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No heat 2nd floor - Mid 1950's Monoflow T System
Hi everyone. Sorry I've been away. Its been an interesting summer and I've been busy.
Since I'm a semi-regular here I suspect I know the problem. But, figured it would be best to verify that and likely learn something I don't know.
The weather has cooled off and my heating system has automatically started as it should. But, the 4 cast iron baseboard radiators on the 2nd floor of the house are cold; and the 5 cast iron baseboard radiators on the 1st floor are warm. Mid 1950's Monoflow T system (1 1/4" iron pipe, 1/2" risers/returns)
Fall 2006 replaced original boiler and B&G pump with a a Vitodens 200 with an internal primary circulating pump, a low loss header, and a secondary Taco 007-F5 circulating pump. Both pumps are currently running (or at least the motors are). Water is being circulated through the low loss header by the primary pump.
Perry's theory: Secondary pump is not working properly (shaft broke, impeller degraded, etc)- and primary pump cannot develop enough head to circulate to 2nd floor of house, especially with the low loss header.
I've discounted air binding as why would all the 2nd floor radiators and none of the 1st floor radiators air bind. I could see that if only 1 radiator was cold.
What other things could it be?
Additional questions? If I'm going to drain the system to replace the Taco 007-F5, should I also replace the primary pump as well (or are they known to last for multiple decades). Should I change the air charge/pressure maintenance tank and the make up water reducing pressure valve as well? Any other suggestions on overall system maintenance or improvements after 14 years?
Note that I rebuilt the Vitodens 200 last year with a main control board (it failed), a new fan (bad vibration), and a few other parts. It runs well.
Life is worth living if you do it well...