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

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 is satisfied when all of the following conditions are met:

1. The measured temperature (via the pool temperature controller) has reached or fallen below the heat threshold.
2. The normally closed (NC) Boiler Disable relay contact (part of the pool automation system) is closed, indicating that no fault is observed.
3. The boiler temperature controller low operator relay contact is closed, indicating that no faults are active.

At this point:

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

Stage B: Flow/Temperature Interlocks

The following interlocks must be satisfied to proceed:

1. The High Temp latch is not set (in the Honeywell L4006E, with a reset pushbutton located on the front side of the boiler).
2. The Water Flow switch is tripped, indicating that sufficient flow in the loop is present.

At this point:

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

Description pending.

Stage D

Description pending.

Stage E

Description pending.

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

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.

Adjustments

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 during filter back-washing. 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 flame sensor unit is a consumable item and may need to be replaced at a regular interval (every two years?). If the pilot valve (PV) is open, but the main valve (MV) never opens, it is likely that adequate flame is not being detected. This can be verified by measuring the microamp current output of the flame sensor and should be done by 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.

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).