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Automag Relay Question

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Toothed
Toothed Member Posts: 4
in Oil Heating

Hi All, new to the forum.

I recently purchased a home with an older Automag zone valve system. Oil furnace, hot water baseboard heat.

A recent problem has come up where all zones are heating when one zone calls for heat. I know that these automag zone valves fail open so I am thinking that this is an electronic problem as opposed to all of the valves being non-functioning. I have even replaced a few of the valve heads with new ones to confirm that and no change.

My question is I cannot seem to figure out what this separate relay is, it is on the side of the control board. It is hooked up to the hot water tank which I believe is the priority zone.

Here are some photos of the relay. There are no markings on it. The only similar relay that I was able to find is the Automag CNV84 ( picture attached)) which is a 3 wire to 2 wire relay. Is this what I should be changing out?

I dont think the problem is with the main control board, as thermostats are working correctly and kicking on/off furnace when it calls for heat. The problem is that power is not going to the valves to close them, and that the hot water tank is not regulating a constant temperature.

Thanks for any help or guidance you can give.

PXL_20260117_144030840.jpg
PXL_20260117_144300845.jpg
PXL_20260117_144618717.jpg
PXL_20260117_145030190.jpg
PXL_20260117_145035296.jpg
Screenshot 2026-01-17 115756.jpg

mattmia2

Comments

  • Toothed
    Toothed Member Posts: 4
    PXL_20260117_144030840.jpg PXL_20260117_144300845.jpg PXL_20260117_144618717.jpg PXL_20260117_145030190.jpg PXL_20260117_145035296.jpg Screenshot 2026-01-17 115756.jpg
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 19,798
    edited 4:37AM

    That looks like a standard run of the mill relay. 24 volt coil 24 volts to terminal 1 & 3 powers the coil.

    contacts 2 & 4 are normally closed with no power to the coil

    contacts 5 & 6 are normally open with no power to the coil

    The contacts reveres operation when the coil is powered. Look closely at the relay the terminals are usually marked

    I think the 24 volt coil is the two white wires. Terminals 4 & 6 are connected internally. It is a single pole double throw relay

    mattmia2Toothed
  • mattmia2
    mattmia2 Member Posts: 15,879
    edited 7:11AM

    you have to trace things with a meter. there could be a transformer or fuse that is bad or something like that or a wire that is broken off somewhere. that type of wire will snap off really easily if you nick it when you strip it. i can't really think of a reason why there would be a single relay in front of all of the zone valves. the relay that is screwed to the framing might turn off all of the heating zones when there is a dhw call.

    that is just a standard inexpensive hvac relay, it has nothing specifically to do with thermostats.

    Toothed
  • mattmia2
    mattmia2 Member Posts: 15,879

    i don't think there are any electronics there, i think that is just a set of insulated bus bars from the telecom or alarm industry repurposed to wire the zone valves.

    Toothed
  • 109A_5
    109A_5 Member Posts: 3,612
    edited 8:59AM

    Some information here.

    https://forum.heatinghelp.com/discussion/68252/older-automag-zone-valves

    Apparently those zone valves need power to close, and they stick easily, they also may run on DC current instead of AC current like most modern zone valves do.

    Your black plastic box looks like a relay with a date code 8943 (43 week of 1989), and the crimp connections look pitiful.

    image.png

    These may be relays also.

    image.png

    I suspect the thermostats energize the zone relays and the zone relays then cut off the power to the zone valves so they open allowing the water to flow.

    I also suspect for DHW (Domestic Hot Water) priority it is controlled by an aquastat or DHW thermostat that controls the black plastic relay and it simply may disable power to the space heating thermostats or the zone relays' coils, so they can't be energized to shut off the DC power to the zone valve coils.

    Not sure where the AC to DC conversion is, maybe in the junction box. What is under the cover of the junction box ? I suspect the relays are all AC powered but that is just a guess.

    More pictures of the whole control system may help.

    image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    Toothed
  • mattmia2
    mattmia2 Member Posts: 15,879

    pretty sure these are bus bars, don't see how the screws are insulated from the metal.

    image.png
  • 109A_5
    109A_5 Member Posts: 3,612
    edited 10:10AM

    It looks like this may be a full wave bridge rectifier, the AC to DC conversion. If the yellow wires are the 24 VAC and all the zone valve control equipment may be after the rectifier and all the relays may have DC coils.

    image.png image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • mattmia2
    mattmia2 Member Posts: 15,879

    there aren't any relays other than the one that is probably doing dhw priority(or firing the boiler from the end switches). those are the busses that supply the zone valve and thermostat for each zone and the combining of the end switches. the rectifier could be bad and keeping the zone valves from closing but the end switch fires the boiler.

    Toothed
  • 109A_5
    109A_5 Member Posts: 3,612
    https://forum.heatinghelp.com/discussion/comment/1882789#Comment_1882789

    Yes that would make sense and the thermostats open for a call for heat, the black plastic relay is for DHW priority, it interrupts power to the upper bus bar.

    I've seen older equipment where the whole base plate is the insulator like the plastic relays are now, however I like the bus bar theory. Makes more sense with the wiring and screw count.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    Toothed
  • 109A_5
    109A_5 Member Posts: 3,612

    What model is the main control board? And what model are the zone valves.

    Can you post pictures of each ?

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • hot_rod
    hot_rod Member Posts: 26,925
    Screenshot 2026-01-18 at 9.30.06 AM.png

    I think these are basically a solenoid type valve, powered close.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Toothed
  • Toothed
    Toothed Member Posts: 4

    Thanks all for the replies, much appreciated. During my research I did find that this is a standard SPDT relay. I have one on order that will be here Tuesday. I will update once I change that out. I will also take photos of the control board.

  • Toothed
    Toothed Member Posts: 4

    Would that rectifier be easily removed and replaced if once I change out the SPDT relay and still have same problem? Hopefully there is a model# on it to help find a replacement. It seems as this entire system is somewhat obsolete. I am not crazy about the open fail scenario, that seems more appropriate for a dump zone than having them for every zone valve.

  • hot_rod
    hot_rod Member Posts: 26,925

    There are two versions of the Automag zone valve the AA is a DC, they offer an AC version also.

    So if you start changing components be sure they are all "on the same page" regarding current and voltage.

    It looks like a bit of a homemade wiring and power source for those zone valves?

    Maybe the electrician worked for "Ma Bell" at some point based on the wire and terminal block :)

    Screenshot 2026-01-18 at 10.24.05 AM.png
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream

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