Automag Relay Question

Toothed · January 17

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.

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Toothed · January 17

EBEBRATT-Ed · 4:30AM

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

mattmia2 · 7:10AM

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.

mattmia2 · 8:13AM

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.

109A_5 · 8:46AM

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.

These may be relays also.

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.

mattmia2 · 9:47AM

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

109A_5 · 9:54AM

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.

mattmia2 · 10:32AM

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.

109A_5 · 10:35AM

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.

109A_5 · 12:47PM

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

Can you post pictures of each ?

hot_rod · 4:31PM

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

Toothed · 4:57PM

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 · 5:01PM

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 · 5:29PM

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 :)

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109A_5 · 6:34PM

I kind of doubt the full wave bridge rectifier for the AC to DC conversion is defective. If it is defective it would probably short out and that would probably cause the 120 VAC to 24 VAC transformer to fail. Diodes and bridge rectifier like that rarely fail open like a blown fuse.

You really need a multimeter and figure out what is really going on. Rolling the dice and saying I'll replace this may be a waste of time and money. So far the only thing I see that I don't like is the crimps on the push on connectors to that relay. But since you have moved that relay all around you may have noticed a poor connection there.

Does any part of the control system seem to work normally or show any signs of life ?

109A_5 · 6:42PM

One thing I don't like about the 'open fail scenario' is you are paying for electricity to shut the heat off. So all summer long unless you shut the system down you are paying to have those zones to not have heat. You probably can't shut it all down if it is also used to make your DHW too.

Toothed · 7:36PM

https://forum.heatinghelp.com/discussion/comment/1882838#Comment_1882838

I for sure plan on changing out the connectors to that relay, Previous job was poor at best. Good to know about the rectifier. System seems to work fine other than all zones heating when calling for heat, and the priority hot water tank not regulating it self. All zones seemed to have failed open so heat is going to all zones anytime there is a demand. I am hopeful it is the relay but if it ends up being something more severe I will be ripping it all out and going to an standard Taco normally closed system. Thanks for your input!

Toothed · 7:38PM

Thanks for sharing hot_rod. I have the AA valves. I have bought a few extras and swapped them out as my first thought for repair was changing out the zone valve head. But no change. They are not closing and are in a failed open scenario.

109A_5 · 7:49PM

You mentioned a main control board. Does it have relays ? Picture, model ?

" I dont think the problem is with the main control board "

Since the zone valves 'fail safe' is open providing heat is there power to the zone valves ?

If that black relay is for DHW priority (I'm not convinced) I would think if it failed you would have normal heat or just DHW depending on what failed inside the relay.

OR you have multiple issues.

Automag Relay Question

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