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Tech Tips for vav/zoning (Just click on 'Answer:')
Q: hi we have a job vav doble duct, can you helpme
Submitted by: salvador leal, service tech. alliance heating and air cond.
Answer:
A: We can develop the control scheme (electric or pneumatic) & drawings, supply the controls and the VAV boxes. Call us at 800-227-9800.
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Q: Need help for Barber Coleman VAV pneumatic type need some information on balanceing or even doing a retro fix
Submitted by: Milt Henderson, Taggert Student center Mat.Sup. Utah State University
Answer:
A: The best retrofit solution for pneumatic VAVs are the KMC CSC-3000 series controllers. The CSC-3011-10 and CSC-3025-10 are the rulers of the pneumatically operated drop ceiling. I prefer the CSC-3025 as it seems to set up a little more quickly. You can see both of these controls on the Parts Search area of this site. Dont hesitate to call us for help with accessories and such.
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Q: I am looking for a small system to replace the early Carrier-Parker stuff.
Any suggestions?
Submitted by: Ed Weber, President EMS Service Company
Answer:
A: Depending upon your application, you may want to take a look at Honeywells RapidZone at http://customer.honeywell.com/rapidzone/. Honeywell presents an economical solution, as well as many useful tools and wizards for contractors use.
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Q: I NEED A SUGGESTION ON SETTING UP A VELOCITY CONTROLLER FOR A DUAL DUCT A/C SYSTEM. NEED A SIMPLE SYSTEMATIC APPROCH. THANK YOU.
Submitted by: Jesse Serrano, HVAC MECH HOSPITAL
Answer:
A: In dual duct systems, 2 velocity controllers are required: 1 for the hot deck and 1 for the cold deck. The velocity controller on the hot deck should be set up with ZERO as a minimum ventilation setting, and a normal maximum flow setting. The cold deck should be set up with whatever the minimum ventilation requirement for the space is for a minimum setting, and a normal maximum setting. This approach keeps the space from overheating, while supplying minimum ventilation for comfort and health. If you have further questions call us at 800-227-9800.
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Q: I am currently working on a job involving running new pneumatic tubing from siemens 192-202 tstats to Carnes VAV NO boxes with roberbertshaw actuators 8-13 psi range. I have several stats also controlling some siemens pneumatic valves, 1", 3-8 psi range. I plan to run 5/32" twinned tubing from the vav box to the stat, and tapping off the main air line at the box with 1/4" tubing and making all terminations at the box. I also plan to run 1/4" tubing from the vav box to the valve actuator on the selected boxes.
My question is, Is the 5/32" pneumatic tubing sufficiently sized for the application.
Submitted by: Scott Deans, HVAC Tech. Controlled Air.
Answer:
A: The line from the thermostat should go to the T port on a volume reset controller. The branch or B port on the volume rest controller should go to the actuator. Main air should be connected to both the thermostat and the volume rest controller. The box should have static pressure pick-ups that should be connected to the high and low pressure ports on the volume reset controller. As to the size of the tubing, 1/4" should suffice for all. Call us to help you through the appliaction if you are not sure.
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Q: I am looking for a direction sheet to use with the Siemin's program to calibrate VAV's
Submitted by: Kay Stevens, tester/balancer ITB
Answer:
A: Consult your local Siemens branch office.
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Q: I can't get enough cfm out of a end of the run vav box. I have done extensive work to correct the problem. My question is this. on our blue prints, the airhandlers static pressures our anywhere from 4.0 to 4.3 . The building is 19 years old, and since as far back as I have found, our S.P. controllers have been set at an average of 1.0. What do I do??
Submitted by: Scott Barlow, Mechanic RMH
Answer:
A: This is a common problem in VAV systems. Unfortunately there is no easy answer. VAV systems are like a big apple pie that everyone is supposed to get a piece of. If someone at the front of the line takes two pieces, someone at the back wont get any. First I would check the set up of each box in the line, from front to back. Each box should be set up to provide the required amount of ventillation in cfm per head, based upon occupancy of that space, and the ASHRAE standard. Once this is verified, make sure the thermostats are calibrated correctly. From the thermostats, go to the equipment to insure that it is running up to capacity. Check the ductwork for anything that may inhibit flow. Beyond that, give us a call.
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Q: a varible air volume system has all new
controls the fan runs,but the throttle cylinder will not throttle. There is air to the volume controller, but no air to the throttle cylinder,and we replaced the control cylinder 4 times. the vav throttle cylinder still will not throttle. The air lines are all clear.
Answer:
A: If by throttle cylinder you mean the actuator, it could be that the diaphragm in the actuator is leaking. Replace the diaphragm.
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