Process Boiler #2 Conductivity-Based Blowdown & Deaerator Settings
Measure Overview
This proposal would add the following requirements for all newly installed process steam boiler systems with capacities at or above 10 MMBtu/h:
- The boilers have an automatic surface blowdown controller that is programmed to be controlled by conductivity, and
- For systems that use the boiler steam header to pressurize the deaerator, the deaerator regulator pressure must be set at or under 5 pounds per square inch of gauge pressure (psig) and between 2 and 5 psig for boilers with tubes not rated for oxidizing conditions.
The requirement would apply to all sites with new process steam boilers, including replacement boilers and boilers in additions to existing facilities, with the following exceptions:
- systems with condensate return above 90% in new construction and additions where the boiler systems are contained in the addition.
- boilers with makeup water treated by a reverse osmosis (RO) system.
- boilers employing blowdown heat recovery.
This proposal would require updates to compliance documents and a verification of blowdown controls, deaerator control settings, and qualification for applicable exceptions by a field technician.
Boilers used in oilfield production and utility and municipal power generation are not expected to be within the scope of Title 24, Part 6.
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This measure page will be updated as the 2028 code cycle progresses. For questions or suggestions, submit feedback to [email protected]. Please include the measure name in the subject line.
View the Energy Commission's proceedings and available proposed code language by visiting their CEC 2028 Proceedings Website page.
Scope of Proposed Code Change
| Building Type(s) | Construction Type(s) | Type of Change | Updates to Compliance Software | Third Party Verification |
| Nonresidential | New construction, additions, alterations | Mandatory | No updates | Add new verification requirements |
Justification for Proposed Change
High conductivity in boiler water indicates high mineral content, which leads to fouling of the boiler heat exchanger tubes, increased thermal stress, and lower boiler efficiency. In addition, high dissolved solids concentrations can lead to foaming and carryover of boiler water into the steam, which can foul downstream components, trigger water hammer, and accelerate system wear and tear. To limit the levels of suspended and dissolved solids in steam boilers, water is periodically or continuously discharged or “blown down.” This surface blowdown removes dissolved solids that accumulate near the surface of the boiler water.
Given that blowdown discharges hot water, it also results in fuel, water, and chemical losses. Manual boiler blowdown is typically excessive, resulting in unnecessary losses. Automatic blowdown systems avoid excessive blowdown by monitoring and maintaining water conductivity within manufacturer-specified setpoints. This eliminates the need for operators to make manual valve adjustments and offers the following benefits:
- Fuel, water, and chemical savings
- Improved conductivity control which can extend boiler useful life and slow efficiency degradation
A deaerator is a pressurized vessel that removes dissolved air from steam boiler feedwater to protect the system from corrosion and ensure high heat transfer rates. Deaerators heat the feedwater to temperatures that release the dissolved gases (mainly O2 and CO2) from the water and are present in nearly all large boiler systems. At higher pressures, water boils at a higher temperature, so higher pressure setpoints heat the feedwater to higher temperatures, using more energy. As pressures increase, more dissolved gases are removed. A higher deaerator pressure provides a greater margin of assurance for removing dissolved gases but also results in greater steam losses.
Deaerators are commonly operated at pressures that are higher than necessary. Overpressurization leads to excess venting, and underpressurization can lead to insufficient air removal, which can lead to oxygen pitting and corrosion on contact surfaces. Ensuring proper deaerator pressurization saves energy and has no additional cost for end users.
Preliminary statewide natural gas savings from an automatic blowdown requirement are estimated at 0.47 million therms per year. Preliminary savings calculations and assumptions can be found in the blowdown and deaerator pressure savings calculations document. In addition to the energy benefits, these practices would reduce local photochemical smog and improve air quality. The value of improved air quality is amplified by the consideration that many industrial facilities are located near Low- and Moderate-Income (LMI) housing, which is disproportionately exposed to lower air quality.
Relevant Documents
Round One Utility-Sponsored Stakeholder Meeting Materials
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The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.