Into mysteries? I love ‘em!
Apparently, so could Declan P. McManus.
If this story is a bit familiar, it’s a re-make of a 3 year old blog – updated for 2013.
Now, on to our mystery…
Boiler changeout, 80,000 BTUH load, 5 zones valves (not replaced), new expansion tank, feed valve and air scoop topped off with a Taco 3-speed 0015. The old boiler had an old Taco 3-piece 110 series circulator.
New boiler heated great, but there was one problem.
The zone valves banged like crazy!
Anyone who watches the detectives knows you start by asking questions. After all, zone valves don’t bang just because they feel like it. Something changed…
Do all five zone valves bang all the time?
If all five are calling and one closes, does it bang then?
Does the banging occur when only one or two zones are calling, and then one closes?
We learned the banging only happened when one or two zones were calling. When all five zones were calling, no bang.
Let’s examine the evidence more closely. Everything’s new, including the circulator. They replaced the old 3-piece Taco 110 with a Taco 0015 3-speed circulator. When the 0015 made noise, our wholesaler was told to swap out the Taco and use a Grundfos 15-58 3-speed instead.
Still banging. On all three speeds.
As a great mystery-solver from years past would say:
The solution, as it is with most mysteries, is in the details. In this case, it has to do with pump curves.
Submitted for your approval are three pump curve charts – for the Taco 110, the Taco 0015, and the Grundfos 15-58.
The Taco 110 is what we call a “flat-curve” pump – it’s a high-flow, low-head circulator, perfect for zone valve applications.
The Taco 0015 and Grundfos 15-58 are so-called “steep-curve” pumps – lower flow, but higher head pressure. These are great for radiant floor heating, and well-suited to be zone pumps for panel radiator or baseboard jobs using copper or PEX tubing.
The only substantive change in the system was in the style of circulator.
“Zoiks! A clue, Scoob…”
Time for you to put your thinking cap on. What’s making these zone valves bang?
And what are some of the options for making it go away?
Yep – it’s a Mystery Dance, alright…
“Don’t bury me ’cause I’m not dead yet…”
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