[clarke]

To be honest I haven't looked at system status data at 10F but I get high stage heat from both the HP and heat strips at other times.


If I go for a separate system for the lower level, is there an overwhelming reason to go for one option (elec baseboards, minisplit heat pump, dedicated split system, hydronic) over the other given the climate and the small heat loss of the floor? I'd like to separately zone all five major rooms if possible.

Cold Feet,

I'm having difficulty with the 60MBTUH heat loss of your 25 year old 1600 sq. ft. home and the size of the heat pumps that are being recommended. Beware heat pump systems with those capacities will generate 10+ air changes per hour and it will be uncomfortable living conditions.
Your system does not function properly at 40F. At that temperature you have more then enough capacity. You should balance the distribution system to deliver more air to the lower level. This will lessen the heat input to the upper level and allow the system to run long enough to heat the lower level. One way to do this is to throttle the dampers in the upper level registers. I don't recommend this because it changes the fan static pressure. A well installed duct system should include damper regulators at each take off to each register and balancing should be accomplished using these dampers.
Better yet install one of the many zone control systems available. My personal favorite is the system manufactured by ARZEL TECHNOLOGIES.


Good luck with your project
sg

 

[Cold Feet]

jjou812 and clarke:

Downstairs is ducted with a very short 8x12 metallic feeder leading into two 8" round metallic ducts. Upstairs is fed off a 9x20 metallic trunk. The only balancing control I have is through the register louvers. The upstairs (old) duct work doesn't have dampers and the installer refused to install dampers on the new (basement) ducts. Closing all the vents upstairs makes no difference--I tried it last heating season.


I'd like to replace the windows, but the price tag to replace all of them is between ten and one hundred times the cost of having the ducts fixed or installing a separate heating system for the lower level. I don't have the spare funds right now.


I'm fairly confident I did the loss calculation right but I'll post the measurements for one room if anyone is volunteering to check my work for systemic screwups.

 

[neophytes serendipity]

jjou812 and clarke:

I'd like to replace the windows, but the price tag to replace all of them is between ten and one hundred times the cost of having the ducts fixed or installing a separate heating system for the lower level. I don't have the spare funds right now.


I'm fairly confident I did the loss calculation right but I'll post the measurements for one room if anyone is volunteering to check my work for systemic screwups.

FYI: Check out the window selections in HVAC-Calc.

It only takes a couple of keystrokes. Watch the loss/gain numbers.

Hint: Single pane windows with storms perform pretty darn well.

 

[Brian GC]

No. Upstairs will be at the thermostat set point; downstairs will be 7-10 degrees colder.

This has been attributed to the lower level ductwork rather than the unit sizing.

Coldfeet,
As we all know, heat rises. Do you have an open floor plan that allows the heated downstairs supply air to immediately ascend upstairs? If so, an increase of volume to the downstairs will make little improvement. The bottom of my stairway is always cold because there is no ceiling to hold the heat down. I know of other houses that are always cold downstairs because of very open floor plans and high ceilings.

Also, where is your return air register? Is it in the ceiling at the top of the stairway? IMO, if it is mounted high in the house it is causing part of the problem. Not only is the heated air rising to the upstairs, but it is being sucked out and reheated. All you’re left with is the cold strata of air on the first floor which is minimally affected by the heater.

Few HVAC pros agree with this theory. They either do not want to understand airflow and air density or they want to continue installing heater returns on ceiling because it is an easier install.

So, I agree that your problem is probably ducting, but not necessarily the supply ducting.

1.

2. Replace the single pane windows.

Window replacement is a large part of my business. Unless your windows are very drafty, it is my opinion that window replacement will have little affect on heater performance. What dual pane windows do best is help retain heat, which in turn will help save on unit cycling. If the heater doesn’t heat the house, the windows can’t hold it in.

Brian

 

[Cold Feet]

Do you have an open floor plan that allows the heated downstairs supply air to immediately ascend upstairs?

It's a hybrid plan. The upstairs level is open plan and is connected to the downstairs hall via an open stairway. The downstairs hallway leads to five rooms, each of which has well-fitting doors that are almost always closed.

The hallway is chilly (~66 degrees) but 61 is not unheard of in the larger rooms--despite the fact that they're isolated from convecting with the rest of the house.

Also, where is your return air register? Is it in the ceiling at the top of the stairway?

I've got five spread between the two levels. Upstairs is served by a single 24x4 (duct size) return at the top of the stairway. The basement has four 12x4 returns--one in the hall, one each in three of the rooms. All returns in the house are mounted at floor level.

I did some smoke tests last heating season. There's no rise up the stairway. At tread height, air goes downward into the basement. From about 2' above tread height to at least 6' above the level of the main floor, there is no air movement. Light a scented candle here and the smell will linger for 24 hours or more, even with the air handler fan running continuously.

As for the basement rooms, the only air movement other than infilitration and via the supply & return registers is under the doors. This air is cold , and in two rooms, flows into the rooms from the hall. There's no hot air escaping above the doors.

Given what I've seen with smoke tests I don't think I'm losing heat upstairs.

 

[clarke]

jjou812 and clarke:

Downstairs is ducted with a very short 8x12 metallic feeder leading into two 8" round metallic ducts. Upstairs is fed off a 9x20 metallic trunk. The only balancing control I have is through the register louvers. The upstairs (old) duct work doesn't have dampers and the installer refused to install dampers on the new (basement) ducts. Closing all the vents upstairs makes no difference--I tried it last heating season.


I'd like to replace the windows, but the price tag to replace all of them is between ten and one hundred times the cost of having the ducts fixed or installing a separate heating system for the lower level. I don't have the spare funds right now.


I'm fairly confident I did the loss calculation right but I'll post the measurements for one room if anyone is volunteering to check my work for systemic screwups.

Cold Feet,

Installing storm windows would be beneficial. U value of a wood framed single pane clear glazed window is U .9 with storm U .55 significant improvement. Your distribution is another issue. You state that when you close all the registers in the upper level nothing changes. When you do this does the air flow to the lower level increase. You can get an idea with just a piece of toilet tissue. Use the tissue as a vane type air measuring instrument and note how far the air displaces the vane with the registers in the upper level open and closed. If your air flow doesn't increase. This can happen because of ( a loose fitted damper at the register and you did not change the flow by closing the damper again use the tissue, excessive duct leakage, your lower level trunk line is tapped into the plenum creating excessive static pressure at the tap or a combination of any of these and more.
Your description of the distribution in your home suggest a simple zoning installation which would balance your system.

sg

 

[Brian GC]

I've got five spread between the two levels. Upstairs is served by a single 24x4 (duct size) return at the top of the stairway. The basement has four 12x4 returns--one in the hall, one each in three of the rooms. All returns in the house are mounted at floor level.

I did some smoke tests last heating season. There's no rise up the stairway. At tread height, air goes downward into the basement. From about 2' above tread height to at least 6' above the level of the main floor, there is no air movement

As for the basement rooms, the only air movement other than infilitration and via the supply & return registers is under the doors. This air is cold , and in two rooms, flows into the rooms from the hall. There's no hot air escaping above the doors.

Given what I've seen with smoke tests I don't think I'm losing heat upstairs.

There may be rise up the stairway. If air goes downward into the basement as you stated then an equal amount of heated air is escaping into the upstairs. The upstairs return may be removing this heat before it can descend to the downstairs.

Downstairs returns are a big plus for a heating system but there is obviously more going on with your system. I said windows will not make or break a heating system but maybe yours are drafty in combination with heat rising upstairs.

Blocking the upstairs return may yield positive results and shed light on the problem. However it may restrict the intake to the unit beyond what is recommended. But I doubt it would hurt the unit if done temporarily as a test.

This was currently discussed extensively on another thread “suffering upstairs”. The OP blocked the downstairs return and got positive result in the AC mode. This may be your problem in reverse. But again, blocking returns should only be done if the unit is not stared for air.

Brian

 

[Cold Feet]

The upstairs return may be removing this heat before it can descend to the downstairs.

How would that work? Wouldn't hot air be too buoyant to sink?


My working theory on stair airflow is that the cold downflow is air being pulled into the downstairs return registers. The rising heated air would be coming out of the upstairs supply registers.

Naturally this is predicated on the upstairs return being undersized. I don't know enough (read: any) Manual D to figure this out conclusively but a single 26x4" (duct size) return seems a bit small for 11 6" supply registers.

Blocking the upstairs return may yield positive results and shed light on the problem. However it may restrict the intake to the unit beyond what is recommended. But I doubt it would hurt the unit if done temporarily as a test.

I tried that last heating season, too. Blocking the upstairs return helps the smaller, warmer, rooms but has no measurable effect on the larger, colder, rooms at the ends of the house. I don't remember what effect it had on the hall.

Blocking the upstairs air vent increases TESP on the system from 0.31" to 0.35".



I get another dimension to this problem at this time of year: contradictory demand from the two floors. Due to solar loading during the late afternoon, upstairs will rise to 77+ while the basement holds firm at 67. Zoning would prevent HP cooling from chilling the basement but keeping the air mixed well enough for the basement to get warmer would be better.

 

[Brian GC]

How would that work? Wouldn't hot air be too buoyant to sink?

My theory is that if the supply adds warm air into a room and a return is not mounted high on the wall to remove it, it will continue to accumulate on the ceiling. Also, if returns are mounted low on a wall or downstairs it will continue to remove the cold strata of air on the floor or downstairs. Eventually as the downstairs cold air is removed the upstairs heated air will descend.

My working theory on stair airflow is that the cold downflow is air being pulled into the downstairs return registers. The rising heated air would be coming out of the upstairs supply registers.

If cold air from upstairs is flowing down the stairs it is displacing the heated air on the downstairs ceiling, which is rising up the stairway. The same amount of air that goes down the stairs must go back up… cold down – hot up.

Naturally this is predicated on the upstairs return being undersized. I don't know enough (read: any) Manual D to figure this out conclusively but a single 26x4" (duct size) return seems a bit small for 11 6" supply registers.

It does seem very small for that amount of supplies. Is that the only return or are there other returns? Do you have a single or split system? And, where are the returns mounted downstairs? Where is the unit located?

I tried that last heating season, too. Blocking the upstairs return helps the smaller, warmer, rooms but has no measurable effect on the larger, colder, rooms at the ends of the house. I don't remember what effect it had on the hall.

Whenever you get near a stairway or ceiling return the heat is racing upward and leaving the room. The rooms furthest away from the stairway should be the warmest unless the supplies are weak or there is a ceiling return just outside the room.

Your problem IMO is either volume of supplies or placement of returns. Do not underestimate the affect of returns.

Brian

 

[heaterman]

Start with the duct system upgrade to get the available heat to the areas where it is needed (manual D). Then address the heat loss issues associated with the single pane windows. Either replace the windows as a unit, retrofit new thermal eff. sash, or at a minimum install high quality storms. Most window companies will do replacements on a piece by piece basis so you would not have to do a complete upgrade all at one time. Even though I am in the HVAC business, I tell my customers and potential customers that the smart money is in weatherization.