HVAC Questions? Ask an HVAC Expert for Answers ASAP
An expansion tank, as the name suggests, is a small tank partially filled with air whose compressibility reduces the shock caused by water hammer and absorbs excess pressure that occurs as a result of thermal expansion. It is usually used to safeguard appliances such as closed water heating and domestic hot water systems from getting damaged due to this excessive pressure. Expansion tank problems can vary from leakage and blockage to a more serious problem that leads to a complete malfunction. Listed below are a few questions answered by the Experts on issues related to expansion tank problems.
Some expansion tanks are designed with a bladder. This is basically an outlet to let out any excess water. Some tanks do not have this bladder. If they don’t have a bladder, they will generally have a valve on them to allow the water to drain.
The problem described above points to the possibility of a leak. If you have pipes running beneath the ground floor, you may need to lift the floor boards, locate the leak and get it fixed to solve the problem.
Ideally, an expansion tank should be set at a certain pressure depending on the height of the unit. Usually the pressure is around 12 Pounds Per Square Inch (PSI). If water is being emitted from the expansion tank, the problem could be with a faulty diaphragm. The air bleeder valve is a typical example of a part which needs replacing every few years. However, this should not prevent the water from circulating. A system will either have a pump or a circulator. A pump’s role is to propel water while a circulator moves the water. Pumps are usually big while circulators are 16 square inches in area. To check why the water is not circulating, you will need to dismantle the pump from the system after ensuring power is going through it, and check if there an obstruction or block causing the problem.
An explanation with regard to how expansion tanks work will help you understand your issue. Expansion tanks are meant to absorb the excess volume of water on expansion caused by heating. Check if your new expansion tank carries a charge. To do so, pressure the system to about 1.5 bar. Next, set the central heating on maximum and watch the pressure gauge. If the vessel is functioning correctly, the pressure may rise by 0.25 of a bar after which it will remain in that position indefinitely. On doing this, if the pressure continues to rise and crosses the 3 bar mark, the pressure valve should open and get rid of the excess pressure. Once the system is allowed to cool, the pressure should fall below the initial 1.5 bar. Hence if the pressure valve is the culprit, it may discharge a constant drip but usually does not release a greater volume of water.
One of the ways of checking if the expansion tank has become faulty would be to open the red cover of the pressure fitting. It resembles a c-valve stem of a bike. Using a screw driver, push the center of the stem inward. If a lot of water is released from the valve system, it indicates that the bladder of the tank is leaking water or that it is not retaining the water properly.
Expansion tanks are part of a larger domestic water heating system. These systems could contain other components which when affected can influence the functioning of the water heater. To determine if the issue lies solely with the expansion tank can be tricky and complicated to an untrained eye. Moreover, dealing with pressure systems requires care and caution. To diagnose expansion tank problems correctly, help, information and guidance from an Expert can prove very useful.