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Help! Unusual system design problem

Davew773 Member Posts: 5

I have a ~30 year old house with a brand new high efficiency boiler (forced hot water) that was installed at the end of last year's heating season and wasn't fully tested. I am now experiencing a problem that my installer seems to have a great difficulty solving.

There are 3 zones in my "main house" area and I have a secondary attached garage with an inlaw over it which has another 3 zones. The main house doesn't have an issue and heats properly.

The second garage/inlaw is fed from a single line to a manifold with 3 zone valves and controller. The single line comes from the boiler and there are no valves between the garage and boiler and water is fed from a pump on the return line on a inlet manifold coming from the return which pushes water through the boiler towards the garage. (there are zone pumps for the main house that this line bypasses).

Now, in the garage, the supply line comes into the manifold where the pumps are to the 3 zones, but there is a connection between the hot supply and cold return, which I don't understand why it's there. This was existing with the old boiler and retrofitted with new pumps for the new system. Now, I can feel hot water in the supply line up to the point of the pumps, and sometimes it'll get pumped through the zones, but most of the time it doesn't.

My guess is that when the zonekicks on, it sometimes pulls from the return and mixes the water, never fully pulling just hot water.

I keep telling the installer to remove this "loop", but he keeps grasping at straws.

As a picture is worth a thousand words, I've attached one.

Thanks in advance for your help!


  • Zman
    Zman Member Posts: 7,551
    Primary/secondary gone wrong

    Can you post a sketch of the whole system?

    It looks like an incorrect primary/secondary arrangement.

    More info needed...

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Ironman
    Ironman Member Posts: 7,353
    Can't really tell..

    From your pic, but it looks like that may be a pri/sec loop. If that's the case, water is taken off from the first Tee, pumped to the secondary loop and returned through the second Tee.

    More pics, showing the overall piping, or a diagram would be helpful.

    See the attached diagram for an illustration of pri/sec piping.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Davew773
    Davew773 Member Posts: 5

    Here is a sketch and a couple of pics of the boiler area.

    Hope this helps!

    Thanks again!

  • Davew773
    Davew773 Member Posts: 5

    The supply and return go to two different pipes.

    Theoretically, if you remove that loop at the end, the return water would still get back to the boiler.

    Please forgive me, I am an IT guy and not a HVAC tech or plumber.
  • Ironman
    Ironman Member Posts: 7,353

    According to your diagram, that is a secondary (actually tertiary) loop. The piping principal remains the same. You need another circ to move water through the loop between the boiler and garage. You could remove the two Ells at the end of the loop and cap the supply and return there, but it looks like installing another circ would be easier and probably more beneficial. You may need an additional relay for the extra circ if you don't have provision in the garage zone control.

    Your installer did a neat job; it looks like he takes pride in his work. One other thing needs to be corrected though: your circ's need to be repositioned so that the motor is horizontal. You cannot install wet rotor circ's with the motor vertical, or semi-vertical as yours are. The bearings are water lubricated and the end bearing will trap air and go bad if left like that. It's in the instructions - but who needs them?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Davew773
    Davew773 Member Posts: 5
    Thank You!

    Thanks Bob... I finally convinced my installer to take out that loop at the end of the tertiary loop.

    Interesting about the circulators being installed improperly. I'll see if he's willing to reinstall those.

    You're right about his overall work. It does look very nice. I am just surprised at his lack of knowledge about this problem and the circulator install issue. Very frustrating, however, given the amount this system cost me.

    Thanks again!

  • RobG
    RobG Member Posts: 1,850
    edited November 2013

    I just checked the literature and these pumps should be mounted with the motor upwards.

  • bob_46
    bob_46 Member Posts: 813
    Position of motor

    Rob I think you might have misinterpreted the instructions .
  • knotgrumpy
    knotgrumpy Member Posts: 211


    Unless it is there, but just was not in your sketch, you are still going to need a pump on that loop. 

  • Harvey Ramer
    Harvey Ramer Member Posts: 2,239
    Ha Ha!

    Most definitely! How else could you make the water flow? It's funny when you have to turn the circulator end for end to make the water flow the right way, there is always that bothersome wall there and you have to turn the motor either up or down to get by ;-)

  • JohnNY
    JohnNY Member Posts: 3,226
    18 psi?

    Most pump manufacturers' literature states specifically that you can't mount the pump with the shaft vertically unless the system is pressurized to a minimum of 18 psi.

    Grundfos doesn't give you that.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
  • Ironman
    Ironman Member Posts: 7,353
    Adding Circ.

    Instead of removing the Ells at the end of the loop, I'd install the circ at the manifold near the boiler. You could wire it parallel with the boiler circ so that it comes on when the boiler is fired. That will keep water moving in the piping between the garage and the house and may help prevent freezing. It may use a little more gas, but shouldn't be that much if the pipes are insulated.

    Or, you could add a pump relay there such as a Taco SR501 and the pump would cycle with any call for heat from the garage.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • RobG
    RobG Member Posts: 1,850

    I was looking at the instructions for the UPS Series 200.

  • Davew773
    Davew773 Member Posts: 5
    Thanks again everyone

    You guys are awesome! Thanks for all your efforts.

    I will let you all know how it pans out.

    I'm pretty sure that once he removes the Ells that the increase in supply pressure should help the circulation up to the zones.
This discussion has been closed.