Can additional 24V Transformer power multiple C-Wires for multiple zones for Taco ZVC404-EXP?

enzo4

I'm adding an additional 24V HVAC transformer to power C-wire for the zones for my Taco ZVC404-EXP. Can I use a single 24V transformer for all the zones or do I need an additional transformer for each of the 6 zones? I'm using this setup http://www.taco-hvac.com/tmp/ExternalxfrmerZVC-4Powerrobbingthermostat.pdf that Taco recommends for "Power Robbing Thermostat".

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Details:
I have two old Taco ZVC404-EXP (to power 6 zones). Unfortunately the old Tacos do not have a single COM port nor additional C ports on each of the zones.

I have referenced https://forum.heatinghelp.com/discussion/172451/ecobee3-taco-zvc404exp-c-wire and faced the same issue, I cannot connect use the neutral on the left (J4) as the common/COM/C. Heater will start when connecting R<->C.

Based on this thread: https://www.reddit.com/r/ecobee/comments/92i5xj/ecobee4_and_taco_sr503_zvc406/
"I have a ZVC406. When I contacted Taco they instructed me to purchase another external 24V HVAC transformer and provided me with a specific "Power Robbing Thermostat" wiring schematic PDF. They, perhaps conservatively, cautioned the transformers would not be able to provide enough power for the board, zone valve controllers, and multiple ecobees.

http://www.taco-hvac.com/tmp/ExternalxfrmerZVC-4Powerrobbingthermostat.pdf"

Jamie Hall

It's not a matter of how many zones, it's a matter of how many VA the transformer can put out. Just get one transformer -- and make sure it's big enough.