ME's, HVAC Techs, Armchair Mechanics: I need direction on a new system

[daepp]

My wife and I recently purchased a home built in 1990 but meticulously copied from a home near Santa Barbara built in 1910. The house has two air handler/furnaces in the basement and two compressors located on the south side of the house.

I have the 1990 plans, and they show only one system. But it looks very much to me that the second system was added at the time of construction.

It is a mostly one story home with 15' open-beam ceilings for all 1st floor rooms, except part of the northern first floor has 10' ceinings due to two bedrooms and a full bath being above on a 2nd floor. 2nd floor has 10' ceilings, and HVAC registers come down from attic above.

From 1990 to 2014 the house was approx 3400 sq. ft. In 2014 a guest bedroom and full bath were taken from two of the three tandem spaces in the garage, and now the house is 3700 sq ft.

HVAC System #1: runs all of 1st floor - including the newer guest bedroom - except the master bedroom and the 2nd floor.
HVAC System #2: runs master bedroom on 1st floor and all of second floor.

Both systems are in the basement, which is under the norther east entryway as well as under the two-story part of the house. A large chase (with ductwork, maybe some romex and the exhaust flus for the furnaces and water heater) leaves basement ceiling and heads up through 1st floor, 2nd floor, 2nd floor attic and then daylights above 2nd floor roof.

The entire home (excepting the guest room) is above a large crawlspace where a great deal of duct work lives. and registers in the walls are served by these below-the-floor ducts as there is no ceiling in most of the home (all open beam). Underside of all floors are fiberglass insulated.

Walls are all 1 foot thick (stucco exterior, plywood, 2X6, plaster interior). They are full of pink fiberglass insulation.

Roof is traditional 2-piece clay tile, with paper and plywood sheathing throughout. Structurally it appears to be 2 X 12 rafters on 16" centers with 10" of pink fiberglass insulation between the rafters.

Windows are original 2-pane glass casement. Some are clearly leaking (moisture on the inside).

The heat load (sun) is on the south side of the house, which is where the kitchen and the guest room are located.

Problems I know About:
- All components are original and on their last legs
- 2nd floor gets too hot if you're trying to heat master bedroom even just a little.
- There is no door between 1st and 2nd floor.
- The kitchen and guest bedroom are at the end of a long run on HVAC 1, and guest room has zero airflow so much as I can tell. Both guest room and kitchen are cold.
- The returns for both systems are together in the same spot and seem drastically undersized to my (untrained) eye.
- Master has no return, so door must be left open. Can be a little bit of a bummer when guests are over.
- Just my wife and I live here probably 320 days a year. Kids and spouse/S.O.'s come and stay periodically, but for the most part we don't use the upstairs and guest room.

Unknowns:
- We have not lived here (Inland So Cal) during the summer so we know little about cooling.
- I have replaced all of the bad (some of it rat-eaten) flexible duct work that I've been able to find so far, but I have not tested either system for leaks.

Photos (w/my crude drawings below - sorry, I'm an accountant turned contractor and I can't even draw a stick figure...):



Yellow - where the heat comes from
Red - I'm guessing is the hottest area of the house (and future location of solar panels)
Green - general location of guest room and kitchen
Blue - entryway, with basement below and two-story portion above




Yellow - heat load (a repeat I guess)
Black - location of 1st floor master bedroom
Blue - two-story portion where extra "overflow" bedrooms are located above 1st floor




Garage shot showing roof type and a part of the guest room on the right




Stairs up to 2nd floor landing and bedrooms. No door or barrier between 1st and 2nd floor





Utility Basement




Crawl Space




(Realtor-staged photo) Ceiling

In our last home we went with a high SEER unit with one air handler/furnace, one two-stage compressor and two thermostats for two zones. Added automatic dampers allowed for one zone to work while the other was idle. Not sure if dampers might help the overheating upstairs or not.

I’m open to installing new “trunk” ducts, adding returns or even a
Mini-split for the guest room (although not preferable considering our electricity rates in CA!)

[Noah930]

I can offer no useful HVAC advice, but that's a beautiful home, Dave.

We remodeled our home a year ago, with an addition as well. The GC's HVAC guy came out to take a look. We had battled weak AC all along our course of ownership. The HVAC guy took one look at our system, agreed that it was the unit was a bit undersized for our current application (let alone the addition which would add another 500 sq ft), but that it was the restrictive size of the ducting that really was our problem. The AC unit worked. The ducts weren't leaking. But the AC was working too hard to breathe through the existing too-small ducting. Replace the ducting with larger diameter stuff and it would immediately help (though with our planned addition the AC unit would be too small for the entire house, so we wound up replacing everything).

[daepp]

Very good to hear - thanks.

[Evans, Marv]

I'm not an HVAC guy either, so can't offer any specific suggestions. Our place is smaller than yours - 3200 s.f. It has 10 ft. ceilings throughout. One thing I figured out, especially during winter, was that the air could become stratified with the warmer air rising & leaving the cooler air below. That is with two, 20 in. square returns. So I felt the air needed to be circulated more. I bought two fans, one for the living room area (it's pretty open with the entry, dining area, kitchen & "sunset room") & one for the master bedroom. They are quiet (went through a couple of fans to find sufficiently quiet ones) & adjustable in terms of vertical and horizontal circulation patterns. They reduced the amount of time my heating system cycles on & off & mix the air. Maybe you could benefit from that kind of thing. If I knew what I know now, I would have installed a couple high in the walls in strategic locations with grates during construction.

[Cajundaddy]

Very nice digs, San Antonio Heights?

These multi-level HVAC issues are far above my pay grade but I know a guy in the IE. He does all our HVAC work on the residential and commercial properties. Very skilled and reasonable.

[daepp]

Originally Posted by Cajundaddy

Very nice digs, San Antonio Heights?

These multi-level HVAC issues are far above my pay grade but I know a guy in the IE. He does all our HVAC work on the residential and commercial properties. Very skilled and reasonable.

Padua actually, but that’s a great guess. Maybe shoot me a PM with his contact info?

At this stage I’m trying educate myself so I can at least know what to ask for - at a minimum I think I need to zone off the second floor so I don’t cook my guests I’m the winter, and so I don’t cool unused space in the warm months.

[daepp]

Marv - re fans, I have a ceiling fan in the master, and I know they’re often reversible. Your comment reminds me to check and see if I can switch its direction of spin and retrieve some of that warm air! Thanks for that!

[MBAtarga]

In our previous home, my AC guy added a duct in the Master Bath where it was constantly warm, and also increased the size of the return for the Master Bedroom from 8" to 10" (maybe 12"). That solved most of the imbalance in our upstairs ventilation. Duct work is probably the cheapest/easiest means of controlling air flow and balancing the system. In our case, the blower was in the attic so it was very easy access.

[cabmandone]

I'd consider a zoning system for your application. It's going to be expensive but you mention the systems are on their last legs. Honestly that duct system looks a bit sketchy IMO.

[908/930]

Very nice place,

Something for you to look at, is the speed of the blower motors on the air handlers set too low? Also as you mentioned if the return ducts are not up high the heat just sits up there, altering that to get the warm air to the air handler would help lots.

[john70t]

Originally Posted by 908/930

Also as you mentioned if the return ducts are not up high the heat just sits up there,

I was thinking along the natural lines.
Cooling would be a lot more important than heating in Southern California I was thinking.
Opening a 2nd fl bedroom window would let that trapped heat escape out and create a vacuum draw through the long portion of the house.

Big overhangs+breeze+stone floors is nice cooling.

[look 171]

Dave, have your HVAC contractor re-calc the duct work. Spit the upper floor and the lower, ask them to see if automatic dampers are needed. A good HVAC designer will be able to answer those questions for you. Problem with a lot of those guys is that they sometime bid the job so cheap by using the existing duct so they get the job but the engineering fall short. The other problem is the house is finished, and that makes it harder for them because most guys dislike hacking up a finished homes. How many returns do you have for each unit? Ask about dual air returns for each system. Sometimes, just an additional return in the far end of the home will make a huge difference in terms of air flow through those "dead" areas. The runs maybe a bit long and too "skinny" a duct. Nice home BTW. Where the heck of Padua? Izdat north of the college?

[cabmandone]

FWIW. low/no airflow to a room is typically due to poor supply duct design and lack of adequate return ducting. Ask a good HVAC company about a "Zoning system". This system splits the space into zones using a temperature sensor for each zone. If a zone doesn't need heating or cooling the dampers will typically be set to allow a minimal amount of air to pass and force the air to zones that need heating or cooling. Again, it's a pricey system but you get more balance and based on the layout of your home, yours will be a bit difficult to balance without the use of zoning.

[billybek]

Getting a good contractor in to have an in person look will go a long way to getting these systems to work as a system.
That ducting I can see in the photo looks to be mostly flex ducting. I can't even imagine the loss of flow due to resistance from this type of ductwork. Plus the fact that they look like they have been flattened and that significantly reduces the flow area and increases resistance to air movement.
If possible, I would have them re run the mains (supply and return) in hard duct that is seam taped ad insulated. Accessible zoned dampering at the trunk or diffuser or both would be a good thing.
The advice of going to a zoned system varying the airflow based on temperature is a good one but may be expensive.
The solar panel install on the sunny side of the roof with an air space under them will reduce the heat load on the upper floors and ceiling space.
There are tons of options out there. A properly installed and set up system will likely pay for itself in reduced energy consumption.
I would not be afraid to look into mini splits that could handle a difficult zone to service from the existing mechanical area.
I was looking at one the other day that the indoor coil looked like a painting frame that the home owner could change to suit the decor.

[red-beard]

A few outsdide suggestions

1. Create a Master bedroom only zone. The easy way is to add a mini-split type unit to the master. You can leave the existing ducting in place.
2. Continuing, make the upstairs the main zone for the second circuit. Move the thermostat to the second floor
3. You said all of the equipment is on its last legs. Replace it. But replace with TRUE varible speed technology. NOT two-speed, but a system using varible frequency drives. These systems can speed up and slow down as needed to give exactly the amount of cooling needed, saving a lot of energy. This said, the pricing on the units is higher, but the price difference between a standard single speed replacement and the VSD units will pay off in a few years, especially with California energy prices.
4. On the VSD Air Con units, don't by the "top" model, buy the next level down. The difference between 25 SEER and 23 SEER is not enough to make a difference.
5. Consider a "geo-thermal" heat pump. These reject the heat energy into the ground instead of the air. The heat sink is more consistent and the cooling cost are much lower in the summer and heating much lower in the winter. These can be very pricey, so keep your eyes open if considering.

[wdfifteen]

Originally Posted by cabmando

FWIW. low/no airflow to a room is typically due to poor supply duct design and lack of adequate return ducting. Ask a good HVAC company about a "Zoning system". .

I have a zone system in my house and it sucks. It’s 16 years old and hopefully they have improved the systems in the past 16 years.

[Zeke]

The point about air return is important. You can't imagine how many houses I've been in where there is no gap under say a bedroom door and no transfer vent in the wall to a hallway, etc. where the return air register lives.

As an example, a typical boot for the average bedroom is 6 x 12. Actual sq in of air flow will be less so let's call it 60 sq in. To equal that, a typical 30" bedroom door would need to be cut 2" above the finish floor to allow free return flow. Don't take my example literally because many times things work well enough w/o having enough room under any given doorway to allow a small cat to crawl under.

Booster fans. And auto dampers. Any large home is going to have a sophisticated duct design. Simply sizing ductwork according to Manual J isn't going to be ideal. Number of bends and a 1000 other factors require 'balancing' after the fact.

Your tech will need one of these called a capture hood. Use it both with the door open and the door closed.



Or you can spend a lot of money guessing.

[BK911]

Zone dampers.

[daepp]

Originally Posted by look 171

Dave, have your HVAC contractor re-calc the duct work. Spit the upper floor and the lower, ask them to see if automatic dampers are needed. A good HVAC designer will be able to answer those questions for you. Problem with a lot of those guys is that they sometime bid the job so cheap by using the existing duct so they get the job but the engineering fall short. The other problem is the house is finished, and that makes it harder for them because most guys dislike hacking up a finished homes. How many returns do you have for each unit? Ask about dual air returns for each system. Sometimes, just an additional return in the far end of the home will make a huge difference in terms of air flow through those "dead" areas. The runs maybe a bit long and too "skinny" a duct. Nice home BTW. Where the heck of Padua? Izdat north of the college?

Hey Jeff - thanks for the input!

- Def need to look at automatic dampers between 1st and 2nd floor!
- I'm not afraid to open up the walls (if necessary), and if new (larger) ducts and returns are needed most will be under the house (easy access).
- Each unit currently has only 1 return, and they are combined into one entry point on the 1st floor above the units.
- And def want to explore adding additional returns to "pull" air to/from the furthest reaches of the system.
- Padua - that's an informal name for the area north and east of the colleges - kinda rural and not at all like the Village (no sidewalks, no street lights etc.) The area sits in the foothills beneath Mt. San Antonio de Padua (Mt. Baldy!) Maybe 10 years or so ago it was unicorporated LA County, but it was eventually annexed into the city of Claremont.

Thanks again Jeff!

(PS - I know you know a LOT about housing - if you're ever gonna be in the 909 let me know - I'd love to get your input on the above - and a whole lot more!)

[scottmandue]

Crusty old HVAC guy here from the dark ages.

1. Combining upstairs/downstairs is no bueno, it will always be hotter upstairs and you will never balance the temps.
2. I did a few big installs in Rolling hills with two and even one with three split systems and NEVER combined returns. Rule of thumb is you want the return is the same area as the supply.
3. Low air flow to add on's is typical, believe it us crusty, stinky, beer guzzling A/C guys actually calculate the size of every room and design the duct work (and air handler) to deliver a specific CFM for the square footage. So when you add on a room and extend the duct work to put in another grill guess what?

A lot of options but I don't have time to study your post (at work now) and think about your situation.

On some installs we would drop a package unit next to the house and build a metal plenum/duct work to connect to the duct under the house