Controlco Blog

While one of our contractor customers was at the counter in our Sacramento branch picking up an order, he brought up another issue he was trying to solve.

This specific issue had to deal with comfort and the questionable functionality of a Honeywell zone valve. The tenant was uncomfortable and complained to the property manager that the zone they were occupying never seemed to heat up (reach set point). Our contractor customer checked the valve for 24v power and witnessed minimal stroke but could not do much else with the tools he had on hand. All he knew at this point was that the actuator was receiving power and moving.

To help narrow down the possibilities we provided him with a quote and specifications for 3 different Analog Signal Generators….Dwyer ASG, Dwyer CSG and Johnson Controls M9000-200. The customer selected a simple handheld model from Dwyer (not needing all the functionality of the more robust models).

With this handheld tool from Dwyer the Field Tech will be able dial up a 0-10v or 4-20mA signal to provide a control signal appropriate to the actuator he wants to test. By knowing for certain which signal the actuator is receiving, the Field Tech can easily determine if the actuator is behaving appropriately to that input signal…and from that, he can determine if it’s the actuator or the original control signal being sent that is the primary issue. He is also going to use the device to set up outside air damper/mix air damper arrangement on roof-top units to ensure the dampers are in a proper relation to one another and allow the correct amount of outdoor air for ventilation.

One simple tool in this Field Tech’s toolbox will now alleviate any guesswork as to where the problem originates in this and similar cases…not to mention the time and money saved as opposed to buying the “wrong” part to fix the problem when you’re operating from an “educated guess.”

Applications where an Analog Signal Generating device can be of use: troubleshooting transmitters, transducers, motors, and actuators”

“A while back a local dairyman came to the Bakersfield branch with a problem. It seems the controls on the fans that move air through his cooling condenser were causing problems and jeopardizing large batches of milk. This condenser is the heart of a system that cools milk from cow temperature to a safe storage temperature.
The system works by blowing air over a heat exchanger that is part of a loop filled with anhydrous ammonia. The ammonia gives up its heat to the air, and then a second closed loop of brine gives up its heat to the ammonia in another heat exchanger. This chilled brine is then circulated through a third heat exchanger which cools the milk. By monitoring the pressure of the ammonia in the primary heat exchanger the amount of airflow needed to cool it can be determined.

The control scheme in use involved two pressure switches and two across-the-line motor starters. When a certain pressure was reached, the first pressure switch tripped, starting the first fan motor. When a second (higher) pressure was reached, the second pressure switch tripped, starting the second fan motor. The problem with this system came in while Fan A was running and Fan B was idle. Because they are both in the same cabinet, Fan A would draw air in that would be pushed out through Fan B, causing Fan B to spin backwards. When fan B tried to start up while spinning backwards it required a much greater current to reverse direction than it would have if starting from a standing start. This made the overload protection for Fan B trip to protect the motor. In effect, Fan B was now useless.

Luckily for our intrepid dairyman, Controlco had a solution that would not only control his fans in a better way, but also save him money on energy. We designed and built a panel that used a Square D Altivar 21 VFD, a Red Lion P-16 loop controller, and a Wika S-10 pressure transducer to modulate the speed of both fans at the same time. In order to insure that product would not be lost in the event of a VFD failure, we included a bypass circuit that will put line power to both motors if the VFD faults out. We also included a means by which each motor was individually protected from overload and could be “locked out” and “tagged out”. How’s that for a feature rich panel!?!

This panel is now in use and performing exactly as intended. No longer does this dairy farmer have to worry about losing an entire day’s production to a control failure. Also, instead of the head pressure on the ammonia loop bouncing up and down within an acceptable range, it now stays at a constant point determined by the loop controller. Because of the way a VFD modulates motor speed, he is also using less energy to run these fans.”

The challenge: increase the operational efficiency of a 3-story medical office building in Oakland.

The approach: apply outdoor air reset to the constant supply air temperature setpoint.

The problem: the 25-year-old staged-cooling rooftop unit is controlled by a simple Honeywell W7100 discharge air controller. A retrofitted DDC controller on the unit monitors and modulates a VFD added to the fan, but does not stage the unit or otherwise control the discharge temperature. The W7100 controller has remote setpoint terminals available, but requires a 0-500 ohm resistance.

The solution: with a 0-10Vdc modulating output available on the Auto-Matrix DDC controller, an ACI transducer (the DRN-3.1 voltage-to-resistance transducer) allows for remote control of the supply air temperature. The 0-10Vdc signal is scaled by the DRN3.1 across 0-500ohms, which the W7100 controller sees as 40-90F. Now the supply setpoint can be altered manually by a service technician, or can be altered automatically with an outdoor air temperature reset algorithm.

The results: the HVAC service contractor is happy with the increased functionality, and the customer will enjoy increased building comfort and energy efficiency, even from their aging AC unit.

“A few months back, HFS Enterprises came to the Bakersfield branch and asked us to quote price and availability for a Dynalco digital temperature gauge. HFS installs and maintains stationary, natural gas powered engines, primarily for irrigation pumping. This gauge was used in conjunction with a type J thermocouple to display the temperature of the catalytic converter on these engines.

I soon found a source for the Dynalco gauge and was shocked to learn that it cost almost $500.00, without the thermocouple. I knew we could offer a solution that would do the job as well or better than the Dynalco unit, and for less money. The solution I arrived at was a Red Lion CUB5TCR0 thermocouple input panel meter, inside a NEMA 4X enclosure also manufactured by Red Lion. This combination costs HFS $167.00 and is just as accurate as the Dynalco product they were using before. Plus, the Red Lion meter is easier to read.

HFS was delighted. In fact, they were so happy that they told two other companies in his line of work about the new temperature display. Both of those companies now purchase these meters and type J thermocouples from us on a regular basis. In fact, we’ve sold over 200 of these meters in the last 18 months.”

We are excited to see the new site! Continue to watch for updated postings from the Tech Support department.

Welcome to our new website. There is a lot of work left to do. Please feel free to comment here and let us know what you think we can do to improve the overall experience!