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Recent content by tombmech

  1. tombmech

    pnuematic thermostat calibration?????

    Ashereng, I see from other posts that you have the "FAQ" included in your regular signature. My bad for thinking it was specific. Please accept my apology for thinking otherwise. Mea culpa.
  2. tombmech

    pnuematic thermostat calibration?????

    Have you familiarized yourself with smiley faces that are blinking? That is described in detail in item #9 in the FAQ's you helpfully cite. On the other hand, I spent a large portion of my career replacing antiquated, pneumatic controls with DDC components. Replacing instead of repair became...
  3. tombmech

    pnuematic thermostat calibration?????

    Throw it away and get something digital. ;-)
  4. tombmech

    One or two HVAC units?

    Two units is the Cadillac option. Better in almost every instance, but technically, not necessary. In fact, it is one of the ways I judge builder quality in house shopping. With commercial/industrial applications, you can get into significant building airflow problems if a definite...
  5. tombmech

    water heater / chiller pumping arrangement

    No one ever said an expansion tank wasn't needed - only that it's not the tail wagging the dog with respect to the position of the pump in the circuit. I'm sorry, but the whole point of pumping a utility medium is to serve a device - pump+device. The rest are just "nice-to-have" accessories...
  6. tombmech

    water heater / chiller pumping arrangement

    High rise buildings sometimes change the advantages of "pushing" through the chiller. In those cases, the return head is of sufficient pressure that NPSH is not a concern, but pressure drop through the chiller, when you already have a huge head to make up, is disadvantageous. If you are...
  7. tombmech

    Retrofitting or Replacement of Large Capacity Chillers

    I agree with imok2's suggestion completely. Good advice.
  8. tombmech

    water heater / chiller pumping arrangement

    P.S. I admit that an air separator is probably a good idea for a hot water circuit, perhaps even mandatory. It is not needed at all for chilled water. Here's the original question: Again, any discussion of an air separator is just "clouding" the issue (sorry for the pun). It is not...
  9. tombmech

    water heater / chiller pumping arrangement

    TBP, * sigh * No one disagreed that positioning is important. Please let me state it again, more clearly: A. The question was how to position the pump relative to a water chiller in chilled water circuits vs. positioning the pump in water heater circuits. B. Stanlsimon stated "It has to do...
  10. tombmech

    water heater / chiller pumping arrangement

    ??? TBP, Perhaps I've misinterpreted, but no one was talking about air separator location, anyway. Stanlsimon interjected that as a reason for pump location relative to a water heater vs. a chiller. (Refer to original question for this thread.) I merely stated that air separators have nothing...
  11. tombmech

    water heater / chiller pumping arrangement

    P.S. Air separators have little to do with the issue, since many systems function quite well without them. If you use them, the description above is valid for correct placement, but their actual requirement is often a debated topic.
  12. tombmech

    water heater / chiller pumping arrangement

    Pressure is the point, but for slightly different reasons than stated. If you are referring to a water heater, then you have a storage tank. If the storage tank is not at the highest pump head of the system, then you've wasted your pump energy by pumping into the tank - not into the system...
  13. tombmech

    Does your HVAC engagement includes build. therm. protection calcs?

    Well, that is the problem isn't it? Sorry, I have no answer to lawyers and judges who think they know Engineering - except to vote (assuming you can) for the politicians that will change them.
  14. tombmech

    Oil recovery problem in water cooled centrifugal chillers

    A purge device is a proven - and actually necessary - piece of equipment on most low-pressure chillers (R-11, R-123). They are not really useful on high-pressure machines (R-134a). The refrigerant contamination most often occurs on the negative pressure side of a low-pressure centrifugal -...
  15. tombmech

    Hydrogen in the built environment

    Tell the Mayor he will need to budget for more Cold Fusion generators.
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