Taco Fuelmizer (SR501-OR) with SR504

Hi everyone,

First time poster here but have read these forums for years. Im adding a zone to my natural gas boiler and would like to add the outdoor reset control too. Right now I have a Taco SR503 3-zone switching relay, all space heating baseboard zones. I need a 4th heating zone.

The SR504-EXP and the P700 outdoor controller seems like an expensive upgrade. Can I accomplish the same end result with the SR501-OR and the SR504-EXP? It would be even better if I can keep the SR503 and use the 501-OR as my 4th zone and OA reset but I think that's not possible because I would need the Tstat zone on the SR501-OR to tie-in the SR504.

Any guidance is appreciated.

John

 

Honeywell makes one but it's not cheap. Looks like taco and tekmar use outdoor reset with a expansion module.
https://www.supplyhouse.com/Honeywe...riority-for-4-zones-of-pumps-or-2-wire-valves