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Why don't home HVAC units have variable temps like cars?

BrunoPuntzJones

BrunoPuntzJones

Lifer
While in the summer it's not a big deal as I want the a/c blowing as cold as possible, in the winter it's very irritating.

The air blows out of vents at like 120F. So it's hot as shiznit near the vents. The rooms get extremely stuffy almost instantly.

Why aren't home HVACs like cars in that you can adjust the temp of the air?

I'd much rather have the heater blowing at 90F for 20 minutes than 120F for 5.

But the only options are on and off 🙁

 
Originally posted by: BrunoPuntzJones
While in the summer it's not a big deal as I want the a/c blowing as cold as possible, in the winter it's very irritating.

The air blows out of vents at like 120F. So it's hot as shiznit near the vents. The rooms get extremely stuffy almost instantly.

Why aren't home HVACs like cars in that you can adjust the temp of the air?

I'd much rather have the heater blowing at 90F for 20 minutes than 120F for 5.

But the only options are on and off 🙁
Click to expand...

Partially close the vents.

More complicated ideas:

If gas, see if you can install a valve that lowers the flame.

If Electric, see if you can lower the wattage going to the element.

Kinda like underclocking your HVAC unit. 😛
 
Because it's more energy efficient to have the furnace/AC unit run at full capacity, rather than blend in un heated/cooled air with the output from the unit. (that's how your car can adjust the temp output...it blends hot/cold with "fresh un-altered air" to get that "just right" temp.
 
Car heaters adjust the temp by mixing cold air with the hot air I think... you're not really wasting any energy by doing that, because it's just using the heat from the engine to heat your car.

I can't say I ever noticed the phenomenon you're talking about when I had forced air heat. It was never uncomfortable to me.
 
Woops mods edited the title.

I've partially closed the vents before, but then they make a howling noise. Just a real hassle to get the temp to where I want it without baking in the process.

They could at least give folks an option other than just hot/cold, regardless of inefficiency.

The blower speed in cars is most efficient at full blast, but at least you can turn it down.

I guess I wouldn't mind 120F so much if it wasn't on full blast...

So perhaps instead of changing the temp of the air it is creating, change the speed of the blower.
 
Originally posted by: BrunoPuntzJones


So perhaps instead of changing the temp of the air it is creating, change the speed of the blower.
Click to expand...


Be very careful of that.

In a gas unit, slowing the blower could lead to a cracked firebox, and a nice case of CO poisoning.

In an elecric unit, it could lead to the unit overheating and causing a fire.

Lower the element or gas input before fooling with the fan.
 
Originally posted by: BrunoPuntzJones
Woops mods edited the title.

I've partially closed the vents before, but then they make a howling noise. Just a real hassle to get the temp to where I want it without baking in the process.

They could at least give folks an option other than just hot/cold, regardless of inefficiency.

The blower speed in cars is most efficient at full blast, but at least you can turn it down.

I guess I wouldn't mind 120F so much if it wasn't on full blast...

So perhaps instead of changing the temp of the air it is creating, change the speed of the blower.
Click to expand...

I think you'd want to increase the speed of the blower to get more air flowing through so the air doesn't heat up as much.

Like the A/C in your car - if you turn the blower up, the air is actually less cold.
 
Cars only have one temperature too.

The variance is achieved through mixing heated/cooled air with air from outside. This is practical (even necessary) for a system that is always on and that only has to control a small space, but setting up the blending doors and actuators for something the size of a house would be very expensive.

ZV
 
I wasn't going to fool with the blower or elements, just tossing ideas as to figure out a way around it. Not really needed since it's in the 80s already.

Another idea similar to the vehicle style would perhaps run a duct from a window to the inside intake. This way it is pulling in 40F air and heating it, rather than pulling in 70F air and heating it.

 
Originally posted by: BrunoPuntzJones
I wasn't going to fool with the blower or elements, just tossing ideas as to figure out a way around it. Not really needed since it's in the 80s already.

Another idea similar to the vehicle style would perhaps run a duct from a window to the inside intake. This way it is pulling in 40F air and heating it, rather than pulling in 70F air and heating it.
Click to expand...

Doing that would make your heating bill ridiculously high.
 
Originally posted by: Amused
Originally posted by: BrunoPuntzJones
I wasn't going to fool with the blower or elements, just tossing ideas as to figure out a way around it. Not really needed since it's in the 80s already.

Another idea similar to the vehicle style would perhaps run a duct from a window to the inside intake. This way it is pulling in 40F air and heating it, rather than pulling in 70F air and heating it.
Click to expand...

Doing that would make your heating bill ridiculously high.
Click to expand...

My bill in the winter is about $25 a month. I hardly run the heater (all electric) because it's so freaking hot with it running.

Mind you I'm in east Texas so it doesn't even get below freezing but a couple of days a year.
 
They make furnaces with variable speed blowers, they are expensive but gaining popularity so I've heard. These units also have a dual stage burner to keep the fire dept from visiting you on a regular basis.
 
See if the blower is variable speed. Many are. You hook up blue and black wires, you get one speed. Hool up Grey and black, you get a different speed. It should be printed on the schematic inside the access panel to the blower. It could be a quick operation to move a wire from one place on a terminal block to a different place on the terminal block.
 
Blowers usually have 3 or 4 speeds. Red is low(heat) blue(not used) and black is high(cooling) white is neutral. You could move the black wire from cool to heat. If its electric the air shouldn't be that hot coming out anyway. On a gas furnace you can soldier over or cap off one of the orifaces that restricts the gas flow to the burners but on a cold day it probably won't heat the house.
 
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