i took it OA was resetting the discharge air setting?the static sensor and discharge air locations are critical to the AHU reacting to the swing from anything but max air.when that VFD is installed the ramping signal is going to depend on it being in a general location to track the air might want to look into its location.8 boxes on the same level as the system 1.5" is to high for such a medium application.one thing i've seen with VFDs when the space is comfortable and the boxes are floating to maintain area set points..the VFD screen should be at 25Hz to 30Hz
Yes the discharge air is reset from OA. Above 80 OA it maintains 55 DA, below 75 OA it resets to 60 DA. Hasn't been too much time below 75 yet here in Florida so most of my experience on this account so far has been with 55 DA. I did drop the static to 1.3 but will try going down to 1" to see what effect that has.
tweeking that static by 10ths is a good way to go trying to get the minimums not to cool the spaces.anoter question,how are the compressors being staged thru either a UCM/TRANE style digital controller or....VAV rooftop Trane staging controller(W7100 type item).the maximum air setting for the spaces on the boxes are you hearing major air out of the registers during cooling....any self powered VAV reheat units around the perimeters...
Being staged by the Summit outputs directly to LSV's and compressor contactors (2 stages). Haven't noticed any objectionable air noise, but haven't really listened while they were calling for maximums either. When you say self powered, if you mean fan powered boxes, no none of them on this job, just standard VariTrane dampers with electric reheat..
AREA: This is where you will set up temperatures and individual set points related to individual areas. You can set AREAS to control any group independently from other AREAS such as office space, floors, common areas, warehouse, etc. etc. The area itself is unique as your space can be subdivided for individual temperature control, and also has the capability to have different start and stop times. This is helpful when as an example you have subdivided areas and or have different tenants on individual floors or areas which require different schedules such as holidays or if necessary exclusion dates can be created. This information is available for your use at the bottom of the screen located in the help menu. You should familiarize your self with the help screens which are available at all windows. It is very helpful to have more than one AREA so that individual times can be established.
VAS: Variable air volume air systems (VAS) is made up of VAV boxes, air handling equipment which supplies hot or cold air to boxes.
In addition ventilation equipment such as Outside air VAV boxes, make up air fans and building exhaust fans. VAS works with AREA CONTROL where it receives start and stop status through the TIME of DAY SCHEDULING. Remember it is the AREA which helps manage the VAS to control operation of all the VAV boxes and air moving equipment.
VAV boxes are listed as MEMBERS which are related to the VAS and controlled by the AREA which it serves.
This is where you set up the votes for your VAS and when changes are made you will need to reset the votes. This needs to be checked and if not maintained will give you an erratic control which you are experiencing. Such as in the case where a remodel has occurred and originally you had 10 VAV boxes but you now actually have only 8. This will alter your votes.
CPL: Custom Program Language allows for custom programs and calculation which cannot be done in other applications in Tracer summit. This is somewhat difficult to do and changes to CPL are not recommended at first. In order to familiarize your self you may want to open CPL and print out its program. When exiting do not save changes. You should be able to review the list of VAV's and UCM's which will be responsible for the temperature reference. This is accessible and listed in the CPL editor. You will need to locate the VAV's in CPL and verify they actually exist as well as positioned where there temperatures are accurate.
As far as the set up of the DX system you should set the static pressure to 1.5" W.C. which is the design of your VAV box and will give you the best accuracy and a good starting point for the commissioning of your system. This VAV box is capable of working with less static and much more up to 3" but should not be necessary for any setting other than 1.5" especially when balancing.
You will need to verify actual static pressure 2 thirds downstream of the air handler with a Magellanic gauge to confirm accuracy of your set point which controls inlet guide vanes. It is required to have a higher static than some have suggested so that when under a full load you will have an average of 1.5". Unless you want to stand around and regulate this control as needed...Let the equipment do the work. Lowering your static will do nothing whatsoever. As a matter of fact, the higher air static will identify problem areas such as dumping from a VAV box which has a bad motor or air valve. This can be checked by overriding control and closing or opening the air valve and checking air flow at the display.
Your balancing will be set up as two positions- Minimum airflow and maximum airflow. Minimum is based independently for cooling and more important for heating which will require airflow to meet its requirements. You will need to command the VAV's to self calibrate which is done in the set up. This is done by selecting calibration and choosing a Binary output for its operation. You will need to save it and wait a minute. Then choose its reference which is indicated by the threes (...) as its reference.
In addition the calibration should be scheduled to perform by itself which is done through scheduling just like you would start and stop. This may need to be set up in CPL if its not already set up.
It is not recommended to alter the set up for the VAV's other than set them up as their actual size. If you have a 12" round inlet it should be set up to it's corresponding CFM output which is around 2000 CFM. The air flow ring is designed to individually fit each different size box and accurately measure CFM.
I hope this helps.
Trouble shooting is not part of the repair............understand the symptoms and you will find a solution.
Why not just raise the cooling setpoint on the individual vav box to please each zone thats an issue. This can be done in Tracer.
While you have been receiving great information in this thread(minus a rebuttal against one of maxsters post), one other thing I have come across with the same issue you are having at more than one location. When you are checking your static pressure are you doing it from the front end or have you actually took your magnehelic and checked it. I've seen jobs designed to run 1 to 1.2" that with the IGVs completely shut the system would maintain 2" because of the air bypassing through the center part of the IGV where the shaft passes.
Can you get a set of plans? If so have you checked some of your vav settings versus what the plans say? Has this been an ongoing issue on a new building or old building? Have you also checked to see if the static pressure sensor is set correctly or the right range was used for the job? For static I usually use a 0-5" sensor.
Again everything that has been posted has been right on, just something else for you to look at.
The problem with doing this (which has already been done by the way) is the minimum airflow setting of the box still allows enough air to overcool the zone. The two easiest fixes are to lower the minimum to zero or lowering the static set point slightly (and checking to be sure the duct static is actually what the sensor is reading). Being a DX system we just need to be sure we don't short cycle the condensing unit if too little air flow is going through the system.
Originally Posted by gwoner
Alcomech really understands the intricacies of Trane Summit and his knowledge sharing is very much appreciated.
Great suggestions about actual vs computer read out static pressures, thank you. It is a 10 year old building.
Originally Posted by joey791
Excellent synopsis of Trane Summit Alcomech, thank you very much.
Originally Posted by alcomech