How to balance a pex manifold?

Ed Lentz_2

I have a 4 zone pex manifold. It is a Stadler Viega Brass manifold.

I have poor heat transfer in two of the zones. They are fairly the same length, if I remember right. Put the system in over 15 years ago. The controller is a Stadler Basic (Rebranded Tekmar I am told). I did some crude temp measurements using a instant meat thermometer on the Pex itself near the manifold coupling. Here is the results. In the temp difference between source and return

Zone 1 28 degrees
zone 2 5 degrees
Zone 3 3 degrees
Zone 4 10 degrees.

The zones that are the coldest are 1 & 3

I have searched all over on balancing, but nothing specific on this manifold. Is it just a matter of adjusting the valves on the source for each zone? I have no way to ascertain the flow rate. Would it be possible to have an air bubble in a zone or two? That would keep the circulation to a minimum wouldn't it? I do have air traps
installed. One other question, the Oventrop on the right. What is it's purpose? When I installed this I had the help of a Master Boiler Installer. He spent hours drawing up my system , sold me the stuff and stood inspection with me. He has since past away so I am left to some of my own failing memories (

Thanks for any ideas

hot_rod

If it has worked in the past, I’d suspect that Oventrop not opening fully. I think it is a master ZV for the entire manifold, or is it an adjustable TRV.

Ed Lentz_2

It is a TRV But only moves from 1 - 3 Never was to clear on ist purpose there

Ed Lentz_2

How does that valve open, on a downward force or up?

hot_rod

So it has a sensor into the room? Higher number typically higher temperature. Remove the head and it should be wide open, full supply temperature

Ed Lentz_2

I removed the TRV and the house is 5 degrees warmer this morning. This is a good thing. I also opened all the valves to allow full flow on all the zones.