Table of contents
- Understanding Apollo Pressure Relief Valve BTU Ratings
- How to Calculate the Required BTU Rating for a Pressure Relief Valve
- Key Factors to Consider When Selecting an Apollo Pressure Relief Valve
- Common Apollo Pressure Relief Valve Sizing Mistakes to Avoid
- Apollo Pressure Relief Valve Sizing Example
- Apollo Pressure Relief Valve Maintenance and Inspection Tips
- How Control Specialties Helps Select the Right Apollo Pressure Relief Valve
- Frequently Asked Questions (FAQs)
Not all pressure relief valves with the same pressure rating provide the same level of protection. The key difference is often their BTU/hr capacity, which determines whether a valve can safely relieve excess heat during an overpressure event.
Proper valve sizing depends on your equipment's maximum heat input, operating pressure, and the valve's certified relief capacity. An undersized Apollo pressure relief valve may open at the correct set pressure but still fail to discharge heat quickly enough, increasing the risk of equipment damage, safety hazards, and code compliance issues.
For boilers, water heaters, and other heating equipment whose relief requirements are expressed in BTU/hr, pressure setting alone doesn't establish adequate protection. The selected valve must also provide certified relieving capacity equal to or greater than the equipment's required heat input while matching the correct service, temperature, connections, and certification.
This guide shows how to match your system's BTU rating to the right valve, avoid common sizing mistakes, and understand the key factors that influence proper relief valve selection.
Understanding Apollo Pressure Relief Valve BTU Ratings
A pressure relief valve's performance depends on more than its pressure setting. Its BTU/hr rating determines whether it can safely discharge the heat energy generated by your system.
What Does a BTU/hr Rating Mean?
A BTU/hr (British Thermal Units per hour) rating indicates the maximum amount of heat energy a pressure relief valve can safely discharge during an overpressure event. For boilers, water heaters, and hydronic heating systems, this rating determines whether the valve can relieve heat quickly enough to prevent excessive pressure buildup.
It's important not to confuse BTU capacity with the valve's pressure rating. The pressure rating specifies the PSI at which the valve opens, while the BTU rating defines how much heat energy it can safely relieve.
Even if a valve has the correct pressure setting, insufficient BTU capacity can leave the system inadequately protected.
Why BTU Capacity Matters
Heating equipment continuously adds energy to the system. If a control component, such as an aquastat or high-limit control, fails, pressure can rise rapidly as heat continues to build.
To maintain safe operating conditions, the relief valve must discharge fluid at a rate equal to or greater than the system's maximum heat input. Proper BTU sizing helps:
- Protect boilers, water heaters, and piping from overpressure.
- Maintain compliance with ASME and local safety codes.
- Reduce the risk of equipment damage and unplanned downtime.
- Improve long-term system reliability.
Apollo Pressure Relief Valve Capacity Certifications
An Apollo Pressure Relief Valve, manufactured by Conbraco, is certified to recognized industry standards, giving engineers confidence that its published relief capacity meets established safety and performance requirements.
Key certifications include:
- ASME Section IV Certification: Verifies the valve's certified relieving capacity for low-pressure heating boilers and hot water heating systems.
- CSA Capacity Certification: Confirms that the valve has been independently tested to meet certified discharge capacity requirements.
- Factory-Tested Performance: Applicable Apollo valve models are manufactured and tested according to the certification and performance requirements associated with the selected product and service.
Certified BTU capacity is determined by the valve's model, orifice size, and pressure setting. Two valves with similar connection sizes or appearances can have very different certified relieving capacities.
Because of these differences, engineers evaluate safety devices based on certified performance data rather than physical dimensions alone. They also consider complementary equipment, such as Industrial Control Valves, to ensure the entire pressure control system operates safely and efficiently.
How to Calculate the Required BTU Rating for a Pressure Relief Valve
Proper relief valve sizing involves more than matching the system pressure. To ensure safe operation and code compliance, the valve's certified BTU capacity must equal or exceed your equipment's maximum heat input.
Step 1: Identify the Equipment's Heat Input
Start by locating the equipment's BTU/hr input rating on the manufacturer's nameplate or technical documentation. This value represents the maximum heat energy the system can generate and serves as the minimum certified capacity required for the relief valve.
Common equipment includes:
- Boilers
- Water heaters
- Hydronic heating systems
For example:
A boiler rated at 500,000 BTU/hr requires a valve with a certified capacity of at least 500,000 BTU/hr, provided the valve also meets all pressure, service, connection, and certification requirements.
Step 2: Verify the Required Pressure Setting
Next, confirm the valve's set pressure based on your equipment and system specifications. Consider:
- Maximum Allowable Working Pressure (MAWP)
- Normal operating pressure
- Equipment manufacturer's recommendations
An incorrect pressure setting can create operational issues, even when the BTU capacity is correct.
- Set Pressure too Low: Frequent nuisance discharge and unnecessary downtime.
- Set Pressure too High: Reduces safety margin and increases the risk of excessive system pressure.
Some steam systems also use a Back Pressure Regulating Valve to maintain stable upstream pressure. While it doesn't replace a pressure relief valve, it helps improve overall pressure control throughout the system.
Step 3: Compare Your Requirements With Apollo Valve Specifications
Once you've determined the required BTU capacity and pressure setting, compare them with the certified specifications of the Apollo pressure relief valve being considered.
| System Requirement | Apollo Valve Specification |
|---|---|
| Equipment BTU/hr Input | Certified BTU Capacity |
| System Pressure | Valve Set Pressure |
| Pipe Connection Size | Inlet and Outlet Connection Size |
| Equipment Application | Appropriate Apollo Valve Series |
Because Apollo valves are available in multiple sizes, pressure settings, and certified capacities, always verify the manufacturer's published capacity chart for the exact model. Certified performance data, not valve size alone, determines the correct selection.
For systems that also require accurate pressure reduction, products such as the Fisher 627 Regulator can be integrated to maintain consistent downstream pressure.
Key Factors to Consider When Selecting an Apollo Pressure Relief Valve
Selecting the right Apollo pressure relief valve involves more than matching pressure and connection size. Evaluating the following factors helps ensure reliable overpressure protection, regulatory compliance, and long-term system performance.
1. Equipment Type and Application
The valve must be suitable for the specific equipment it protects, whether it's a hot-water boiler, steam boiler, water heater, or hydronic heating system. Different applications have different certification and performance requirements, so using a valve designed for the intended service is essential.
Even if your system uses Honeywell Pressuretrol Controllers to regulate normal steam pressure, those controls are not a substitute for a properly sized pressure relief valve. The relief valve serves as the final layer of protection if a pressure control or safety device fails.
2. Valve Set Pressure
The valve's set pressure should match the equipment manufacturer's specifications and never exceed the Maximum Allowable Working Pressure (MAWP) of the protected equipment.
When determining the correct setting, consider:
- Maximum Allowable Working Pressure (MAWP)
- Normal operating pressure
- Manufacturer recommendations
- Applicable safety codes
A pressure setting that's too low may cause frequent nuisance discharge, while one that's too high can delay pressure relief during an emergency, increasing the risk of equipment damage.
3. Certified BTU Capacity
A relief valve is only effective if it can discharge heat as quickly as the equipment generates it. That's why the valve's certified BTU capacity must always equal or exceed the equipment's maximum heat input.
Follow these best practices:
- Match or exceed the equipment's BTU/hr rating.
- Verify the certified capacity from the manufacturer's published data.
- Compare capacity ratings for the exact valve model and pressure setting.
- Don't assume a larger valve automatically provides greater relieving capacity.
Since Conbraco manufactures Apollo relief valves under recognized industry standards, engineers can rely on certified performance data instead of estimating capacity based on valve size alone.
4. Connection Size and Installation
Correct installation is critical to ensuring the valve performs as intended during an overpressure event. Inlet and outlet connections should match the system piping, and discharge piping should be properly routed to prevent flow restrictions.
For reliable operation, make sure:
- Inlet and outlet connections match the piping system.
- Discharge piping directs fluid to a safe location.
- The valve is installed in an accessible location for inspection and testing.
- Installation follows applicable code and manufacturer guidelines.
Like other industrial control valves, pressure relief valves should be inspected and tested periodically to confirm continued performance.
5. Temperature and Fluid Compatibility
The valve materials must be compatible with the system's operating temperature and the type of fluid being handled. Poor water quality, corrosion, sediment, and scale can reduce valve performance and shorten service life.
If the system contains debris or suspended solids, installing a Thompson Strainer upstream helps prevent contaminants from reaching the valve, reducing wear and supporting more reliable long-term operation.
Common Apollo Pressure Relief Valve Sizing Mistakes to Avoid
Proper relief valve sizing is essential for protecting equipment and maintaining code compliance. Avoiding these common mistakes can help ensure your Apollo Pressure Relief Valve delivers reliable performance when your system needs it most.
1. Selecting a Valve Based Only on Pipe Size
A larger pipe connection doesn't necessarily provide a higher relieving capacity. Two valves with identical inlet and outlet sizes can have significantly different certified BTU ratings depending on their model, orifice size, and pressure setting.
Best Practice: Always verify the manufacturer's certified capacity chart instead of relying on connection size alone. This is especially important when comparing different Industrial Control Valves or relief valve models.
2. Ignoring the Equipment's BTU Input
A valve that fits the piping may still be undersized for the application. If its certified BTU capacity is lower than the equipment's maximum heat input, it may not relieve pressure quickly enough during an overpressure event.
Best Practice: Confirm the equipment's BTU/hr rating from the manufacturer's nameplate and choose a relief valve with a certified capacity that meets or exceeds that requirement.
3. Confusing Pressure Rating With BTU Capacity
Although closely related, pressure rating and BTU capacity serve different purposes. The pressure rating determines when the valve opens, while the BTU/hr rating determines how much heat energy it can safely discharge after opening.
Whether you're selecting an Apollo valve or a Kunkle Safety Relief Valve, both specifications must be evaluated independently to ensure adequate protection.
Best Practice: Verify both the valve's set pressure and certified BTU capacity against the equipment specifications before finalizing your selection.
4. Replacing a Valve Without Verifying Specifications
Replacing a pressure relief valve based solely on its physical dimensions can lead to performance and safety issues. Even if two valves have the same connection size, they may differ in certified capacity, pressure setting, or application approval.
Before ordering a replacement, verify:
- Valve model number
- Certified BTU capacity
- Set pressure
- Connection size
- Required certifications
- Intended application
This same approach applies when specifying products such as Velan Valves, where certified performance, not appearance, determines compatibility.
Best Practice: Always cross-reference the replacement valve with the original manufacturer's specifications to ensure it meets the same pressure, capacity, certification, and application requirements.
Apollo Pressure Relief Valve Sizing Example
The following example demonstrates how to apply the sizing process to a commercial boiler.
System Details
| Parameter | Value |
|---|---|
| Boiler Heat Input | 750,000 BTU/hr |
| Required Relief Pressure | 125psi |
Valve Selection Process
Step 1: Identify the equipment's maximum heat input (750,000 BTU/hr).
Step 2: Select an Apollo Pressure Relief Valve with a certified BTU capacity that meets or exceeds this value.
Step 3: Confirm the valve's set pressure is 125psi.
Step 4: Verify the appropriate connection size and required certification (ASME Section IV or CSA, depending on the application). Verify the exact certification and code marking required for the boiler, water heater, jurisdiction, and selected valve model.
Result
By matching the valve's certified BTU capacity and pressure setting to the equipment requirements, the system receives reliable overpressure protection while maintaining code compliance.
Apollo valves should be selected using the certified data, service approvals, pressure settings, and capacity ratings published for the exact model for demanding heating applications.
Apollo Pressure Relief Valve Maintenance and Inspection Tips
Even a correctly sized relief valve requires routine maintenance to ensure dependable performance throughout its service life.
Recommended Maintenance Checklist for Apollo Pressure Relief Valves
- Inspect the valve regularly for corrosion, leakage, or physical damage.
- Check for seat leakage that may indicate wear or debris contamination.
- Test the valve according to the manufacturer's recommendations and applicable safety codes.
- Replace damaged or heavily corroded valves instead of attempting field repairs.
- Ensure discharge piping remains clear of obstructions and unauthorized modifications.
Routine maintenance should extend beyond the relief valve itself. Installing a Thompson Strainer upstream can help minimize sediment and debris that may affect valve performance.
Likewise, facilities should inspect the Steam-Operated Condensate Pump during scheduled maintenance to help maintain clean boiler water, improve system efficiency, and support long-term reliability.
How Control Specialties Helps Select the Right Apollo Pressure Relief Valve
Selecting the right Apollo Pressure Relief Valve involves more than matching a connection size or pressure setting. It requires evaluating your equipment's BTU input, operating pressure, application requirements, and applicable code standards to ensure reliable overpressure protection.
Control Specialties, an industrial equipment supplier, works with engineers, contractors, OEMs, and maintenance teams to recommend pressure relief valves that align with the specific demands of each heating or steam system. Whether you're replacing an existing valve, upgrading aging equipment, or specifying components for a new installation, our technical team can help identify the appropriate valve based on certified capacity, set pressure, and system conditions.
Beyond Apollo pressure relief valves, Control Specialties offers a comprehensive range of steam and process control solutions for facilities where electrical power is limited or unavailable, including:
- Fisher Control Valves
- Fisher MR95/MR98 Regulators
- Fisher 1301F-2 Regulators
- Honeywell Pressuretrol
- Steam-Operated condensate pump
Sourcing these components from a single supplier simplifies procurement while helping ensure compatibility across your steam and hot water systems.
Do you need help selecting the correct Apollo Pressure Relief Valve? Contact Control Specialties for expert assistance with valve sizing, certified capacity verification, replacement recommendations, and application-specific guidance to help keep your heating system operating safely and reliably.
Frequently Asked Questions (FAQs)
Can I replace an Apollo pressure relief valve with a different brand?
Yes. Provided the replacement valve has the same set pressure, certified relieving capacity (BTU rating), connection size, temperature rating, and required certifications for your application. Always verify compatibility with your equipment specifications before making a substitution.
What information do I need before ordering an Apollo Pressure Relief Valve?
To select the correct valve, have your equipment's BTU input, maximum allowable working pressure (MAWP), required set pressure, connection size, application type (boiler or water heater), and the existing valve model number if you're replacing one.
Does every boiler require an ASME-certified pressure relief valve?
Most commercial and residential boilers installed under applicable codes require an ASME-certified pressure relief valve that meets the equipment manufacturer's specifications. Using a properly certified valve helps ensure regulatory compliance and reliable overpressure protection.
When should an Apollo Pressure Relief Valve be replaced instead of repaired?
Replacement is generally recommended if the valve shows visible corrosion, leakage after reseating, physical damage, failed testing, or no longer meets the system's pressure or BTU capacity requirements. Installing a new, properly sized valve helps maintain safe system operation.
Can Control Specialties help verify the correct Apollo Pressure Relief Valve for my application?
Yes. Control Specialties can help you identify the appropriate Apollo Pressure Relief Valve by reviewing your system's BTU input, operating pressure, application requirements, and existing valve specifications, ensuring you receive a solution that meets both performance and safety requirements.
Can I install a valve with a higher BTU rating?
Yes. A pressure relief valve can have a higher BTU rating than your boiler's heat input, provided it has the correct set pressure, connection size, and required certifications. However, always follow the equipment manufacturer's recommendations and applicable code requirements.
Where can I find the boiler's BTU rating?
The boiler's BTU rating is typically listed on the manufacturer's nameplate, equipment data label, or product specification sheet. You can also find it in the installation manual or by contacting the manufacturer if the information is unavailable.
