Balancing valves at end of radiant panel loops?

Jonathan Stevens

Many thanks for the response. I should perhaps have said plug valves, but the same objection applies to those as well. It is a radiant panel system, ca. 1953. The panels are in the ceiling. For the last decade we have had endless problems with air in this system. I just moved the pumps to the hot side of the boiler, installed a new air separator (the old B&G boiler fitting was not properly installed, I think) and diaphragm expansion tank, and finally managed to bleed all the air out. It has been working for three days now.

There are two "zones" (with the simple control system of a pump controlled by a thermostat) and 16 panels. Because of the way the piping is set up, after my changes the secondary pump now pumps into the primary supply riser and is turned off for now. There is only one set of manifolds. All the supply piping is taken from tees off the supply riser and many of those are buried in the structure. However, if I reverse the flow of the primary pump, I can have both zones running, pumping away from the expansion tank, through the manifolds and valves, through the panels, and finally into the 1-1/2" riser. I have now read nearly everything on heatinghelp.com about panel heating and only find the following: "Balancing valves should be installed in each individual coil branch, either on the supply side or on the return sided--whichever is the more practical location" from http://www.heatinghelp.com/pdfs/163.pdf.

I can see no objection to reversing this, as the few branches from the riser are pitched down from the riser to the panels (as recommended in the vintage literature), the riser extends an extra few feet in the attic for bleeding/air cushion purposes, and there are no check valves in the lines. Let me know what you think.

If this works I want to replace the manifold/valve (Milvaco 1354) combinations with something more manageable and less leaky. I only have about 8" of each line to work with, though.

Jonathan Stevens
Rockford, IL

Jonathan Stevens

Balancing valves at end of radiant panel loops?

Greetings,

I am curious why the balancing valves were placed at the manifolds at the end of the loops in 1940's-50's radiant panel systems. Wouldn't it make more sense to put these at the warm side? These are little butterfly valves in Milvaco manifolds and are nearly impossible to balance.

Jonathan Stevens
Rockford, IL

Tim P. Tunstall

Balancing valves

Jonathan, for clarification, is it radiant panels or a radiant floor system?

With the exception of main branch piping, balancing valves are almost always positioned at the end of loops or return sides when it comes to terminal units. Usually a control valve would be on the supply.

Also, while it is possible to balance a system with a butterfly or standard ball valve, it can be difficult to achieve accurate flow rates because you only have 90 degrees of rotation to control flow. This is especially true with low flow situations like a radiant loop. For best results I would recommend a “Y” pattern, multi-turn, globe-style balancing valve like Macon Balancing or Tour & Andersson produce.