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  1. CountOlaf

    Need for diffuser or grille in elec room

    Adrienne: Good point, but in this particular situation, the fan/motor won't be running at 0" ESP---the return duct will be routed to the other end of the space and includes straight length, grille, fire damper, couple of turns, etc.; and of course there are internal static pressure (ISP)...
  2. CountOlaf

    Need for diffuser or grille in elec room

    nuuvox000: Kind of what I thought, just checking with the HVAC "team" to see if there is some obscure code item prohibiting an open ended duct that I don't know about. I haven't recalled seeing this, although I have seen open ducts for things like combustion air. Regarding balancing, the unit...
  3. CountOlaf

    Need for diffuser or grille in elec room

    Yes, sorry wasn't clear. I intend to "dump" the cool air into the space from the RTU via a downcomer of ducting (basically a framed opening with some minor ducting from the RTU thru the curb and roof penetration). I was just contemplating whether or not I actually need an air terminal device...
  4. CountOlaf

    Need for diffuser or grille in elec room

    RTU on a "roof" of a small building (electrical room)/space within another building. For the supply downcomer (with return being ducted from the other end of the room), do I really need to have a diffuser or grille on the supply opening (or any ducting for that matter except for the bit that...
  5. CountOlaf

    Damper Sizing Conventions

    Your 5 to 7.5 in-lb/SF seems in-lne with the recommendations Belimo has for selecting actuators (albeit, for new dampers presumably). I don't know how much of a fudge factor you'd have to add for age. Given some of the standard actuator sizes, you might have to go to 2 actuators even using...
  6. CountOlaf

    Maximum flow through pipe question

    Well, I first looked in my tabulated hydraulic handbooks to save me from doing a hand-calc or looking for an on-line calculator...but no matter which of the three methods, it's all based on either the Darcy formula or Hazen-Williams equations. Anyway, your numbers are off most of the tabulated...
  7. CountOlaf

    Maximum flow through pipe question

    Ooops...that was for 100' of pipe. For 60' it would be more like 31 gpm. Now of course, this was based on a straight pipe, no other fittings and losing the full 60 psi in that 60' of pipe run (i.e., going from 60 psi down to 0 psi at outlet).
  8. CountOlaf

    Maximum flow through pipe question

    I'd say you're closing in on 25 gpm (quite a decent velocity however).
  9. CountOlaf

    Sovent System Help

    Richard: A sovent system is a special drain/vent system within a multistory building which eliminates the need for a separate waste (soil) and vent stack. Basically a wet vent. The main "oddball" componets are deaerator and aerator fittings--you need (at least) one of these components at each...
  10. CountOlaf

    Sea Coast Treatment

    There was a posting on this very topic from December: "Protective coatings on ACCU in coastal area's"--might want to check out.
  11. CountOlaf

    Fire damper in duct through wall yes or no

    There is an exception in the International Mechanical Code (IMC) (607.5.3) where ducts penetrate fire partitions (other than group H occupancies) if the duct does not exceed 100 sq. in. (0.06 sq m.), which the 160 mm would qualify for. There are a few other requirements to meet this exception...
  12. CountOlaf

    The cooling water thermodynamic analysis ??

    First off, just to clarify, does that "TR" stand for tons of refrigeration? The "rules of thumb" equations I posted before mean that the gpm required for the condenser is "typically" about 1.25 times more than that required for the evaporator. This number, similar to your 1.17, is presumably a...
  13. CountOlaf

    ATS System

    I'm with EEJaime--could be Automatic Throwover Switch (pretty much synonymous with the Transfer). Basically a device switching from one power source to another (automatically) like a redundant power feed or UPS. Might want to bring an electrical engineer on the trip :).
  14. CountOlaf

    generator stack

    saffa, I'm not sure exactly what else you need, but I'll try to clarify further. I obtained the stack-to-wind-velocity ratio rules of thumb from SMACNA's "Guide for Steel Stack Construction", 2nd Ed. Generally speaking, the purpose of having a higher stack discharge velocity than the...
  15. CountOlaf

    generator stack

    some of this is what the other responders to this post have said, but for the sake of completeness... Take a look at or try to obtain the cut sheets with operating data on the generator. There should be a section on the exhaust where it lists flow rate a rated output (CFM), exhaust temperature...
  16. CountOlaf

    The cooling water thermodynamic analysis ??

    I don't usually work in SI units, but in the English system, the rules of thumb are: GPM (for the evaporator) = (tons x 24)/delta T GPM (for the condenser) = (tons x 30)/delta T So, the 3 gpm/ton you're thinking of applies to the condenser water (e.g., cooling tower water) with a 10 deg delta...
  17. CountOlaf

    Hot water heater setpoint?

    I agree it's not a bad idea to set at 140F and "master mix" it down--one larger device is probably cheaper than a whole bunch of smaller devices. Plus, you can conceivably get away with a smaller tank size at 140 than you could if you design for 120. Still, I think it's all overkill/hype (and...
  18. CountOlaf

    Hot water heater setpoint?

    I thought Legionella was more of an issue at the "tepid" temperatures normally seen in say cooling tower systems where it was first discovered (e.g., 95-105 deg F.)? Anyway, regarding your question, anything over about 116 deg F is scalding to the touch, so 120 deg F at the heater is usually...
  19. CountOlaf

    3" Steel Pipeline on Bridge - Allowing for expansion

    Are you exiting the bridge vertically on both sides? If so, perhaps you could anchor the center point, and then each "L" would only have to acount for 7/8" expansion. As far as anchoring at the base, why not concrete? If you don't want the gas pipe to contact the concrete, a "sleeve" could be...
  20. CountOlaf

    Die Electric Section for Well pump

    The purpose of the dielectric is to prevent galvanic action between metalic pipes made of different materials, if they are placed in an electrolytic medium (water typically). In other words, you need the dielectric if and where you're switching from one type of metallic piping system to another...

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