Posts Tagged ‘pneumatic controls’
Some of us may have customers who have encountered the pesky old Trane VariCone or air valve style VAV boxes. This outdated technology often consists of worn or broken end switches and/or burnt out damper motors. Due to an overpriced retrofit solution from Trane, end users generally learn to deal with some of these boxes in their building just not working. Here at Stromquist we can provide our customers with a relatively painless and low cost retrofit solution using Honeywell D690 dampers and Honeywell ML6161 floating actuators or the MARD zone control damper assembly.
These 9 easy steps will get the box up and running. The first install should take about 4 hours, and once your customers are familiar with the process they will be able to cut the retrofit time down considerably.
Step 1. Determine the diameter of the box being retrofitted.
Step 2. Provide the customer with the proper size Honeywell D690 and Honeywell ML6161 actuator or Read More
Even with all the great new technology in HVAC controls, there are still many pneumatic buildings out there. If you happen to be someone who has to work on pneumatic controls, you know it can be frustrating when you have a problem with the system. Here’s a good troubleshooting procedure from Jerry Condiff, the instructor who teaches a great pneumatics class for us here at Stromquist every year. Jerry has been in the HVAC controls field for over 30 years and really knows pneumatics.
Pneumatics Troubleshooting Procedure
Start at the thermostat or controller. Check to see if the thermostat will put out a high pressure by turning the set point to its minimum setting. The pressure should be high on the output gauge. If not, try adjusting the calibration screw.
If no air noise is distinguished, check to see if air is present in the supply line into the thermostat (this will require removing the stat from the mounting bracket). If supply air is present but there is no air bleed noise or output pressure, the restrictor is plugged or the nozzle at the bleed port is dirty. Check and clean the nozzle or clean out the restrictor.
If there is no pressure output but air bleed noise is present, check for an air leak behind the mounting bracket. Check the air hoses that are connected to the mounting base for deterioration. Check Honeywell stats for broken plastic air nipples in the back of the mounting base.
If no air leaks are found, plug the branch line of the stat with a jumper hose connected from the supply line to the main or supply to the stat. If pressure builds on the branch gauge, the branch line of the controlled device (valve, damper or pressure switch) has a leak. You may also make up a tool consisting of two 5/32 lines and a barbed gauge tee and a 30# pressure gauge. Connect one end of the hose to supply and the other to the branch port on the mounting base. If you do not read any pressure on the gauge, the branch line has a leak. If pressure builds, the stat is bad and will need to be replaced. Use a squeeze bulb and gauge to check controlled device diaphragm for leaks. If no leaks are present, the branch line hose has a leak and needs to be replaced.
This procedure may not cover every potential issue you run into with your pneumatic system, but it should at least be a good start, and I hope you find it helpful. Happy troubleshooting!
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