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Christian Egli_2

Isn't this similar in concept to an injection system? where you control loop heat by injecting more or less hot water to the otherwise tempered water. Of course the loop flow rates are constant with injection systems, but the heat content is not, just like in your deltaP - PID.

Since injection systems are great, this new deltaP should be great too. Bonus: more inexpensive electronic and much less of the costly hardware. The PID seems absolutely necessary. I think you need more tweeking that just ON OFF control.

Thermostatic valves are a way to go too, but they don't offer the cusotmized-to-your-home tuning the PID does. And anyway, PID electronic control is or will be cheaper to buy and install than solid hardware can ever hope to be.

Here is one concern:

Say you have a radiant floor coil and the call for heat is very small. Then the deltaP system would only pump a trickle of water down the loop. No problem with the BTU content but the stream will move very slowly and thus the water would quickly cool in the first few yards of pipe. The result in the room might be non-uniform floor temperature.

This problem would not be a concern with radiators but the mutli pump injection system might still have an advantage for floor heat.

Paul Rohrs_4

Sounding board

I was enjoying Wayco Wayne's post about being a Circaholic and thinking about the use of circulators instead of zone-valves. My thinking then took me to ∆P differential bypass valves being used with zone valves. The next step would then be to have this differential pressure circulator used as a "zone circulator".

So now, with this grundfos ∆P circulator (available in the US only with the Vitodens (?)), the additional use of the differential bypass will be rendered useless. As zone valves open and close, the ∆P circulator will ramp the flow rate up and down like a variable speed circulator. Fine. Great.

What about zoning with these ∆P circulators and using a T-stat with PID logic? As a zone of radiant floor heat falls below the setpoint and calls for heat, the PID logic in the stat will recognise how far below setpoint it has fallen and will speed up the flow rate until it nears the t-stat setpoint and then will gradually reduce the flow as it achieves the setpoint. In essence, a variable speed circulator that recognizes coming out of a setback mode and can "boost" the flow-rate, in addition to a reset control that will boost the water temp as it comes out of setback.

Any PID T-stats on the market that will work in conjunction with this soon to be released circulator? I think it would be an added benefit for comfort as well as efficiency. I know that Swampeast Mike loves his TRV setup and a mono-pumping zone is great for his particular setup, but new construction radiant floor heat (multiple zones) seems like it would be another step forward for the industry.

Any other thoughts on this?


Regards,

PR

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bob_50

Control

I would rather modulate temperature than flow. A 50% reduction in flow only gives about a 10% reduction in output. I would like to see a system with micro-zones that has a continuous flow rate in all zones all the time that modulates temperature in each zone. All that and cheap and easy to install. This is easy to do on large systems. The controls are way to expensive for residential. bob