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  1. cdxx139

    ROOM ACH RATES, VAV

    Air Balancers and controls contractors are not checking the design, they are executing the design. Last time I did an exam room, we used an AIA guide, and it was 2 ACH of ventilation air and 6 ACH of total air, with no VAV during occupied hours. knowledge is power
  2. cdxx139

    Carrier HAP Block Load

    HAPS had a "Block "load Calc" software module separate from its lead program. I tried it many years ago and ended up just using the regular loads program and made the building one space. knowledge is power
  3. cdxx139

    VRV system with ventilation system on a Apartment/Condo building

    1) code will tell you when the bathroom exhaust needs to run 2) code tells you what the minimum corridor ventilation is, you may need it increased to provide makeup air depending on your design. 3) depends, you can keep them pressurized. Also some codes do not allow the corridor to be used as a...
  4. cdxx139

    CLTD Method Again

    Great resource KYROUS From memory CLTD you have to select a few different times of the year to confirm the largest load, and you hope one of the few was close to your worst case. The beauty of software is it calculates the full 8000+ hours of the year. That seems like a lot of work for...
  5. cdxx139

    Filtration for Makeup Air Unit for Bakery

    Ive done some kitchens and dont recall any filtration requirement. I suggest specifying Merv 8 pre filters and Merv 13 final filters, and the ownere can decide not to use the MERV 13's. knowledge is power
  6. cdxx139

    Entry Vestibule Heating

    I size it for 10 cfm/sf of every sf of door open to the outdoors. But really, I put the biggest Cabinet Unit Heater I can fit, or the architect allows. knowledge is power
  7. cdxx139

    What is the better system for an auditorium?

    You are comparing PTACS to a 90 ton air cooled chiller? Seems like a very big difference, especially in cost. ASHRAE Systems? bible has a chapter (one of the first 5) that will help you put together a system comparison chart. You may want to also consider a middle of the road option with a...
  8. cdxx139

    VAV design guide

    Trane has great training resources. http://www.tranebelgium.com/files/book-doc/24/en/24.i2joahta.pdf then you can graduate to: https://www.newbuildings.org/sites/default/files/A-11_LG_VAV_Guide_3.6.2.pdf knowledge is power
  9. cdxx139

    Heat gain of AC pump motor vs DC

    Thank you for the input Lionel - we don't have the existing pump efficiencies. But from ASHRAE equation (a governing international engineering body), the existing pump would need to be over 98% to not require space cooling. I don't know pump motor efficiencies, but from the age alone of the...
  10. cdxx139

    Heat gain of AC pump motor vs DC

    You are correct Groovy, I just found a chart that said minimum efficiencies for 500 HP motors should be in the 95% efficiency, so I update my calculation to reflect that and am more line with your estimate. I also fail to understand why cooling is currently not required, but we both did the...
  11. cdxx139

    Heat gain of AC pump motor vs DC

    Thank you for the insight, Here is additional background that will answer specific questions GROOVYGUY & COMPOSITE PRO & BRIAN PETERSON- I used ASHRAE formulas for heat gain of a motor. See attached. Equation (4) is when the motor is in the conditioned space but the driven machine is...
  12. cdxx139

    Heat gain of AC pump motor vs DC

    Hello Electrical Engineers, We are changing out 3 600 HP DC motor pumps and changing them over to AC. My job is to provide the cooling in the room for this massive heat gain, which comes out to about 500,000 Btu/hr, which may require a 50 ton chiller @ 1.2 kW/ton is 60 kW. The existing pump...
  13. cdxx139

    Acoustic insulation in supply & Return Duct up to 3 Mtrs

    For me leaving out the acoustical insulation is a function of: Is the unit located near a sound sensitive space How many elbows is in the ductwork Does it serve noise sensitive spaces. Good questions to ask an acoustical consultant, the next time you work with one on a project. knowledge is power
  14. cdxx139

    Lowering Heat Exchanger Supply Temperature

    Replacing the terminal units along with the boiler will probably not be worth it to your client. (depending on the client and project, which you provided no details). I like your idea of replacing the boiler with a condensing boiler for effieicncies (if the boiler is at its life expectancy -...
  15. cdxx139

    Cooling Load Calculator for RTU

    Bell is a great book, but giving somebody that doesnt know loads, a bunch of rule of thumbs, can really get them in trouble. knowledge is power
  16. cdxx139

    Temperature sensors in a digester with mixer to control the boiler

    I think what I am missing is the importance of the boiler is for the pickup load, when they first fill the digester tank with potentially 50 degF sludge, and the boilers need to pick that up to 95 degF within 24 hours. So I will size the boiler as small as possible to meet that load, so it is...
  17. cdxx139

    Temperature sensors in a digester with mixer to control the boiler

    Also attached is a quick sketch, showing the internal mixer, with the motor located over the cover. The Heat Exchanger is built in the center of the mixer pole with propeller built in. Hot Water is supplied to and from the HX. Again, I don't see the need to control off of the heating water...
  18. cdxx139

    Temperature sensors in a digester with mixer to control the boiler

    Thank you all for your feedback. Yes the draft tube is internal to the digester. See attached photo from the same manufacturer. You were looking at the EDT model, and I am talking about the RDT model, which you suspected. My concern with temperature sensor from a manhole of the roof, will be...
  19. cdxx139

    Temperature sensors in a digester with mixer to control the boiler

    Thank you for providing insight bimr. That is how I would typically control an HVAC equipment such as chiller or hot water system, but I am having trouble understanding the correlation between the return temp from the HX and the digester temperature. To put real numbers into the equation. The...
  20. cdxx139

    Temperature sensors in a digester with mixer to control the boiler

    It is what they call a "draft tube mixer". That portion is selected by another group, My scope is to provide utilities. It has a jacketed heat exchanger dead center, and pumps the sludge (10,500 GPD) from the bottom of the tank, through the center HX and up to the cover so it pushes out to the...

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