Boiler Signal

MechTech_2

I have a client that wants thermostatic rad valves on all their rads, all the rads connected to a manifold in the mechanical room, and all fed by a single variable speed pump. My question is, how do I get a signal to the boiler when they have a space heating demand. And no they don't want t-stats and actuators.

Brad White

Space sensor and/or Outdoor Reset

Many heating systems operate without any interior sensor. I had a Viessmann Vitodens 200 that ran entirely on an outdoor reset curve and constant circulation, with TRVs on the radiators. (Most, not all, I admit; not a candidate for pressure-responsive control.)

The system worked off the boiler controller and that included scheduled up times and sleep/away times. Without these, the system would run 24/7.



I both presume and hope that you would have ODR anyway for ideal comfort and energy savings.



The next step up is a room sensor which gives some feedback to the system (a question it never could ask itself before, "how am I doing?").



In my own house I have both, ODR and programmable thermostats. The circulators run constantly and the stats impose a heat demand, limited by what the ODR control dictates. Works very well. But without thermostats, just ODR with good curve control can work just fine.

MechTech_2

Also have some

high temp heat emitters, so the low temp Jaga rads would need a mixed water temp. I was hoping that the variable speed pumps had an internal end switch, or maybe there was a reliable flow switch I could put in line.

Brad White

Not sure I follow

Each temperature circuit will require its own circulator and the lower temperature circuit its own mixing valve (as you stated). Given that boilers fire with wide differentials sometimes, I like to use mixing valves on all circuits, even if the high temperature circuit is approximate to the boiler temperature. Tighter control that way.



Each circuit can be constant circulation -with low Watt circulators of course- and control is by varying the temperature.



What I am not clear on is what flow the flow switch would respond to in your sequences. Maybe think about how you want the end result to be and work backwards from there? Could be my own lack of understanding your vision.