Troubleshooting Electronic Zoning Systems

Zoning is a great enhancement to a HVAC system. However, there can be some bugs in implementation if you are not vigilant during installation. Problems we face during service calls normally fall into two classes: 

1. Something is intrinsically incorrect in the application or installation.
2. There is a problem in the system’s operation or a component.

There are two main zoning system types: electronic and pneumatic. The difference lies in how the dampers are closed and opened. The blog discusses the best way of troubleshooting electronic zoning systems.

Start by checking the system first:

Start with checking how the system is performing during full airflow, with all blowers running and dampers open. This is also a good chance to verify that the dampers of the zoning system are not stuck.

After you have confirmed full airflow, observe the result after shutting down a zone. There has to be considerable increase in the air delivery in the rest of the zones. Also, there should be absolutely no more air transported to the zone that has been shut down. Repeat the same test for all of the zones.

Problems you may find:

System zone board

Most of the system zone boards come with an onboard diagnostic LED. Analyze it for potential trouble codes.

Board failure is not a common occurrence. Therefore, when it occurs it is very important that you find out the reason rather than simply swapping the board. For instance, a poor wiring work can be one of the biggest causes of board failures. Another reason behind board failure is inadequate power. Most experts advise that a separate 24V transformer be utilized to power the system. Has a separate transformer been used in this case? Was the transformer sized according to the size of the hardware connected?

Input sensors

These are utilized for measuring return and leaving air temperatures. In case a low or high temperature trip has taken place, did the input sensor reset? What system operation has to occur for causing the sensor to trip? Are you aware of the trip temperature points? Incorrect placement of sensors can also cause trouble. Is the air sensor located at a place where radiant furnace heat can instigate nuisance trips?

Orphan zones

While two-zone designs permit us to fragment system capacity, a third or fourth zone can lead to unintended consequences. For instance, you have a system where zone one takes 35% of the conditioned space, the second takes 40%, and the third zone is 25%. What’s the likelihood of a glitch in the system with merely twenty five percent of the system calling? In case the system obtains a call for operation from only the third zone, the enhanced noise level and air delivery can lead to complaints.

A zoning system helps multiple thermostats to turn off and on the same system; sequence cool, heat, and fan calls. Troubleshooting a zoned system requires knowledge of the logic of zoning. It is best to contact a skilled technician to service a troubled zoning system if you are not well versed with your HVAC.