Best Of

Gee…I still qualify. Would love to take the test just to see where I end up after all these years. The only thing that bugs me about the qualifications is the working at substantial heights. Forgetaboutit!

GGross The Viessmann CU3A appears to have Pump Modulation Output 0-10VDC…this is from the manual (147 above). Sounds like you would select a pump with appropriate head and GPM that plays well with variable DC output and then select that output in the programming phase for the setup. Guessing there are no proportional pressure pumps that will work with 0-10VDC…sounds like it wouldn't make sense anyway as it conflicts or defeats the purpose of the variable 10VDC. Guessing you would eliminate the TRV's and rely on thermostats so that route would be a pretty solid departure from the current plan.

There seem to be a number of people that have made constant circulation work with direct load and TRV's. I'm not 100% sure which way I'm going to go but I could always repipe for P/S if the TRV's close and we hit the limit regularly on the CU3A due to lack of flow. Thinking the Viessmann app would start sending me codes at that point and I would inform Management (the wife) of my error in judgement which would trigger an "You are an Idiot" code but not from the CU3A.

Alan (California Radiant) Forbes Love your story about a client that won't talk to you. Ha…that's the nature of this beast. I am beginning to see how every install must be different in ways that cannot be foreseen…and at some point you have to have the space to try new things…. If not…you back up…and change course….therefore the wires in the wall. It's def got an element of art, intuition and experience. I am happy to be doing all this in my own home..without anyone expecting me to defy physics….or have every answer.

I will consider the P/S or keep it as a backup plan…not sure yet. For the moment I am thinking of keeping a number of bathroom rads or undersized rads (laundry) without TRV's as a safety. But ask me after I read one more post here..and it changes again. ;)

I got pricing from the Viessmann distributor here in Denver for the Vitotrol 300A thermostat (allows most if not all of the functionality of the boiler control) thermostat and room sensor and will probably order those. Sounds like the system will work better with these along with outdoor reset.

Thank you, Billy...glad it worked out. You were a great student! Mad Dog

Is out & posted. Filing date is NOW. $50 Bucks an hour! Do you got what it takes? I tutor students for this exam as well. Don't miss out…

Mad Dog