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Secondary loops doesn't move the water

mknmike Member Posts: 82
OK.  I admit I made a few changes.  I removed two radiators that come off one 1.5 set of pipes at the end of the two lines. I did not expect that to cause this problem because most of the radiators seem to come off the main "trunk" pipes in pairs that make their own individual loops, just like the radiator I just installed that had been removed, leaving two plugged pipes in our bedroom. 

Here's what I see as the important aspects of our setup regarding the flow:

- At 2" and a 1.5" return line merge into a 2" cast

- Downsize to about 1.25" copper (vertical going down)

- T with a boiler drain (vertical going down)

- 90 to horizontal

- Honeywell Supervent with an expansion tank on the bottom

- Ball valve (in open position)

- 90 degree, still horizontal

- 90 degree to vertical (going up)

- T - to primary loop return. (there's a grundfoss pump inside my triangle tube for the primary loop which can be set to low/med/high, and it was set to low)

- T to primary look supply (T's are actually touching eachother, very little mixing area)

- 90 to horizontal

- 90 - still horizontal

- ball valve with flange to connect to taco circulator

- taco circulator

- ball valve on flange to taco

- brazed in 1/2" cold water supply (from top of this horizontal pipe)

- 90 to vertical (which was leaking on the vertical side and I heated and added flux and solder to fill the tiny hole)

- Big 2" cast 90 with a small 1/2" pipe in it, switches to horizontal.

Some info:

- I drained the boiler to do 4 things:

(1) connect radator where one was removed and the two pipes were plugged.

(2) remove long rusted kitchen baseboard radiator for kitchen renovatsions

(3) remove third floor bathroom radiator for bathroom renovations

(4) fix the leak in the supply pipe copper (did not disconnect, just heated and addded flux and silver solder, can't imagine I clogged the 90.)

- The pipe on the outlet side of the Taco never gets warm. 

- Pipes between the Supervent and the taco pump are hot, boiler stops combustion when water reaches ~105 F, but temp rises to almost 120 some times when it fires because it is heating such a small amount of water.

- The taco almost always seemed loud and ran hot from day one.  It sounds quiet when running, but I can hear it running.

- I had high velocity central air installed this spring, and the unit was wired to the same thermostat, and it seems to be wired correctly as the pumps seem to turn on when they are supposed to.

- I did vent all the radiators from bottom to top, and vent the boiler, but I do hear gurgling in the boiler, more-so when I switch the internal pump speed to med or high.

- I did have the outlet side of the taco pump disconnected to completely drain the leaking copper fitting.  I reconnected it and figure my next step is to see if there is some obstruction at the pump. 

- I don't know how to check if there is an obstruction in the super vent because the installer did not put a valve in between the supervent an the rest of the system return.  So the whole system would need to be drained again. 

Any ideas?  Would a picture help? 

Could it be as simple as nothing wanting to flow because I took out two radiators off?  I thought all the radiators were connected in parallel and this would not cause such a problem. 


  • mknmike
    mknmike Member Posts: 82
    Pic of return and supply in copper

    Trying to upload first pic

    Sorry the pic needs to be rotated 90 to the right. (Top is on left side of pic. Not sure what happened there.)
  • Ironman
    Ironman Member Posts: 7,375
    Air Bound

    More than likely, you're air bound. The MBR (SuperVent) can do nothing to remove air that is trapped above it. It can only remove what passes thought it.

    The larger pipes compound the problem as the velocity of water is probably below the minimum of 2 ft. pr. second needed to force air downward - if you had flow.

    The air is gonna have to be removed from top, including the pipes you capped off. You could try partially loosening the caps slightly until nothing but water comes out, but that is risky. Putting fittings with bleed ports on them would be the safer approach.

    Once you've don that, increase the static fill pressure temporarily to 25 psi and bleed the air with the system cold and the boiler and pump off.

    Then, return the static fill pressure to 12 psi for a two story house, 18 psi for a 3 story.

    I'm assuming the piping is correct.

    Where is the circ located: before or after the expansion tank connection?

    Posting pics would be helpful.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • mknmike
    mknmike Member Posts: 82
    Got a little spirt of air removing pump

    Got some air spray with water while removing the outlet side of the pump. Maybe there was just air trapped in the pump?

    Is my cold water feed on the wrong side of the pump? Should it be on the inlet side instead of the outlet side? It seems that the cold water inlet would create a higher pressure at the pump outlet before the pump even starts.


    I just now removed the flow check valve. The higher pressure and an air gap in the pump... I hope I didn't destroy the taco by running it dry for about 5 hours.
  • Ironman
    Ironman Member Posts: 7,375

    That circ must be mounted with motor shaft horizontal. You need to rotate it 90*.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • mknmike
    mknmike Member Posts: 82

    All pipes are cold other than the boiler outlet on the primary loop. Yeah!!!

    Thanks HeatingHelp!

  • mknmike
    mknmike Member Posts: 82

    I guess it is an obvious trick to connect the inlet side of the taco pump first, and loosely connect the outlet side. Then open the inlet valve to fill the pump with water until it sprays or drips consistently out of the loose outlet connection. Then tighten it down.

    I would like to say "I'm learning" but this seems like some pretty obvious crap.
  • mknmike
    mknmike Member Posts: 82
    You sure are right!

    By George, I think you are right! That circ shouldn't be horizontal, or at a relative high point. More bad work by my installer.

    I'm kind of kicking myself for not installing a valve prior to the supervent while I had the system drained. I assume that would enable me to totally re-pipe my primary-secondary loop connections, prepping for future zones too.

    Live and learn... a little at a time.

    At least we got heat!
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    The genius that installed the baseboard emitters...

    In my house, I had the tiny baseboard units (three feet long) replaced by 14 feet units of Slant/Fin. The contractor put no bleeders up there. When I asked why not, he said that baseboard units do not require bleeders. Well they did install purge valves and got almost all the air out. None seemed to come out when the purge valves were opened (hose submerged ij a bucket). But I could sure hear the air bubbling through, though there was not enough air to prevent the baseboard from working.

    I have a microbubble resorber in there and it eventually allowed the air upstairs to dissolve into the water and get removed by the resorber. But that took several months because the outdoor reset often runs that zone at 110F and is difficult for the resorber to remove the air when it is so cool. If the system does not have so much air in it as to be air locked, you could use one of those fancy air eliminators (Spiro Vent or the Taco Pawl Ring type) and have patience. If the air is too bad, it may harm the circulators.
  • mknmike
    mknmike Member Posts: 82
    Air bound was right!

    I still hear some gurgling, but it's a lot better than no function at all. I think without the check valve or with the correct filling technique, I would have had at least gotten some water into the circ pump. This seems like hydronic 101. I really should have known better, but 3 AM and tired with a cooked brain, it didn't even occur to me. The worry monsters got me thinking that either the AC company messed up my wiring, or I screwed up by removing the two radiators. It sure is a relief to know my problem was just procedural. Shwew!

    Thank you guys!

    Oh... I had a moisture problem behind a baseboard radiator (not original to the house) that had to come out to work on the moisture problems. After looking at the rust/rot on the back side of the unit, I'm thinking maybe the radiator was the source of the moisture. I can't wait to get that thing out of the house and pressure test it for curious it sake.
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