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radiant pumping

aldefed
aldefed Member Posts: 32
I have something going on that does not make sense to me.  I have a primary/secondary setup.  On the secondary, I have a UPS 15-58 FC pump, the primary a Taco 007.  The secondary pump feeds (3) 1/2" pex manifolds (each manifold supplied by 3/4 copper, about 20 feet for the longest run).  The manifolds have 2, 3 and 4 loops with the longest loop being 250 feet.  I can only seem to get .2 GPM per loop (according to the flow controls with them wide open).  Even if I change the speed of the pump, there is very little change at the flow controls.  I am also using a Taco i series mixing valve to mix my primary water down.  I would have expected a change in flow with the speed change and these flows seem low for the pump even at the slowest speed.  What am I missing?

Comments

  • lchmb
    lchmb Member Posts: 2,997
    How

    are you piped on the mixing valve?
  • aldefed
    aldefed Member Posts: 32
    mixing valve

    It's a three way.  C-mix, A-return, B supply from primary loop
  • lchmb
    lchmb Member Posts: 2,997
    ok

    and your circulator is pulling from the mix side of the mixing valve correct? Sorry in my area we see alot of people pumping at the mixing valve, which as it close's restrict's the flow..
  • aldefed
    aldefed Member Posts: 32
    see pic

    I've attached a picture of the mixing setup.  The primary loop runs from 130 to 180 degrees.  Right now my mix temp is 80 degrees.  My reset will be set to about .4 since I know I only need about 110 degree water on the coldest days.
  • lchmb
    lchmb Member Posts: 2,997
    curious

    I see the circulator is pulling off the mix side of the mixing valve (c) but where does the pipe go to the right?
  • aldefed
    aldefed Member Posts: 32
    nowhere

    The pipe to the right is a header for more circulators, they are just capped off.  I put them in just in case I needed to add another in the future.
  • lchmb
    lchmb Member Posts: 2,997
    I

    have never used the I series with out door reset. Reading the directions It does have a reduced out put for boiler protection. It would be flashing a code if this were the case. Have you checked flow/head pressure to make sure the 15-58 is the circ that you need? Have you checked for obstructions in the mixing valve body?
  • aldefed
    aldefed Member Posts: 32
    calcs

    I am not using the boiler protection function.  Here is what I figured.  The longest 1/2" pex loop is 250' and I got a calculation of 2.25 feet of head (from an online calculator).  My longest branch of 3/4" copper is 20' and I got a loss of less then 1 foot of head.  According to the mixing valve literature, IF I was pulling 4 GPM it would have a loss of 4 feet of head.  This adds to a total of about 7.  The literature of the circulator says that at 7 ft of head its flow would be 3GPM (on low speed).  At medium speed its flow would be 7 GPM.  If I did the calculations correctly, I do not see why my GPM on my flow meters does not change when I change the speeds.  If I add the flow from all my loops I am at 1.8 GPM (unless the gauges are not very accurate).  The other thing I tried is shutting off some of the manifolds too see if the GPM changes on the other open ones and it did not.
  • lchmb
    lchmb Member Posts: 2,997
    what

    happens if you put the circ on low speed? Do your guages change?
  • aldefed
    aldefed Member Posts: 32
    slow speed

    I am currently on slow speed.  When I increase the speed, I see very little change on the gauges.   The house is very well insulated and I only need .2 GPM or less per loop to get a 10 degree drop.  It's more of a curiosity as to why I don't see a flow change if I open up my flow controls and increase the speed of the pump.
  • lchmb
    lchmb Member Posts: 2,997
    first thought

    is when your increasing the circ your increasing head pressure. And of course wondering how accurate the guages are...
  • aldefed
    aldefed Member Posts: 32
    gauges

    I have to add three more loops tomorrow.  When I purge those I can see how long it takes to fill a 1 gallon jug and see if that matches the GPM readout of the gauges.
  • CMadatMe
    CMadatMe Member Posts: 3,066
    edited October 2011
    Delta

    Whats your delta across each loop? I also don't see 12" pipe off the tee before headig into my circ.
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • aldefed
    aldefed Member Posts: 32
    10 degree

    I run with a 10 degree drop across my loops.  There is only 5" between the T and cir.
  • Gordan
    Gordan Member Posts: 891
    Direction

    I would ensure that the circulator is pumping in the correct direction - that is, the inlet is toward the mixing valve and the outlet is toward the supply manifold. The arrow is cast into the volute, but that can't be seen on the picture, and the motor assembly can be turned in 90 degree increments so its position is no indication of the inlet or outlet orientation.



    Further, I'd make sure that the supply manifold is the supply manifold, and the return manifold is the return manifold. Flow direction through flow setters and disc valves is important.
  • aldefed
    aldefed Member Posts: 32
    Flows

    All of the flows are correct.  I added 2 more loops to the system yesterday and the GPM went down on the other loops.  I increased the speed of the pump and they did go up slightly.  I have 1 more loop to add today and will check the accuracy of the flow meters.  The one other thing I noticed is that the noise of the secondary loop increases greatly when I change the speed of the pump. 
  • Gordan
    Gordan Member Posts: 891
    The noise indicates a restriction

    Can you try to narrow down where it's coming from, and use that as the starting point for troubleshooting? Might be hard with the copper being such a good sound conductor, but...



    If it's all over, then that would indicate that there's a lot more flow through the pipe than the flow indicators indicate.
  • aldefed
    aldefed Member Posts: 32
    noise

    It sounds like it's around the mixing valve, mostly in the return line.  I guess the mixing valve could be restricting me, in which case I should have gone with a four way valve.  According to the specs, it has much lower restriction.  Right now I have 12 loops running barely .2 GPM each.  I will have 2 more to add in the near future.
  • AlexS
    AlexS Member Posts: 69
    I dont want to hi-jack your thread...

    but I have the same issue.  12 loops run with a Taco OOR secondary pump and I show very little flow on the flow meters.  I still get a 15-20 degree Delta T and my floors are toasty.



    I also have a noise, but mine comes from a 3 speed OOR pump on the primary side.  It's brand new, but that sucker is getting pulled real soon. It drives my wife nuts.
  • aldefed
    aldefed Member Posts: 32
    test

    I did a test after I hooked up my last loop.  I basically ran my secondary without the mixing valve.  As soon as I did this, the noise went away but I still only had a small GPM increase.  I raised the speed of the pump and then I did get an increase of double the flow, also with no noise.  It would seem to me my pump is not correct.  Either the pump curves I saw are not correct or I have alot more head loss than I am calculating.  Any thoughts?
  • CMadatMe
    CMadatMe Member Posts: 3,066
    Heat Loss

    Lets forget about the flow for a second. What is the heat loss you arentrying to overcome in each room that is supplied by each manifold. According to my head loss calculator for Pex you have .9ft of head on a loop of 250 with 120 degrees of 100 percent water. On a 30% Glycol mix it would be 1.8ft of head.



    Your 20' of 3/4" pipe is about 1.6ft of head. Your I-Valve which looks to be a 3/4" Union style at 4gpm has a head of 1.82ft. That would give me 4.32ft of head. What is the heat loss?
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • NRT_Rob
    NRT_Rob Member Posts: 1,013
    flow meters

    are usually also balancing valves. try "opening" the loops or loop balancers further. on our manifolds you twist the flow meters to do this but other brands may have dedicated balancing adjustment valves on the opposite manifold.



    we have found that once a flow rate is dialed in, it's *almost* like a flow setter... pump adjustments almost don't matter (as long as it's over the minimum, of course).
    Rob Brown
    Designer for Rockport Mechanical
    in beautiful Rockport Maine.
  • aldefed
    aldefed Member Posts: 32
    heat loss

    For the last 3 years I have been running at .2 GPM with a water temp. of 90 to 110 with a 10 degree delta (those conditions keep the house around 70).  At that time I was only running 5 loops with a Taco 5000 series mixing valve.  This year I added an addition which added 9 more loops and I installed the iseries so I wouldn't have to manual change the water temp as it got colder outside.  The addition is better insulated than the old part of the house so I know I will be able to run at the same conditions.  I also run it 100% circulation.  The way it is running now, it heats the entire house just fine.  The pump is very noisy and my flow meters will barely move even though they are wide open.
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