Closing 1st floor Registers

[robertc65]

In the summer when running the AC I can get significantly more air flow from the 2nd floor registers by closing some of the registers on the 1st floor. Now that I'm running the furnace I still experience the same lack of airflow to the 2nd floor registers as I do in the summer. Is it OK to close some of the 1st floor registers? I'm thinking that doing so may cause more heat to build up inside the furnace. I realize there is a limit to how many I can close before suffocating my system, but should I be concerned about closing maybe 4 out of 9 registers on the 1st floor?

Thanks

Rob

[pstu]

You need a pro to do this but... I submit that IF you could get a measurement of ESP (External Static Pressure) before and after closing those registers, and if ESP was within spec after, then at least it would not harm your furnace. Temperatures inside the furnace would not get too high because airflow would be within specification. Am I right on this, pros? I am a homeowner myself.

For this to succeed you need a margin of safety, and all too many houses are designed with such lousy ductwork that you may not have this margin. We hear on this board about duct systems which cannot stand this handling, and my own house has had ESP measurements where it *never* was within spec for the blower even with everything wide open.

In the absence of getting your ESP measurement done, or something other test chosen by a pro, I would hesitate to do what you propose.

Hope this helps -- Pstu

[fortressofcomfort]

I can't recommend closing any registers... you need to close down the airflow much closer to the plenum. In other words, look for DAMPERS close to the plenum. The reason is if you close a register, the ductwork between the plenum and the register is still pressurized and any small leaks will cost you big $$$$ in hot air leaking into unconditioned spaces.
Off the top of my head, closing 4 out of 9 registers sounds like a bad idea.
I agree with pstu, sounds like a pro might be needed on this one.

[sleeeper]

As a homeowner, I wanted to change dampers to re-balance my system. I had a new heat pump/all new duct work installed recently.

The installation included a "balancing," which turned out to be "there is air coming out of all of the registers". I asked my installer about re-balancing to account for the dramatically different heating/cooling needs between the two sides of my house, and was pointed to the dampers and told how I could adjust them.

Since I was worried about damaging my new system, and the installer didn't seem to care as much as I think he should, I bought a Dwyer Mark II Model 40 (measures 0 - 1.0 W.C).

I'm not sure about my installation begin correct, but at least I know the baseline with the dampers open and using the filter the installer provided.

I installed the low pressure side to a pitot tube about six inches in front of where air enters the air filter. I connected the high pressure side to a pitot tube six inches from where air leaves the blower.

With the dampers open all the way, I get 0.36 WC/ESP. With the dampers the way I want them, I get 0.43 WC/ESP.

The spec sheets for my air handler list stats for ESP to 0.5, and says it must be installed with less than 0.7 ESP, so I figure unless my measurement setup is way off and the "dampers all the way open" setup is in reality 0.65 ESP I should be fine.

[dash]

Originally posted by pstu
You need a pro to do this but... I submit that IF you could get a measurement of ESP (External Static Pressure) before and after closing those registers, and if ESP was within spec after, then at least it would not harm your furnace. Temperatures inside the furnace would not get too high because airflow would be within specification. Am I right on this, pros? I am a homeowner myself.

For this to succeed you need a margin of safety, and all too many houses are designed with such lousy ductwork that you may not have this margin. We hear on this board about duct systems which cannot stand this handling, and my own house has had ESP measurements where it *never* was within spec for the blower even with everything wide open.

In the absence of getting your ESP measurement done, or something other test chosen by a pro, I would hesitate to do what you propose.

Hope this helps -- Pstu


I agree,nice explanation too.

Plus they'll need the fan data chart for your model,to know what the cfms are,dampers opened or closed.I'd suggest closing them partially ,rather then 100%,while testing the ESP.

[Edited by dash on 11-06-2006 at 04:57 PM]