Help with Hydronic system

[rmorey]

Dadster, I appreciate you taking the time to look everything over, thanks for that.

The non potable hwt is designed as our backup when we go away for the longer term. (More than 3-4 days). I can shut down the stove, close the main loop valves and open the non potable hwt valves to keep the house floor warm. The glycol will keep the rest from freezing.

Regarding the other points, confirm, mixing valves, close Ts etc. are all hooked correctly.

 

[ultrarunner]

Most of my cousins have hydronic with large, well insulated buffer tanks... the temp swing is minimal.

The heat source varies from propane, wood, coal, heating oil and solar.

 

[westcliffe01]

Rmorey, have you spoken to the controller manufacturer on whether the way your system is laid out is compatible with the controller you are using ?

Just something to consider: If you go to automationdirect.com, you can buy PLC systems for $250+ Yes, you would have to do some studying to figure out code, but you could make the system operate in a totally customizable way. If you do some poking around, you may even find a local automation company willing to help you with the code.

Do a flow chart of what the system has to do and all the decision points. Make sure all the sensors are accounted for. PT-100 temperature sensors from Omega run about $50 each and are very accurate. Get a cheap data acquisition system similar to this USB-6000 - National Instruments which will let you know what the current system is doing. For tracking mixer valves you would need to either measure their actuation voltage or connect a potentiometer to the operating lever so one knows what is going on.

With some data, one can have a much more sensible discussion with the supplier of the controller and determine if they have a better solution, hardware changes or if you just need a different control strategy.

We built a home on the side of a lake. Power is 4 km away (3 miles). Solar was our only option, so we installed a 4kW system to handle our electrical requirements. We installed a wood fired 125,000 Btu boiler in the workshop to feed a 60,000 Btu/hr load. (+\-30,000 Btu/hr house, 30,000 Btu/hr workshop).

Installed 1/2" Pex Al Pex, loops are 12" apart. Each floor has 3 - 300' loops, fed from a single manifold.

Heatloss Calculations

GRUNDFOS 2699 FC pump feeds a 1" Pex main loop from boiler to house to a sidearm exchanger and back to workshop with 6 GPM/13.6' head loss. After the sidearm, secondary loop (close "T's) feeds a GRUNDFOS Alpha pump with 2 GPM/ 9.5' head loss.

Back at workshop, another secondary loop same as house. 2GPM/9.5' head loss.

Boiler manufacturer made me put a 140 degree thermic "T" valve in return line at the boiler, to keep temps above 140 degrees.

When no call for heat, or just one load calls, everything works fine. When all loads call, the cold water from floors, return to boiler and floors begin to heat. Cold water begins to cool boiler. Eventually, boiler temp drops below 140 degrees and valve closes, sending main pump output to return of boiler. Temps go up, valve opens, hot water goes to load, and cycle continues. Stove never shuts off and load never gets satisfied. Can't figure out what I've done wrong. Could use your ideas.