocks

The list below includes interlocks with electrical interfaces only and is intended to align with the CSD-1. This table is for reference only; the CSD-1 should always be considered the master.

Control/Device	ANSI CSD-1 Reference(s)	Manufacturer	Model	Setpoint (align with CSD-1)
Low-Water [Fuel] Cutout	CW-110 CW-120 CW-150	ITT	PS-851-M-120	N/A (not adjustable)
Forced Circulation	CW-200 CW-210(b)	ITT	FS-251	N/A (not adjustable)
Water Temperature	CW-410(b)	Red Lion	T4820219	82 °F
High Water Temp Limit	CW-210(b)	Johnson Controls	CC450CCN-3	180 °F
Combustion Air Switch	CF-220	Cleveland Controls	AFS-1	0.5" WC
Purge Air Flow (Pre-Ignition)	CF-210	UTEC	1003-638A	30 seconds
Flame Safeguard (Primary)	CF-310 CF-320	UTEC	1003-638A	N/A (not adjustable)
Flame Detector (via RBI 3316-0327)	CF-310 CF-320	UTEC	1003-638A	12 µA

2021 Electrical Overhaul

The pre-overhaul boiler control wiring in May 2020.

In 2021, a significant effort was made to overhaul the wiring in the boiler. Observed issues included:

• A literal tangle of wires, many removed from the wire tracks and/or excessively long, arranged without an apparent effort towards neatness. It's really not clear how much of the wiring was installed at the factory this way, or how much of it was worsened by numerous service efforts throughout the years.
• Burned insulation on a few wires, presumably from a known overheating event that occurred shortly after installation.
• A wiring mistake (not consistent with the schematic).
• Use of aluminum MC conduit (outside of the unit) in a corrosive environment.
• A great deal of dirt accumulation throughout.

Debugging and servicing the unit were very difficult.

The overhauled boiler control wiring in May 2021.

The overhaul also resulted in a few additional changes:

• The Johnson Controls C450CCN-3 was moved to an external location for enhanced monitoring by a human operator.
• Relay coil taps were added to add monitoring of operating conditions by an external PLC. These connections are documented in the pool systems automation Boiler Auxiliary drawing.
• Re-routing of some electrical in new liquid-tight conduit.

Known Issues

The following issues are known as of September 2021.

Low-Water Cut-Off

The implementation of the low-water cut-off (LWCO) could potentially be improved. In the present design (as found in 2020, where the control transformer is cut off):

• The pump could theoretically continue to operate following a low-water trip per time delay relay TD4.
• The loss of control power prevents detection of a low-water condition by the PLC; the PLC does not even "see" a demand for heat when the cut-off is tripped.

Options to consider:

• The T7CS5D-24 relay in the LWCO is rated for a 12 A load at 120 VAC. Move T1 (C1 pin #4) from terminal 1 to the output of the LWCO. This would serve to immediately disconnect the pump upon low-water trip.
• Reconnect the control transformer to terminal 3 (per RBI drawings). Disconnect the LWCO relay contacts and remove the factory jumper from H to C (to confirm). Insert the LWCO contact between terminals 17 and 18 in the boiler (remove jumper "F" per RBI drawings).

Power Switch

The power switch does not disconnect the control transformer. This is fixed by reconnecting the control transformer to terminal 3 (as suggested above).