Category Archives: Commercial HVAC

How Does an Expansion Tank Work? HVAC Hydronics

how does an expansion tank works.

The difference between a steel expansion tank and a bladder type expansion tank.

Expansion Tank Basics – Types

What is an expansion and how does it work? I get that question all the time even though I have written an extensive article on expansion tanks.  The two most common expansion tanks you will see in HVAC applications include the bladder type expansion tank and the steel type expansion tank.  The steel type expansion tank needs some basic maintenance from time to time to ensure it doesn’t become waterlogged or overfilled which would defeat the purpose of having an expansion tank. For more on the basic maintenance of a steel expansion tank and how to properly fill it check out this article.

How Does an Expansion Tank Work

How does an expansion tank work and why do you need one in your boiler or chilled water system? If you have a hot water boiler system (not a low pressure steam boiler – there is a huge difference between the two) or a chilled water system (not many chilled water systems in residential but I have seen them) then you have a closed loop piping system that runs to either convectors, radiators, or a coil or two somewhere in the system where the main heat exchange process takes place. Inside this piping is water (sometimes a water/glycol mix but that is mainly in commercial applications) and when water heats and cools down it expands and contracts. The piping system along with the parts of the boiler or chiller that have water cannot handle this expansion and contraction with breaking or busting open. Therefore in every hydronic system there is an expansion tank to handle this expansion and contraction. An expansion tank is basically a shock absorber that absorbs this expansion and contraction of the volume of the water.

High Performance HVAC Air Conditioning and Heating Systems

How Does an Expansion Tank Work


Replace Air Conditioner Compressor | HVAC Refrigeration

Replace Air Conditioner Compressor Decision | HVAC Refrigeration Question

Replace Air Conditioner Compressor | HVAC Refrigeration – Question – Richard – I am an HVAC technician and have read all of your articles on refrigeration and compressors. Great information and it has helped to hone my skills and offer better service for my customers. Thanks! I was wondering what your experience is with replacing compressors. How do you arrive at the decision to replace a compressor technically speaking of course? I look forward to reading your answer. Brett

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Unit Heater Mechanical Room Equipment Protection

Unit Heater Mechanical Room

How Water Unit Heater in a mechanical room

Unit Heater Mechanical Room Equipment Protection – Mechanical rooms have very important equipment that needs to be protected. Often mechanical rooms are not conditioned and subject to outside temperatures and freezing conditions that can freeze piping inside the mechanical. For that reason mechanical rooms often have unit heaters located there to protect piping and other things that cannot be frozen or subject to freezing conditions. The components and sequence of operation are fairly simple. The main components in a hot water unit heater include a fan, a valve, and of course the piping and coils along with the cabinet.

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Disconnect and Electric Motor Starter with Overloads

Disconnect and Electric Motor Starter is used for turning the power off and on the an electric motor used in HVAC applications. It also has overloads built into the starter so if one of the windings begin to pull too many amps the overloads open the circuit and the motor stops operating. Motor starters can be used for single phase and 3 phase motors and offer a manual way to turn the motor off or disconnect the electricity to the motor to prevent it from starting for maintenance or repair of the motor or peripheral systems. Control wiring can be integrated into the motor starter for automatic control and or monitoring. Monitoring usually occurs with auxiliary contacts or status contacts near the starter. Some solid state motor starters will also detect and stop a motor if it is turning backwards. It is important when troubleshooting motor problems that the technician understand the motor starter and the limitations of the motor starter.

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Chiller Barrel Evaporator for Chilled Water Systems | Air Conditioning

Chiller Evaporator Barrel for a smalled air cooled chilled water system

Chiller Evaporator Barrel

Chiller Barrel Evaporator – A chiller evaporator barrel exchanges heat between one refrigerant and another. Usually the primary refrigerant is R-22, R-134A, or some other blend or alternative HFC. The secondary refrigerant is water. This water is circulated throughout the building where it passes through piping and coils. This is generally in most cases a forced air coil where the heat is removed from the air by a heat exchange process with the water and the coil. The cooler air is then forced through duct work and into the space to be conditioned.

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