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Heating, Air Conditioning, Fridge, HVAC/want to have manual fan control on furnace


furnace wiring
furnace wiring  

I have a Carrier 58BV100-2B furnace, no AC and a HOneywell RTH230B Thermostat. I want to have manual fan control to ventilate and filter the air. Attached are wiring diagrams for both. 3 wire heating sketch #2.3.3 and the wiring diagram by Carrier is what I have to work with. However the Furnace diagram does not indicate a heat relay as on the thermostat, but does indicate a connection between the "heat relay" and the transformer symbol. My furnace does not have a heat relay. Note the furnace diagram shows a relay with cross line thru it. Is that significant? Can this be wired for manual fan control at all?

Connecting a wire from the G on the stat to the G in the unit should allow you to turn the fan on using the fan function on the t-stat.  It might be possible the unit is not currently wired as the diagram, which would then require a bit of troubleshooting to get this working as you want them to.


Heating, Air Conditioning, Fridge, HVAC

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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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