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  1. KiwiMace

    ORP analyzer

    ORP is oxidation-reduction potential, similar in appearance and operation to a pH probe. I have little true understanding of their exact purpose in life, but are used to measure the strength of certain redox chemical compounds. Having spent an early part of my life fixing them, the most...
  2. KiwiMace

    ACMV: Summer vs Winter

    At 16 degC, I probably wouldn't bother heating or energy recovering. A few degrees of delta t will help it not do what willard3 correctly said it would. ACMV is an acronym replacing HVAC in countries that do not normally require heating.
  3. KiwiMace

    Foxboro/Eckart SRD991 Positioners Overheating

    Ask Foxboro to come on over and sort it out. Until then, use low dewpoint instrument air for the casing purge, and if you reduce the pressure abruptly into the casing with a restrictor the air will adiabatically cool. Make sure you add a nice sintered vent!
  4. KiwiMace

    Ahu condensate drains

    An overflow trap into a floor drain implies that the floor drain is 'directly' piped to the sanitary system. Condensate needs to go to an indirect drain (typ. a 2" air gap) to prevent sanitary backflow from entering the HVAC system. I am not sure that this configuration is accepted by the code...
  5. KiwiMace

    Air Change Rate (Ventilation System)

    When you have open drive chillers + pumps with a lot of heat load in the room, you can quickly get to a point where it is easier to install an AHU to manage the heat load than deal with a huge ventilation rate. 15 ACH is 27500 m3/h (16000 cfm) = lots of big propeller fans with a wall of your...
  6. KiwiMace

    Why cut of nipple on a manometer?

    You have had a shocker, so just cut it off and carry on. Fire the new guy, he knows too much.
  7. KiwiMace

    Ahu condensate drains

    No, nothing to do with volume and you can't put 2 x 1" traps in series to make a 2" trap. It is all to do with hydrostatic head. If the static pressure in the AHU exceeds the pressure of the water column in the drain then the air pressure will suck or blow the water out of the trap depending...
  8. KiwiMace

    Solution pump Error and cooling water Pipe size

    That pipe is well undersized, but as long as the right flow is arriving at the chiller input at the right temperature, then there should be no basis for the supplier to pin it on the condenser water. There should be a service call, not a phone call. The maintenance contractor or vendor rep...
  9. KiwiMace

    bypass decoupler pipe in primary/secondary chilled water system

    The bypass should offer a low pressure direct return for the primary loop. The point is to decouple any influence of the primary loop from what is going on in the secondary loop and vice versa. If there is a similar pressure drop to your connected network as Drazen has suggested then this...
  10. KiwiMace

    bypass decoupler pipe in primary/secondary chilled water system

    I would say the bypass at the bottom of the drawing was intended for flushing, low flow or commissioning reasons and it would normally remain closed. If this valve is open, you will short cct the chillers and get a high return temp. The bypass near the primary pumps is the decoupling bypass...
  11. KiwiMace

    on coil off coil temperature

    This is school question. No, you need at least one more piece of information.
  12. KiwiMace

    Distance Between Exhaust and Intake

    My old US company used to cookie cutter an exhaust extension up above the unit to add a bit of distance and reduce the chance of the exhaust being entrained in the OA. Rectangular SS duct with a drain hole.
  13. KiwiMace

    Packaged Unit Good Performance Range

    The flow rate of any fan is only relevant when considered with the system pressure drop. The upper limit of airflow is most likely linked to the lowest pressure drop.
  14. KiwiMace

    Maintenance tunnel ventilation

    My worksite is laced with tunnels: Shallow service tunnels are naturally ventilated with intermittent risers. This is a useful approach as the risers also provide an access point for getting lengths of pipe in. Deeper tunnels are mechanically ventilated, with point to point supply and extract...
  15. KiwiMace

    Energy conservation of Chillers

    As a starting point: If any of your AHUs require chilled water, then you have to run your chiller. You can save energy in the operation of the chiller with such things as a VSD compressor, unfortunately this and most other options are design time decisions and retrofit is not always...
  16. KiwiMace

    Recommended Chiller Leaving/Returning Water Temperatures

    The basic chiller specification starts at 42 degF with a dT of 10 degF. Most chillers can be configured to run over a fairly wide range of temperatures, the dT usually stays around 9 - 10 though.
  17. KiwiMace

    Fume Hood Fan Sizing

    The hood vendor should provide the pressure drop/requirements for the hood, and you need to calculate the rest of the system from make-up through to exhaust. Use the 4 x rule as a check - any filters in the system are often allowed at a fixed final (loaded) dp, which does not count into the...
  18. KiwiMace

    foundation fieldbus confusion

    No, Analog Input or Outputs in FF (or by any other digital protocol) means that the data point represents a linear signal, continuously variable over the given range. Digital I/O is a state that is changing between on/off. You still call it an 'analog' input even though the data is...
  19. KiwiMace

    Highlgiting multiple sheets

    As a repeat offender I sometimes change the tab colours when I am working between multiple sheets, makes the highlighting stand out better.
  20. KiwiMace

    VFD Centrifugal chillers - suitable for locations with very little wet bulb changes

    Starting the chiller with a vfd or not won't be a big factor in your restart time following power outage. What matters most is that when the chiller gets power back, the chiller controls initiates a sequence to ensure the oil system and compressor are all well before allowing a restart. This...

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