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I appreciate the really fast response from [imok2], And my question was answered. But I need an expression I can load into a PLC. This freeware will be great for checking things out. Thanks...

I am upgrading some cooling tower controls and would like to monitor sump temperature as compared to ambient wet-bulb temperature. My weather station reads dry-bulb and relative humidity. I'm willing to assume constant barometric pressure. Does anyone have a nice set of expressions I can use...

Pneumatic is a given on this project, I don't have a choice. I planned to put each valve (chilled water and steam) on separate air lines and pressure sources (I/P transducers). So each could be operated over the entire 3 - 15 psi pressure range and there would be no interaction. I assume the...

We are replacing chilled water and steam valves that have pneumatic actuators. The steam valve operates between 4 and 8 psi. The chilled water valve operates between 9 and 13 psi. We still want to use pneumatic actuators, but we have an electronic control system that can drive both valves...

I just joined a food manufacturing company that has four(4) 200-hp boilers. The operator runs all four units at about 20 - 30% rated load. He says that we want to minimize flue gas temperature in order to maximize efficiency. Running at 25% keeps the flue gas temperature down. Is this the...

We have 29 air handling units on the roof of a machine shop that covers about 25 acres. Chilled water and steam are used to maintain space conditions, although we cool for most of the year because of internally-generated heat. We modulate air dampers to control return, relief and make-up air...

We have four (4) large centrifugal air compressors (900 - 1500 hp) that run at constant speed to supply a general 100-psig header in our factory. The air demand is somewhat variable and it takes the capacity of 2 or 3 compressors to meet the plant requirement. On occasion, we vent air to the...

This is industrial space conditioning. The controls have been dead for at least 10 years. We just run all 14 AHUs all the time, with chilled water valves wide-open. No complaints from the plant, but we think we are using too much energy. Our new control will allow us to reset the discharge...

We have some 20 year old AHUnits, each rated about 60,000 cfm. They have chilled water and steam coils. They also have twin supply fans (vane-axial with pitch control). The pitch controls are frozen in random positions, resulting in actual air flow of 60 to 80% of rating. I vote to toss the...

Would someone please suggest a web site / source for historical weather data? I need heating and cooling degree days by month for 2001 - 3 in southern North Carolina, US. Thanks.

The target valve position range does not map to 0 - 100% pump speed. The customer just thought 60 - 70% was a nice "sweet-spot" for valve operation. I have implemented several of the group's suggestions and we do not see oscillations. We are now resetting pump speed periodically...

Actually, the customer side is quite stable. The flow is steady and the entering water temperature only varies a few degrees. Somehow, we take that situation and make the secondary outlet temperature oscillate. Control scheme... We modulate a water valve on our side of the heat exchanger...

Thanks for your interest... Here are more details... We usually run 3 of 4 chillers (in parallel). The outlet temperature is 39 to 40 deg F. The total volumetric flow rate is about 10,000 gpm. The secondary water flows at a fairly constant rate determined and controlled by our customer. We...

I have two(2) 1000-ton centrifugal chillers and four(4)variable-speed pumps sending 39 deg F chilled water to the primary side of eight(8) plate and frame heat exchangers. My customer circulates water on the other (secondary) side of the heat exchangers. My obligation is to hold 42 degress F...

There are dozens of fan coil units in the plant, there are air-handling units, refrigerators, freezers, and also units that make chilled water, some cool a brine loop. Not much chance of getting my arms around all that equipment. I'm interested in energy management, just want to know the...

I have an engine room with ten (10)ammonia screw-type compressors (400 - 1250 hp) pulling suction (5# and 25#) on an ammonia system in a large manufacturing facility. I want to measure the cooling load. I can get compressor motor currents, ammonia temperatures and pressures. But don't I need...

Any words of wisdom on the practical limits of HART protocol in terms of loop length, etc. for digital communication of instrument transmitter data in a factory? Wire type/size, maximum number of transmitters, noise problems, etc. Is this the right forum? Thanks.

We are rebuilding some large (20,000 cfm)industrial air handing units that use chilled water for cooling. We have control of individual dampers and can also modulate the chilled water valve and fan speeds. We plan to optimize the AHU controls for minimum energy. We also plan to modify the...

Clarification - I need to estimate the volumetric flow rate in my compressed air system (90 psig) based on pipe size. What velocity might the original pipe designer have designed for?

I need to install flow meters in our plant air system (90 psig). Total capacity of all compressors is about 7500 cfm. The only other information I have is pipe sizes (4, 6 and 8 inch steel, and 2-inch copper) Please suggest a typical design velocity or other method to estimate flow meter...