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Recent content by DrRTU

  1. DrRTU

    Ceiling fire dampers

    I believe you have a simple membrane penetration of a rated assembly. This is common in multi-family high rise buildings. At most, you need a RD at the point of communication with the occupied space. You will find this with ceiling mounted exhaust fans which have a RD above the ceiling grille...
  2. DrRTU

    Need to cool water flow from 160 deg F to 60 deg F - kicking around ideas

    A plate and frame heat exchanger coupled with a hot well / cold well on the cooling side with chiller is the most common way to do this. The cold well side is cooled via fluid cooler or tower as the tower sump can be dry when located indoors. Indoor sump will eliminate PG/EG as the cool source...
  3. DrRTU

    MAX A/C with Single-Phase Power

    Two (2) sets of twinned furnaces (bottom or both side rtn) or 2 Reznor/Sterling/Modine roof mounted indirect furnaces with Two 5 ton ACCUs off to the side. Stage the ACCUs. Captive air does this with multiple 5 ton ACCUs ontop of the AHU. 5 ton single phase are very poor at starting. This all...
  4. DrRTU

    Steam control valve sizing

    As others have stated, you need to define the inlet and outlet steam conditions. You only advised inlet pressure – superheated? At saturated entering and 14.7psia leaving, you can calculate a Cv of both control valves based upon a “critical” valve. Size main line piping for DP at the mass flow /...
  5. DrRTU

    Steam control valve sizing

    You will need a little more information on the glycol process to do a selection. I gather the small feed was selected as the fine temperature control to give the CV improved LWT control. I suggest you select your valve mfg rep and have them help with the application of body(s) and actuator(s). A...
  6. DrRTU

    Fire Smoke Damper for Shaft Enclosure

    If the roof assembly is not rated, then you need a fire damper at the OA duct penetration at the bottom of the rated shaft. A SFD could be applied but a FD with the correct rating should meet your requirements. I have seen a roof rating issue such a parking garage in which the shafting must be...
  7. DrRTU

    HAP report cooling load difference

    The high OA flow is driving the load. You are correct with the design condition of 107F DB. I review the Air System Design Summary output to see which parts of the envelope, internal loads, fans/pumps or ventilation which are driving the load in terms of SHG and LHG to the zone. This design...
  8. DrRTU

    Multiple VAV Zones, sizing of the main heating coil

    In a classical VAV system, central AHU heating requirement is calculated from the greater of 1. Supply air tempering requirement or 2. Morning warm-up heating requirements. These values are found in your load calculations.
  9. DrRTU

    Its bad..but HOW MUCH bad it is?

    You will need to utilize an engineer with experience in design of duct systems. SMACNA and ASHRAE have duct design guides and apps that present flow vs. dp. I would simulate the system with a load estimating software based upon fan eff. and power cost. You will end up with a delta operating...
  10. DrRTU

    Gas Tight Dampener

    The type of damper you are looking for is called "bubble tight". Read the application guides for construction details and actuator applications. http://www.greenheck.com/products/detail/69
  11. DrRTU

    Its bad..but HOW MUCH bad it is?

    You need to look at the complete system to evaluate the damage. I ask what is the end game? Are you trying to check the fan or go after others that are responsible for this design? As others pointed out, an offset of 2 elbows is not the only issue. Entry fittings into and exiting the elbows...
  12. DrRTU

    COOLING TOWER SELECTION WRONG

    Cover the basics first with known data. 1. Hire a balance contractor to measure the condenser water flows. Inspect all strainers and pressure gauges first. Verify sump inlets and header nozzles. Run thru combination of pumps. The 6” is undersized for 1350 gpm - tower isolation vlv may not be...
  13. DrRTU

    COOLING TOWER SELECTION WRONG

    Bos88, I agree 2700 gpm is needed but read the second paragraph, the wording sounds like 2 single cell units makeup to be the “tower” with motorized valves. With a common header they should have stated total flow.
  14. DrRTU

    COOLING TOWER SELECTION WRONG

    Re-reading your posts and documents, you have two nominal 450 ton towers with two 450 ton chillers and one common condenser water system at a total of 1350 gpm. It looks like the single cell tower was run at 1350 gpm. You have a condenser water issue. Should the tower data have been run at 675gpm?
  15. DrRTU

    How to accurately measure mass flow through server vents using an anemometer

    Purchase a Flir or Fluke IR camera. Reading flow on the little fans is impossible outside a lab. Cables and racking will cause your test methods to fail. Heat and dirt is the failure means, don't chase the heat removal medium but look at the heat via IR. Cards, drives, inlet / outlet...
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