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  1. mech4321

    VAV box minimum flow setting

    I am wondering if VAV boxes minimum flow setting can be adjusted higher without rebalancing the min/max with a TAB contractor. For example, adjusting via the BAS the minimum flow from 25% to 35% to increase the outdoor air fraction in the spaces. The box sensor will be able to read the flow. An...
  2. mech4321

    Very high velocity in fire sprinkler pipes

    NFPA 13 doen't not impose max velocity anymore. FM ask for 30 ft/s in aboveground piping. The replacement of the existing piping will affect operations in tenant spaces and cost more than a fire pump, so I was looking for a midrange value to reduce de fire pump capacity and replace only a...
  3. mech4321

    Very high velocity in fire sprinkler pipes

    Thanks for your replie What would be the maximum acceptable velocity from your opinion, in order to avoid replacing too much piping. Piping is in good condition (scedule 40). Ultrasound tests done on the entire piping indicate that the pipe thickness lost is only 8%.
  4. mech4321

    Very high velocity in fire sprinkler pipes

    For a retrofit project with a 40 years old sprinkler system. Would it be acceptable to have branch lines and main pipes at a water velocity of about 110 ft/s. A high rated fire pump would be added, but this would avoid replacing the small diameter piping in the existing tenant spaces. Is there...
  5. mech4321

    FLA vs power consumption vs motor hp

    The power factor and efficiency where not applied to simplify my calculation (assuming that these value where not high enough to get that big differance (32 and 9 hp)). Here is the spec attached of the equipment. Can somebody tell me a way to estimate the consumption at steady load. The...
  6. mech4321

    FLA vs power consumption vs motor hp

    I understand the concept of PF and Efficiency. I was wondering why the differance is so big even with these values applied. So I can use the FLA to calculate the consumption at steady full load? I heard about the running load amp which could be 50% of the FLA? Is this value applicable to...
  7. mech4321

    FLA vs power consumption vs motor hp

    Hi, We have to evaluate the power consumption at steady load of a fluid cooler which have at 600V an FLA of 23A. That would give approximately kw = 600 x 23 x 1.73 = 23.9 kw or 32 hp. However, the fluid cooler has only a total of motor of 6 x 1.5 hp = 9 hp (plus a small amount for the...
  8. mech4321

    consumption vs FLA vs motor hp

    I tought that the starting load is related to the LRA (locked rotor amperage) which can be estimated to 5 to 6 times the FLA? Alex
  9. mech4321

    consumption vs FLA vs motor hp

    Hi, We have to evaluate the power consumption of a fluid cooler which have at 600V an FLA of 23A. That would give approximately kw = 600 x 23 x 1.73 = 23.9 kw or 32 hp. However, the fluid cooler has only a total of motor of 6 x 1.5 hp = 9 hp (plus a small amount for the controls). Where does...
  10. mech4321

    Ductwork condensation

    I agree with the psychometric chart and the theoritical dew point temperature, but in fact, it is unlikely to see uninslated ductwork sweating in open ceiling altough supply air is at 55F and room temperature (or return air) at 75F 55% r.h. I am thinking now to create an air return in the...
  11. mech4321

    Ductwork condensation

    Adding insulation on this existing ductwork hidden above sheetrock would cost a lot of money. Since we don't have much moisture generation in this place (beside outside air which is dehumidified at cooling coil), do you think we can take the risk of adding a DX coil without having major...
  12. mech4321

    Ductwork condensation

    Hi Guys, We want to use an existing uninsulated fresh air ductwork hidden in ceiling to cool a post office by adding a DX cooling coil at the supply. Should we be concerned about the condensation on the ductwork exterior surface hidden in ceiling which is not a return air plenum (no air...
  13. mech4321

    dielectric fittings for black with S/S

    Hi everybody, We just installed a new stainless steel condensate return tank. Is it necessary to use dielectric fittings to connect black steel piping on it? Any danger of galvanic corrosion between stainless and black steel over the years? Thanks Alex
  14. mech4321

    acoustical liner

    I will install a liner in the first 10 feet of supply (10 tons, split system). Should I do the same in the ducted return?
  15. mech4321

    coil freezing

    I want to install a new split system York, 10 tons, 2 stages with air bybass. Do I need to install a temperature sensor in the supply to prevent coil freezing.

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