DIY Home Improvement Forum banner
1 - 2 of 2 Posts

· Registered
2 Posts
Discussion Starter · #1 · (Edited)
I am looking to upgrade 3 old Honeywell relays that control the hydronic circulator pumps on my boiler.
Pictured Here

The problem with the current setup is the need for a common wire to power my smart thermostats. They are power robbing from one another and so I purchased a SR504-EXP-4 which has a three wire setup for a common.
The problem I am running into is the wiring guide from Taco does not really make sense with my boiler.
I have a Burnham Low pressure Gas Boiler with a honeywell aquastat that stays at a constant 210 degrees.

The current setup has 2 thermostats and a domestic hot water heater aquastat for a total of 3 switching relays.
Im confused about the 24v relay which is wired straight from the 3 Honeywell relays and then into the "TT" on boiler aquastat.
Pictured Here

Does the Taco Board replace this 24 volt relay?

The boilers L1 and L2 wires currently run to one of the Honeywell switches
and the "TT" is wired from the 24v relay.

The Taco board does not discuss anything regarding L1 an L2.
Pictured Here.

Apologies on the orientation of the photos but some photos were flipped during upload.
Can anyone help?


· In Loving Memory
42,671 Posts
You can connect your boilers 120 volt wires to the same 120 volt input terminals of the zone panel.

Not sure what that relay is being used for. Unless it shuts down the other zone when the water heater calls. If that is the case, then yes, the zone pane will provide that function itself.
1 - 2 of 2 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.