Why are balancing valves not required with Caleffi TankMixer using cross?

MatthewPK

When using series 521 MixCal Caleffi notes that you should use two balancing globe valves to address temperature creep during zero-flow conditions. (Diagram on pg 7 of the installation guide here: https://www.caleffi.com/sites/default/files/media/external-file/01050_NA.pdf

This approach is likewise explained and recommended in the excellent "Coffee with Caleffi" video here (around the 44 minute mark)

https://www.youtube.com/watch?v=EDzFCwDxvVg

However, on the instruction document for the Series 520 TankMixer here: ( pg 10 https://www.caleffi.com/sites/default/files/media/external-file/NA10482.pdf )

The instructions suggest that no balancing valves are required if you use the cold-water cross.
How can this be? Looking at the documentation for the cold-water cross I don't see how it can eliminate the need for balancing valves.

In the same 520 installation document, on the same page, it instructs you to use balancing valves if you do not use the cold water cross. So I don't think it's a difference in the 520 vs 521 valve design.

hot_rod

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https://video.search.yahoo.com/yhs/search?fr=yhs-ima-st_mig&ei=UTF-8&hsimp=yhs-st_mig&hspart=ima&p=caleffi+520&type=q3000_set_bcrq#id=1&vid=74dba65efce45e08b46f11b397bb6de5&action=click

MatthewPK

https://forum.heatinghelp.com/discussion/comment/1805149#Comment_1805149

Hi hot_rod!
I've seen those documents and the linked video. That's where my confusion comes from. You see in the Caleffi installation video that you linked he makes no mention of needing balancing valves on the recirc system. Indeed as shown there are none. The Cold-water-cross connects to the mixing valve with no control between it and the recirc pump.

Do you see what I mean?

Here is the screenshot from the installation instructions for the 521

Notice the call for the globe valves (for balancing). Those align with the video I linked before,
But those valve are absent from the 520 instructions.
Here's a link to the timestamp in the video I had previously linked:

https://www.youtube.com/watch?v=EDzFCwDxvVg&t=2585s

hot_rod

the 520 valve has the ability to shut off the hot port if the cold water supply fails. So this is how it can prevent temperature creep without the need to balance the recirc flow.

I believe the 520 is now dual listed as a 1017 and 1070. As such it needs that 100% shut down function, and a cap that limits the mix temperature to 120f.

I have a video showing how the 520 actually works, water flowing through it, cold water gets shut off, flow stops. Actually reduces to a dribble so it can still sense what is going on.

if I can find it😗

MatthewPK

https://forum.heatinghelp.com/discussion/comment/1805156#Comment_1805156

Ahhh ok. So the 520 series valve can totally shut off the hot supply but the 521 cannot.

Will the 520 series continue "cold" flow (like a 1071 valve) which in this case will be circulated temperate water? Or will it terminate all flow?

hot_rod

1071 is an emergency equipment valve, eye wash stations, etc. I’m not sure how it operates. I don’t think we offer a 1071 to test.

MatthewPK

https://forum.heatinghelp.com/discussion/comment/1805160#Comment_1805160

Yep. I think I have the info I need. Thanks!
The sell-sheet for the 520 says this:

"Tight hot water close-off:
Prevents recirculation temperature creep.
Improves pump’s aquastat service life."

So I think this explains why the balancing valves are not required — The hot can be close off entirely on the 520, but it's always a little open on the 521.