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  1. DavidButler

    URGENT: question about rebar detail around windows in basement wall

    Correct, the distance between end walls is 47 ft. If I understand this correctly, you're saying the dominant (constraining) load is along the height of the backfill, not the width of the wall, right? I'm curious why the IRC would stipulate buttress every 50 feet?
  2. DavidButler

    URGENT: question about rebar detail around windows in basement wall

    As noted in any earlier comment, my structural engineer made it clear that the floor diaphragm, which is set inside and anchored to the basement wall, is a key part of getting the 6" wall to pass. Even without that detail, I wouldn't dream of backfilling without the floor system in place. BTW...
  3. DavidButler

    URGENT: question about rebar detail around windows in basement wall

    @Dik, Section A on your attachment answers my question about positioning double perimeter rebar. Thx. The 21" distance I mentioned is to top of wall (beginning of above-grade framing). I think those hook prescriptions are where there's a nearby adjacent surface that's perpendicular to the opening.
  4. DavidButler

    URGENT: question about rebar detail around windows in basement wall

    @NS4U, I'm overseeing the project myself. The only impact will be during backfill. I'm guessing the bobcat can position 90% of the dirt without violating the 5 ft restriction. I'll have a couple of extra men on hand to assist with bringing backfill up to final grade adjacent to the house.
  5. DavidButler

    URGENT: question about rebar detail around windows in basement wall

    @dik wrote: > At openings I run horizontal and vertical wall steel past the opening by 2' @jayrod wrote: > My own spec for openings in residential walls is just additional straight rebar on all sides that extends a minimum distance past the opening. My design already has the extra full height...
  6. DavidButler

    URGENT: question about rebar detail around windows in basement wall

    Wow, I appreciate all the replies! There were a couple of logistical reasons that would have been much more consequential than concrete cost that drove my desire to go with 6" if at all possible. The engineer's first pass at 6" thickness had two #4 rebar matts, which he agreed would be...
  7. DavidButler

    URGENT: question about rebar detail around windows in basement wall

    I'm in the process of building the basement for my own new home. As an engineer myself, I understand each engineer develops their own prescriptive or 'template' designs for certain common details. In that context, there's a detail in my structural engineer's wall rebar design for which I'd like...
  8. DavidButler

    Valve flow-pressure relationship, a theoretical question

    @11241, my original post questions this assumption. But your point, which echoes what SPDL310's wrote, properly recognizes that friction (due to roughness) doesn't contribute much to overall valve resistance. I'm satisfied that the velocity exponent for a valve is probably close to 2.
  9. DavidButler

    Valve flow-pressure relationship, a theoretical question

    Thanks for your reply. I didn't mention in my op but I also regressed the fan coil pressure drop curves based the manufacturer's modeling tool. I checked several models & sizes and the exponent comes out to 1.88 +/- 0.01. For similar reasons that you posit for valves, we can expect fan coils to...
  10. DavidButler

    Valve flow-pressure relationship, a theoretical question

    I created a spreadsheet to calculate hydronic loop pressure drops. To make the spreadsheet more functional, I regressed several AquaPex friction tables for the velocity range of interest. AquaPex tables are unusual in that they account for water temperature, providing a higher degree of accuracy...
  11. DavidButler

    calculating loop pressure drop with variable pumps in series

    The tank lid will have 4" XPS and high reflectance/low emissivity coating on top. Upper 4 feet of tank body (corrugated culvert) will have three layers of flexible EPS wrap (~R-18), middle 4 feet will have two layers and the bottom portion one layer, with 1" XPS under the slab. I'm not sure yet...
  12. DavidButler

    calculating loop pressure drop with variable pumps in series

    These chillers are little 2-ton monoblocks with an integrated variable speed pump (the WiLo I referenced in my previous comment) and a Mitsubishi inverter compressor. The chiller's control board uses PWM to maintain the user-selected LWT and Hx delta-T. The chiller's internal control board...
  13. DavidButler

    calculating loop pressure drop with variable pumps in series

    See concept drawing. This is for an off-grid home near Phoenix. To take maximum advantage of TES capacity, the load side flow rate will vary from less than 1 gpm with single zone call for smallest zone and water is in low 40's, up to about 13 gpm when water temperature climbs into low 60's...
  14. DavidButler

    calculating loop pressure drop with variable pumps in series

    Ziggy wrote "don't forget the system curve" Well, that's why I asked the question... I need to know the PD's at every point in the loop to develop the system curve, no? Since my original post, I found a very helpful resource for this exact scenario: Caleffi Idtronics #17 Thermal Storage in...
  15. DavidButler

    calculating loop pressure drop with variable pumps in series

    LittleInch wrote: "as your pumps are pd type then flow can be assured regardless of pressure loss" But I need to know what the losses are at various conditions in order to select my pumps. Depending on what's happening at the Tee, the worst case may be when both pumps are operating. The system...
  16. DavidButler

    calculating loop pressure drop with variable pumps in series

    Attached is a diagram showing how thermal energy storage (TES) can be installed in parallel between chiller and load. The 2nd page is an excerpt from an ASHRAE Journal article by Kent Peterson on which this design is based. When only the chiller is operating, the zone valve on the fan coil is...
  17. DavidButler

    trade-offs with low velcocity (laminar flows)

    @hydrae... owner is investigating tanks, but there's no basement and no space to spare, so the tank will be buried outside, near the house. I recommended a vertical tank to minimize surface area and avoid the potential for poor lateral mixing with a low-boy or horizontal cylinder. The Fairbanks...
  18. DavidButler

    trade-offs with low velcocity (laminar flows)

    With the current design, the pump will gradually ramp up during an extended period of reserve ops as storage gradually "loses its cool". The controller will make this happen based on a sliding delta-T. Sorta like a delta-T reset curve based on EWT. So the pump only operates at relatively high...
  19. DavidButler

    trade-offs with low velcocity (laminar flows)

    @hydrae, by 'thermal storage inside the fan coil unit', I assume you mean the mass of the fan coil and coil circuit volume? In any case, the dynamic viscosity of 42 degree water is a lot higher than at 63F, a big reason why Reynolds numbers are so low during nominal ops. When water is cold, the...
  20. DavidButler

    trade-offs with low velcocity (laminar flows)

    @Ed, thanks for the tips on water processing. One of my team members has implemented large non-pressurized thermal storage on a couple of projects in Fairbanks. He used trucked water (by necessity) but it wasn't particularly clean. His loop water is now turning gray after one heating season. My...

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