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How To Replace A Faulty Thermal Expansion Tank On A Hot Water Heating System

By Edited Nov 13, 2013 1 0

How To Replace A Faulty Thermal Expansion Tank On A Hot Water Heating System

How To Replace A Faulty Thermal Expansion Tank On A Hot Water Heating System, is something you will need to know if your heating system incurs a blast of air from a blowout in this device. Faulty expansion tanks are a common problem and this type of repair is needed eventually in almost every hydronic heating system.

Thermal expansion tanks are used within a closed loop system. They absorb the thermal expansion, that happens when a boiler heats the water. We need to keep the system pressure at a constant set rate and this apparatus helps us to achieve this.

When water is heated, the action causes thermal expansion and the space required to hold the water becomes larger. Within a closed system filled with water there would be no room for this expansion to occur. This would cause a rise in pressure and the pressure relief valve on the system would blow when the pressure reaches thirty pounds per square inch.

A thermal expansion tank has a charge of air filling half of the tank. The other half ties directly into the system and there is a rubber diaphragm in between the two halves. As water is heated and it expands, the air charged side absorbs the expansion by letting the air be compressed by the force of the heating water pushing against the rubber center.

Air is very easily compressed and liquids are almost impossible to compress so without this important element, it would be very difficult to maintain a stable pressure. Constant system problems would occur and this is what happens when this rubber diaphragm blows and the charge of air gets introduced to the system.

Not only do we loose our expansion absorbing ability but we now have the means for an air lock within the loop. This can happen when a circulator pump gets a slug of air and looses prime. The circulation is lost and we experience a heat outage within that zone.

When this occurs we can also cause the circulator pump to fail and burn out. This happens because the pump is trying to pull air and it can't. The pump eventually overheats do to the fact that it is running constantly with the thermostat never being satisfied because there is no heat circulating.

The sound of running water within the pipes and baseboard on a system like this will tell you that unwanted air is in the system. While a bad expansion tank is not the only way air can be introduced into a hot water heating system, it is one of the more common ways.

Testing an expansion tank is as easy as tapping the two halves. The top should sound dense and full when tapped the bottom should have a hollow ringing sound. Two distinctly different sounds indicate that your tank is good. Two taps that sound the same, usually means your tank is blown and flooded with water. This means the tank will need to be replaced.

This job can be done by the average home owner with a little insight. Some systems will have a valve that can be shut to isolate the expansion tank. If this is the case with your system then all you have to do is shut the valve and unwind the tank from the fitting it's in and then wind in a new one.

If however you have no valve, specifically set up for this task, then you may need to shut down the water feeder on the boiler. This valve is usually a half inch copper line that will come from the city water supply or your well. It feeds the system and we don't want water coming in while we have the system open.

After the water is off. Use a bucket and open any boiler drain on the system to drain the pressure. If you close the fill valve and all the air vents, then you will get very little water out. Once the water stops, usually from 1 to 4 gallons will come out. Then you can close the drain and the system will be under a slight vacuum.

Unwind the expansion tank from it's fitting and wind in a replacement tank. The water can then be turned back on to the system. Check the job for any visible leaks and then open the air vents. Restart the system and observe the pressure to make sure it is within the normal operating pressure of twelve to twenty five pounds per square inch.

Listen to the piping after a couple initial minutes and see if there is any air in the lines if air is present and you can hear gurgling or rushing water then the entire system will need to be purged and this is done with a hose at the boiler through boiler drains that should be installed in conjunction with a ball valve to force the water through the loop and out the drain, pushing any air with it as it goes.

After properly purging the air from your system the job is complete. Knowing How To Replace A Faulty Thermal Expansion Tank On A Hot Water Heating System, has just saved you a very expensive service call. Plumbers now charge between 75 and 125 dollars per hour to come to your house and work on this type of system.

Water Worker G12l Thermal Expansion Tank With Male Pipe Thread
Amazon Price: $63.85 $52.94 Buy Now
(price as of Oct 19, 2013)
Amtrol ST-5 THERM-X-TROL Expansion Tank, 2 Gallon (140N43)
Amazon Price: $69.00 $51.50 Buy Now
(price as of Oct 19, 2013)
Amtrol ST-42V THERM-X-TROL Expansion Tank, 20 Gallon (144N177)
Amazon Price: $967.32 Buy Now
(price as of Oct 19, 2013)


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