Pool Boiler Temperature Controller: Difference between revisions
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== Overview == | == Overview == | ||
The boiler temperature controller | The boiler temperature controller ensures that the [[Pool Boiler|pool boiler]] internally operates at an optimal temperature. It does so by providing [[#Low Operator|Low Operator]] and [[#High Operator|High Operator]] interlocks. | ||
This controller does not manage the pool temperature. That functionality is handled by the [[Pool Temperature Controller]]. | |||
In the system, a circulation pump (shown in the <b>Boiler Loop</b> section on page 2 of the [[Process Flow Diagram]]) force-returns some amount of hot water from the boiler outlet to the inlet. This helps to maintain an elevated operating temperature (i.e.. 120 °F or greater), reducing the risk of condensation forming on the heat exchanger that can cause damage over time. Unfortunately, various factors may prevent the circulation pump from maintaining the proper temperature such as improper valve settings, trapped air, or pump failure. Air may be regularly introduced into the system while [[Cleaning the Strainer Basket|cleaning the strainer basket]] or [[Backwashing|backwashing the filters]] may cause the pump to operate improperly. The boiler temperature controller in place prior to 2022, a Johnson Controls C450CCN-3, did not detect low-temperature operation. | |||
The | The controller cannot resolve fault conditions. Instead, it notifies the operator of a fault condition, which usually requires manual intervention. | ||
The design has the following key principles: | |||
* The controller functionality shall help improve boiler function and longevity without adding unnecessary complexity. | |||
* The core function (temperature control) shall be performed by a proven, durable controller. In this case, a Euroterm 3508 was chosen due to its enhanced logic control capabilities. | |||
* The [[Pool_Systems_Automation|automation system]] shall not be required for operation. Failure of other components should have minimal impact upon its operation. | |||
While the automation system is not required, it will have a communication link to the controller for monitoring purposes. | |||
== User's Guide == | == User's Guide == | ||
TBD. | === LCD Display === | ||
An LCD display on the front of the controller indicates the measured temperature of the boiler manifold (top-most value). A graphical bar shows the value relative to the typical minimum and maximum operating bounds. Temperature thresholds for a [[#Low Temperature Fault|Low Temperature Fault]], [[#Stage 2|Stage 2]] operation, and a [[#High Temperature Fault|High Temperature Fault]] are displayed on the subsequent lines. All temperatures are displayed in degrees Fahrenheit. | |||
The <tt>OP1</tt> and <tt>OP2</tt> indicators (beacons) indicate that [[#Stage 1|Stage 1]] and/or [[#Stage 2|Stage 2]] operation is active, respectively. An <tt>ALM</tt> indicator is associated with a fault condition; user intervention may be required to restore boiler operation. Blinking <tt>H</tt> and/or <tt>J</tt> indicators indicate communication port activity. | |||
=== Stage Monitoring === | |||
At this time, no feedback is provided to the temperature controller to verify which stages are active; external conditions/faults may prevent firing stages. See [[Pool_Boiler#Operation|Pool Boiler Operation]] for further details on how the controller contributes to the boiler interlocks. | |||
=== Operating States === | |||
The simulated screen captures below show various operating conditions that the user may encounter. The measured temperature and thresholds shown may vary. | |||
<gallery> | |||
File:Boiler TC - Normal Operation.png|Normal Operation | |||
File:Boiler TC - No Stage 2.png|No Stage 2 | |||
File:Boiler TC - Boiler Fault.png|Boiler Fault | |||
File:Boiler TC - Low Temp Fault.png|Low Temperature Fault | |||
File:Boiler TC - High Temp Fault.png|High Temperature Fault | |||
</gallery> | |||
==== Normal Operation ==== | |||
During normal operation, no user intervention is required. Both [[#Stage 1|Stage 1]] and [[#Stage 2|Stage 2]] heating is enabled. | |||
==== No Stage 2 ==== | |||
The boiler temperature is greater than the [[#Stage 2|Stage 2]] threshold, and [[#Stage 2| Stage 2]] is disabled as a result. This is not a fault condition, though it may indicate sub-optimal operation. Only [[#Stage 1|Stage 1]] heating is enabled. | |||
The [[#Stage 2| Stage 2]] threshold is the temperature value to the right of the <tt>Stg2</tt> identifier on the display, and should typically be set to <span style="background:yellow">TBD</span>. To adjust this threshold, see the [[#Threshold Adjustment|Threshold Adjustment]] section below. | |||
If this state is active, [[Pool_Boiler#Recirculation_Valve|adjustment of the recirculation valve position]] should be considered. Since operating only in [[#Stage 1| Stage 1]] produces less heat, the ability to heat the pool is reduced. This is primarily an issue where the amount of heat loss in the pool exceeds the capability of [[#Stage 1| Stage 1]] heating (i.e. the pool cools faster than it can be heated). | |||
==== Boiler Fault ==== | |||
The boiler has not fired [[#Stage 1|Stage 1]] is response to a <b>Call for Heat</b>. This is an informational fault only; it does not disable either stage. This fault is only applicable if the <b>Call for Heat</b> signal is wired to the controller. | |||
==== Low Temperature Fault ==== | |||
The boiler temperature is less than the low temperature threshold and both stages are disabled as a result. The low-temperature threshold should typically be set to <span style="background:yellow">TBD</span>. This is a latching fault and must be cleared via the front panel before the boiler will operate. | |||
Before attempting to clear the fault, the source of the fault should be cleared. See the [[Pool_Boiler#Low_Temperature_Fault|Pool Boiler Low Temperature Fault]] section for further information ([[Pool_Boiler#Recirculation_Valve|recirculation valve adjustment]] may be needed). | |||
==== High Temperature Fault ==== | |||
The boiler temperature is greater than the high-temperature threshold and both stages are disabled as a result. The high temperature threshold should typically be set to <span style="background:yellow">TBD</span>. This is a latching fault and must be cleared via the front panel before the boiler will operate. | |||
=== Threshold Adjustment === | |||
Threshold adjustment is typically not necessary or recommended. Instead, it is recommended that the system be evaluated for deficiencies. | |||
If a parameter must be adjusted, press the scroll button (left of the down arrow) to move the up/down cursor to the desired parameter. Press the up/down keys to adjust the temperature. Internal bounds limit how high or low a parameter may be adjusted. Use extreme caution in adjusting each parameter, as each could have significant impacts upon boiler operation. | |||
=== Other Buttons === | |||
The "A/MAN" and "RUN/HOLD" buttons are not presently active. Pressing either button has no effect upon operation. | |||
== Theory of Operation == | == Theory of Operation == | ||
| Line 30: | Line 87: | ||
=== Low Operator === | === Low Operator === | ||
The low operator is activated when the following conditions are true: | The low operator is activated (the relay contact is closed) when the following conditions are true: | ||
* The RTD is producing valid feedback (not shorted or open-circuit). | * The RTD is producing valid feedback (not shorted or open-circuit). | ||
* The boiler temperature is below the | * The boiler temperature is below the high temperature fault threshold (timing rules apply). | ||
The low operator may be released when any of the prior conditions are no longer met. In addition, it may be released when: | The low operator may be released when any of the prior conditions are no longer met. In addition, it may be released when: | ||
| Line 48: | Line 104: | ||
=== High Operator === | === High Operator === | ||
The high operator is activated when the following conditions are true: | The high operator is activated (the relay contact is closed) when the following conditions are true: | ||
* All conditions for the low operator are met | * All conditions for the [[#Low Operator|low operator]] are met. | ||
* The boiler temperature is below the second stage threshold (timing rules apply). | * The boiler temperature is below the second stage threshold (timing rules apply). | ||
== | == Controller Hardware == | ||
=== As-Shipped Configuration === | |||
When shipped from the factory, a long configuration code is printed on the side of the controller to identify the configuration. The code on the installed controller is decoded below: | |||
{| class="wikitable" | {| class="wikitable" | ||
| Line 111: | Line 168: | ||
|LO | |LO | ||
|Isolated Single Logic Output | |Isolated Single Logic Output | ||
| | |May not be used. | ||
|- | |- | ||
!IO Slot 2 | !IO Slot 2 | ||
|D4 | |D4 | ||
|DC Control | |DC Control | ||
|Will not be used. | |Will not be used; see modifications below. | ||
|- | |- | ||
!IO Slot 3 | !IO Slot 3 | ||
|TK | |TK | ||
|Triple Contact Input | |Triple Contact Input | ||
| | |May not be used. | ||
|- | |- | ||
!H Comms Slot | !H Comms Slot | ||
|PD | |PD | ||
|Profibus with D-type Connector | |Profibus with D-type Connector | ||
|Module is an AH026222U002. | |Module is an AH026222U002 (visually identified). | ||
|- | |- | ||
!J Comms Slot | !J Comms Slot | ||
| Line 230: | Line 287: | ||
|- | |- | ||
|Lgc2 2 | |Lgc2 2 | ||
|Logically ORs the | |Logically ORs the output of <b>Lgc8 1</b> and the control loop output to produce a Stage 2 control signal. | ||
|- | |- | ||
|Lgc2 4 | |Lgc2 4 | ||
| Line 236: | Line 293: | ||
|- | |- | ||
|Lgc8 1 | |Lgc8 1 | ||
|Logically ORs four inputs, all inverted, from <b>Alarm 1</b>, <b>Alarm 2</b>, <b>DigAlarm 2</b> and the signal break output (<b>SBrkOut<b>) from <b>IO.PV</b>. The output is active unless any of the alarms are triggered or signal break is active. Essentially inhibits operation of Stage 1 and Stage 2 in the event of a fault condition. | |Logically ORs four inputs, all inverted, from <b>Alarm 1</b>, <b>Alarm 2</b>, <b>DigAlarm 2</b> and the signal break output (<b>SBrkOut</b>) from <b>IO.PV</b>. The output is active unless any of the alarms are triggered or signal break is active. Essentially inhibits operation of Stage 1 and Stage 2 in the event of a fault condition. | ||
|- | |||
|Loop 1 | |Loop 1 | ||
|Operates an on-off control loop with a setpoint (Stage 2, displayed on the controller as "Stg2") and feedback via the conditioned RTD measurement. | |Operates an on-off control loop with a setpoint (Stage 2, displayed on the controller as "Stg2") and feedback via the conditioned RTD measurement. | ||
| Line 247: | Line 305: | ||
|} | |} | ||
== Definitions == | |||
=== Stage 1 === | |||
The term "Stage" refers to the amount of heat that the boiler is requested to produce. During "Stage 1", only the lower-output burners are active. | |||
=== Stage 2 === | |||
During "Stage 2", both the lower-output and higher-output burners are active. The maximum amount of heating is occurring. | |||