What is this (mixing system on vintage PEX hydronic manifold)?

wvukidsdoc

So in preparation for laying out a new system at my father‘s house, I am trying to understand some of the old system. Dad installed this assembly somewhere around 1995 to 2000. He did not build this assembly himself, bought it from a early online supplier. This assembly “failed him about 15 years ago, with him thinking the three-way mixing valve failed, but honestly, it could be the pump or control system as well. Up until that time he states the assembly was regulating the temperature to the under floor PEX he had installed in a new addition, and added to the floors of old areas. At some point “it died” and for 10+ years has a bypass hose somewhat randomly mixing from a port closer to the return side of the boiler. Mind you for context, the boiler circulator is circulating to the entire house through zone valves, this is not primary secondary unless somewhat unintentionally. Again, I do not know what has failed, if the circulator even still runs, if it was inadvertently acting as a system circulator, or only for mixing. I’m trying first to understand exactly what is going on here as it was initially sold/intended. It would seem to me that the circulator here, possibly variable speed, has a control (the orange dial has temperatures in centigrade) as the mixing device. If so, what is the three-way mixing valve doing? I thought for a second it might be intended for boiler return temperature protection, but the outlet isn’t going in that direction, is rather feeding back into the manifold. I actually tried Google lens to see if I could even find a similar picture to the control to know what/who made it but alas, being from the early days of the Internet, no luck. I am unfortunately 10+ hours away, dad really can’t get to this anymore, he broke his femur last year, ended up with a short leg. My sister sent me pictures and video last weekend. I’ve bought the new boiler, and want to have most everything together before I go down for two weeks. For context, right side beyond the shut offs going to supply and return to the boiler, left side is just 5 loop PEX hydronic manifold set. Also for context, despite dad saying it did, this may never have truly “worked.”

TIA to anyone that can tell me what was initially going on here. Again, I used to be a mechanical engineer, but gave that up about 20 years ago. So I’m only partially an idiot.

John

mattmia2

The gray box with the orange knob is probably an aquastat. The 3 port valve with the knob is a thermostatic mixing valve. My guess is when the piping is hot because of a heat call the aquastat turns on the radiant loop circulator that moves flow through the mixing valve pulling some from the radiant returns and some from the boiler based on what the mixing valve senses to make the low temp water for the radiant. One of those 3 parts has failed or isn't getting power.

If you are using a mod con boiler and have no high temp loads you can make low temp water directly from the boiler and eliminate the mixing. You could also do outdoor reset that way.

Big Ed_4

It is a pump station with a pressure release bypass . The electric mixing valve I have to assume is controlled by out door sensor .. There should be another control to operate the mix … But it never worked you say ?

wvukidsdoc

https://forum.heatinghelp.com/discussion/comment/1901217#Comment_1901217

Ahh, probably it is an aquastat in a well at that. As I don’t think the pump is continuously variable speed, since it looks like the top of it is the standard Grundfoss 3 speed housing. What I don’t get then still is the mixing valve. The inlets would be from the return side of the Pex manifold on the left, and the return side back to the boiler on the right with the outlet going up back to the supply side of the Pex manifold. It would help a lot if I knew which direction this pump runs, I think I imagine an arrow on it pointing down, but that could be anything on the label. Again, I don’t think this circulator has anything to do with actually circulating through the Pex manifold loops, but I could be entirely wrong. I spoke to dad tonight, he does maintain that this thing worked fine, regulated the temperature for 10 or 15 years. His sense again was that the mixing valve failed, but he doesn’t recall why he thought that. Today was his 85th birthday, so I’m not going to hold that against him.

Replacing the 30 year-old Dunkirk boiler with another brand new Utica/Dunkirk boiler. No mod/con so returns have to stay hot. However, to the right of this are a further 6-7 high temp baseboard loops, with their returns coming in after this manifold. My plan is to ditch all of this, have a primary loop through the boiler with a secondary using most of the original high temp manifold piping for the high temp, run another secondary to replace this assembly for the low temp. Mostly, I was just trying to figure out what this thing was.

Also less there be any confusion, the top is the hot side supply, the bottom is return. I have no idea why he has the red handle on the bottom shut off and the blue handle on the top.

mattmia2

you can't have the boiler circulator just magically mix return water from the radiant loops with the hot boiler water, regardless of if it is a thermostatic or motorized mixing valve or injection mixing, you need a circulator for the radiant loops to move the return water to make the cooler water.

the box kind of looks like the right colors for something made by belimo. it could be a strap on aquastat. it cold be a proportional actuator for a 3 wat valve too. you need to see it from more angles.

since the red knob valve has 3 ports, not 2, i don't think it is a pressure bypass valve.

it is common for thermostatic mixing valves to get stuck, it may need a rebuild kit or to just be delimed in acid.

hot_rod

that was fairly common euro station in the early systems. Stadler, Viega, Ivar, EHT were some of the brands

What brand is the tubing? These were often part of a pex manufacturers kit that included tube, manifold, mix station.

If you find a name on the tube or manifold, search at that website for legacy documentation.

Kaos

It kindof looks like that the thermostatic mixing valve provides boiler low temperature return water protection and an electronic mixing valve for setting the space heat loop temp.

wvukidsdoc

I did initially think the same thing but the mixed outlet of the valve (presumably as it is the center port and as it has the temperature well) is back up to the supply side, not out toward the boiler return. Honestly presuming the pump is pumping upwards, injecting return water into the supply side, it would seem that both the pump and the thermostatic mixing valve are essentially doing the same thing.

mattmia2

the mixing valve can't move water, it can only adjust the ratio. it needs the circulator to move the loop return water through it.

i don't think the circulator is modulating, i think it is just controlled on/off.