Arrived onsite for issue with one zone over heating. Found a fault in a zone valve. Initially attempted changing just the Honeywell head unit but had to change the entire zone assembly and install new purge drain. While installing new parts smelled natural gas. Homeowner elected to change gas valve. Came back 1/2 to improve the securing of the pilot tubing to the gas valve. System is operating as it should. Used CO meter around the home and gas appliance. Did not measure CO in the home.
