Modify existing furnace to allow constant blower run

Old 09-09-14, 12:21 PM
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Modify existing furnace to allow constant blower run

I have a standard domestic gas furnace. The remote thermostat has only a 2 wire run back to the furnace. I wish to run the furnace blower for long periods to circulate cooler air through the house during the summer. I can push the manual over ride button in on the high limit switch, which achieves this. Is it possible for me to add a second switch in parallel with the over ride button outside the furnace so that I don't need to open up the furnace to operate it? Is this a safe practice?
Old 09-09-14, 06:08 PM
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Running the blower full time usually results in mediocre results and a higher electric bill.

That button on the fan thermostat is mechanical so there is no way of extending it.

You could add a small fan center. That's a small transformer, junction box and relay. This would be worthwhile if you had an extra wire to the thermostat and a FAN ON postion on the thermostat.

You could also add a second switch.... like a light switch.... and connect the terminals to the blower wires in the fan thermostat. You would be connecting the two switches in parallel.

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