ques about Pri sec radiant piping

tlj000

I've attached a couple of pictures of a piping setup that looks odd to me. I have not seen a setup with a circulator in between the the tees and it seems that the primary loop should be flowing in the opposite direction. Will this work?

Mark Eatherton

I've seen that system before...

and it confused the living crap out of me when I first laid eyes on it.



It has a sensor bulb that monitors outside air temperatures, and changes the two 3 way valves to increase the supply temperature as it gets colder outside, and vice a versa when it warms up.



The manufacturers name escapes me, but I remember is it German, and if memory serves me correctly, the company was absorbed by the Uponor group of companies quite some time ago. In fact, the president of that company USE to write the hydronic heating articles for Contractor Magazine. I think I took over his job.



It is a real PITA to purge, requiring removal of the non electric operators. You have to hold your mouth just right and stand on one leg to get it to purge :-)



This ain't your grandpas P/S system...



ME

tlj000

viega

I am told it was designed by Viega. That the company your thinking of?

Mark Eatherton

Yep...

That is the one, and the instructions that come with it (we found some someplace) are NOT a whole lot of help. It use to be the Stadler Corp before it became Viega, and the guys name was Joe Fiedrich. An early pioneer in the hydronic writing field.



Are you experiencing an issue or just curious about the methodology?



ME

tlj000

low aquastat

I was there for an energy audit. The home owner says he has been having a problem with it, a couple of zone that won't go above 68. I noticed that the boiler aquastat was was cutting off at 100. I  don't generally mess with customers equipment so I suggested he have his heating contractor look into why it's shutting down at 100.  The primary loop should not go below 140 right? 

When I looked at the second boiler in the home, an oil fired hot water system. the aquastat was set to 240. I'm thinking he may need a new heating contractor.

CMadatMe

Good Ole' Joe

Yup that looks like a station and was Stadler. Joe also is the inventor of Quik Trak and Climate Panel..He also had his hand in bringing Viessmann to the US. He was ahead of his time and those of us who had the chance to learn from him wish him nothing but the best. By the way that was the good ole NR-32 Mark was refering too. Basically a capillary that sensed outdoor temp and by fluid movement opened and closed a diverting valve. They were the cornerstone when we first started doing radiant in the early 90's.



Here are all his articles in Chronological order. Pretty interesting reads when you compare to what he was saying and today. I was able to get these through his permission to share them. If you google him you can't find them anywhere.

Jean-David Beyer

primary loop should not go below 140

I am just a homeowner with a mod|con gas boiler; my largest zone is in-slab radiant.

The temperatures I run in the slab are from 75F to 120F depending on the outdoor temperature. The heating zones (I have two) are in the secondary loop, with the boiler in the primary loop. I imagine the primary loop runs slightly hotter than the secondary, but by no means up at 140F except when running the indirect DHW that is connected across the primary loop.



If you are running a condensing boiler, you pretty much want the primary loop to run under 130F; the lower the better provided you get enough heat into the secondary loop, and it pretty much all goes there. My boiler has temperature sensors in the secondary loop that control the primary loop temperature. It got down to 12F today and I was putting 110F water into the slab.



Only if you are running a non-condensing boiler should there be any need to run over 140F water to prevent condensation. For in-slab radiant, that is. Other radiant heating schemes may require higher temperatures. It depends on the heat loss, and the radiant emitters.

tlj000

constant circulation

I see Joe is a fan of constant circulation. That being said the layout makes a little more sense. Just outside of the picture there was a thermostat and a temperature  differential control. I don't think he would be a fan of all the exposed copper in a cold uninsulated basement.

CMadatMe

Nope He Wouldn't Have

He would have told you to insulated and in the same breath told you to leave the darn thermostat alone and let it fly!





That was the way. NR-32 (Outdoor Reset) or WM-32 (Indoor Reset). Do a heat loss, do a proper design and let it fly like a bird..



Attached is the current instructions but they follow the same principles..

tlj000

circ location

The actuator and outdoor reset make sense. But with this setup if the demand called for hotter water temp the actuator would open and pull water from the primary loop but will it just dump back into the primary loop on the other side of the circulator. seems to me that you would what two closely spaced tees on the low pressure side of the circulator.

Mark Eatherton

Confusion...

Is the root of all evil...



Techs look at this device (like yourself) sand say it doesn't make any sense, rip it out and replace it with something that makes sense.



I honestly can not explain exactly how it is that it works, but it obviously works, or there wouldn't be thousands of them out there working perfectly fine.



I do remember that it was a P I T A to purge out tho....



ME

Dino_2

Pressure Differential

The mixing set up works on pressure differential.

If you notice the primary and secondary have their own pump.  There is nothing that will create flow unless you interfere with the flow.  Once the valve starts to close, it will force flow to through the pump discharge (higher pressure) side connector.  Once this happens, you create a pressure differential, hence flow from the primary to the secondary and vica versa.

It's quite simple, though it does confuse many.