Furnace vs. Heat Pump

[Kate]

My last house had a heat pump. One winter I closed off several vents to rooms that I do not use, thinking it would warm up the rest of the house faster, and cheaper. Wrong. It shut down, and a guy came out and fixed it for $60 by adding a booster. Not exactly sure what that was all about but it worked for the last eight years I lived in that home. He also told me that with a heat pump you cannot close off the vents.

Now, in my present home, I have a furnace only. Is it safe to close vents in several bedrooms that I don't use.

Thaanks.

Kate

[DK]

I've been doing it for 30 years without a problem. But I also do it for cooling without a problem.

[HVACTECH2]

No it isn't. You need a certain amount of air flow through a furnace which is usually what all the vents are sized for.

[Joseph Meehan]

It is more a matter of degree. If you close off too much the total air flow becomes less, you loose efficiency and your overall cost may go up to heat less area. You also can tax the equipment so it may fail and you can end up paying repair cost. It is not possible to give an accurate direct answer on-line to your question since there are so many variables. Even on site it would be difficult and to get any kind of accuracy would require quit a bit of calculation. The usual answer is going to be, don't do it, as it is the safe answer.

My guess, and what I would likely do. Partly close off those bed rooms. Make sure all other vents, including those that may be in the basement or utility room are full open. Also make sure your filter is clean and keep it that way.

[trader4]

Like many others, I've done it for a room or two, with no problems. You have to do it with some common sense though. Closing off a register forces the air to now flow through less openings. If you close off enough, air flow becomes too restricted, which is what sounds like happened in your previous experience.

If it's never to be done, then why do they install registers all over the place that can be controlled and shut?

[Al Moran]

You should not close vents in any rooms. It effects the static pressure of the system and on a gas furnace can cause your system to overheat and trip on the high limit switch.

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[trader4]

If closing the registers in any room is so bad, then why does every house I've ever lived in have registers that can be fully closed? In any properly designed and installed system, you'd have to close a hell of a lot of registers to reduce airflow to the point that the high limit switch cuts off the furnace.

[Al Moran]

You are correct when you say "any properly designed system" and therein lies the rub. Most systems I see are not designed properly, as in no load calculation done, no airflow calculation done... I could go on all day about the hack stuff I see every day, in short, closing the duct work is not recommended by the manufactures of most systems. It causes excessive static pressure on the ducts which affects airflow, which can cause a limit to open and in extreme cases can cause the heat exchanger to crack. If you want to close yours then have at it.

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