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MattsAwesomeStuff t1_j0ufg6k wrote

Reply to comment by Semanticss in Closing off an AC vent by flyingGoatPenis

> Closing just one duct has tripped my blower fan in the past from the change in air pressure.

That's not how motor load on a fan works.

The more you block it up, the lower power the fan consumes.

This is counterintuitive to some people, but is a fact.

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WKS01 t1_j0v6gpa wrote

That is not entirely true, it depends on the type of fan being used. In a constant torque motor the fan would increase amp draw as it attempts to overcome the higher external static pressure.

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MattsAwesomeStuff t1_j0vgyqm wrote

> In a constant torque motor the fan would increase amp draw as it attempts to overcome the higher external static pressure.

... is that the type of fan used in whole-house HVAC systems?

... no.

[Edited to add, see below, in some cases, actually yes]

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WKS01 t1_j0vlqkl wrote

There are Manufacturers that do use constant torque motors in residential furnaces though. Trane S8X2 S8X1 and S8B1, Carrier Comfort and Performance series, York TM9Y, Bryant Preferred and Legacy Line are just a few that use constant torque motors for the blower fan. Basically every Manufacturer offers a lineup that consists of different series that use VCA (Variable Speed Constant Airflow), VCT (Variable Speed Constant Torque) and FCT (Fixed Speed Constant Torque).

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