Wiring TACO SR502-4

That board only has two relays. It can be done but you will need two more relays and the knowledge to wire them in. Or you could just get a zone controller with a primary pump relay.

@STEVEusaPA, good call. I missed the pump relay in the aquastat.

The pump relay on a aquastat come on when call for heat is on the T terminals. The burner firing is a separate switch controlled by temperature of the water. the pump will run as long as something is calling for heat. The burner will cycle to maintain water temp as long as the call for heat is active.

@jackw please post a schematic of your piping so we can make sure we understand how your pumps need to be controlled.

First time I ever saw an installation manual with no wiring diagram at all.
Is there a wiring diagram inside the cover or could you take the cover off and show a picture?
In a normal situation, the X-X from the Taco (in your first pic) would go to X-X or T-T on the boilers aquastat.
Your primary circulator would be wired to C1 & C2 on the aquastat.
So any call for heat (1, 2 or both zones-circs on the left) triggers the primary circ to run (the one next to the boiler), which is what you always want.
Super clean soldering, overall very nice work.

@STEVEusaPA from what i saw it is a thankless water heater and triggers on flow. no wiring or external controls. Unless you saw something different.

@HVACNUT , I usually use a drafting table. And you can see why! My kids actually draw much better.

@JackW , might want to get the SR502-EXP Mentioned above then. It would be a cleaner install.

Yes the Zone 1 and Zone 2 terminals will get wired to your pumps. H to the black wire in the pump and N to the White wire. These Primary pumps as your schematic all them are actually "Zone" pumps. Because each one serves a Zone of your heating.

The pump that serves the Bridal Loop with your boiler is your Primary Pump. This will need to run anytime a Zone calls for heat. This can be done many ways.

What I drew is a way to use the Dry Contact Switch that would normally be used to tell a Boiler that heat is needed. The "XX" terminals on the board a just a switch that closes any time Zone 1 or Zone 2 call for heat. This switch will not handle much load and is not designed for 120 volt power. So to use this switch we need to install a 24volt coil Relay that is capable of handing the load and voltage of the pump.

The Relay in a Box model RIBU1C would work well here. Since the "XX" terminals are a Dry Contact or Isolated Contact 24 volt Power needs to be supplied to one contact. When the switch closes the 24 volt power will be supplied out of the other contact. this power get wired to the 24V coil wire on the relay and the Coil Common wire goes back to the common of the 24 volt supply.

The RIBU1C also has a 120 volt coil wire. This would not be used. just put a wire nut on it.

There will be three wires left. Common which will get wired to a 120 volt Hot (L1). The N.O. wire (Normally Open) will get wired to the black wire in your pump. The N.C. (Normally Closed) wire will not be used and must be capped with a wire nut. The white wire from the pump goes back the neutral of your 120 volt circuit.

I can draw it out in more detail if needed. Just give me time to sit down a the drafting table or have one of my kids do it for me smile:

I'm just now realizing that you probably do not have all the controls you need for this install looking at the picture. This looks like two in-floor heat manifolds. Is it PEX Pipe in Concrete? Or one of the other methods. Is there flooring on top and if so what kind?