Advice for adding actuators to a system with a Taco 504 switching relay.

Old 03-21-16, 01:01 PM
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Advice for adding actuators to a system with a Taco 504 switching relay.

Thanks in advance for your help.

I am a do-it-yourselfer who is in the process of installing a radiant floor heating system as part of a multi-phase remodel project.

The first phase of the project is complete, and working great. It's large 3 loop zone controlled by a single thermostat, so I purchased a Taco 504 switching relay with priority, to control that heating 'zone'. I also have indirect DWH connected to the priority zone on the relay.

Currently the Zone Pump, Boiler System Pump, and DWH Pump are all controlled by the Taco 504. No pumps are currently controlled by the Boiler (Lochinvar WHN085). It's possible this will need to change.

Now I find myself getting ready to add more heating zones - a 5 loop manifold broken up into 3 separate thermostats, but using a single zone pump.

When all is said and done, I will have 4 heating zones plus one DWH priority zone.

I am using Uponor Stainless Steel manifolds, and I have the choice of using either 2 wire, or 4 wire thermal actuators. I haven't decided on what is needed - so I guess the first question is to collect that input. Currently I am assuming the 2 wire units (I need 5 and they're much cheaper). I am open to using 4 wire actuators if they simply the process (if they do, I couldn't figure out how).

The big question is how to wire all this together - it seems like I have two choices:

Choice 1- Add a slave 'zone valve control' for my new, three thermostat expansion, then then wire that into the switching relay, such that when any thermostat calls for heat, it triggers that single zone on the switching relay - so the pump(s) power up correctly. This seems like the way to go, but is seems that would require the zone control end swtich connections to attach to the switching relay thermostat inputs - would that work?

Choice 2 - Add a larger 6 zone switching relay, and wire all these 3 new thermostats to their own zone. But, in that case, I am not sure how (or if it's possible) to then have any call for heat start the single zone pump....

Any help is greatly appreciated - thanks in advance!


Last edited by Erockalator; 03-21-16 at 01:20 PM.
Old 03-21-16, 04:54 PM
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Join Date: Jul 2007
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With a modulating boiler and OD reset you should have the IWH to the boiler domestic terminals along with the IWH pump. This will override OD reset so the water heater heats up quicker.
As far as the other zones wire the end switch of the actuator to the thermostat connections of the zone panel.

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