Home HVAC Quandry

[Norm K]

The scope of knowledge here never ceases to amaze me. Here's hoping the Pelican brain trust comes through once again.

Our main floor master bedroom is overly cool most of the year. On A/C days it over-cools and on furnace days it under-heats. We've tried a wide combination of vent openings: all open, all closed, some fully open with others fully closed, some partially open, etc. but nothing seems to make a dent in the problem. Making this room comfortable means the rest of the house is either too warm or too cold, depending on whether the A/C or furnace is running.

I presume, since it's the furnace fan that pushes air for both systems, that they share duct work (traditional home HVAC do, right?) which should eliminate the possibility that run-length or shape would account for the ability for the system to heat/cool equally. And yet, the airflow of cool air is noticeably greater than that of warm air.

It's a pretty good-sized home - 5,600 sqft, two story with a finished basement. The room in question is on the main floor (basement below, but the second story doesn't extend over the MB) and is on the opposite end of the house from the furnace room. Because the cool air flows so well (almost too well) however, it seems as though that warm air should as well ... but it doesn't. Hell, I would figure that the warm air would flow more efficiently, given that it weighs less than cold air.

What am I missing?

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[asphaltgambler]

A few questions. Do you have one unit for your whole house or separate units for lower and upper floors? Also what tonnage are the unit(s) rated for? Lastly, have you always had this issue?

[cabmandone]

Is the ductwork accessible in the basement? It is odd that it cools well but struggles in heating.

[Bigtoe32067]

I had the exact same problem in mine but mine is a 4000sqft one story with two units. To make the master comfortable than it was too hot in the boys rooms on the other side of the house and the to make the boys rooms comfortable, the master was way to cold.

We had an hvac company come out and air balance all the ducts and it fixed the problem. I think it was relatively cheap to have them come out and do this. Somewhere around a couple hundred bucks.
You might call around and see if you can get someone to come out and air balance your ducting to better manage the air flow.
Good luck
Tony

[Norm K]

Originally Posted by asphaltgambler

A few questions. Do you have one unit for your whole house or separate units for lower and upper floors? Also what tonnage are the unit(s) rated for? Lastly, have you always had this issue?

1) Single units

2a) Hate to be a rube, but I don't know. The furnace is a Rheem RCBA-6089GG24XI. I got only one hit on a quick internet search - showed a Rheem 90

2b) A/C compressor is a Ruud 5 Ton

3) Yes, but we've been in this home only a year and a half.

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[Norm K]

Originally Posted by cabmando

Is the ductwork accessible in the basement? It is odd that it cools well but struggles in heating.

Nothing accessible. Every square inch of this home is finished - even the garage has baseboard and crown molding.

Dude, I thought you might be one who could help solve this riddle.

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[Norm K]

Originally Posted by Bigtoe32067

I had the exact same problem in mine but mine is a 4000sqft one story with two units. To make the master comfortable than it was too hot in the boys rooms on the other side of the house and the to make the boys rooms comfortable, the master was way to cold.

We had an hvac company come out and air balance all the ducts and it fixed the problem. I think it was relatively cheap to have them come out and do this. Somewhere around a couple hundred bucks.
You might call around and see if you can get someone to come out and air balance your ducting to better manage the air flow.
Good luck
Tony

I have someone who's done a lot of work for us over the years scheduled for October 29th. The receptionist (who is also the owner's wife, so she's been around it for many years) didn't offer much hope but we'll see what they can do.

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[techman1]

I recall an "Ask this Old House" episode. Room sensors and smart vents . You were able to add zoning to a house without extensive duct work and adding dampers.

Cabmando, heard anything about this?

[Scott Douglas]

So since the whole house is finished, there's no way to tell if the ducting is insulated or not, correct?

[Norm K]

^^^ Correct.

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[911 Rod]

We have the same problem with a 2 story house. Master on second floor with western exposure.
In the summer we close all the bottom story vents and in the winter close the top story vents.
Also a heater/fan in the master bedroom. We found keeping the 2 doors to the master open helps.

[stomachmonkey]

Originally Posted by asphaltgambler

....Do you have one unit for your whole house or separate units for lower and upper floors?...

Originally Posted by Norm K

1) Single units


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That kind of answers the question both ways.

A single unit for the entire house or a single unit per floor.

A single unit for a 5,600 sq ft home feels very wrong.

If the Master is really the only issue then take it off the main system and drop a mini split to handle that one room on it's own.

They are cheap, require minimal construction, and are DIY in most cases.

[Norm K]

Single unit for the entire structure.

I've considered a mini-split but unless something has changed in the last year they're just plain ugly.

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[MysticLlama]

Can you measure the air flow?

Lots of setups, and moreso in places that are humid, run the AC faster.

So a system will tend to have 2 or 3 blower settings, from slower to faster:
1.) House Fan + Heat / AC
2.) House Fan / Heat / AC

If it's running the AC and really forcing it in there, it'd be too cold, and also would not be pushing enough heat to warm it up on the flip side.

A couple well placed dampers to choke it during AC times and choke something else to get more heat that way might help.

The all open/all closed not helping much though does seem like insulation or something else too though.

[1990C4S]

^^^ That was my thought, different mode fan speeds..

[dad911]

Originally Posted by Norm K

Single unit for the entire structure.

I've considered a mini-split but unless something has changed in the last year they're just plain ugly.

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Mini-split does not have to be ugly. You can get concealed and ducted units for in the house.

I've never seen a single unit for a house that big.

[biosurfer1]

Originally Posted by Norm K

I've considered a mini-split but unless something has changed in the last year they're just plain ugly.

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Check out the Daikin Emura...not beautiful but I dont think they take any more away from a room than several rectangular vent cutouts in a ceiling.

[Norm K]

Originally Posted by biosurfer1

Check out the Daikin Emura...not beautiful but I dont think they take any more away from a room than several rectangular vent cutouts in a ceiling.

The vents are in the floor which, come to think of it, I probably should've mentioned, as that oughta help the warm are while hindering the cool air.

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[Norm K]

Originally Posted by techman1

I recall an "Ask this Old House" episode. Room sensors and smart vents . You were able to add zoning to a house without extensive duct work and adding dampers.

Cabmando, heard anything about this?

I like this idea and, now that you mention it, I've actually seen powered vents. Seems as though one or two of these in the right vent openings might help to pull warm air to the room when the furnace is running.

Nick?

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[biosurfer1]

Originally Posted by Norm K

I like this idea and, now that you mention it, I've actually seen powered vents. Seems as though one or two of these in the right vent openings might help to pull warm air to the room when the furnace is running.

Nick?

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If the system is sized and designed correctly, closing vents is not recommended because the airflow should be optimized as is. Unless you have a VFD fan, closing vents changes the airflows/pressures which just wastes energy and doesn't help with the problems.

Speaking of airflows though, you mentioned you have floor mounted registers...seems like you have a fairly large house which would mean fairly long duct runs? Do you have any inline booster fans? Perhaps the hot/cold air isn't getting to where it needs to be?