Cold Upstairs reduced airflow - OT

[snowman]

My upstairs is either chronically cold, or chronically hot, depending on the weather.

This is a problem with all of these little houses that I live in, and I don't know anybody on the block that's figured out a solution (other than a window AC unit upstairs, or secondary heating upstairs).

I am considering installing a duct booster. Does anyone have any experience?

Before someone asks, there is no cold air return up there, but the stairway is wide open, so there is no need.

[RKW]

I change the floor vents and duct dampers from the furnace every major change of season to help with situations like this. Once you have tweaked everything in mark the damper handle positions on the duct work directly with a sharpy as "W" and "S" or winter and summer if you prefer. Seem to have worked well for us over the years.

[Evan]

If it is cold upstairs first thing to do is to check your attic insulation. Even if there is what looks like enough it may be moisture saturated from inadequate vapour barrier.

[Highpower]

My upstairs is either chronically cold, or chronically hot, depending on the weather.

This is a problem with all of these little houses that I live in, and I don't know anybody on the block that's figured out a solution (other than a window AC unit upstairs, or secondary heating upstairs).

I am considering installing a duct booster. Does anyone have any experience?

Before someone asks, there is no cold air return up there, but the stairway is wide open, so there is no need.

I have the same problem in my house. It got worse when I had a new furnace and A/C unit put in a couple of years ago. They replaced all the duct work in the basement and threw out all the dampeners, but didn't install new ones. :mad:

So now my daughters upstairs bedroom hardly gets any air flow at all now because the duct for that room is at the very end of the main trunk. I've been thinking about a booster for that as well, so I would like to hear some input on this also. :o

[snowman]

Insulation is a known issue, but that isn't going to change this season. The roof is first on my list.

When the furnace is running and I am at the upstairs vent, with all of the other dampers except that one closed down somewhat, I can't even feel airflow. I have passed a chain on the end of a drill to clean out the lint, but it didn't make a difference.

[Evan]

Block the other vents with a phone book or three and see if any air gets through. A common mistake when putting in air ducting is to run the same size duct to all the vents. That results in lower and lower velocity the farther you get from the furnace. A properly designed system will reduce the duct size of the main distribution duct each time air is removed from the main duct. This does two things. It maintains the air velocity which means the warm air gets to the far end while it is still warm. It also increases the system pressure which which also increases velocity and heating efficiency since tha air is circulated more often.

Dampers are not a solution since they introduce more friction and retard the flow of air. Once past the damper the the air will be traveling even slower than before since the damper introduces not just a restriction but produces a great deal of turbulence. The ideal system does not require dampers at all as it will be balanced to provide adequate flow to each register which then may be regulated at the register. That does not reduce system efficiency.

[snowman]

The duct sizes are a known problem. All of the houses built in this subdivision have the exact same problem.

I am just curious if actually increasing the boost in the duct will heat the air.

[Evan]

It will lower the efficiency by lowering the pressure in the heat exchanger. The amount of compression is so slight that it won't contribute any heat and besides, that heat is already in the house anyway. The way to fix it is to address the known problems.

[TGTool]

My wife's office at the university also suffered from being at the end of the duct system and was either too hot in the summer or too cold in the winter. I removed the diffuser and installed a miniature box fan behind it to pull more through the duct. I think in your situation too a pull system might do more good than any adjustment you can reasonably make to the push.

[Your Old Dog]

I have retrofitted forced air. To get air upstairs I had close all the first floor dampers a bit. The shortest runs closest to the furnace get closed the most. That's what the dampers are for.

For summer air conditioner I made a square Roman column that rest on the floor and covers the cold air return. It goes all the way up the wall to about 2" from the ceiling. The back of the column is open but the edges that touch the wall have weather stripping to control air. I want all the cold air return to be taken off the top of the column where all the hot air is. It works a treat.

Just for the hell of it, If I were you I'd close all the first floor dampers and leave the upstairs dampers wide open just to see what happens. I'd also make damn sure the cold air returns weren't blocked. Your air isn't blown out of your furnace, it is sucked out by the suction of the cold air returns pulling the cold air out of the room. Some housewives think there is cold air coming from the cold air returns because it is always cold by them? That's because they suck the cold air.

Hope I haven't been too basic with you. Just sharing my observations. Your shorter runs can be dampened down, that's what the dampers are for.

[A.K. Boomer]

I have a bathroom vent that's on the lame side, It puts out a little more with slight restriction on some other vents - vents that really need to be restricted some due to them being so short of runs --- My furnace plenum is just a big box on top of the furnace so does not run lengthwise to the house so its not about reducing the plenum size as you go, but there has been effort in making longer runs with an inch larger pipe and fittings...

I put my effort into insulating the long run to the bathroom vent and its acceptable now. (the pipe is in the basement which gets quite cold)

Snowman I think that if you can install a booster it will do nothing but help --- if you get more airflow without restricting other vents too much then your furnace efficiency will stay high and you will also have another factor that helps you along, the more flow the warmer the air going up -- this is critical -- right now your "stacking" the air due to it cooling before it even reaches its destiny --- long vertical runs can benefit greatly if the airflow is kept at a level to where it does not cool as much so its a win win, go for it. but make sure the pipe is clean first --- a long vert. run with a few fittings thrown in can be a perfect lint catcher.

[RichardG]

Can you put a cold air vent through the floor at the farthest from the stair well that should help and check your squirrel cage fan you would not belive how dirty the vanes get it can cut down the air flow by half with just a little bit of dirt on them.
Richard

[darryl]

I think I would do as Evan suggested- block all the other ducts and see if you have any wind upstairs then. If you still have very little air coming through the duct, then you have to find out why. Maybe the fan isn't running fast enough to overcome all the restrictions to air flow. The filter is one, corners in the ducting will interfere, poor sizing of ducts (which has been mentioned), improper installation of the blower-

Some blower motors are multispeed by way of how the power plug to the motor is oriented. You might check that out.

You're talking about lack of airflow, not lack of heat in the air. But that could also be the case, which could mean that the furnace is undersized for the house.

Something else to consider- if there isn't enough airflow through the heat exchanger, the air that does come through might be quite hot. If you find that the closest heat vent is giving out too hot of air, then maybe you can augment the airflow by suction at the point where there is little to no airflow (your upstairs). A fan unit of some kind placed over the vent to suction air into the room might work. But if the air through the closest vent is only mediocre warm, then by the time any air reaches extended vents there would likely be little heat left in it.

You're saying there's a street full of similar houses with similar problems- I'll bet some contractor cheaped out and installed only the minimal furnaces he could get away with.

If you find that by blocking all vents and opening only the upstairs vent gives you heat up there, then the procedure would be to have the upstairs vent completely open, then carefully open others only enough to feel some air and heat flow through them. This is a balancing act- you have to be left with some upstairs airflow in order to get heat there, even if that means that other vents are mostly closed. If the closest vent to the furnace spews overly heated air still, then your furnace is probably big enough. But if that closest vent becomes only barely warm, then you don't have enough heated air to do the house properly, which means the furnace is too small. If that's the case, you'll probably find that the best way to add heat is directly to the cold rooms via an electric heater.

All the heated air is within the house, so if it's lost in ducting before it can enter a room, then it's heating another space in the house. The total heat in the house would be the same, but it's easily possible that what's lost in the ducts is escaping by some other means. If a good sized duct goes through a crawl space where outside air can absorb the heat, then there it goes. As has already been stated, if the air is moving too slowly through that duct it will give up most of it's heat to it. If it can be determined that this is happening, insulating the duct might help.

I'm no hvac person, but I have a prairie heritage so I know something of heating issues :)

[A.K. Boomer]

Some blower motors are multispeed by way of how the power plug to the motor is oriented. You might check that out.

)


This is a really good point --- this could be your "booster" ----
if you have this option then you use it and restrict the other vents to an acceptable level, it keeps your furnace efficiency up and allows for better flow upstairs,
The electrical bill will be slightly higher but if it saves you from installing a booster then you save that expense. (plus your booster would take juice to run anyways)

Not an ideal system but one you can live with...

I do have another higher motor setting but did not have to go that rout...

[bborr01]

Snowman,

I faced a similar situation with a lakefront rental home that I own.

The place had been added on to with two attic type bedrooms.

The only heat vent upstairs was one that was as far away from the stairway as you could get. By the time the heated air made it through a few elbows and a lot of distance, probably 35 feet, it didn't have a lot of velocity.

I bought a duct fan at the local home improvement store for about $30 as I recall and installed it upstairs near the register. Have not had a complaing since.

My tenants also just use a window air conditioner to cool the whole place by placing it in the upstairs. Of course it doesn't hurt that the place is in a wooded setting and is well inlulated with good windows.

You may want to consider an energy audit to see if your problem is related to your heating system or more of a insulation/window problem.

Brian

[Evan]

I do not understand this business of dampers in the ducts. It is a poor way to regulate the flow of air. I have never lived in a house with forced air heat that had dampers. Up this way the flow of air is regulated by heat registers with shutters. That is much more effective and easier to adjust. It eliminates turbulence in the duct system. Dampers provide a place for lint and dust to collect as they slow the flow of air and create turbulence. That decreases the efficiency of the system. If I had a house with dampers I would open them wide open, or if at all possible, I would rip them out permanently. In place I would install floor or wall registers with shutters. They are cheap, widely available and sized to fit any size vent.

http://ixian.ca/pics8/floorvent.jpg

[bborr01]

I do not understand this business of dampers in the ducts. It is a poor way to regulate the flow of air. I have never lived in a house with forced air heat that had dampers. Up this way the flow of air is regulated by heat registers with shutters. That is much more effective and easier to adjust. It eliminates turbulence in the duct system. Dampers provide a place for lint and dust to collect as they slow the flow of air and create turbulence. That decreases the efficiency of the system. If I had a house with dampers I would open them wide open, or if at all possible, I would rip them out permanently. In place I would install floor or wall registers with shutters. They are cheap, widely available and sized to fit any size vent.

http://ixian.ca/pics8/floorvent.jpg

X2 on that.

Brian

[Liger Zero]

You need a new motor.

http://rochester.craigslist.org/bfs/2049523841.html

[darryl]

Well, it is heavy duty- maybe it would be enough

[Liger Zero]

What I want to know is who the hell buys a boiler feedwater pump motor off of god-damn CRAIGSLIST anyway?

I can imagine the backlash in the newspaper: "...local nuclear power plant under investigation for buying critical safety components off of Craigslist." LOL

[snowman]

You need a new motor.

http://rochester.craigslist.org/bfs/2049523841.html

Dang....you must have some big squirrels in your part!

[RKW]

And just for clarity, this is a damper.

http://t0.gstatic.com/images?q=tbn:ANd9GcReT7Ucg_mfUVa9DT-GAO4E_Zp28-vRW-BJDdz1bMtT4VrBIYU&t=1&usg=___tiVw5NmB4cu2a3vgOIq_ROI9ww=

Many times the terms vent/register and damper get interchanged.

[A.K. Boomer]

I did not know that they used those in heat systems - Now I know what Evans talking about and I would have to agree -- the only thing I could see them being useful for is the fact that installed close to the furnace it keeps the pipes pressure down and therefore you will not "bleed" heat out as much through all the connections esp. on long runs...

If both the register and the "damper" type are adjusted for identical CFS then the register will have more heat loss unless it's 100% totally sealed around all the joints...

[garagemark]

If you choose:

http://www.grainger.com/Grainger/wwg/search.shtml?searchQuery=duct+booster&op=search&Ntt=duct+booster&N=0&sst=subset

[Evan]

There isn't any heat loss once the heat is in the ducting since it all stays in the house. What suffers is delivery and efficiency. Introducing obstructions in the ducts is just plain stupid design. With regulated registers it still allows for laminar flow right up to the register and if the register is closed then the entire length of duct the feeds that register is essentially static and disappears from the system. Further, it doesn't introduce turbulence that will slow the flow and disrupt the insulating boundary layer along the walls of the duct. That allows dust to collect instead of passing through the system cleanly.

[Steve Steven]

cOULD BE A BROKEN JOINT OR POOR SEALING OF JOINTS
Steve

[Your Old Dog]

There isn't any heat loss once the heat is in the ducting since it all stays in the house. What suffers is delivery and efficiency. Introducing obstructions in the ducts is just plain stupid design. With regulated registers it still allows for laminar flow right up to the register and if the register is closed then the entire length of duct the feeds that register is essentially static and disappears from the system. Further, it doesn't introduce turbulence that will slow the flow and disrupt the insulating boundary layer along the walls of the duct. That allows dust to collect instead of passing through the system cleanly.

Maybe on a smart home but home is stupid. The two heating ducts for the living room are only about 12 feet. The one that leaves the same manifold to head upstairs has to cross 20 feet of basement, thru an elbow and start it's journey to the second floor, probably another 15 feet or so. It is roughly 3 times longer then the living room.... phone calll be right back.....

I'm back. If air loosely follows the same laws as hydraulics do I'd expect the shorter run to get more air more forcefully then the air headed up stairs through 35 feet of cold duct work. It would be "the path of least resistance".

We change our filter every month all year long as we have central air. My A coil was just cleaned this year by the installer. I watched him so I'd know how to do it. AFter 7 years of operation he was only able to find about the equivalent of 1 or 2 tablespoons of dust in the coil. The basement dampers had little effect on dust control.

[Highpower]

If both the register and the "damper" type are adjusted for identical CFS then the register will have more heat loss unless it's 100% totally sealed around all the joints...Interesting. That is what I used to do with my old heating system since it had dampers in the basement ductwork and I have the adjustable wall registers upstairs. I would put all the registers wide open and adjust the dampers to level out the heat in each room.

Now I have a new furnace that is 1/4 the size (physically) of my old 1940's "Singer" furnace. The new unit has a two stage blower on it unlike the old single speed furnace, but the squirrel cage is also now 1/4 the size of its predecessor. The registers on the ground floor have to be almost completely closed now to get any heat on the upper floor. And then, the farthest duct from the furnace gets no air flow at all to speak of.

However........ I do notice the seams in the new duct work (basement) leak like a sieve now so I suppose I should start there.
(DUH!) So my next question would be silicone or duct tape??? The HVAC company used silicone around the plenum joints but didn't put squat on the duct work.

I don't even want to think about what the old duct work was wrapped and sealed in. :mad:

[RKW]

Smart homes tend to use the automated or actuated dampers. There is also the type that inflates and deflates totally cutting off air to that duct. These are generally installed as close as possible to the furnace itself. Adding these features also requires the use of a controller and more thermostats (one for each room or zone) and/or occupancy sensors. This way each zone can be controlled better with a single furnace by inflating and deflating the dampers as needed.

I couldn't find the best picture, but this web site shows a pretty good diagram with a pneumatic damper bag further down:

http://www.homecomfortzones.com/products/works.php

Naturally this stuff costs a fortune since it is specialized. Are we fully OT of the original OT now? ;-)

[A.K. Boomer]

There isn't any heat loss once the heat is in the ducting since it all stays in the house.



Just depends Evan, most of the houses iv been in that have crawl spaces and the furnace in them also are vented some at the foundation --- this really means that a ducted system could save some efficiency if the joints are not sealed...

[A.K. Boomer]

Are we fully OT of the original OT now? ;-)



If O.T. means "On Topic" then yes we are;)

Keep going RKW something else Iv never heard of is pneumatically controlled damper bags, but it really is in keeping with the topic..