Air blower - variable airflow measures?

[Darro]

A small electric motor (1/4hp?) drives the blower which ventilates and pressurizes the hallways in our small apartment block. The blower draws too much cold air into the building during the winter. It would be far too costly to install a heater to warm the air as it's drawn in from the outdoors.

If a small variable-speed or multi-speed electric motor is available, we were thinking that we could manually adjust the airflow to suit outdoor air temperatures by increasing or decreasing the speed of the motor.

Can anyone provide any practical feedback on this idea, or offer other suggestions on how we might be able to alter the airflow from time to time?

Thanks in advance, Darro

[John Hines]

Mechanical dampers that open and close a vent, based on an electrical signal?

For example

[PaPaPeng]

An air damper might be an easier solution. Restrict the outside air from entering the system but maintain the internal airflow.

[Darro]

I really appreciate your helpfulness, but I think that restricting incoming air would be like putting your hand over the end of a vacuum cleaner hose while it's running, and restricting outgoing air would be like putting your hand over the exhaust port of a running vacuum cleaner -- the motor would probably burn out.

Any other suggestions?

Thanks, Darro

[PaPaPeng]

Okay. I am not quite sure how the heating system in your apartment works.

I live in a bungalow where there are separate outside fresh air intake ducts for the gas furnace combustion air and another one for the room air. If I restrict the intake duct for the room air, all the motor fan will do is the circulate the in-house air more often. It will never overload the motor because there is no possibility of the leaky (inside house) air ducts ever developing a differential pressure to overload it.

[go fish]

call these people and ask them if their product will do the job you are requesting

[SJF]

Throttling of the flow through centrifugal impellers (pumps and blowers) is quite common. It actually relieves the load on the motor since the product of volume times velocity which represents the total work delivered by the motor is reduced.

[Chet Hayes]

If this system is running as described, it's a bad system for most of the climates in the US, regardless of the blower speed. All you're doing is blowing cold air into the building, which is precisely what buildings go to great lengths to avoid. To do this correctly, the system should have a heat exchanger, which minimizes the heat loss.