How would I make the matching connection on the new board?

lost11

State: NY
Switching Relay: Argo ARM-6P https://www.supplyhouse.com/Argo-ARM6P-6-Zone-Expandable-Switch
Water: Burnham Indirect Water Tank https://www.supplyhouse.com/Burnham-AL50SL-AL50SL-Alliance-Hydrastone-Lined-Indirect-Water-Heater-9530000-p
Boiler: Burnham Gas Boiler
Fuel: Natural Gas

Figure 1: Current Burnham Indirect Water Tank

The output contacts go into the priority thermostat and the transformer hot and gnd connected to the 24V AC and common on the board (B and F from Figure 5, left)

Figure 2: Argo ARM-6P switching relay that needs to be replaced



Figure 3: Here's the boiler and wires that go to a switch that eventually goes into the isolation switch on the relay board "E" Figure 5 below


I was thinking about replacing it with a Taco 6 zone with a priority https://www.supplyhouse.com/Taco-SR506-EXP-4-6-Zone-Switching-Relay-w-Priority . It doesn't have that 24VAC/Common terminal. Each thermostat has common.
Figure 4: Taco switch diagram


Figure 5: Trying to match existing (left) to potential new board (right)


Figure 6: The Boiler schematic where I assume would be E from figure 5


The only connections I can't match on the new board would be the E (isolation switch on the old board) and F (24v transformer from indirect water tank). The closet thing to F I find on the manual for the water tank https://s3.amazonaws.com/s3.supplyhouse.com/product_files/AL50SL-Install.pdf would be this:

Figure 7: installation, operating and service instructions for AllianceSL Indirect - Fired Water Heater, Switching relay Wiring Diagrams, for Switching Relay R8845U or SR 501

Where I would jump the HOT for the 24V transformer to the "R" of the zone. And the common would be connected to C. Is that right?

Or forget about trying to install the Taco and replace it with another Argo for a 1to1 replacement.

Thanks in advance for taking the time to read this. And any advice you could give me would be great.
Why was I thinking about replace it with the Taco? Well that taco unit has commons, so it should work flawless with smart thermostats. Unlike the Argo

Your new Argo ARM control should work well with all standard and most programmable setback thermostats. In the event the programmable thermostat you are using causes the control board relays to chatter, you will require an external 24V power supply (transformer) and an Argo IR882 Isolation Relay.

Alan (California Radiant) Forbes

“The only connections I can't match on the new board would be the E (isolation switch on the old board) and F (24v transformer from indirect water tank).”

On the new board, E would be X-X MAIN. 

To provide 24 volts to your indirect, wire as shown on your last drawing. 

EdTheHeaterMan

@lost11
The power circuit in the water heater control is independent of the end switch in the water heater control. So you can use any 24 V transformer to power the water heater control.

Try this configuration to power up the water heater control.





I would like to know if you are using the new control because it has dedicated C terminals for each thermostat?

You may not need to change the control if that is the only reason to change.