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hydronic coil circulator size

margsuarez
margsuarez Member Posts: 54
edited April 2015 in Gas Heating
Hello Heating Helpers,

I am new to homeownership and contracted to have my first boiler installed about a year ago. Forgive me if I get any of the terminology wrong below.

I have a question about the sizing of the circulator for the 3-coil hydronic coil in my ADP B-series air handler (BVRM..31). Currently it's a Taco 0015 running on low setting, on the CH1 secondary loop off the boiler (Triangle Tube Prestige Solo 110). I have CH2 con an equivalent pump (the Grundfos 15-52) also set to low and feeding 2 stories (total 1000sqft) of radiant floor (WarmBoard), which is my primary heat source. Air thermostat is set a couple degrees colder than floors (using it only as backup). To add mass to my system (boiler is oversized) I had set the boiler to turn on both pumps, even if only the floors were calling for heat. I found that this gave me longer burn times and also had a chance of heating the air circulating when my HRV turned on the air handler.

Recently, the CH1 pump started making a grinding noise (motor is warm), so I went back to running CH2 only - CH1 will not run unless temperature falls 2 degrees colder than the floors.

I read the manual for the ADP air handler and computed the head loss of my hydro-air loop. I only have about 10 feet of pipe with about 17 90's (21 if you count the other secondary loop tees and the "dead end" stubs on the supply and return manifold). At any rate, using ADP's computation chart, I figure i have about 2.7 - 3.0 feet of head.

I read that the Taco 0015 is oversized for this hydro coil. To get the 3gpm recommended by ADP I would need 12-14feet of head. I read somewhere also that too much velocity can wear out or damage the coil.

Should I ask my plumber for a smaller pump? Perhaps the 0015 can be repaired under warranty and kept as a spare, as it is equivalent to the DHW, CH2, and internal system pump.

Or should I not worry about it, and just replace the 0015? A smaller pump would also use less electricity.

Thanks for your guidance
marg

p.s. would like also to hear ideas about dialing in my boiler to get the most benefit out of my radiant setup.
Triangle Tube Prestige Solo 110 with Trimax Controls (3x oversized)
950 sqft of WarmBoard on 3 floors, 5 loops acting as one zone

Comments

  • margsuarez
    margsuarez Member Posts: 54
    p.s. I called ADP and they told me when they provide a circulator with this air handler it is a Taco 006.
    Triangle Tube Prestige Solo 110 with Trimax Controls (3x oversized)
    950 sqft of WarmBoard on 3 floors, 5 loops acting as one zone
    icesailor
  • Ironman
    Ironman Member Posts: 6,585
    The 015 is probably more circ than needed, but to make that determination, btu requirements, line sizes, piping methods and other data is needed. Height doesn't factor in a closed loop.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • margsuarez
    margsuarez Member Posts: 54
    thanks for the response. I did the calculation suggested by ADP. I guess my question is since the 0015 is too much circ, is that detrimental to my equipment?

    or does that just affect the BTUs? I don't care about that so much since the hydro coil is there for only back-up heat (I am heating the floors, which are able to heat the house, even this past February-March in NYC). the air handler is used of course in summer for AC but also in winter for humidification and all year for HRV/exhaust. I figure if primary loop is warm anyway we might as well circulate so air has a chance to be warmed if air handler kicks in. doesn't seem to detract from the floor heat. in fact it seems to help lengthen the burn times.

    according to my calc the 006 is too big too. again I don't care about the BTU transfer, I am more worried about wear and tear on my hydro coil.

    thanks again
    marg
    Triangle Tube Prestige Solo 110 with Trimax Controls (3x oversized)
    950 sqft of WarmBoard on 3 floors, 5 loops acting as one zone
  • Ironman
    Ironman Member Posts: 6,585
    It's not detrimental as long as the flow velocity does exceed 5 fps.

    It appears that you left the 2.2 ft of head for the coil out of your calc?

    Also, dynamic head increases as gpm increases. As head increases, pump gpm decreases. So, you would need to know the head for the coil and piping within the pump's curve to know what you're actually pumping. Measuring the pressure differential at the inlet and outlet of the pump would give you your head and that would tell you your gpm when compared to the pumps curve.

    3 gpm may be the ideal flow for your heat loss, but actual system conditions very seldom match up with that. Especially with fixed speed circulators. The goal is to size the circ so that the actual flow falls within the middle third of the pumps curve.

    If you choose to replace the circ, you might consider a delta Tee circ like Taco's Viridian where you could set it to achieve the desired flow. Keep in mind, that with a 68k btu coil, if it's set to a 20* delta T, you'll be moving 6.8 gpm. That's assuming your SWT and CFM are at rated conditions. Lowering the SWT and/or CFM will lower the output of the AHU.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • RobG
    RobG Member Posts: 1,850
    You have a ten foot run with 21 tees?
    Rich_49Ironman
  • Ironman
    Ironman Member Posts: 6,585
    RobG said:

    You have a ten foot run with 21 tees?

    I missed that. Good eye, Rob.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • margsuarez
    margsuarez Member Posts: 54
    not tees, 90s. I counted all in entire loop. Brooklyn basement, tight installation. with primary loop connections underneath boiler.
    Triangle Tube Prestige Solo 110 with Trimax Controls (3x oversized)
    950 sqft of WarmBoard on 3 floors, 5 loops acting as one zone
  • njtommy
    njtommy Member Posts: 1,105
    What size is your piping to the AHU. typically 3/4" copper is good for 4 gpm or 40,000 btus at 12psi. 1" is 8-9gpm. so even though your pump is over sized doesn't mean your running that high of a gpm thought the coil.
    on the other side the installers could of oversized to the pump trying to get gpm flow up to keep the discharge air temp higher. what temp are you running you water at?
  • margsuarez
    margsuarez Member Posts: 54
    3/4" piping, boiler pressure is 15psi. I don't believe the installer gave any thought to sizing the pump as it was left in place by the boiler installer and just connected by the AHU installer.

    I have boiler profile to send 100-120degF water to the floors, and 120-140degF water to the AHU, but as I said I am not using it for primary heat...

    just want to know if I should request a different size pump to replace this failing 0015.

    am I understanding this correctly that the 0015 on Low, with 3ft of head, would be 11gpm? how will this affect heat output if desired flow is 3gpm for my pipe size and water temp? will the increased flow damage anything?

    thanks again
    marg
    Triangle Tube Prestige Solo 110 with Trimax Controls (3x oversized)
    950 sqft of WarmBoard on 3 floors, 5 loops acting as one zone
  • njtommy
    njtommy Member Posts: 1,105
    Your 0015 pump can not flow any more then the piping will allow. So there for you are only flowing 4gpm with a pump that is rated much higher. This could very well be the reason your pump is dead or noisy. I would highly recommend going to a smaller pump like a 006,007, or a delta t pump set at 20 degrees.
  • margsuarez
    margsuarez Member Posts: 54
    thank you very much.
    Triangle Tube Prestige Solo 110 with Trimax Controls (3x oversized)
    950 sqft of WarmBoard on 3 floors, 5 loops acting as one zone
  • Zman
    Zman Member Posts: 7,001
    njtommy said:

    Your 0015 pump can not flow any more then the piping will allow. So there for you are only flowing 4gpm with a pump that is rated much higher. This could very well be the reason your pump is dead or noisy. I would highly recommend going to a smaller pump like a 006,007, or a delta t pump set at 20 degrees.

    This advise is solid. The circ is sized incorrectly. That led to the premature failure.
    The circ does not know what pipe is attached. It does not stop at 4 gpm. The actual gpm in your system with the 0015 depends on the exact characteristics of the coil and piping. As flow increases so does resistance. The OP is correct to be concerned about pipe erosion due to excessive velocity.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • margsuarez
    margsuarez Member Posts: 54
    Thanks for the advice. So am I correct in thinking that a Delta-T pump is overkill for this application (closed-loop, fixed load hydronic coil)? I see the Taco 006 would be slightly oversized (7gpm @ 3ft) and the 003 about spot on. But the Grundfos Alpha and the Taco Bumblebee are priced about the same as the 003.

    I am thinking I will have my plumber install a Grundfos Alpha; that way I will be able to adjust the flow to match my intended BTUH output. There should be some energy savings there, too, right? At 2 gpm the Alpha is at 5 watts. Your thoughts?

    Thank you again
    marg
    Triangle Tube Prestige Solo 110 with Trimax Controls (3x oversized)
    950 sqft of WarmBoard on 3 floors, 5 loops acting as one zone
  • njtommy
    njtommy Member Posts: 1,105
    I really like the Taco bumble bee pumps. yes it could be over kill for your system, but it will also adjust its speed when you have a higher or lower load on the system.
    You really won't save a lot of $$ for electricity usage they Taco figures about $20 per year or heating season.
    https://dhblogtaco.wordpress.com
    http://jbblog.flopro.taco-hvac.com/anthonys-voice-redux/
  • margsuarez
    margsuarez Member Posts: 54
    Thank you for the info and advice. I ended up getting an Alpha, just for the AH loop. Circulating whatever was in the boiler loop (just making DHW now) on constant speed 1 showed 2gpm and 7watts. Can't use "auto" mode beacuse it starts at 4gpm and much higher head pressure than what I need. I think it is going to work for my purposes (using AH as additional emitter, with radiant floor the primary source). Will send update during heating season.

    If the new Taco Delta-Ts are more commonly available in the winter I'll consider upgrading the pump for the radiant floors. However I'm using a single 0015 feeding a manifold with actuators for zoning, and from what I read Delta-P might work better for this application.

    all the best
    marg

    Triangle Tube Prestige Solo 110 with Trimax Controls (3x oversized)
    950 sqft of WarmBoard on 3 floors, 5 loops acting as one zone