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Type: Posts; User: guitarboyled

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  1. Replies
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    Electric Heater... SCR, SSR, TRIAC

    On the following design would a SCR, SSR or TRIAC be required?

    http://img688.imageshack.us/img688/4663/neptronic2.jpg

    When do we need them?

    Are they usually in the heater, in the termostat...
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    What is this "pulse thing" in comparison to...

    What is this "pulse thing" in comparison to 0-10vdc, 2-10vdc, 4-20mA?
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    http://img194.imageshack.us/img194/8539/neptronic....

    http://img194.imageshack.us/img194/8539/neptronic.jpg
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    Thanks guys with the illustration (figure 3.18...

    Thanks guys with the illustration (figure 3.18 page 8) of this electric duct heater and all your input I finally understood.
    ...
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    I'm confused... Are they 24 VAC or normaly...

    I'm confused...

    Are they 24 VAC or normaly open dry contact? Or are these the same?

    Is the 24v coming from the heater controler?
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    Again that sheet specifies that... Digital...

    Again that sheet specifies that...

    Digital Inputs: Relay dry contact
    Economizer Output: 0 to 10 VDC
    But it doesn't specify what Y1, Y2, W1, W2 are

    Newbie here... if you know what it is please...
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    I have the spec sheet and installation...

    I have the spec sheet and installation instructions too

    but can't see where they specify what type of control links the thermostat to the heater controler.

    Maybe it says and I just can't...
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    Thermostat "Energizes on call" Y1 and W1

    Working with the Johnson T600 series thermostat

    And Y1, Y2, W1 and W2 are "Energizes on call"

    Is this a 0-10VDC signal or a 24v output... is it pulse or on/off.
  9. Also NFPA 96 indicates that fire dampers are not...

    Also NFPA 96 indicates that fire dampers are not to be installed on exaust ducts of cooking hoods. Would this also apply to the residential?
  10. I found that NFPA 90A doesn't apply to the...

    I found that NFPA 90A doesn't apply to the venting of clothes dryers. Would this imply that fire dampers are never used on cloths dryer ducts?
  11. Dryer and Stove hood dire damper ?????

    http://img24.imageshack.us/img24/7241/woodframe.jpg

    Building: 3 story / 15 unit condo

    If I have a fire rated ceiling and my duct riser (3.25x10) crosses that barrier to go outside do I need to...
  12. Pressure loss through a dryer vent hood

    Hi again guys
    I'm trying to figure out the pressure loss through a dryer vent hood. Can't quite find anything in the ASHRAE loss coefficient tables. But I have an old version.

    ...
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    Help with fan, pressure, flow, rpm

    I have a system with 3 filter section (pre filter, medium and HEPA)

    I took these measurements with the HEPA filters out (therefore less pressure drop in the system):

    5700 CFM, 5.3" H2O and 2100...
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    I know about the rule, what I really want to know...

    I know about the rule, what I really want to know is specifically where it comes from.
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    More specific questions: I presume for a two...

    More specific questions:
    I presume for a two stage single compressor system... the size of the evaporator and condenser remain the same.
    Does the Evaporator coil (ADP) remain at the same...
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    Pro membership where? Thanks for the link...

    Pro membership where?

    Thanks for the link Powell I will check that out!
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    Some A/C applications seem to have a two stage...

    Some A/C applications seem to have a two stage compressor.

    Low stage (used in normal conditions 80% of the time) and high stage (used during high demands 20% of the time).
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    Refrigeration help required

    Looking for a good book to understand some refrigeration concepts.

    Want to understand concepts like 2 stage compressors vs 2 compressors vs 2 circuits cooling system.

    Do they come with...
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    My Outside Air is at 90F, 50% HR and 38.4...

    My Outside Air is at 90F, 50% HR and 38.4 BTU/lb
    My Inside Return Air is at 70F, 50% HR and 25.4 BTU/lb
    My Air Mixture is around 76F, 53% HR and 29.1 BTU/lb

    The Air Mixture will exit the...
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    Nice software but what I want really is a rooftop...

    Nice software but what I want really is a rooftop or split system selection software nothing more. To analyze the psychrometric side of things, not really to calculate charges.
    Want to observe the...
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    It's only for learning purposes. I'm new to the...

    It's only for learning purposes. I'm new to the industry and I work in an office where I can't test any equipment to see how it reacts to changing entering conditions or set point.
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    Can I find one online? Any company at all,...

    Can I find one online? Any company at all, doesn't matter?

    Anyone has the Lennox product selection software?
  23. Obviously I was referring to the air leaving the...

    Obviously I was referring to the air leaving the cooling coils before any type of reheat.

    From a calculation point of view, do we consider that it's almost always at 90% RH.

    For instance is the...
  24. Air leaving cooling equipment always 90% ???

    Is the air leaving cooling equipment always considered to be at 90% RH?
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    Need a software AC UNIT SELECTION

    Looking for a selection software (air cooling unit any brand) that would provide me with different pyschrometric specs.
    Where I can punch in a required room conditions or entering air conditions and...
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    It's a real scenario but I don't have all the...

    It's a real scenario but I don't have all the details and haven't been on site yet. We still don't have this contract.

    I believe it's one single zone (large open space with no windows).

    What...
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    Yes, same air flow Problem is with two...

    Yes, same air flow

    Problem is with two compressors running, cooling capacity is off the chart.

    Following two figures show normal curve and off the chart curve.

    What happens when the end...
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    I took the design conditions + machine specs and...

    I took the design conditions + machine specs and I come up with those graphs.
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    Rooftop unit too strong

    Psychometric chart

    I have a 2 compressor 60 ton unit serving a zone that really only requires 35 tons of cooling.

    http://img6.imageshack.us/img6/640/psychoi.jpg

    With two compressors the end...
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    ok so it varies (350, 400, 475, etc.) but...

    ok so it varies (350, 400, 475, etc.)

    but where does the figure come from??


    1 ton = 12000 BTU/h = 400 CFM of cooling
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    CFM required for cooling

    I was told that a good approximation for cooling air volume is:

    Tons of refrigeration x 400 = CFM

    Can anyone explain where the 400 comes from?
  32. I understand the dew point is 56F for that given...

    I understand the dew point is 56F for that given value.

    But isnt the entering fluid temp the temperature inside the evaporator? Therefore more or less the ADP?
  33. I didn't calculate anything I just pulled a...

    I didn't calculate anything I just pulled a straight line between the SHR and the 100% HR curve crossing the entering air value (DB, WB)
  34. Entering Fluid Temp, SHR and ADP heat pump

    Looking at a water heat pump spec sheet

    CAPACITY DATA (all performance at 650 CFM and 5.0 GPM)
    COOLING 50F to 100F

    Trying to figure out the following info:

    Entering Fluid Temp. (50 F)...
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    It's the customers demands... They understand the...

    It's the customers demands... They understand the cost. Have to go with it
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    In other words its easier and more precise to...

    In other words its easier and more precise to get the SHR from the manufacturer of the unit.

    Next question is the temperature of Freon inside the cooling coil, SST and TD what is the relation...
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    Is there a way to acculate calculate the SHR if I...

    Is there a way to acculate calculate the SHR if I don't have the unit's spec sheet?
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    That's a big size opening... this approximation...

    That's a big size opening... this approximation needs to be as accurate as possible.
    Should the market be in positive pressure? Wouldn't it be better to avoid hot air coming in?
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    The mall is at 72F and 50% HR The supermarket...

    The mall is at 72F and 50% HR

    The supermarket needs to be at 65F and 50% HR

    The customer wants it like that.

    I have to calculate the gain or loss on the supermarket side due to the air...
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    .

    .
  41. Replies
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    air traveling from different spaces

    Here is my problem

    I have a supermarket connected to a mall (common area) entrance 16'x8'.

    Temp in the mall 72F
    Temp in my supermarket: 65F

    I'm eitheir loosing cool air or gaining warm...
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    I was told that most of the time for standard...

    I was told that most of the time for standard units we simply use a SHR of .70.

    Is this correct?
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    SHR and ADP

    Hi again guys

    I know my room air specs, outside air specs and mixed air specs. How do I figure out the ADP or SHR of a cooling unit? Are those given values for a specif unit?
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    What if a relatively small new addition is added...

    What if a relatively small new addition is added to an existent building. Would the unit providing air be called a secondary central unit or a make-up?
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    Therefore, if nothing is sucking important...

    Therefore, if nothing is sucking important volumes of air out of a room, it won't require a makeup.

    Technically an exact same unit could be used as a central unit in one application and as a...
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    Generally speaking, wouldn't the central unit be...

    Generally speaking, wouldn't the central unit be capable of compensating for exhaust fans, kitchen hoods, industrial ovens?

    The makeup is more than just a fan, it can heat or cool the air right?
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    Rooftop central unit vs makeup

    What is the main difference between a rooftop central unit and a makeup unit?
  48. Actually it's a sparger design but I can't find...

    Actually it's a sparger design but I can't find any info for designing one
  49. Replies
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    Static pressure vs. friction ???

    Whats the difference between static pressure, static friction and friction (ductulator)
  50. Multi-Jet or self balanced duct design ??

    Hi guys

    New to the Forum and also new to the HVAC industry.

    My first question concerns what I believe is called a multi-jet design or self balanced without any dampers required.

    I can't...
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