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  1. jvithayapun

    Mini-Split Q

    so does that mean you would get the rated max cooling only at the highest fan speed?
  2. jvithayapun

    Mini-Split Q

    If an indoor unit is rated for 7500 btu/h cooling capacity, and has 3 fan speeds of 212/282/353 cfm. Does this mean that Only the highest fan speed of 353 cfm will provide 7500 btu/h of cooling? If so, how would I calculate how much cooling the low speed of 212 cfm would provide? thanks!
  3. jvithayapun

    Why are residential splits more efficient than commercial?

    Im looking at some Carrier condensers and the residential (ex. model 24APA760---30, 5 ton) has a SEER=16, EER=13ish. Then if you look at the commercial models (while it is 1 ton more) a 6 ton unit has an EER=11. I think I have seen this pretty common across the board from different...
  4. jvithayapun

    Who is leading nowadays for condensers in terms of efficiency?

    is there a website that you could provide? i tried googling it with no luck. thank you.
  5. jvithayapun

    Who is leading nowadays for condensers in terms of efficiency?

    Im looking for around 15 ton condensing unit with a high SEER/EER rating. Who is leading the pack nowadays in terms of energy efficiency. This will air cooled preferbly r-410.
  6. jvithayapun

    Hot water heater setpoint?

    thanks for the replies. any comments as to why many heaters come preset at 120F though?
  7. jvithayapun

    Hot water heater setpoint?

    yeah, i was thinking about just using 140F at the heater based on ashrae, and then running to mixing valve to bring the temps down. but then it got me thinking why most factory set points of water heaters are 120F if in fact at this temp legionnella is still prone to growing? I have read from...
  8. jvithayapun

    Hot water heater setpoint?

    Im a little confused on what the setpoint for say a standard electric hot water heater for an office building should be which serves sinks and such. I have read in ashrae that 'service water temperature in the 140F range is recommended to limit the potential for Legionella growth'. Ive also...
  9. jvithayapun

    DUCTINGS LOSSES

    could be leakage somewhere or static pressure from ductwork. just by looking at random fan curves, a 1 inch increase in static pressure can cause an 8000 cfm decrease.
  10. jvithayapun

    Split system question

    disregard last post, i found my error. the h that gives me 15.52 is roughly 41db/41wb. i believe this would be correct?
  11. jvithayapun

    Split system question

    ok, so if i use Qt = cfm * 4.5 * deltaH 24000 = 425 cfm * 4.5 * deltaH deltaH = 12.54 Now assuming EAT=75F at 50% then h=28.15 so 28.15-12.54 = 15.61 = h leaving coil Im looking for some random point with about 100% saturated air and i am coming up with 25 db/ 25 wb that gives me a...
  12. jvithayapun

    Split system question

    Say a split system is rated at 2 tons Total MBH=24. Assuming the t-stat is set at 75F and the fan in the unit does 425 cfm. So: 24000 = ( 425 cfm) * (1.1) * deltaT Therefore deltaT = 51.33 Does that mean if my room is set to 75, my EAT=75 and my LAT off the coil is (75-51.33)=23.7F? Im...
  13. jvithayapun

    VAV Systems and Air Changes

    ...air changes per hour AHU outside air % = 20% total heat gain = 850 btuh EAT=57 required room temp=75 so you will need AIR CHANGE RATE (1000 ft^3 * 6 ACH)/60 = 100 CFM OUTSIDE AIR CHANGE RATE (1000 FT^3 * 2)/ ( .2 * 60) = 166 CFM in this case you would need to supply 166 cfm of air to...
  14. jvithayapun

    Discharge temperature of diffuser during heating

    I have tried looking and found a range b/w 80-130F as a good heating discharge temperature. I have also read that aiming for 105F is a good spot. When adjusting the heating cfm, do you adjust it up and down until the discharge temperature reaches a certain temperature you are aiming for? And...
  15. jvithayapun

    Specifications for Solar Hot Water Heater?

    Does anyone know where a specification for these systems can be found?
  16. jvithayapun

    Why residential water heaters do not require expansion tank?

    so all houses with no expansion tank do not have a backflow/checkvalve at the water meter i assume?
  17. jvithayapun

    Thermosyphon Solar Hot Water Heater question about Expansion Tank

    On a side note, the storage tank has a pressure relief valve. does this not take care of the water expansion, therefore not needing an expansion tank?
  18. jvithayapun

    Thermosyphon Solar Hot Water Heater question about Expansion Tank

    ok. does it matter where the tank is positioned? 1) between the backflow preventer (from city supply) and storage tank? 2) or between the storage tank and the solar collector?
  19. jvithayapun

    Thermosyphon Solar Hot Water Heater question about Expansion Tank

    In a thermosyphon solar hot water heater, assuming there is a backflow preventor/check valve from the city supply, does it require an expansion tank or does the storage tank above the collectors act as a tank for some expansion as well? Thanks
  20. jvithayapun

    Why residential water heaters do not require expansion tank?

    As the question states, I was wondering why residential water heaters do not require expansion tanks?

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