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Old 10-20-2010, 11:10 PM   #1
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Refilling Cast Iron Radiator System

I followed the details on how to fill a Cast Iron Radiator but didn't pay a ton of attention to the PSI thing. All of the sudden my basement starts flooding after about 15 minutes of filling the system. Did the PSI get too high and back up through the Boiler? Is that possible? Can you give me some specific guidance on what this could have been and how I avoid it?


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Old 10-21-2010, 06:23 AM   #2
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I have never heard of "refilling a radiator". If you need to refill the system, there should be a supply valve for doing that. If you are unsure of what you are doing, call someone that is. Hot water heating systems are closed systems. If there is leaking, something is not properly connected or a drain valve is not closed.


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Old 10-21-2010, 09:00 AM   #3
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Your heating system installation has a cold working pressure and a hot working pressure (in pounds per square inch). Iteratively (in a back and forth manner) you bleed each radiator one at a time and then go downstairs and admit more water to the system using the supply valve keeping the pressure near the cold value (some editing done here). Large radiators may need to be bled halfway at a time before more water is added. After you are all done, add more water to get to the cold pressure if the pressure is too low.

Do not just add water until the flow stops. The household water pressure is somewhat higher than the maximum pressure (hot working pressure) in the heating system during normal operation.

The expansion tank also needs to be calibrated. The method varies with the tank and the system. If the expansion tank has too much water in it then the pressure will go up too high when the furnace comes on and water will spill from the pressure relief valve and all over the place. Then when the furnace cycles off (or if during the refill process you bleed too many radiators in a row before adding more water) the pressure will drop too low and if you tried to bleed the next radiator, air will be sucked in rather than bled out.
The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.

Last edited by AllanJ; 10-22-2010 at 08:47 AM.
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