Taco 700 Reset - where to put sensor?

Joe Mattiello_2

Attached is the operational manual for the PC700-2. Please refer to page 2 of 2 of the typical piping drawing for the suggested location of the boiler sensor for the PC700-2. Be sure the sensor has good contact with the pipe for good transfer of temperature for accurate reading.

Joe Mattiello
Technical Support Technician
Tel. 401-942-8000 X 484
Fax. 401-942-2360
1160 Cranston St
Cranston, RI 02920
joemat@taco-hvac.com

David_24

Taco 700 Reset - where to put sensor?

I have a Taco 700-2 reset control being used on a ZVC-406 zone controller (and using a SR506 in combination as outlined below). They are all working very well! The question is about where to put the boiler loop temp sensor. I now have it on the common output manifold of my 3 boiler sources, measuring the supply temperature. My electric boiler brings the water temperature up to target very quickly - the 700 will kick the boiler off before that temperature water can get fully circulated in the radiation loop, although that location of the sensor works better with the propane boiler because it comes up to temp more slowly. I have considered moving the 700 temperature sensor to the return "T" from the radiation loop - so that the 700 kicks-out when the loop comes to the set temp rather than the supply. The manual says put sensor at supply point, but again, with the speed that the electric boiler brings the temp up, perhaps the return-T idea would even it out. (?) Any thoughts on this?

For info - here's how I set-up the 700. Off the boiler loop, I have a circulator fed DHW loop, a circulator feeding 4 zone valves for upstairs convection, and a circulator feeding a mix valve for in-slab radiant. I used a Taco ZVC-406exp to control the 4 zone valves, and also the thermostats for the in-slab and BoilerMate. Then I used a Taco SR506 to make a nice way to feed 110v to all the circulators in the system. The Taco 700 reset was connected to the ZVC-406, which allows full-temp for the priority DWH, and controls boiler temp for both the in-slab and zone valve circuit. I paralleled the end switches on the zone valves to fire that circulator through the SR506 (used jumpers on the end sw connections in the ZVC406). I used a 24v relay on the in-slab zone valve output of the ZVC406 to fire that circulator in the SR506. And used the priority zone contacts in the ZVC406 to fire the DWH circulator in the SR506.

I used a group of 24v relays for "steering", and a 240v relay in the electric boiler to determine if the steering relays should set-up for electric boiler or propane. The steering relays determined how the "boiler end switch" and the "pump end switch" of the ZVC-406 would be applied.

The WM GV-3 was reset by routing the "Pump" end switch to the TT connection of the boiler, and the "Boiler" end switch (controlled by PC700) in series with the high-limit control of the boiler. With the TT contacts maintained throughout the thermostat call for heat, and the high limit switch opened as determined by the PC700, the boiler circulator continues to run and works beautifully with the PC700.

For the electric boiler connection - look for a separate post "Seisco temp jack-up and reset connections"

Ted_9

Taco

I havent installed one, but did you check their web site. you can down load all of their manuals.

http://www.taco-hvac.com/

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EJW

Taco 700

David_24

Thanks!

For the comments. Yes, I have read the manuals and installed the sensor per their instructions, resulting in the situation described above, where the faster electric boiler appears to be cut-off little too quickly, or too many on/off cycles.

The Taco 700 does appear to be quite intelligent with regard to how quickly the water temperature rises. With the electric, it sees the water come up so fast that it turns the boiler off in advance of the target temp on the first cycle, then may let it go slightly over on the second cycle (probably an attempt to not short-cycle the boiler - although not so important with the electric). But on the GV-3, it sees the temperature coming up much more slowly, and on the first cycle will allow the temperature to come up over the target a little. It's obviously computing the speed at which the temperature comes up. I probably should be happy with the way it's working right now.... it does work very well. Thanks again..