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Inches of Mercury
11-10-2005, 10:21 PM
I'm currently going to school for HVAC, so forgive me for the many ignorant questions I'll ask. Here's my first:

I was curious about what happens to the air when you close the vents in your house all the way. I've asked 2 instructors at school and received 2 different answers. 1 guy says to never close your vents all the way. If you do this, the system is still pushing air to that vent, and it will back up only a little, creating turbulence. He suggests closing a vent no more than halfway. The other instructor says it's ok to close the vents you don't need heat or A/C in (i.e. the basement) because the air will back up and go to another room in the house.

So what's the best thing to do in this situation?
newbietech
11-10-2005, 10:32 PM
I would think that it would cause the static pressure to go up, increase noise and in general restrict the airflow which would cause coil/heatexchanger to not get the correct cfm across it. Incorrect airflow could cause the unit to go out on high limit or raise system pressures in a heat pump(which raises the amp draw and decreases efficiency)
jerry-in-grapevine-tx
11-10-2005, 11:16 PM
Are you talking about closing all the vents? If so why. You can close off a couple of vents without a problem but not any more than that, without restricting some airflow. which could cause the unit to freeze up in the a/c mode or maybe trip limit in heat mode.
Inches of Mercury
11-10-2005, 11:20 PM
No,not closing all the vents! The basement (don't spend much time there) and the bathrooms (don't really need much heat there)...
jerry-in-grapevine-tx
11-10-2005, 11:24 PM
Then it shouldnt be a problem at all. Some air may be forced out the other vents but not that you will notice or have any effect on anything.
idahotech
11-12-2005, 05:28 PM
closing 1 or 2 vents wont hurt the system to much provided the system was designed properly,, but closing 2 many will cause the furnace to over heat... shortening the life of the heat-exchanger or blower..I recomend closeing your basement vents off half way... any heat in the basement will rise naturally and will make any time you do spend in the basement more comfortable.
gonefishing
11-12-2005, 05:54 PM
If the indoor unit is ECM drive, be prepared to buy a new module soon. Older units were not such a problem, but as seer ratings increase, units become more and more critical in airflow balance and critical charge.

Regards.......
dan sw fl
11-13-2005, 05:43 AM
Originally posted by lawsonjt
The other instructor says it's ok to close the vents you don't need heat or A/C in (i.e. the basement) because the air will back up and go to another room in the house.

So what's the best thing to do in this situation? Close the diffusers ~ 70%
AND make sure the Static Preussre at the blower does not increase signficantly.

In other words, do not decrease the overall air flow.
docholiday
11-14-2005, 01:49 AM
Try this...

Put a piece of duct tape over your mouth and cram one finger up your nose, now run around the block like this a few times and see if closing some vents has some effect on your performance.
Inches of Mercury
11-14-2005, 09:59 AM
Originally posted by docholiday
Try this...

Put a piece of duct tape over your mouth and cram one finger up your nose, now run around the block like this a few times and see if closing some vents has some effect on your performance.


I see what you mean. So, closing the vents is a bad thing. Gotcha.
Mr HVAC41
11-14-2005, 02:00 PM
i like that!!!!
philbiker
11-14-2005, 03:33 PM
Do a seartch for posts authored by me. I recently asked the same question and got 4 pages of answers. Massive detail and lots of divergent opinions.

My bottom line: Close them 1/3 and it may be worth it without hurting the system.
docholiday
11-14-2005, 04:10 PM
Originally posted by philbiker

My bottom line: Close them 1/3 and it may be worth it without hurting the system.

Key word is "May"... Every system is different, and unless the ducts were sized to accomidate adjustments, it is probably not good blanket advice.
Mr Bill
11-14-2005, 04:14 PM
Originally posted by docholiday
Try this...

Put a piece of duct tape over your mouth and cram one finger up your nose, now run around the block like this a few times and see if closing some vents has some effect on your performance.

But what about some of the folks that breathe out the behind they will not get it. :D