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That Made Life Easier in the HVAC Controls Biz
Part one of two
Every now and then I like to think back and reflect on my life and my
career, remembering what it was like living and working without some of
the things we now take for granted. Like, remember when we didn’t have
cell phones? Or worse, remember having pagers? Like, you’d be out of
the office, driving, and you get paged, with some unrecognizable phone
number, only to then have to find a pay phone somewhere to make a phone
call to someone, and you don’t know why or even who! I think we were
better off a generation before that, when we had no phones and no
pagers, basically no way to get in touch with if we were away from our
Even that aside, I think we’re living in pretty good times, technology-wise. So many things have been developed to make our jobs easier, and while some of these things may seem mainstream now, once upon a time they simply didn’t exist. Can you imagine? Well I can. So I bring to you a two-part series on some of the things that have made my job easier over the past twenty years or so. I think I’ll start with…
This is what one manufacturer called them back when they were a relatively new product. Other manufacturers took the idea and improved upon it in various ways. Before the “self-contained relay”, all we had were the combination relay/base setup that required you to mount the base inside an enclosure of which you’d wire out from. Now we have these handy little “hermetically sealed” relays with wires passing through a conduit stub. Makes life easier in a lot of situations. Just ask any control systems electrician!
Direct-mount damper actuators
Oh man! I remember when these babies came out. A manufacturer’s rep gave our company a presentation on these. At the time all we had were the foot-mount damper actuators that connected to dampers with a combination of linkages, ball joints, and crankarms. I remember being just a newbee, fresh out of school and green as could be. One of the elder service technicians expressed his skepticism with the new concept, studying the sample actuator that was being passed around and stating that it “would never work”, elaborating that the whole concept was just another hairbrained idea that wouldn’t stand the test of time. Boy was he wrong! And for all of those mechanics that had to install the old-fashioned actuators, and all the technicians that had to maintain these dinosaurs, there was no looking back. I simply can’t remember the last time I was involved with a new installation that required foot-mount damper actuation. I suppose there are still applications for it, obviously in retrofit situations and such, but the damper actuator that mounted directly to the shaft of the damper was truly an innovation that changed our way of doing things. No doubt about it.
Strap-on temperature sensors
Was a time when these were “frowned upon”. An immersion temperature sensor was (and is) the preferred method of sensing water temperature in a pipe. But this required installation of a well that the sensor would fit into. Which required no water to be in the pipe. Not a problem in new construction. But what about a retrofit application? Or an “after-the-fact” scenario. Use a strap-on sensor! The argument against these used to be that they aren’t as accurate as an immersion sensor if they aren’t installed correctly. While that may be true, if they are installed correctly, they are quite accurate. If the application doesn’t require pinpoint accuracy, then this is the way to go. And even if the application does require an accurate and consistent measurement of the temperature of the water within the pipe, there’s still a strong argument for using such a device. Just make sure that it’s installed properly, use thermally conductive compound between the sensor and the pipe, and get it out of an area where it could be subject to damage, and you’re good to go!
Ball-style control valves
The venerable globe valve is the “traditional” control valve. Long before anyone got the idea of putting an actuator on a ball valve, the globe valve was fully adapted to electric actuation. The body of a globe valve has a stem protruding through the top if it. Lateral (up and down) motion of the stem, and thus of the plug assembly inside the body, translates into variable flow through the valve body. An actuator is mechanically linked to the valve body, and operates the stem, moving it up and down. Globe valves are generally available in the range of ½” to 6”, and are suitable for two-position and modulating control for both water and steam.
Enter the electric ball valve. When these first came out, there was a little bit of resistance to specifying them, at least within the consulting community. Gradually, ball valves came into their own as a low-cost alternative to the globe valve, at least for applications requiring smaller size valves. Inside the body of the ball valve is…a ball. With a hole through the center of it. And a stem fused to the top of it, that protrudes through the body of the valve. Rotation of the stem, and thus of the ball with the hole in it, translates into variable flow through the valve body. An actuator is mechanically linked to the valve body, and operates the stem, turning it back and forth.
Ball valves are available in the range of ½” to 3” (or larger), and are generally limited to use with two-position and modulating water applications. Given the same size ball and globe valve, the standard ball valve can handle quite a bit more flow through it than the globe valve. Application-wise, this basically translates into being able to use a smaller ball valve than a globe valve, for a given required flow capacity. A good thing when it comes to cost and value. Just be careful to size that valve correctly, so that you don’t end up with an oversized control valve in a proportional control application!
Variable frequency drives (VFDs)
The VFD has come a long way in the time since I’ve entered this industry. I remember seeing one of these on a wall in a mechanical room and asking “What the heck is that big old thing?” The answer I got was something along the lines of “…varies the speed of the fan motor, that is, whenever it’s not broken down.”
So to elaborate on that, a VFD is an electronic piece of equipment that can vary the speed of an electric motor as a function of some control signal received by it. The VFD will vary the power delivered to a motor, typically a three-phase motor. More specifically, the VFD varies the “frequency” of the electrical power delivered to the motor. Standard power in the good old US of A is 60 cycles per second, or 60 hertz (Hz). If the cycles per second were able to be reduced, so too would the power be to the equipment consuming the electricity.
So a VFD can vary the frequency from 0 to 60 Hz, as a function of a control signal received by it. The variance in frequency translates directly into a variance in speed of the connected motor. In HVAC applications, VFDs are primarily applied to fans and pumps. In the old days, a supply fan in a VAV air handling unit would have its volume of air varied by either inlet guide vanes or (ugh!) discharge dampers. Neither of these methods of air volume control was very efficient. With the introduction of the VFD, we were able to eliminate these mechanical means of controlling air volume, get more precise control, and save energy all at the same time. First cost and reliability of these devices have historically been “bones of contention”. Yet with prices (and physical size) continuously coming down, and reliability going up, technology has taken this one time luxurious (and potentially problematic) alternative to the status-quo in many of the more demanding HVAC applications that abound.
Tip of the Month: Think back to something that was the “norm” when you first started in this industry. If you have any longevity, you’ll be able to find something that has been improved upon via the marvel of modern technology. Even simple things such as hardware and the way things are fastened and secured, have come a long way in a relatively short time. Then, challenge yourself to come up with something that could still be improved upon even now…gives me a great idea for a future column!
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