How to automatically vent domestic hot water recirculation loop

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after the circ line leaves the mech room where does it go?
I am wanting to know
1] how it ties in at the end of the run
2] what changes of elevation does it make?
3] fittings and valves in system
I am concerned that your pump only has a 3' head listed.
I see more than 3' 9'' of head in the mech room. and the water still has 50' to travel
I am concerned you do not have enough head pressure in that pump to circ the water
so ..in theory,, the water is not circulating it is sitting static

Features

  • Silent operation
  • Integrated external sensor cable - simply mount the sensor on the hot water supply pipe
  • One-touch operation - settings are easily changed using only the fingertip
  • 6 feet line cord
  • Insulation shells for fast installation
  • Lead free brass housing eliminates risk of corrosion
  • Compact design facilitates installation in confined spaces
  • Maximum flow 2.2 GPM (0.5 m³/h)
  • >>>>>>>>>>>>>Maximum head 3.9 ft (1.2 m)<<<<<<<<<<<<<<<
  • Liquid temperature 36°-203°F (2°-95°C)
 
Taco 400 auto air vent. Replace the uppermost 90 above the pump and boiler drain with a tee. The Taco 400 is 1/8 inch threads, adapt to that and purge the system and you’re good. A lot of people don’t have vents on their loops and they work. I would like to figure out why you’re getting this problem uniformly every 10 days.
 
frodo said:
after the circ line leaves the mech room where does it go?
I am wanting to know
1] how it ties in at the end of the run
2] what changes of elevation does it make?
3] fittings and valves in system
I am concerned that your pump only has a 3' head listed.
I see more than 3' 9'' of head in the mech room. and the water still has 50' to travel
I am concerned you do not have enough head pressure in that pump to circ the water
so ..in theory,, the water is not circulating it is sitting static

  • >>>>>>>>>>>>>Maximum head 3.9 ft (1.2 m)<<<<<<<<<<<<<<<
Click to expand...
Correct me if I'm wrong, but I think the head loss calculation doesn't include the heights in a recirculation loop but only the lengths, fittings, pipe material and diameter. Without getting into all the nitty gritty, I will make the claim that both in theory and in practice, the head loss is not an issue.
 
RenewDave said:
Taco 400 auto air vent. Replace the uppermost 90 above the pump and boiler drain with a tee. The Taco 400 is 1/8 inch threads, adapt to that and purge the system and you’re good. A lot of people don’t have vents on their loops and they work. I would like to figure out why you’re getting this problem uniformly every 10 days.
Click to expand...

Thank you chiming in, RenewDave. Do you think installing the vent at the elbow you mentioned is a better idea than, say, somewhere on the horizontal run in that same high region of the loop, maybe near the ball valve?
 
True! The only head loss in a closed loop piping system would be the friction loss. Sort of part of the reason it is referred to as a "circulator".

Greenthorn said:
The last time I purged the system, I closed the valve below the pump, and opened the hose bib and let a gallon or so of water out. That worked just fine and I've seen several days now of the system working fine. So that purged that one section of visible pipe between the draw-off valve and the cold water connection to its right.
I'm trying to use some of the information I've gotten in this thread (thank you again) to figure out the problem. A month ago, I would purge the system by first closing one valve near the pump and flushing water through the hose bib, then opening that valve and closing the other valve near the pump. I wasn't being as scientific, but the system worked, so I could just go back to playing solitaire for a while.
Click to expand...
Assuming the valves near the pump, you mention, are the 2 globe valves for the 2 recirc loops, that sounds good provided you shut off the ball valve located on the discharge side of the pump to isolate the cold water from running back. A garden hose should be connected to the draw-off valve to properly purge the each of those 2 loops. i.e. one globe valve open at a time.(although I thought one of those 2 loops was not completed.)
 
I was trying to follow the thread but the photo posted in #1 post shows as a link to another thread about a chrome p-trap. ???????

IMG_7691.JPG
 
frodo said:
https://us.grundfos.com/content/dam/GPU/Literature/ALPHA/98532861-0714-UP-ProductGuide.pdf

page 40


ok guys, someone explain something to me, teach me

how do you figure a circulating system that has openings at the faucet is a closed loop system?

a closed loop system is ''closed loop'' like a boiler loop

in a circ system the air can exit via the faucet. so it is not ''closed''
Click to expand...
It's a closed loop while it's circulating back to it's source.
Sure when a sink faucet is open, any air that can reach the faucet would come out, however, as we know we have at least one example, at the water heater, where an air trap was created after the pump, by going up, to the right and then down again. Kinda like the same reason an air vent(manual) is recommended at the return side of baseboard water heating systems.

In terms of head requirements of the pump, it should not have to overcome any elevation head. Just look at it as creating a differential between the suction side and the discharge side of a pump that's located within a 70 psi hydraulic system.
 
frodo said:
https://us.grundfos.com/content/dam/GPU/Literature/ALPHA/98532861-0714-UP-ProductGuide.pdf

page 40


ok guys, someone explain something to me, teach me

how do you figure a circulating system that has openings at the faucet is a closed loop system?

a closed loop system is ''closed loop'' like a boiler loop

in a circ system the air can exit via the faucet. so it is not ''closed''
Click to expand...
Just looked at that link you provided on the grundos pumps. page 40.
Pretty much confirms what @Greenthorn had said,,,
"The pump uses two temperature sensors, one within
the pump and the other connected to the pump by a
cable installed on the hot-water flow pipe."
It's just too bad it doesn't explain the philosophy behind it.
 
frodo said:
https://us.grundfos.com/content/dam/GPU/Literature/ALPHA/98532861-0714-UP-ProductGuide.pdf

page 40


ok guys, someone explain something to me, teach me

how do you figure a circulating system that has openings at the faucet is a closed loop system?

a closed loop system is ''closed loop'' like a boiler loop

in a circ system the air can exit via the faucet. so it is not ''closed''
Click to expand...

Frodo, better sources such as the Caleffi videos previously mentioned will describe head loss/friction in better detail, but the way I think of it is: yes, you have to pump the water uphill, but you get all that energy back when it comes back down the hill, minus friction. Also, the vast majority of the time the faucets are closed and so any detailed calculation of head loss just considers the faucets as some fitting with some equivalent length of pipe as a factor.
 
Diehard said:
That is weird!
This is what we see when we click on it.

I'll bet you're using a cell phone.:confused:
Click to expand...
yes I was and thanks for the photo.
P.S. Now I'm going to check the #1 post and see what's there
 
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