PC702 equivalent for cooling?

Joe Mattiello

Hi Brian
I'm not sure how to answer your question. However, I will forward your Thread to the design engineer for the PC702 to get his suggestion.
Taco, Inc.
Joe Mattiello
Technical Service Technician
joemat@taco-hvac.com
401-942-8000 X 484
www.taco-hvac.com

archibald tuttle

pc702 equivalent for cooling?

I have a building with hydronic fan coil units that take heated water and chilled water to provide both heating and air conditioning.

I have two staged teledyne 9600 Hot water makers (got the HWM so I could run at higher pressures than 30PSI to eliminate airlocking on high floors - WM boiler mate will only take 45 so that is the new upper limit but that solved virtually all my problems) for heat and use a TACO PC702 controller for staging and setback.
It has worked pretty well except the Warm Weather Shutdown function does not work. It is always calling for heat even once the outdoor temperature exceeds the WWSD. It is registering the outdoor temperature and the setback works fine, so I can't figure what they heck could be wrong.

Anyway, that is a bit of an anomaly that has perplexed me, but the real question of the day is I'm looking for a controller that would perform similar functions albeit in reverse for our chiller. We have a Trane chiller with two 7 ton circuits. There is a really simplistic internal staging control which works strictly on whether the temperature of the return water is more than 5 degress above the setpoint in which case it calls both compressors.

I'm not as worried about addressing the staging although I expect it could be done with a little bit more efficiency and automatic lead changing (I put in a two way switch in the control circuit and manually change the lead each season).

Anyway, I more interested in getting a 'cold weather shutdown' (the reason I immediately started talking about the WWSD not working on the 702) incorporated with a 'setup' temperature caller. I suppose if it was really brainy it might incorporate humidity but virtually anything would be better than what I have now which is nothing. This tower runs 24/7 to keep cold temps. If no units call we're not losing that much but it is just silly. Of course the obvious immediate approach would be an outdoor thermostat that kills when temperature goes below say 65, but before installing that I thought I would ask if anyone has run across a PC 702 equivalent for cooling.

The temperature differences between desired room and hydronic medium are not as much in cooling mode, so I would imagine that the 'setup' would be at smaller margins or operate at 5 degree outdoor increments instead of one degree if it is not feasible or reliable to try to regulate the feed temperature within smaller units than 1/2 a degree.

BTW, thanks for all the advice I received regarding circulator gaskets in my last post. I went with the Taco rings for the 0012 which, since I live 15 miles from their home facility in Cranston, RI, I was able to get right at TACO. As Joe Matiello, who got me the gaskets, pointed out in the thread their material composition is supposed to be more resilient and provide 'recovery' from expansion and contraction. (I really appreciated this accomodation as I was in ASAP mode, but for folks who aren't right around the corner, maybe TACO could take to sending a few extra sets of 0012 gaskets to any wholesaler who sells the pump along with some 'LARGE PRINT' material explaining why this gasket material is designed to outperform flat gaskets - nobody is more resistant to looking into little details like this than your average plumbing supplier). I always wished the 007 rings were just a little beefier, more like the crossection for the 0012. I am also interested in looking into the goretex material that was mentioned. Thanks again.

Brian