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  1. #1
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    Treatment facility

    Need some advice here. I attached a pic of the floor plan for a treatment facility. The issue we are having is uneven temperature. There is 1 tstat per unit, and the tstats are in one of the rooms. So when that 1room where the tstat is gets satisfied the ubit shuts off, regardless of how the other rooms are. Simple solution, leave doors open...doesnt work. Clients dont listen, doors get closed, windows get opened. For this type of a setting I think the single tstat setup is wrong. I personally think that using multiple sensors to an averaging thermostat would have been better, but I have never worked with averaging tstats and am having a hard time finding info or good ones. Another thought was to redo the whole set up with VAV's but again I dont have a lot of information on those and in pretty sure this would be the expensive route (to have it done correctly).

    All units are 4 ton split, except for blue, its a 5 ton. Each room has 12x12x1 returns, larger rooms have 16x20x1. This is in Phoenix, az. So we get quite a few days over 100. Looking for suggestions on what can be done to make this better, suggestions on good averaging thermostats or any other info you guys can give. Thanks guys.

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  2. #2
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    First I would never have installed split systems... and I never would have done the setup you've got there.

    Your only alternative is to talk with the building designer or get him to sign off if you're going to continue work, so that you are indemnified when this becomes a bad idea.

    If the building is already constructed and you are the poor guy who's got to try and do something with this..... well sir, you have my sympathies.

    You could theoretically install a Vision Pro thermostat which has the screen electronically locked according to your settings, and you could use hardwire remote sensors which I believe can be daisy-chained together to form an average...but that could simply result in several rooms feeling uncomfortable....unless you are willing to adjust the set points and you don't have a corporate telling you that you're not permitted to change the set points.
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  3. #3
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    Quote Originally Posted by timebuilder View Post
    First I would never have installed split systems... and I never would have done the setup you've got there.

    Your only alternative is to talk with the building designer or get him to sign off if you're going to continue work, so that you are indemnified when this becomes a bad idea.

    If the building is already constructed and you are the poor guy who's got to try and do something with this..... well sir, you have my sympathies.

    You could theoretically install a Vision Pro thermostat which has the screen electronically locked according to your settings, and you could use hardwire remote sensors which I believe can be daisy-chained together to form an average...but that could simply result in several rooms feeling uncomfortable....unless you are willing to adjust the set points and you don't have a corporate telling you that you're not permitted to change the set points.
    Lol...my thoughts are exactly that they should have never had splits systems. Buildings been up for about 10 years. I'm the building maintenance (don't hold the title against me...lol...I'm in school for hvac and hopefully a career change.) for the past 7 years and every summer we deal with their complaints. The thermostats currently have lockboxes and screen locks on them, but in the age of Google they don't work. Only thing my corporate tells me is not to spend a lot of money, which is why its still an issue. We've had companies out to give quotes, they send it to my boss and they say "thats not coming out of our budget". If I were to do averaging tstats I would move them into a room where the clients don't have access. Do you know of any good averaging tstats? Thanks.

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  4. #4
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    Jan 2015
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    Agree with TB, however based on your comments I take it this has already been built and this is an ongoing facility. Here's a not too costly or intrusive suggestion. You could disable the room stat. Place the air handler fan in run (or on) and install a remote tstat in the return air trunk of each section. You should be able to get the parts from your local supply house. I know Grainger has stuff you can use. Yes fan maintenance/replacement will need to be discussed with the owner (like every 2 years) but this will be better than you have

    Good luck

  5. #5
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    Quote Originally Posted by Answer-Man View Post
    Agree with TB, however based on your comments I take it this has already been built and this is an ongoing facility. Here's a not too costly or intrusive suggestion. You could disable the room stat. Place the air handler fan in run (or on) and install a remote tstat in the return air trunk of each section. You should be able to get the parts from your local supply house. I know Grainger has stuff you can use. Yes fan maintenance/replacement will need to be discussed with the owner (like every 2 years) but this will be better than you have

    Good luck
    Thanks, it has been an ongoing problem that I inherited. Its one of those problems where everyone wants it fixed but no one wants to pay for it. Just so I am clear on your suggestion, I would move tstats to room where clients don't have access, run a external sensor up into the return duct (which is pulling air from all rooms so it would be a decent "average"), and leave the fans constantly running (to keep current air temp across sensor?)...this sounds like it could help and seems easier than running sensors to all rooms.



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  6. #6
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    Texas
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    Quote Originally Posted by Crisis1837 View Post
    Need some advice here. I attached a pic of the floor plan for a treatment facility. The issue we are having is uneven temperature. There is 1 tstat per unit, and the tstats are in one of the rooms. So when that 1room where the tstat is gets satisfied the ubit shuts off, regardless of how the other rooms are. Simple solution, leave doors open...doesnt work. Clients dont listen, doors get closed, windows get opened. For this type of a setting I think the single tstat setup is wrong. I personally think that using multiple sensors to an averaging thermostat would have been better, but I have never worked with averaging tstats and am having a hard time finding info or good ones. Another thought was to redo the whole set up with VAV's but again I dont have a lot of information on those and in pretty sure this would be the expensive route (to have it done correctly).

    All units are 4 ton split, except for blue, its a 5 ton. Each room has 12x12x1 returns, larger rooms have 16x20x1. This is in Phoenix, az. So we get quite a few days over 100. Looking for suggestions on what can be done to make this better, suggestions on good averaging thermostats or any other info you guys can give. Thanks guys.

    Sent from my LG-LS997 using Tapatalk
    run the fans all the time and balance the air flow to each room. put the stat in the common return at the airhandler and tune it in! lol

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  8. #7
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    I did 6 or so Drug Treatment Centers and it is EXTREMELY difficult to get an even temp in all the rooms due to diff rooms getting a diff amount of clients,depending, on an hourly change.Some rooms had 6 people and another room had 16 persons. It seemed that ALL the clients have the right to adjust the t'stat to their own desire.

    Just how much air do you get a 12 x 12 return grill and at what static press? Did anyone look at the duct system for actual CFM?

  9. #8
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    Quote Originally Posted by TechmanTerry View Post
    I did 6 or so Drug Treatment Centers and it is EXTREMELY difficult to get an even temp in all the rooms due to diff rooms getting a diff amount of clients,depending, on an hourly change.Some rooms had 6 people and another room had 16 persons. It seemed that ALL the clients have the right to adjust the t'stat to their own desire.

    Just how much air do you get a 12 x 12 return grill and at what static press? Did anyone look at the duct system for actual CFM?
    They try to keep the tstats locked up with boxes and screen lock but they either break the boxes, google how to get the screen locks off, its a pain...lol. I'm not far enough in my schooling to know how to check the static pressure. The companies we had out I dont think any of them checked it either. The 12 x 12 return was for each room if that makes a difference, so 1 unit would have 6 12 x 12's feeding into the handler.


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  10. #9
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    A multi room return duct system has to have a "proper" ducted return. Hold a tissue up to each grill and see what you have. I would not be surprised if the returns closest to the AHU have the greatest amount the of return air.

  11. #10
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    Thread Starter
    Quote Originally Posted by TechmanTerry View Post
    A multi room return duct system has to have a "proper" ducted return. Hold a tissue up to each grill and see what you have. I would not be surprised if the returns closest to the AHU have the greatest amount the of return air.
    Thanks. Ill take a look at that. I know some vents have have some stong suction, almost want to pull the filters through. I have to change the filters almost twice a month.

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  12. #11
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    Thanks to all for the suggestions. I'm not looking for for you guys to solve the problem for me, I know that's impossible. I appreciate the input.

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  13. #12
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    As a next step from the return air sensor option you could replace the diffusers with thermafusers which although they aren't perfect, are cheap to install. You would also need to add a barometric bypass system to avoid overpressurization

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  14. #13
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    It's apparently out of balance. This would be an easy balance. Four ton= aprox 1600 CFM. This is based on the load being more or less equal.
    That's the available air. Divide that by the number of rooms ( most are six) about 267 CFM/room. Some of the spaces might need a bit more calculations but not a serious deal.You didn't list the room sizes so we can't know if they are sized ok. Anyway four tons is all you have.
    Occupants seem to be the unknown here.

    What type of grill/diffuser do the rooms have. If it's a ceiling diffuser they can get lazy and at times need to be replaced with a more aggressive down flow designed for velocity. This can give better mix as long as no one is in the path. Like by a window.
    The 12x12 returns/room should be fine. More than needed.

    The filter plugging up sounds like outside air is being added to the load. If that's the case there's no telling how much is being introduced w/o a measurement. OSA can cancel out a lot of cooling capacity if the designer didn't factor it in. Depending on code a fixed amount of fresh air is required per person.
    I should have played the g'tar on the MTV. MK

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