Boiler relay help

R19 is a three-wire thermostat control. Those relays are no longer made. I would replace it with a RA89A Honeywell relay.

But if you connect two wires from your thermostat R on the thermostat to R on the relay and W on the thermostat to W on the relay it should work. Don't connect anything to Blue on the relay.

If you have 120 volt power into the relay and with the thermostat wires disconnected jump "W" & "R". The relay should pull in if it doesn't it's bad.

When it pulls in the relay contacts should close and whatever is connected to the relay contacts should start

@karter

You're talking a relay that is probably over 60 or 70 years old. No one will have parts to rebuild it. Just buy a new relay.

Hello karter,

It looks like you have the White connected at both ends, which is OK, and the Green connected at one end and the Red connected at the other end, that seems non-functional. I would abandon the Green at both ends.

So at the thermostat;

The Red wire goes to the R terminal.

The White wire goes to the W terminal.

At the the RA89A the Red wire goes to one T terminal and the White wire goes to the other T terminal.

Hello karter,

Did you read this that was posted above ????

It looks like you have the White connected at both ends, which is OK, and the Green connected at one end and the Red connected at the other end, that seems non-functional. I would abandon the Green at both ends.

So at the thermostat;

The Red wire goes to the R terminal.

The White wire goes to the W terminal.

At the the RA89A the Red wire goes to one T terminal and the White wire goes to the other T terminal.

The 20 Volts you are seeing may just be from the Capacitive reactance of the parallel wires and is deceiving you, you need real copper wire continuity.

If there is no other devices in-between the thermostat and the RA89A relay, the Voltage across T-T terminals (RA89A relay) and R-W terminals (the thermostat) should be exactly the same, 24 VAC (or a bit greater) with no call for heat, 0 VAC during a call for heat. Jumping the T-T or the R-W should do the same thing, start the boiler.

If not you may have a broken or disconnected wire.

Since you say you used the Green or the Red with the same negative result maybe the White wire is defective and that may have been the original problem.

Or possibly your thermostat is defective.

Two wires. However if one of the two is proven defective the third wire (since it is already there) could be use as a substitute in this case (the wire color is only a reference to make it easier). All the wires do is bring the T-T terminals of the relay to a remote location in the living space where the thermostat is. So two T-T terminals (T and T), two wires, then the two wires are connected to the R and W on the thermostat. When the thermostat calls for heat, a switch inside it connects R to W, like a little automatic jumper.

That is kind of why they standardized it decades ago, the Red wire goes to the R thermostat terminal the White wire goes to the W thermostat terminal. Often the heating equipment had R and W terminals also, so you just matched it up at both ends, easy. In your case you have additional control equipment so the terminals are labeled differently.

If you think of the wires as red green and white, that will confuse you.

Think of the wires as A B and C. because the wires are colorblind.

the colors are there for humans to know which wire is which at the other end. The colors are not there for the electricity to decide which color route to take. The electriciy can't see the colors. It ain't that smart!

follow the directions that @Jamie Hall gave you .

1. Jumper between T and T at the relay. You say the relay kicks in. Good. It should.
2. connect all three wires together at the thermostat. If the relay kicks in, go to 3. let us know that this step worked. if it does not work, then you need to replace all of the wires in that group. see step 6.
3. disconnect one of the three wires — doesn't matter which, but let's call it wire A — and leave the other two connected. If the relay stays kicked in, stop. Connect those two to R and W at the thermostat. It doesn't matter what colour they are.At this point you are finished. You need not go any further. Let us know if this worked. If step 3 was unsuccessful, then one of the wires that is still connected together is not connected to the relay near the heater. that means that wire A is good and one of the other two (B or C) is not connected to the relay. To know which one is not connected you can connect wire A to one of the other wires. see step 4
4. disconnect one of the two remaining wires you connected in step 3 (Call it wire B) and connect it to the wire A, the wire you disconnected in step 3. If the relay kicks in, stop. Connect those two wires to R and W at the thermostat. At this point you are finished. You need not go any further. Let us know if this worked. Otherwise…
5. Take wire A and connect it to the wire which is left disconnected from step 4 (That would be wire C). If the relay kicks in, stop. Connect those two wires to R and W at the thermostat.At this point you are finished
6. At least two of three wires at the thermostat are NOT connected through from the relay to the thermostat. You will either need to trace the cable through, end to end, to find the disconnection and repair it. Alternatively, run a new cable (at least three wires) and connect it preferably using the colour code.

If none of this works, then you need to replace the wire from the thermostat to the relay. And you only need to use a two conductor wire. But I recommend that you use at least a 4 conductor wire and only use the Red and the White wire and leave the other two color wires disconnected.