ODR: this is driving me nuts...

radioconnection_2

Thanks Brad..

The system does work, but I have to set the Tekmar differential manually to 25%; that bothers me. The boiler is 2X oversized too, which doesn't help.

Let me bounce this off of you. The TV valve modulates the flow to the primary side of the TV as the boiler supply increases between 140 and 165 degrees. After 165 degrees the flow is almost fully diverted from the bypass to the return leg. That means the GPM flow to the CSTs on the primary side is increasing with rising boiler supply temperature, decreasing the flow ratios between primary and secondary. That seems to be the exact opposite of what is desired in this application.

Pete

joe lambert_2

This is driving me nuts. ODR question

http://s117.photobucket.com/albums/o46/radioconnection/?action=view&current=PS-diagram.jpg

Is the above system capable of running full ODR? Or, will it have problems with the supply temperature going to the system from the CSTs? The controller is a Tekmar 260, with the indoor sensor. I am going crazy trying to analyze this in my head.
The TV is 140 degrees, fully open at 165 degrees.

The system is real, and seems to work, but the question is if the temperature rise at the supply to the radiation might be too rapid causing the Tekmar to short cycle the burner. The Tekmar also seems to setting the differential to a very low spread; the typical target temps in winter are under 130 degrees, 120 or less typical..

Pete

joe lambert_2

I gotta stop drinking too much caffine...

Brad, you out there

Brad White_185

The other Peet's (Major Dickison's Blend)

speaking of coffee... try some.

Pete- what is modulating the temperature of the secondary zone? I see the TRV as protecting the boiler (bypassing boiler water back to the return) but that does not give what I would call positive mixing on the secondary side.

Things I would ask to get my own head around this:

What is the boiler flow rate?

What is the radiation loop flow rate?

What is the stable minimum boiler OUTPUT temperature (165 I think you said but want to be sure I understand this).

It seems the way I see it now that you will get some unknown temperature to the radiation. If that radiation flow rate is greater than the boiler loop, the temperature will be less (reverse flows in the closely spaced tees will mix-down at that point). If the radiation loop flow rate is less than the boiler, the radiation will see the boiler temperature. Because this is apparently the controlled variable (indirectly) and I presume it is on-off fire, the temperature swings will be fairly wide, (although the return temperature to the boiler is probably quite stable).

I see the radiation either way getting a wide variable of temperatures that yes, may work but are dependent on stable boiler outlet temperatures. Without a bona-fide mixing device, I cannot see indexing a stable secondary temperature. Given that your boiler return probably has the most stable temperature, it makes sense that the controlled variable, the radiation, also have that kind of control. You could theoretically mix it down and index it with ODR down to nearly room temperature.

What I see anyway and way past my bed-time.

Brad