ASME B31.3 Table 323.2.2 Note 6 excludes impact testing when the maximum obtainable specimen has a width along the notch of less than 0.098 inch. So if you were trying to test a circumferential weld in an existing pipe joint, what pipe sizes/schedules are excluded from impact testing because...
Typically, I've been designing HVAC systems where the return air is about 80 - 90% of the supply air so I have not been worrying about building pressurization. However, now I have a church with a vav ahu and a significantly reduced RA flow. So I have a few questions:
1. At what point do you...
I have a boiler exhaust vent that I am trying to figure out the minimum required insulation thickness for. The vent is a stainless steel double wall pipe with a 1" air gap.
I am trying to select the fiberglass insulation thickness to keep the surface temperature below 130 degrees F for...
When selecting a pump for a closed loop hot water system, how do you calculate the NPSHa?
NPSHa = Static Height - Inlet Friction - 3' Safety Factor
Is the static height calculated from the highest point in the system?
For inlet friction, how far back in the pipe line do you go to calculate...
I have a building in central florida that is being used to dry parachutes. The existing ahu to dry the parachutes is an off the shelf dx split unit. Consequently it takes a week to dry the parachutes. One of the mods I am working on is to replace the ahu so that drying time is reduced to a...
I am doing a load calc for a building that has an open water tank in it. I've found a formula for calculation the evaporation rate for the tank. However, my load software requires a value in btuh not lb/hr. How do I go about figuring out how many btuh this is?
The only thing I could find...
I have a long rectangular computer server room (20' x 70')that I am designing a underfloor hvac system for. The underfloor system will provide air directly to the servers through cut-out floor panels. The problem is that the client wants the hvac units in the far corner of the room. With the...
I have a project to design a parachute drying tower. Basically, it's a tall metal building where they hang parachutes on hoists and run the A/c units heater to dry the chutes. I'm looking for some help on how to calculate drying times and/or how much heat its going to take to dry a parachute...
When you are sizing your chilled water piping and pump, do you typically include the pressure drop for such items as the suction diffuser, flex connections, air separator, etc. or are you mainly concerned with the coil, fittings, valves and such? In all the examples I've seen, only the main...
I just have a general question I have been wondering about: What happens to the airflow when your supply air ductwork is oversized? Say for example, you typically try to maintain a constant 0.1" pressure drop across your ductwork but it's a retrofit job and reusing the existing ductwork...
I have an industrial building in which the ahu's are being replaced. The units are 10,000 - 15,oo cfm units. The new units will be set to provide 100% OA during the occupied hours due to chemicals in the building, and minimum OA during the unoccupied hours. The new units will have VFD's. The...
Does anyone know what happened to the "Tim's HVAC Tools" shareware program? It was a neat little bunch of HVAC calculation tools but when I go to the website to download it, I get one of the web hosting messages that that site is no longer available. Does anyone have a copy of the...
I am working on a project to evaluate different energy recovery methods for some 100% OA ahu's. One of the suggestions I received was to look at using the condenser water from the cooling tower and a heat exchanger to heat the water for the hot water heating coils. Is anyone familiar with this...
I have a project where I have to use a program called BLCC to evaluate a couple of design options. The program is from the Federal Energy Management Program website. This is the first time I've had to do a life cycle cost analysis and was wondering if there was anyone out there who could...
What do you do when there is a big difference between your calculated supply air and calculated exhaust air? I know you want to maintain a negative pressure in restrooms, usually 110 to 120% of supply air, but you also don't want too high of a negative pressure.
It seems that you could either...
