Taco PC205 operation

Petro55

Hello,

Moved into a new house and want to update the boiler piping as it is 20 years old and leaking and also does not have zone mixing or boiler protection. Plaining my new system and trying to understand how the Taco PC-205 wiring and control works. Here is my configuration-
Conventional NoN Condensing Boiler(150degree on 180 off)
Primary/Secondary loop with injection mixing(planning stage ) Debating between this and mixing valve.
3 zone circulators(Taco 007's) for in slab heat.(all 120 degrees)

Questions
1. Using a PC-205 and SR504(might add another zone down the road) Would I wire my boiler pump to the PC-205 or SR504? Does the PC -205 control the boiler pump to increase water temp? Or is it simply on or off when Zone heat is called?

2. On the secondary loop I was only planning to have the 3 zone circulators as opposed to a system pump feeding the zone circulators?

3. All the Taco PC-205 instructions say to install the Boiler sensor on output side(hot side) of the boiler. For Boiler protection it would need to be on the input (cold side) of the boiler?

I am planning to post the existing system as what not todo with a Radient floor system, and my plan to update.

Thanks in advance and looking forward to this project.

Joe Mattiello

hi Petro, I've attached the instruction sheet for Taco PC-705-2, and Taco wiring guide, refer to page 16, with instruction on wiring PC705 to Relay, and location of system pump. ZR terminal is hot whenever any zone call for heat and not affected by outdoor temperature.
Location of system pump should always be pumping away for expansion tank point of no pressure change. Keep in mind if your boiler is non-condensing, you have to operate boiler 140 degrees and above, so your window of opportunity to reset based on outside temperature is 140 degrees to high limit, typically set at 180 degrees. If you have DHW on priority zone, always leave priority on, so control knows you have DHW and will fire boiler to high limit when priority zone calls for heat.
Hopefully this helps, and if you have further questions, please call Taco Tech support at 401-942-8000 and ask for Tech support.