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Old style automag zone overheating

StelRiceStelRice Member Posts: 1
Hope someone can help me out. We have an old style automag system installed in the early 70's. BTW I'm not a technical person. There are two zones. One for the 1st floor the other for the 2nd floor. The 1st floor works fine. The 2nd floor has 4 thermostats. The problem is that if one room calls for heat all the rooms will heat up and keep heating up independent of what the thermostat is set at. I checked the magnetism on all 4 zone valves and the only one that is magnetized is the room that is calling for heat. Why do the other rooms heat up even though they are not magnetized? Also the problem is intermittent! Thanks for any help.


  • EdTheHeaterManEdTheHeaterMan Member Posts: 49

    Old automag valves wrk a little different from the standard 24V Honeywell, Taco or B$G valves. i some of the valves were powered to be closed and no power to open. if someone replaced a control and did not realise this, then all the zones that are on the second floor loop may be open except the one that is calling for heat. That one may be closed. Also some of the valves may be Direct Current or a different voltage value. If you are still using the original control then a qualified technician can test the voltage and AC or DC current.

    if the control is not original your best bet may be to replace the zone valves with current model Honeywell or Taco valves and new operating transformer or better yet a multi-zone valve control panel like a Taco ZVC-6 or equal
  • EdTheHeaterManEdTheHeaterMan Member Posts: 49

    here is some information your tech guy will find helpful

    also Automag valves have less restriction to flow. A 3/4" honeywell valve will handle about 3 GPM or 30,000 BTU or 50 ft of 3/4 baseboard radiator fin

    the 3/4 " automag will handle 4 GPM or about 40,000 BTU or about 67 FT of 3/4" baseboard fin.

    When making a change be sure the replacement devise is equal to the original specification. Or if not ... the lesser value of the replacement is ... at least adequate for the application.

    Finally everything may just right and just needs a good cleaning. take the system apart and flush some clean water thru to remove any debris that may be fouling up the valves from closing completely.
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