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  1. #1
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    Maintenance Mode Toggle/HOA switch

    I had an idea that I have used at two locations now.

    I am installing either a toggle switch or a HOA and using then for Maintenance Mode at the units.

    A toggle switch at chillers or AHUs to place the units in a mode for maintenance techs to do PMs such as turning off VFDs through the BMS and shutting down heating elements instead of just turning off the fan with the VFD so the element have time to cool down or opening isolation valves that otherwise would prevent chillers from running while checking them out.

    I was thinking about HOAs (Cool off Heat) for splits and RTUs again through the BMS instead of jumping them or going to the front end.

    This would also prevent nuisance alarms.

    Has anyone done this before or see any issue that may happen?
    If you're too "open" minded, your brains will fall out.
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  2. #2
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    Lockout/Tagout is the only safe method. Shutdown via BMS is not in acceptable.

    kontrol out
    "Open is as open does." - Forrest Gump
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  3. #3
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    I think you misunderstood. It is not a shut down method its a BMS signal for mechanical techs to use so they can do maintenance. Even if it shut downs something it does not disconnect the electrical.
    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  4. #4
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    Yeah, that's what I'm saying to do maintenance on any device/equipment with potential or kinetic energy you need to lockout/tagout the energy source.

    kontrol out
    "Open is as open does." - Forrest Gump
    "Can't we all just get a Lon?" - Garry Jack
    "BACnet: integration or interrogation?" - The Janitor
    "Open protocols? You can't handle open protocols!" - Nathan R. Jessup
    “What’s that? Aaa… open protocols? Don’t talk about…. open protocols? Are you kidding me? Open protocols? I just hope we can hardwire an interface!” - Jim Mora http://www.youtube.com/watch?v=U7fjDS0jKiE

  5. #5
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    Except if you are checking super heat and subcooling, approach, fan rotation, pressure differential, oil temps, loading unloading, sensor temperatures readings, transducer readings, static pressure, entering and leaving water temps, amperage, and so on.

    Plus it is hard to run a boiler or chiller to check for proper operation if the BMS has an isolation valve closed.
    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  6. #6
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    Hi, I am quite fond of creating maintenance modes. you do need to be careful with critical systems or whatever and it is generally best to consult the mechanical guys first but it can be as beneficial to the BMS engineer as well as the mechanical PPM tech as they can more accurately find potential faults before we arrive for BMS service. what I like to do is set up a timed override for say about 5 mins where the tech can select the mode from either the supervisor or the plantroom panel operator screen. when selected all the valve actuators and dampers will drive from 0-100% and back again or the tech can select which position they will drive to. Also get any VSD's to ramp so the tech can see the VSD and motor operate, things like that. this can be done for each item of plant or whole plant rooms at a time. after the fixed time the plant returns to automatic BMS control. (to save the techs forgetting to put it back) This lets them see the BMS and plant operating.

  7. #7
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    Quote Originally Posted by XcelTech View Post
    Except if you are checking super heat and subcooling, approach, fan rotation, pressure differential, oil temps, loading unloading, sensor temperatures readings, transducer readings, static pressure, entering and leaving water temps, amperage, and so on.

    Plus it is hard to run a boiler or chiller to check for proper operation if the BMS has an isolation valve closed.
    I would not consider the above maintenance, more verification/checkout. Maintenance would be physically working on and /or replacing the components of the equipment.

    kontrol out
    "Open is as open does." - Forrest Gump
    "Can't we all just get a Lon?" - Garry Jack
    "BACnet: integration or interrogation?" - The Janitor
    "Open protocols? You can't handle open protocols!" - Nathan R. Jessup
    “What’s that? Aaa… open protocols? Don’t talk about…. open protocols? Are you kidding me? Open protocols? I just hope we can hardwire an interface!” - Jim Mora http://www.youtube.com/watch?v=U7fjDS0jKiE

  8. #8
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    I have been doing this for years. It allows for a controlled shutdown of DDC controlled equipment instead of dropping power on the equipment. I use a three position switch for Stop/Auto/Reset. Stop and Auto are self explanatory and Reset will clear all software created diagnostics.
    Beware of the prophet trying to make a profit.

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  9. #9
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    Quote Originally Posted by prtadko View Post
    Hi, I am quite fond of creating maintenance modes. you do need to be careful with critical systems or whatever and it is generally best to consult the mechanical guys first but it can be as beneficial to the BMS engineer as well as the mechanical PPM tech as they can more accurately find potential faults before we arrive for BMS service. what I like to do is set up a timed override for say about 5 mins where the tech can select the mode from either the supervisor or the plantroom panel operator screen. when selected all the valve actuators and dampers will drive from 0-100% and back again or the tech can select which position they will drive to. Also get any VSD's to ramp so the tech can see the VSD and motor operate, things like that. this can be done for each item of plant or whole plant rooms at a time. after the fixed time the plant returns to automatic BMS control. (to save the techs forgetting to put it back) This lets them see the BMS and plant operating.
    Commissioning mode! lol I like it. But I don't think I would want that switch on my equipment but it would be a great high pin level front end button.

    I have been doing this for years. It allows for a controlled shutdown of DDC controlled equipment instead of dropping power on the equipment. I use a three position switch for Stop/Auto/Reset. Stop and Auto are self explanatory and Reset will clear all software created diagnostics.
    Yes this is what I am referring too. Does it work well for you? Does your company do both mechanical and controls work?

    We have a BMS that (by a common J named company) has a bad habit of using alot of electrical reheats through the building.

    It was poorly designed to keep building pressure and would freeze the rooms without the reheats.

    When the mechanical guys show up to preform preventative maintenance they don't know anything about BMS so they just shut down the Freq drive. Of course, the reheats turn off by the static pressure switch but they also have manual reset high temps that trip as well. The next week, I or another controls guy has to go through and reset the manual overrides.

    We also have another client that has a 2 pipe system. The chiller and boiler share the pumps by using 2 isolation valves and a 3way bypass. He has no control over his BMS at all. Again a HOA used for Chiller Auto Boiler mode would be great here.
    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  10. #10
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    I've been doing this for years. I normally utilize a software button and an adjustable timer to prevent nuisance alarms during maintenance. I've also utilized physical buttons, but typically I use a momentary button or a spring wound timer. I've had too many problems with people leaving the system in 'maint mode' and then not getting alarms when it was no longer in maint. mode.

    On your reheat scene to me it seems you need a button to send a signal to the VAV's to disable reheat and then instructions to say once button is hit wait 5 minutes before shutting down VFD.
    "How it can be considered "Open" is beyond me. Calling it "voyeur-ed" would be more accurate." pka LeroyMac, SkyIsBlue, fka Freddy-B, Mongo, IndyBlue
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  11. #11
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    Just some thoughts. Keeping in mind that I offer no special insight, knowledge, or experience level. And my point of view is as a controls contractor who installs and sets up this stuff as versus an in-house maint or repair type.

    First thought, in my experience one does not want to over complicate things, hardware or software wise. Fewer components always means just that fewer things to go wrong, be over looked or forgotten, etc.

    Next thought. I can't begin to count the times I've been called to a site on a complaint that our controls for something is not working properly, just to find out someone put something into manual "Off" or "On", manually drove an AO to some value and forgot to put it back to "Auto", and so forth.

    Of course, every situation/installation is unique and may have unique requirements.

    Generally speaking ...

    Software wise, we advise customers to severely limit who can adjust, command, or override from the front end. Typical, ordinary user, in maint dept can only view, change a schedule, or change ordinary space temperature set point (although many customer/owners limit who can do that last item). The ability, right, to change other stuff being limited to as few people as possible, hopefully only those who have more training and knowledge, and who have a vested interest in the overall plant operation and keeping track of what is going on. So it can be undone if needed.

    For routine stuff, like the guy who is gonna change filters, check/change belts, etc we recommend just shutting off power and tagging out. Now, we have done things like including a routine to suppress so-called nuisance alarms for cases like this. But in most cases, not. Typical in 95% of the cases I'm speaking of is for our customer's head of maintenance to require the working to FIRST notify the head guy, or his assistant prior to doing such a shutdown. They knowing that some worker is going to be shutting unit down for routine maint, just ignore alarms. When alarm condition clears, they know the guy is done. If it seems to be taking too long they check on what's going on. Most front ends I've seen have some method for mass acknowledgement of alarms. Easy enough to clear past ones that's returned to normal state. The basic idea is to keep the senior guys who're responsible for the plant in the loop and knowing what's going on and who is doing what and where. And for this kind of maint action, you want the power off and item tagged out anyway.

    System programming wise, in our case the way we do things normally, field controller for whatever unit, will start up unit normally once local disconnects are restored to normal position.

    For cases of system check out, where a tech might want unit running, heating or cooling as case may be, our typical customer head of maint, or his/her trusted assistant(s) will simply change set points or operational mode in order to cause equipment to operate in desired mode. This then makes it possible to do physical equipment checks and at the same time ensures screen points are correctly linked, programs and/or firmware configuration are operating correctly, AO's are outputting correct signal, etc. In short, it's an end to end check.

    In most cases the installed equipment and programs we create have a software adjustable master mode control. Typically ... manual off, manual on, heat mode, cool mode, auto switch. Or some variation of that theme.

    In addition, for larger installation we might include a front end routine to do something like (1st) copy and record all VAV set points then if Heat button is activated, heating set points are all written to 100'F. Done to allow a system load to be put on air handler and VAV heat source. Deactivate button, all VAV's get original SP's written back accordingly. Flashing warning on screen keeps operator reminded that special mode is in effect. At selectable time expiration, if operator has not yet deactivated override, it automatically gets deactivated.

    In most cases, 98% of them I'd guess, customer/owner and staff have found this adequate. And in fact most of them made up, or had us make up for them, written procedures to accomplish each type of desired action. Step by step, in a certain order so as to negate as much as possible any chances of damaging/undesirable results. And, likewise a procedure step by step for restoring normal operation. Often employing a check off sheet used by those with authorization to make such changes. Such directions and check sheets either on paper and/or digitally available on front end by clicking on button.

    All this intended (1) to keep the guys/gals who actually know how stuff works and who have ultimate responsibility for the system in the loop and informed AND in control, Joe Whomever can't just go about willy-nilly doing whatever. Or if he does ... he's just violated rules and if SH*T Happens ... he's responsible personally. (2) Simultaneously check that controls are in fact operating as they should. (3) And minimize issues such as to many complicated add on's to normal system which just add to chances something gets forgotten, something extra doesn't just add one more possible thing to fail, and so forth. An effort to maintain as much KISS as possible.

    Plus I find that forcing the senior operators to routinely go through all this keeps them reminded of just how the system works. Have known many an in-house guy who got training .. years ago ... on his system. But then didn't really do anything with it since except possibly change a room temperature set point or a schedule. Who after all that time can't really remember how this effects that and so forth. I can readily see the difference between one and another. The guys who do the changes from the front end to cause economizer to swing open further for testing, or pumps to speed up or slow down, etc all seem to have a better feel for how things work, and when things do go wrong/astray seem to be better at identifying the issue in the first place and then knowing what to adjust in order to "make do" until problem is corrected.

    Sort of like the principle the Navy used, or used to use back when I was on active duty. While we had systems with automated controls, routinely we'd run practice drill/exercise where operator would have to make changes to system so as to MAKE it do this or that which normal setup wouldn't allow. And sometimes they even made us do it the old fashion way ... all manual. Such made us refresh memory and use it about how things actually worked, were interconnected, and so forth.

    Just some thoughts.

    Not meant to say that others with other ideas are wrong. More to possibly give at least one useable idea to others that might be useable to you.

    Last thought, in one high value installation we did customer did want physical local manual override on certain things and had good reasons for them. But at the same time insisted that we provide physical feedback about those things. For Instance, for an HOA ... we installed method so front end showed position of same.

    Its my thought that one wants to be careful about just exactly what and how one does these things.
    A site where I stash some stuff that might be interesting to some folks.
    http://cid-0554c074ec47c396.office.l...e.aspx/.Public

  12. #12
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    You and me Osiyo feel the same way about how it should be done.

    Unfortunately Louisiana is a whole new form of lazy, stupid, and indifferent.

    The "people in charge" don't wanna know, they don't wanna care, and they don't wanna be bothered. It is really sad and annoying.

    It's why in every contract we have to stipulate in big bold letters, "COMPANY NAME is not responsible for operating the HVAC equipment or any required attached equipment. The changing of temperature, open/ closing of valves, the actions of energizing/de-energizing, or any other routine required by the manufacture to properly run any and all functional HVAC related systems is the responsibility of the owners of such said equipment. Any and all actions or lack of that result in equipment failure or a technician response by COMPANY NAME may result in a fee for said time and materials."

    And there is nothing more annoying then arguing with weekend staff that you are charging them time and time again on a full service contract because they physically shut down the hot water pump and then called you after hours to come turn it on.

    This last job I did they didn't want a front end. I argue and argue with them about the importance of the front end and training people how to use it. They wont do it. So I will nail them for every hour we have a tech there working on the BMS. Since they do there own maintenance and don't have a way to interface with the system, they will be calling alot.
    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  13. #13
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    Chuckle, I understand what you're saying. Have lived in Louisiana, and still have relatives there.

    And one, as a contractor, has to accommodate one's way of doing things to fit the customers one has to deal with.

    Of course ... do as you see best. I did not mean to argue against that. Just pointing out some different views on the issue, and pointing out some pitfalls.

    One thing to consider for cases like the last one you mention. On one of our jobs, a high value system, while the customer wanted local overrides and did have a front end. As a further safety method we monitor the overrides. In some cases this entailed adding some additional relays and contacts so as to monitor positions of selectors. But the net goal was that if something was locally put into some special, other than normal auto position, warning lights at the main entry(s) to the machinery spaces light up ... kind of like a "reminder". In addition info is relayed via the network so that similar light panel in main maintenance office, and in maintenance personnel break room also light up. This customer does have a front end. And warning appears there too. The thought is that then, even if someone is not looking at the front end, to call attention to an issue that may need attention and correction. Everyone, including ordinary janitorial staff is instructed to pay attention to those lights. And that they should get hold of someone unless they know someone already knows about it. Yellow lights for a warn, something operating in over ridden mode. Additionally red lights that flash if any alarm is tripped.

    Another customer, with similar situation, also has a 24/7 security desk manned. Similar lights as described above are installed on a panel there. Head shift security guy has responsibility to monitor those. Logs all activity, and will contact someone off his extensive list to report it. If all else fails, our 24/7 service department is on his list and we get a call.

    Just a thought. One of the big problems is something left in something other than normal operating mode. Methods of handling that are numerous.

    Chuckle, just recently, a couple weeks back, I had to add some routines to a Bacnet system. With this customer, each building has a Maint Super. But such are mostly glorified janitors, with SOME knowledge of HVAC systems. I'm not criticizing them, its all that's expected or demanded of them and they have plenty else to do. Maintenance/repair is done is done by a central repair shop and it's personnel, who handle such tasks for all the customer's buildings.

    Anyway, the wise guys from the central maintenance shop have a bad habit of doing manual overrides (Bacnet priority 8), and then forgetting to null them out when they're done. Have done it over and over again. Resulting in several "warranty" calls to me to investigate "malfunctions" that weren't malfunctions at all. I finally, at this one large building, new, for whom we were the controls contractor had to arrive at a solution. Was getting to be a big PIA. So gave the Maint Super for that building a method he could invoke where for his systems and his only, one simple action and he could clear (null out) all such manual overrides.

    LOL ... He'd had it with those guys forgetting. HE was the one who got the call in the middle of the night or on the weekends. And IAW that organization's rules, he couldn't call the on-call for the maintenance shop until and unless he'd checked out everything himself. (Or his assistant, who covers for him when he's not available.) He had me do it on his authority, and called the repair shop and informed them that they'd BETTER make sure to inform him of any overrides that NEEDED to stay in place for some reason. Otherwise .... sucked to be them. LOL. He finally achieved one of his goals. The central maintenance folks have gotten very meticulous about informing him about what they're doing.
    A site where I stash some stuff that might be interesting to some folks.
    http://cid-0554c074ec47c396.office.l...e.aspx/.Public

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