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Hi all, Is anyone out there using revit for construction phase engineering? ie fan calcs, pump calcs etc? Seems to have a lot of promise. I am and engineer working for a contractor and our drafting is all outsourced (Revit) and then we do the calcs based on the 2d pdfs of the project. Seems...

Hi all, I have a job I need to recommission that has Crane valves, specifically D930 model double regulating type (they are branded "John" which I understand was a local Australian company that licensed them to sell in Australia at one stage about 20 years ago). I cant find any data on the...

Hi All, How do I calculate fan RPM required to maintain constant pressure and halve the volume? If I assume constant resistance to airflow in the system its just a proportional relationship ie half the volume is half fan RPM but the system resistance is going down by the square root of the...

Hi guys, I found a really good guide to controls on the web a while ago but I cant find it again! It was a very good description of how controls should be specified, it had controls 'graphs' (for want of a better word) for all types of systems, I think it explained control loops as well and...

Hi guys, How does this valve get sized?? My approach would be to size it based on the size of the largest boiler/chiller pump. Do you still need to do an authority calc on it ie a 250kpa pump would need a fully open dp of around 65kpa when flowing the largest chiller/boilers water flow. Even...

Hi Guys, I was wondering what peoples experiences with fan and pump static calculation accuracy are (with respect to the final commissioned values for the system installed as per the shop drawings). I have a few questions that the veterans amongst you might be able to help with..... Where do...

Hi guys, According to my CIBSE reference, a three way valve on a coil needs a balancing valve on the bypass line along with one in the return line back to the chiller/boiler. That bypass valve gets set to provide the same dP as the coil when in full bypass mode. Whats the point? at part...

Hi guys, I have always worked in a consulting environment and I was wondering what the 'other side' looks like. I know a little about what they do ie equipment selections, calculations, design for design and construct projects. Can anyone elaborate? I realise that just like in consulting you...

Hi Guys, I am looking at the CIBSE code W for flow tolerances. if my coil needs a flow of 0.1574XXXX l/s and I have a tolerance of +- 10%, what decimal point goes in the coil schedules? I am thinking at if the flow needs to be within 10% then I need the third decimal place, ie 0.157 l/s...

Hi all, I know I need to maintain the min NPSH at the back of a pump (HHW in this case, 80deg C). Could I just pump the system pressure up to a value that will allow me to keep the suction above the min NPSH of the pump? Has anyone seen this done before? I am verifiying a design and the...

Hi all, the title of this post says it all (nearly!). What is the best way of achieving good outside air control in this case? I am thinking that the AHUs will have the return and intake dampers modulate so that the mixing plenum pressure (when not in full economy mode) is some negative...

Hi Guys, I am a HVAC engineer and am trying to understand NPSH better. I understand that you need a minimum amount of absolute pressure at the suction of a pump to prevent cavitation. Some pumps that I have looked at it is 1.5m of head, which is 15kpa or so. In normal HVAC closed systems we...

Hi all, does anyone know of some good hydronic circuit analysis software. I want to test some of my designs under a few different conditions and it would be great to have a piece of software that can show the pressure drops through the various components. thanks for the help

I am sure that this will be an easy Question for someone to answer.....I can be the first engineer to have wondered.....:) Can you produce radiant heat by any other means apart from heating an object? My current understanding from looking at my heat transfer books is that the temperature...

Hi everyone, What is the process for determining how to deal with fumes coming from a process using for instance solvents, or glue? My initial thoughts are obviously to catch it as soon as the fumes are produced, ie close to the bench. But how to determine the flows required, are there...

Hi all, can anyone recommend a good source of information on design of hospital HVAC systems, ie operating theaters, sterile rooms, recovery rooms. Also, in your opinion is a DX system able to be adapted to an operating theatre? I was thinking along the lines of DX unit to treat recycle air...

Hi all, What temp would be recommended to run radiant hot water panels at? I have seen people mixing feed water to panels to keep them down to to 70 degree supply for safety reasons (school environment) but the panels get rather large at such low temps. Any thoughts on this? Is there any...

Hi all, What are your thoughts on a small radiant HHW system of roughly 65kW being supplied by two smaller or one bigger modulating boiler/s? Is there an efficiency dividend? My reasoning is that most of the time through the year here only one boiler would be needed apart from warm-up in the...

Hi all, Does a forward curved centrifugal fan backspin with air flow being pumped through it in the direction that it would ususally move air? I have heard that backward curved fans do this, but i dont know about forward ones! cheers

Hi all, I have a small boiler plant supplying hot water radiators. The boiler has to be outside but we get -10 sometimes warming up to +10 in the day say here. What are the pros and cons of using antifreeze? Is it a problem itself. Apparently some small packaged boilers just fire the boiler...