Loop Circulation Problem

[Medman]

I discovered an interesting problem last night and I hope you can shed some light on it.

I have my EKO 25 plumbed as shown in the manual. The loop begins at the boiler, runs to the house, through the sidearm, and back to the boiler. I have a Taco 1400 pump moving water through about 50 feet of 1.25" black pipe, 280 feet of Pex, and 20 feet of 1" black pipe. The pump is on the boiler return.
Below I have a picture of the piping and HX circ in the house. When the thermostat calls for heat, the Taco 007 shown runs to pump hot water from the loop, through the plenum coil and back to the loop. I used closely-spaced Tees in the primary loop to prevent ghost flow into the plenum coil.

Last night while running the system I noticed that even though the boiler was showing 200* on the controller, the loop temp was only 130* and it seemed that there was no flow to the house. By turning off the Taco 007 in the house, the loop temp immediately spiked from 130 to 170 and the boiler temp dropped to 175*. It seems to me that the Taco 007 is causing recirculation at the closely-spaced Tees which is preventing flow in the primary loop. Pressure in the loop remained constant at 20 PSI. Is this possible? How can I correct for it?

 

[in hot water]

Got a drawing? Remember for primary secondary to work, that primary boiler pump needs to flow. No heat from closely spaced tees unless their is flow across them from the boiler.

hr

 

[Medman]

There is plenty of flow when the 007 is not running, and until last night there was no problem getting heat into the plenum coil. Usual temps are:

Top of Boiler: 185*
Enters Sidearm: 180*
Return to Boiler before bypass: 160*

Total loss of 300' of piping, including sidearm and plenum coil, is 20-25* typically.

Diagram attached - note I have no ball valve between closely spaced tees in my install - I did not have room.

 

[Medman]

There was another thread discussing pump sizing for heat load. Joe Brown has a calculator he uses for this. I did the heat load calcs and it looked to me like the 1400-10 would be enough to move the 85,000 BTU/h from the EKO 25 to the house with the above piping - I need to have 8.5 gpm flow. How would I now verify this flow?

 

[BrownianHeatingTech]

How close are the closely-spaced tees?

They should be within four pipe diameters of each other (eg, if 1.5" pipe, the tees should be no more than 6" apart).

Joe

 

[Medman]

Well, I think that I have answers to both my problems - the danfoss valve is singing, and it is only allowing water to flow to the loop if the temp is above 155*. So, if the water temp in the boiler is less than 165*, the 1400 can pump all it wants but the only flow is in the near boiler piping. With no flow to the house, I can't heat the plenum coil. Once the danfoss sees a boiler temp above 165, it opens (and makes the singing noise) to allow some flow through the loop.
All day I have been experimenting, and I am only seeing consistent heat to the house if I keep the boiler temp above 165*. This seems excessive, especially because I have to keep tending to the boiler to maintain this temperature.
I think the danfoss is the problem. Either by fault or by design it is opening at too high a temp. Does anyone know if I can get a replacement thermostat or adjust the thermostat inside the danfoss?
I'm thinking that I would like to see the return temp maintained about 130 to 135* instead of 155*. This would allow more useful heat transfer to the house. I guess I will try pulling the valve apart tomorrow.