Bladder-Type and Steel Expansion Tank Types for Boilers and Chilled Water Systems

Types of Expansion Tanks for Boilers and Chilled Water Systems

There are basically two types of expansion tanks used in HVAC and plumbing applications that you will find on any given type of closed loop HVAC system including boilers and chilled water systems. These expansion tanks can also be found on hot water heating systems and closed loop pumping systems. There is the bladder-type and the steel type expansion are the two types of expansion tank used in HVAC today. It is difficult to say which is more common but most modern boiler systems use the bladder-type expansion tanks while the steel expansion tanks can be found on many older models and some modern systems.

Bladder-Type Expansion Tank

Bladder-type expansion tank

The bladder-type expansion tank is commonly used in modern boiler and chilled water HVAC systems including some plumbing applications for hot water heating. The bladder-type expansion tank has a rubber membrane inside it that separates water (or fluid) from air. The rubber membrane expands and contracts as the water in the loop expands and contracts when the temperature of the water changes. The air side of the bladder-type expansion tank is pressurized with air and the pressure on the air side of the tank will depend on the many factors including loop size and capacity, system rated pressure, and high and low operating temperatures of the system. The average residential boiler system is typically set at 12 PSI but the pressure on the air side of the bladder type expansion will vary from system to system as stated above.

Steel Expansion Tank

The steel type expansion is commonly used on many older boiler systems and is slowly being replaced as the boilers are being replaced. When some older boiler systems are replaced the HVAC contractor may use the old steel expansion when the boiler system is replaced but that will depend on the type of modern boiler system used to replace the old boiler and the boiler manufacturers installation requirements.

Airtrol Valve on the Bottom of a Steel Expansion Tank

A steel type expansion is simply a cylindrical tank and can be found above the boiler with the piping from the boiler loop running to the expansion. The steel type expansion tank can be found just above the boiler attached to the wall or ceiling or even in the attic. A steel expansion tank does not have a rubber membrane but instead the fluid (typically water) is in direct contact with the air inside the tank. Usually the air to water level inside the tank is 2/3rds water to 1/3rd air. In most steel expansion tanks a special valve is used to make sure the air to water level inside the steel expansion tank is correct. It is a manual valve called an airtrol valve. From time to time the valve must be bled to maintain the appropriate level of water.

Bladder-Type and Steel Expansion Tank for Boilers and Chilled Water Systems

Boilers and Expansion Tanks – Types – Sizing & Troubleshooting Basics – Hydronics

The Basics for Closed Loop Hydronic Systems

Expansion Tanks on Hot Water Heaters

Boilers need expansion tanks to function properly. Expansion tanks can be found on boiler systems, chilled water systems, hot water heating systems, and even on pumping systems with closed loops.

Why do these various systems need expansion tanks and what do they have in common?

Each of these systems including the boiler system have fluid (usually water) inside of a closed loop. The fluid inside the closed loop will expand and contract as the temperature of the water changes up and down. When the water expands it needs a place to go to prevent over-pressurization of the loop system which will only function properly between a certain range of pressures in the various system. The expansion tank allows the water to expand and contract within the operating range of the particular system the expansion is serving.

Any expansion used for domestic water use needs to be rated for domestic water use as it is important to keep the water safe if it is intended to be consumed or if there is a possibility it will be consumed.

Expansion Tanks Basics

Sunday, 15 January 2012 21:25 Last Updated on Monday, 16 January 2012 01:05 0 Comments

Troubleshooting an Electronic Ignition Gas Furnaces – Repair Basics

Troubleshooting an Electronic Ignition Gas Furnace Reapir Basics

Electronic Control Board for an Electronic Ignition Gas Furnace

Electronic ignition for gas furnaces is the modern way for furnaces to light the main burners on modern gas furnaces. Electronic ignition gas furnace technology has evolved from the standing pilot gas furnace ignition systems that continue to be used today however there are less and less standing pilot gas furnaces used today. If your furnace is not working and you want to troubleshoot an electronic ignition gas furnace system it is important to make sure you know which type of ignition system you have for your furnace. Additionally there are different types of electronic ignition gas furnace systems and it is important to differentiate between the types of electronic ignition systems before repairing an gas furnace electronic ignition. We will break it all down for you in this series article.

Most of the major brands for HVAC equipment produce electronic ignition systems for their furnaces or they use a popular recognized brand of electronic ignition such as White-Rodgers, Honeywell, HeatCraft, or Fenwal controls. With any type of mechanical equipment always follow the manufacturers instructions and all safety guidelines and practices including common sense. Even for HVAC technicians repair of HVAC equipment can be frustrating at times to if you are a DIY you may consider calling in a professional. When you are dealing with furnaces safety is very important especially when dealing combustible gases. Be very careful always use common sense and safety first.

If you have a standing pilot gas furnace it is likely an older furnace and this article will not apply to you. The quickest to tell between a standing pilot gas furnace and a modern electronic ignition gas furnace is to look at the gas valve. A valve for a standing pilot furnace will have three settings on the valve knob. Off – On – Light are the three settings where the “Light” is the setting on a standing pilot valve to light the pilot light. An electronic ignition gas valve will only have 2 settings – Off and On. The electronic ignition furnace is basically an automatic ignition furnace whereas the standing pilot furnace, which lights the main burners automatically, requires the pilot light to be lit before the main burners will fire. Lighting the pilot for a standing pilot system is a manual operation while the electronic ignition furnace is completely automatic. If you have the standing pilot furnace then this article is not for you. Please check back later for an updated article on standing pilot furnaces. Understanding this difference between the two different systems is important as you must troubleshoot the correct system.

Sunday, 15 January 2012 17:53 Last Updated on Sunday, 15 January 2012 20:07 0 Comments

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