HVAC Monitoring Suggestions

[aguada]

I am in the process of developing my own user interface program to monitor my HVAC equipment.

I would like to have a USB interface between the sensor circuit board and my PC.

Anyone have any suggestions for a mfgr for a HVAC monitoring (only) circuit board and matching sensors?

To get an idea of what I am working on goto here:
http://members.cox.net/aguada/WW2F_HVAC.htm

Thanks in advance...

[ts ac tech]

I looked at your web page...

First, the graphics are nice and the information shown is good, but if you are trying to break ground and present a revolutionary new way of monitoring HVAC equipment you are many years behind. Virtually every DDC controls package available has graphical interface of some sort. If this is just for your personal use at home, kudos!! Carry on and have fun.

Second, you might think about switching the inputs to your calculations which show your TD's for outside ambient vs return ambient and your return ambient vs supply ambient...they are usually represented as positive numbers.

Finally, to answer the question in the post...to my knowledge most boards communicate with the front end with either RS232 or CatV, and on older boards ARCnet cable, I have not seen one which uses USB. I suspect your goal is to be able to set your laptop next to the board, plug in, and go to work. RS232 and network cable for direct connect to a DDC controls board is fast, I don't think there would be an advantage using USB, but I'm an HVAC tech not a computer tech.

Good luck with the project!!!

[aguada]

ts ac tech,

Thanks for your response.

I am not a hvac tech, and I wanted something simple to indicate GOOD or BAD, and if BAD call a hvac tech to fix it. I looked at some of the state of the art stuff you mentioned.... they are very impressive, however way to much info/data for a non-tech homer owner like me.

If USB is not an option, what CAT V(TCP or UDP) mfgr's do you recommend that would have 8 sensor input monitoring boards (no control) that have a CAT V ethernet interface to the PC.

I not looking for lightning fast, just something that would be accurate and durable, stay calibrated for a reasonable timeframe. I would appreciate any suggestions or recommendations.

[Edited by aguada on 08-04-2005 at 09:30 AM]

[amigo]

there are many USB I/O manufacturers, like:
http://www.accesio.com/go.cgi?p=../digital/usb-dio-32.html


If I were you though I would look into "1 wire" devices.
Slow, but networkable and cheap. have been used in weather stations (which are mainly input points)for years, many starter kits out there and nice little graphics interface packages too.

[aguada]

Amigo,

Regarding..."many starter kits out there and nice little graphics interface packages too."

Any URL's you can provide would be most helpful...I am not having any luck on the web searches (excite, google, etc).

"1 wire" devices... are you refering to 1 wire Sensors... if so... a couple of url's would help me alot.

Thanks in advance...

[amigo]

http://www.audon.co.uk/1-wire_weather.html
http://shops.bizarsoftware.com.au/ATAShop/catalogue/category16/category79/product190
http://www.aagelectronica.com/aag/index.html
http://www.lightningnetwork.org/rabbitweather/
http://www.maxim-ic.com/1-Wire.cfm


HMI Interface:
http://www.weather-display.com/index.php
http://sheepdogsoftware.co.uk/ssds025.htm
http://www.henriksens.net/1-wire/

[aguada]

Amigo...Thank you sir!

I came across this little puppy while referencing the URLs you provided.

What are your thoughts?

http://www.measurementcomputing.com/cbicatalog/cbiproduct_new.asp?dept_id=418&pf_id=1698&mscssid=KT3C4FNG07778GC7PN85U6M35W441PWA

[amigo]

looks good.

I think for your application rule of thumb for system components should be "simple" . Hardware and software.

[aguada]

To All,

Thanks for all your help... I found what I was looking in Air Temp and Airflow sensors at EBTRON. You guys have been most helpful... BTW thanks to the HVAC forum grand poo-pahs for providing this service.

Catch ya'all later on the flip side... when I get this puppy working.

AG OUT

[Edited by aguada on 08-04-2005 at 07:51 PM]

[drrtu]

Nice work on the output side. Your problem is on the input side. I agree with the theory of using the system to give an indication of a problem. The root problem is sensor cost. Wireless is the way to go. I believe you need 8 points. OAT, DAT, RAT, RATwb, Suction line T, Liquid line T, Liquid line P and Suction line P. Using these 8 points and information on the system such refrigerant type & heat output, you get the status of most light commercial & residential systems. Good quality sensors & software will cost over $2,500.00. I have looked into developing a portable system to prove a split system or rooftop is charged and running correct. There are a few out now. By the time I add up hardware, software and throw in a laptop or pocket pc it gets pricy. The price of 8 channel a to d boards and DAS systems have come down.

[aguada]

drrtu,

1st allow me to say that I have greatest respect for HVAC techs such as yourself. From a non-hvac tech home owner point of view I am not the least bit interested in measuring or acquiring detailed hvac data ie the number atom molecules contained one cubic centimeter of ambient air during the latent heat transfer process...(LOL) so-to-speak... that level of detail is what you guys do... and do it well I might add.

I thank you for taking the time to analyze what I am after...

drrtu you nailed it.. "I agree with the theory of using the system to give an indication of a problem."

Let me take that a step further from an average home owner point of view... what I am trying to develop is, something that indicates that the Heat/Cooling system is performing within the design limits specified by the mfgr for size of the home, ducting, location, elevation, etc. I refer to it as the "IT IS WHAT IT IS" system performance factor for the average home owner.

The indications (GOOD vs NEEDS SERVICE), is all I need to know (and all I want to know). If and when I get a NEEDS SERVICE indication, I call my HVAC (Stevensons Air Care) tech, and give him the data as to what the NEEDS SERVICE indication is related to, so when he shows up at my front door, he already has some idea what he is walking into, and in theory hopefully shave off some on-site troubleshooting time to fix the problem, which in-turn saves me some money.

Another angle is the "IT AIN'T BROKE" factor for the average home owner. For example... its 100 degrees ambient outside and I have my temp set at 65 degrees, and the best the system can do is maintain 78 degrees(for example), which by design is absolutely within spec for the system, and therefore, there is nothing wrong with the system "IT IS WHAT IT IS" (sorry the previous statement was poorly written, but I hope you get my point).

Regarding "Good quality sensors and software will cost over $2,500". I totally agree with the good quality sensors part and the Wireless... wireless is way out of my league at the present. I have been lead to believe that Analog sensors are the most durable and stay calibrated longer than the Digital Sensors. I realize that the Analog sensors are slower, but for my use and intent they appear to be adequate... speed is not necessarily a requirement for me right now... my best guess is that a complete poll of all sensors/data can be completed and displayed easily once every 2sec or less, which is more than adequate for my needs.

Currently I am considering the (8 channel input) E-TEMP as my DAQ interface device to connect the sensors to, and upload the sensor data to my PC via Ethernet TCP. http://www.measurementcomputing.com
--The E-TEMP device has a Built-in ambient temperature sensor capability that covers my (OAT) requirement.
--Two more additional Temp sensors to cover my Liquid and Suction line Temps.
--No power supply required, CATV data transmissions are good for approx 130 ft without dropping any 1's or 0's... in my case I only need about 50ft of CATV, from my HVAC equip to my PC.
--The Softwire software is free with the E-TEMP device, and I can tailor my front-end GUI to interface with the Softwire or write my own LAN interface if need be.

--Then attach two of the EBTRON (Dual AirTemp/Airflow) sensors.
http://www.ebtron.com
Two each will cover both my Return/Supply Air Temp and FPM requirements.

I estimate the HVAC DAQ monitoring hardware for my intended design will run me less than $700 retail.

Regarding the additional inputs you mentioned:
RATwb (wb=wet bulb I assume)... what will that do for me data wise, and how do you see that data being used and interupted. I am not questioning your suggestion...remember I am not a HVAC tech, so I have to ask..sir

Liquid/SuctionP (P=pressure I assume). I mentioned that to my HVAC guy... and he said don't go there, he told me it is against the law to put in a pressure sensor in the AC lines. Is there a analog sensor available that can measure internal liquid/suction line pressure...EXTERNALLY? If so, pls provide me some links to some web pages.

DAT? I think AT = Air Temp... D= Dry?

[Edited by aguada on 08-06-2005 at 06:43 PM]

[drrtu]

I think we are both working on a similar product but are on different paths. There are a lot of companies selling data acquisition hardware. Your idea seems more like the “check engine” light on your car. Mine would help a field tech diagnose the problem and could be run at a later date.

I believe you do not have to measure airflow for the following: 1. sensor accuracy – in order to obtain good readings you will have to install a flow grid or conduct a traverse. 2. Output from other sensors will have you looking for an airflow problem. IE low flow can show up as increased delta t or low suction pressure. 3. Cost and calibration. The units I have used in the past have been 4 to 20ma outputs.

You need to check to check both pressures. Subcooling and superheat are two calculated values that are very important. The down side is pressure is a costly to purchase and install.

Return air wet bulb is needed as an input to find out the entering air on the evaporator. Most equipment manufactures can provide charging charts. Most use RATwb. Most wb sensors are also 4 to 20ma. Don’t forget you can always read RH or dewpoint and convert with software. 4 to 20 loops require a power supply.

This vendor has a good line for one stop shopping http://www.omega.com

If you are looking for a very cheap solution, try just using temp. sensors with the system working. IE at known OA and indoor points the system should give similar DAT points. If the output varies from past data you get the alarm. Throw in a delta p switch across the filter and you have a custom data profile of your system.

[aguada]

drrtu,

Thanks for your response...

Yepper..You are EXACTLY correct...."Your idea seems more like the “check engine” light on your car."

Msg received..."If you are looking for a very cheap solution, try just using temp. sensors with the system working. IE at known OA and indoor points the system should give similar DAT points. If the output varies from past data you get the alarm. Throw in a delta p switch across the filter and you have a custom data profile of your system."

Is the Delta-P switch go by another device name...I am having problems finding one specifically designed for Airfilter use/measurement.

Thanks in advance...

[drrtu]

Just a few

http://www.setra.com

http://www.dwyer-inst.com

http://customer.honeywell.com

[mfarris]

aguada,

Since you inquired and wanted info (inputs, outputs and graphical interface & USB) here is another to consider.
Interface is programible to use graphics of your choice.
http://www.bb-elec.com/product.asp?SKU=UD128A8D

[aguada]

mfarris,

Excellent find... sir!

Mercy sakes!

Thank you!

[core]

Hello people

Hate to show up late to the party but if your looking to have some fun and build a custom system them you may want to check out http://www.tri-plc.com this company makes pretty good PLC's and are affordable. The M series allows you to program in ladder logic and t-basic for custom functions comes with pleny of ports for various hook-ups, remote monitoring / modem. Also if you know any programming lang. (Visual basic, C ) you can write your own front end program and interigate the PLC at will for data. I found that this PLC is great for people wanting to learn automation for less then $400.00 bucks!

And if you really wanted to get fancy try building your own room sensors with LM335 transistors great learning experience simple to do. Very powerfull PLC and very affordable.

Core

[aguada]

Core,

Thank you sir for your PLC post.

My apologies for not responding to your post earlier... been out of town on business.

I checked the URL you provided and I found it most educational and a technology that I had not considered...Thanks for the heads up.

BTW I happen to read all the posts to that HVAC Procedures thread... mercy sakes...very interesting to say the least.

Anyway, one of the posts that stood out to me during the feeding frenzy, that caught my eye was yours [Quoted below]. I found it extremely professional and educational, and I can assure you I am going to be asking my HVAC guy why he is not providing me with that kind of data on my system.

"As far as leaving behind a paper trail, you and I in this case see eye to eye. Nothing is more annoying to me then not having past service reports or maintenance reports on the job. I have a separate "tear-out" on my tickets just for a "Job-site file". Also a detailed start-up sheet that shows Velocity pressure, CFM (actual) and (rated), External static pressure, Comp. and motor amps, Voltage, Air temps (delta), Line size, etc....
On the Commercial end I like to go deeper into it Pully (fan) rpm, Pully sizes, air flow readings, motor nameplate info, brake horsepower, belt size, Evap coil performance, etc.... Then after all this is performed the Customer MUST sign off on it and copies are left on the job (in folder) for future troubleshooting, and system evaluation."

[osiyo]

Originally posted by aguada
I am in the process of developing my own user interface program to monitor my HVAC equipment.

I would like to have a USB interface between the sensor circuit board and my PC.

Anyone have any suggestions for a mfgr for a HVAC monitoring (only) circuit board and matching sensors?



Just ran across your post. And read it and some of the responses.

Hmmm. Seems to me that perhaps for the objective you state that you wish to achieve, that perhaps you're getting a bit complicated? As were some of the responders.

After all, how much does a home type furnace/AC system cost? How much would one wish to invest in a monitoring system? What's your level of technical expertise? And if it's not up to the task of accomplishing the project of installing the components, setting them up or calibrating, and testing ... then you'd need to hire someone to do it. Which isn't gonna be cheap.

It's all fine and well to talk about monitoring pressures, currents, delta T's, so on and so forth. But the equipment to do so adequately enough to be worth the effort in the first place isn't cheap. And can involve some installation activities which would be a snap for a good HVAC tech, but which may well be beyond a homeowner's skills. Add, determining WHAT are good minimum and maximum values for each might be a chore for you to determine.

Sems to me it might well be simpler and cheaper to reduce the inputs to the basics, and KISS. Then use commonly available, not very expensive, off the shelf items to get it done.

ie Sail switch or equivalent to detect that the fan is in fact producing air flow. Two standard capillary tube type temperature controllers. Exact make and model unimportant. Each simply needs an appropriate range, and a stick type or coiled cap type sensing element which can be installed in the appropriate place. One for monitoring a call for heat, one for monitoring a call for cooling. What else? How complicated do yah want to get? One or two CTs (current sensors) to verify fan motor and/or compressor motor is drawing current. Maybe a freeze stat located right next to evaporator coils (to warn of icing conditions). Line monitor? To monitor electrical power supply to unit. One can find then in single phase or 3 phase types. Single phase, which is what you would most likely need can be set to trip at a determined by you low voltage setpoint. Or, heck, just wire in a standard relay to the unit power supply. Relay having coil rated for same voltage as unit uses. Couple wires connected to common and normally closed contacts will give yah feedback as to whether or not you've blown a breaker or fuse. Etc.

With whatever of the above you decide to be important enough to know to spend the money on, the only other thing you need is some wire, some misc standard relays, and a few solid state time delay relays. Plus, maybe a 120 to 24 volt transformer, electrical enclosure cabinet, etc. Depends on your design.

Extra relays are used to prevent alarm point monitoring except when proper condition exists. ie They make or break signal line for fan status if fan is called for, or not called for. Same for temperature controller being used as temperature sensor. You want that signal line locked OPEN by a relay unless and until a call for cooling occurs. You'd also add a time delay relay, which would delay the lockout relay from making for a period of time after the call for cool commences. After all, it'll take a while for compressor to start, and coils to start cooling. Set temperature controller/monitor to some reasonable value, ie perhaps 55 or 60 degrees. Wire it so contacts break if temp at coil is less than set point, make if above setpoint. Now you'll have an open or closed dry contact (binary zero or one)which after a suitabe startup delay, after the call for cool, will tell you whether or not unit the coil is getting cold enough to be of any use to you.

Same principle works for the other monitored points.

Pretty simple system, actually. Not all that expensive if you have the skills to do it yourself. Just need to understand basic electricity. Be able to use a drill, screwdriver, wire stripper/cutter, etc. Outputs can be sent to any of many readily available I/O boards that'll plug into most desktop or laptop computers. You only need digital inputs. And a program to read the status of those bits of input. Or, just get some simple 24 volt neon lights that just require you to drill appropriate sized holes in you electrical enclosure cabinet, insert lights and wire em. Some plug in with built in spring clamps that'll hold em in place, others just require you to screw on a retaining nut/washer. Label indicator lights on cabinet door. Done. Simple.

Such scheme as I mention is an old one. And reliable. It works. When I worked for one of the major telecom corporations we had thousands and thousands of such simple monitoring systems. In main and remote switchhouses all over the country. In our case, at the time, we had system both lighting up indicator light on panel inside the switchhouse, so local phone guy knew he had a problem. Plus we sent same info out over a network. Central trouble dispatch center then called me or one of my guys, or one of my peers in another region. Computer program just looked at 8 bit byte to see which bit or bits was set, looked up a table and then produced simple message. "No electrical power to AC Unit 2". Or, "No air flow, AC Unit #3". Or, "High discharge temp on call for cool, Unit #1"

Wasn't much info, but it was something. Better than nothing. At least we knew something was wrong. And almost always knew it BEFORE building temperatures got critically high or critically low. Meaning that regularly a tech was able to get on site before TSHTF.

Of course, at later times we started putting in more advanced systems, DDC type monitoring and control. With remote access which was nice as I could do some rather in depth troubleshooting from home. Perhaps even get enough info to see that while we had a problem, it'd wait til next work day without problems. Thus saving an after hours call out and the overtime associated with it. Which suited most of us just fine as we really didn't want the overtime. Would as soon be in bed.

But even when we went to DDC systems, we didn't install that on every system in every building. We considered a cost-risk ratio. Facilites with a total value below a certain level were left with the simpler (and cheaper) monitoring systems. ie Just didn't make sense to install a total and complete monitoring system with all it's sensors and labor costs involved on something like a Bard wall hanger. Montoring equipment would have cost more than the AC unit cost to replace. Especially if the Bard was hanging on some small remote switch building out in the sticks somewhere. Now if it was a major, urban switch, a different matter. Those buildings had millions of dollars of electronics in em.