HVAC Advice - any pro's out there?

Greebo

Greebo

N9017H - C172M (1976)
Joined
Feb 11, 2005
Messages
10,976
Location
Baltimore, MD
Display Name
Display name:
Retired Evil Overlord
I'm looking for input to help make a decision about work we're going to be having done in our house.

House is 67 years old (1940 construction).
Existing ductwork was designed for gravity (convection) heating system. (Pre-WWII).
Existing furnace is 25 years old, was shoe-horned into existing ductwork.
Axisting A/C is 18 years old, was shoe-horned into furnace.
Approximately 1600 sq ft of space (900 1st floor, 700 2nd floor)

Existing ducts: interior walls, 8x10 grills (gravity heating). 1 return 8x6, on floor of 1st floor dinning room on outside wall.

Heating works ... ok. We don't freeze, and we added 15" of loose fill cellulose in the attic this spring which should help.

A/C works downstairs but not on the 2nd floor. We have window units in the bedroom and computer room. Why it doesn't work is obvious - only one air return and its downstairs...

We have decided that proactive replacement of both furnace and a/c are justified, but being in the technical field, I'm too well aware that if you slap the best CPU in the world in an 8088 motherboard, there's only so much performance you can get. (This is hyperbole, I know you can't put today's CPU's on 8088's...)

So we intend to replace/upgrade the ductwork as well, cause there's no point putting a SEER 16 or 17 A/C on a POS duct system.

So we've have two similar proposals we both like (and one we didn't).
Both proposals involve a single replacement system, approx 90k BTU furnace, 3ton A/C both 2 stage, the furnaces 80% efficient, the A/C's SEER 16.

It's the ductwork we can't decide on.
1) New trunk from basement to attic. New trunk in basement. ALL new vents on exterior walls. Vents on 1st floor run from new trunk in basement. New air return in middle of house on 1st floor. 2nd floor vents in ceiling with air return at top of stairs (central to floor space).

2) New trunk from basement to attic. Re-use existing ductwork for first floor, possibly adding another return. New ducts in ceiling on 2nd floor, but use existing ducts on 2nd floor for 1/2 the return capacity (approx 80 cu/in) and a central return at the top of the stairs for the other half.

Oh, and #2 is super hi-tech equipment with a motherboard located in the furnace/air exchanger region. That worries me... (heat, cold, circuit boards).

Both estimate about same time to complete, both contractors well experienced in working in older homes.

Concerns with #1: LOTS of new duct work in basement. Livable but doesn't re-use any existing.
Pros with #1: Much better airflow efficiency.

Concerns with #2: Less effective airflow, hi-tech electronics located to source of heat/cold temp changes.
Pros with #3: Re-use of existing ductwork keeps feel of house.

We are leaning to #1, but are seeking any other unbiased opinions.

Thanks for your input!

Chuck
 
Unless you are very certain about the quality and integrity of the existing ductwork, I would be strongly inclined to replace it all. Are they proposing to replace with insulated rigid duct, or flex? Cost is greater, but I'd prefer rigid.

All modern HVAC have a certain measure of computerized magic to 'em, so I would not let that worry me too much, as long as you have a warranty that is fairly strong.

What manufacturers are they proposing?

In any event, I'd want to replace your existing stuff no matter what, just based upon the age of the heat exchanger in the furnace. Carbon monoxide is a Terrible Thing.
 
#1 is proposing Rheem and Amana.
#2 is Bryant, exclusively

I did some digging on AngiesList, tho...found 1 report on contractor proposing #1, and it wasn't good. Couldn't get the a/c unit working, at all, and had it pulled and money refunded.

Contractor #2 (partial replacement) much better reports. :/
 
I don't know jack about HVAC but I'd definitely go with ripping out the old stuff and starting over fresh. Cost is nothing compared to CO poisoning. not to mention if the airflow is less than par, you've spent a buttload of money (less than a buttload-plus, true) for.. what? plus your concerns about your hi-tech EQ. Doesn't sound like much of a choice to me really.
 
Greebo said:
I did some digging on AngiesList, tho...found 1 report on contractor proposing #1, and it wasn't good. Couldn't get the a/c unit working, at all, and had it pulled and money refunded.
Click to expand...
Was this a contractor problem, an equipment problem, or a customer problem?

I would not give much weight to one problem report that seemed to be resolved by a refund of money. Try as you might, sometimes you just cannot satisfy the customer.

Other than that, I agree with the others that a totally new system is probably the best. Think resale value.

-Skip
 
Greebo said:
#1 is proposing Rheem and Amana.
#2 is Bryant, exclusively

I did some digging on AngiesList, tho...found 1 report on contractor proposing #1, and it wasn't good. Couldn't get the a/c unit working, at all, and had it pulled and money refunded.

Contractor #2 (partial replacement) much better reports. :/
Click to expand...

Really? I read so many bad things about Angie's scam err... list that I decided to pass. They are known to allow contractors who pay for ads to remove bad reports and post good ones. There are also reports that contractors get called to advertise or suffer the consequences. Note that "lil' old housewife" Angie is a marketing executive.

I found another site: http://www.franklinreport.com

I got a bid for replacing one of my 2 furnaces. (Dukane and American Standard/Trane) Like you, I decided that the really high (90%) efficiently furnaces are not cost effective. I think 2 stage did make sense to me.
 
Last edited:
Chuck, I just spoke with a good friend of mine who is a HVAC installer. He stated he would not recommend a "partial job" as you would not be satisfied with the performance.

His recommendation is to gut the entire system and start from scratch.
 
kevin47881 said:
Chuck, I just spoke with a good friend of mine who is a HVAC installer. He stated he would not recommend a "partial job" as you would not be satisfied with the performance.

His recommendation is to gut the entire system and start from scratch.
Click to expand...

My take, too. And I've watched enough Holmes on Homes to say make sure they seal up all of the seams with aluminum tape.
 
Put a window unit in each room. :D

Seriously, I'd recommend getting advice from a professional HVAC engineer, not a contractor. Contractors install what they have in the warehouse, so if that coincides with what your house actually needs, it's a happy coincidence.
 
The fact that it's the ONLY report on the contractor hasn't gone unnoticed.

He also had good input, IMO, regarding doing dual zones on a single furnace and a/c (using dampers).

My main hesitation here is the re-use of the ductwork idea. Part of me just likes the idea of using some of the original work...
 
Greebo said:
The fact that it's the ONLY report on the contractor hasn't gone unnoticed.

He also had good input, IMO, regarding doing dual zones on a single furnace and a/c (using dampers).

My main hesitation here is the re-use of the ductwork idea. Part of me just likes the idea of using some of the original work...
Click to expand...

I asked the contractor bidding on mine about replacing both with a zoned system. He said I wouldn't like it.

In my own head the thought that the fan and all on a big system has to power up for any zone seems non-optimal.
 
Sounds like the current system does OK on the first level and crappy on the second.

I'd probably go with option #2, replacing the upstairs ductwork and main furnace. The current system is not balanced and this option will provide more heating and cooling where it is needed. In either option the complete system will need rebalancing with baffles and could be done using existing ductwork on the first level with new on the second.

Keep in mind, even with a new system, you may have to open and close vents on the levels to go from the summer months into the cold months. I have to close lower level vents in the summer months and do the opposite in the winter, else it's hot upstairs in the summer and cold downstairs in the winter.

In either case most contractors will try and over sell what is required.
 
Option 3. Leave existing ductwork and replace heat/ac unit(s). Add a minisplit to the upstairs to handle that load. Depending on the layout, there may be some cosmetic issues with the minisplit, but it might be a lesser evil than re-doing the ductwork.
 
Ken Ibold said:
Option 3. Leave existing ductwork and replace heat/ac unit(s). Add a minisplit to the upstairs to handle that load. Depending on the layout, there may be some cosmetic issues with the minisplit, but it might be a lesser evil than re-doing the ductwork.
Click to expand...
No good. We can emulate that by closing all the downstairs ducts, but all the hot air upstairs doesn't get cooled by what little cold air makes it upstairs. With no air return on the 2nd floor to pull the hot air OUT, the cold air sinks and goes down the stairs.

Its the whole putting a cherry v8 engine on a shoddy transmission issue...
 
You have a couple of options....

When faced with the same issue approx 10 years ago (1920's house, 1960's HVAC forced-air system), I opted for a 2-zone system with the highest efficiency equipment I could get (Carrier Weathermaker). The Carrier system had variable speed motors on the compressor and the blower. We zoned the second floor separately from the first floor, with a small fixed vent in the basement. We replaced the laundry chute as a return air duct for the second floor, and used an existing floor-mounted return air duct on the first floor.

I was very happy with the results, comfort wise (I'd not buy another Carrier system, though, Trane is much better). The zoning and variable speed blowers kept the house comfortable with low interior humidity (humidity is as big a deal than temp). Most importantly, it cut the energy bills more than in half.

The other option to consider is putting a second unit in for your second floor (code permitting). Install the unit in the attic with new ductwork.

That's the arrangement we had in San Antonio. We had 3 systems, one for each floor. Package unit for first floor, standard split-system for second floor (gas furnace/electric AC), and split system (electric/electric) for third floor. Advantages: when the first-floor Carrier system broke, we still had AC in part of the house.

As a third option, you might also look at a SDHV system for the house. Use the existing ducts for return air and install new SDHV ductwork for the air distribution.

A friend in Cincy put in a SDHV air conditioner in their 1890's house and retained the hot water heating. They were quite happy with the results of the AC, and they are considering a SDHV furnace as part of the system.

Here's a bit of background on SDHV, found by Google. http://www.miniduct.com/
 
We considered dual-zoning the single system, but the concern there is that in doing so, we'd end up potentially short-cycling the system because we'd be faking out the 3 ton A/C into thinking it needed to cool the whole house when it only needed to do half, and ditto for the A/C.

We also considered the 2nd system to zone the house, but for 700 sq ft, it's not justifiable, IMO.

Had not considered SDHV - that muddies the water somewhat... ;)
 
Greebo said:
No good. We can emulate that by closing all the downstairs ducts, but all the hot air upstairs doesn't get cooled by what little cold air makes it upstairs. With no air return on the 2nd floor to pull the hot air OUT, the cold air sinks and goes down the stairs.

Its the whole putting a cherry v8 engine on a shoddy transmission issue...
Click to expand...

I see you are aware of the most overlooked HVAC problem, good return air is essential to the process.
 
Greebo said:
We considered dual-zoning the single system, but the concern there is that in doing so, we'd end up potentially short-cycling the system because we'd be faking out the 3 ton A/C into thinking it needed to cool the whole house when it only needed to do half, and ditto for the A/C.

We also considered the 2nd system to zone the house, but for 700 sq ft, it's not justifiable, IMO.

Had not considered SDHV - that muddies the water somewhat... ;)
Click to expand...

If you get a compressor that's continuously variable or has multiple speeds, then short-cycling and zoning is a non-issue. Costs a bit more, but is much more efficient. On my old system, the compressor ran at very low speed for significant portions of the day.... that kept the humidity down and didn't run up the bill at all.

For 700 sq ft, you're probably right about the second system, even though you essentially have that now ;) .

SDHV is a great option in older houses.
 
I have a 30 year old Cape, and we redid our heating and cooling 3 years ago. Two Ducts (A and B )for the first floor were built into the slab, with floor registers. Two additional ducts (C and D) were for the upstairs and out to an addition on the back of the house. We were colder than we'd like in the winter and the upstairs was stifling in the summer.

What we ended up with was a Trane high efficiency (80 AFUE on the Furnace, 14 SEER on the AC) system, and we left the downstairs and addition ducting alone. Upstairs, we capped and sealed the existing duct so it only serviced the bathroom. We ran an additional line off the air handler to service the two upstairs bedrooms, and my office (recently created in former garage/workshop space).

We now have four zones. Zone A (using the slab ducts A&B ) covers the main floor of the house. Zone B (using pre-existing ducts C&D) services the addition in the back and the upstairs bathroom. Zone C is the upstairs bedrooms, and Zone D is my office. New returns were added upstairs and in the office too.

While the upstairs walls were open, we replaced the crappy 30 year old insulation with new. We also had our roof redone and they put in a ridge vent, which helps a lot in reducing temps up there.

Net result: House maintains a 20 degree or more difference in the summer, even upstairs. In fact the air conditioning is generally only running in the upstairs and in my office. In the winter, the house is comfy except for the addition, which is due to undersize ductwork and poor insulation (both of which were two expensive to correct at the time). We have a gas fireplace back there which makes up the difference.

Yearly energy costs (natural gas/electric) dropped substantially, probably 30+ percent, and I think the savings will have paid for the work by the time it's 8 years old. We also got a humidifier and electronic air cleaner, both of which really helped with the air quality.

In my opinion, existing duct work, if it's inspected and sealed, is fine (it's just a metal tube/box after all). Just be sure it's big enough for the air you want to move, and take advantage of every opportunity to add insulation while your walls are open.

Don't worry about the computers - normal operating temps for that stuff is -10 to +95 F or a greater range.
 
TMetzinger said:
In my opinion, existing duct work, if it's inspected and sealed, is fine (it's just a metal tube/box after all). Just be sure it's big enough for the air you want to move...
Click to expand...

I agree that old ductwork can be fine as long as it's sized and sealed properly. As to zoning the system, your choice is to balance a single zone system for "normal" conditions (which is normally going to require re-balancing each spring and fall) or set up separate zones for up and down because the upper floor will always require more cooling and less heat. AFaIK with the newer controllers, short cycling isn't normally a problem with such a setup because the overall heat/cooling load will be concentrated on a single floor anyway (top in summer, lower in winter).

And from what you were told by contractor #1 was more about his experience being limited to mostly new construction and him wanting to treat you the same way.
 
#2 actually seems like you'll get a better operating system. We shy away from one or two returns unless we absolutely have to do it that way....it's just too hard to balance the system (you are requiring the contractor to balance the ducting, right?). So long as they can damper the existing ducts that were oversized for convection systems, it should work out better.

3 ton A/C for 1600 Square Feet? That seems oversized. Is that what both contractors recommended based on the heat gain (you did require them to perform heat gain/loss calculations for you, right?).
 
We're looking at a 3 ton 2 stage that would start at 60% (1.6tonish) then go up to full on hot days.
 
Chuck
IMO, go with the best duct system you can. Most problems in renovation/retrofit systems are due to crappy duct work. Also, specify metal duct and not duct board. The duct should be well insulated and vapor barriered as well. I don't have enough info to be more specific, but inadaquate airflow is next to impossible to fix and very hard on heating and cooling systems.
I don't know the winter and summer design temps of Balt. but it's always bad to oversize an AC system. The reason is latent heat which occurs in the form of moisture in the air and must be removed before the air can be significantly cooled. An oversized unit won't do this very well and will short cycle it self to death.
What are the possibilities of two systems in your house? I like the redundancy of an upstairs and downstairs system both with new duct work and separate controls. If one fails, the other will help considerably although not pull an entire load.
I also didn't see what kind of heating system you were going to have, gas, oil, electric resistance, or heat pump. If it's a heat pump, the duct work is more critical than any of the others.
 
We are very strongly leaning towards the all new ductwork at this point.

The furnace, sorry, is forced air natural gas.

The A/C we're looking at would be a 3 ton 2 stage AC which would start at 60% and go up to 100% on really hot days.

Right now I'm leaning towards the Rheem 100k/70k btu furnace (natural gas) 80% efficiency with the 16 SEER 2 stage A/C.

Our 25 yr old furnace which has been working like a champ with the exception of an occasional pilot light blowout -- its a Rheem too. :)
 
If you have a two story house and only one system you definately should go with zoning. You will be happy you did. Around here many two story houses built before the 90's were built with only one system. With the heat and humidity in the south it's downright miserable in the summer due to uneven cooling. I have installed many zone systems in these houses and customers tell me they have a level of comfort that they never thought was possible.

Rheem is pretty good equipment. Bryant/Carrier have good and bad but lately they have been plagued with refrigerant leaks in their R410A systems. Amana is crap. Have a look at Trane before you make your mind up. Keep one thing in mind, the best equipment improperly installed is worse than the worst equipment properly installed. Choose your contractor carefully. I would pick a brand first then go to the distributor and ask them which contractor selling their equipment does the best work. And I don't mean ask the guy working the counter but ask the general manager.
 
Richard O said:
Bryant/Carrier have good and bad but lately they have been plagued with refrigerant leaks in their R410A systems.
Click to expand...

Carrier is crap. 7 year old package unit on the SA house: plate that attached the draft blower rusted/rotted out.... refrigerant leak in the coil.... heat exchanger is nearly rusted out (shop says 'year or two left'). AND Carrier doesn't stock the parts, it took 60 days to get the draft blower plate.

Amana is crap. Have a look at Trane before you make your mind up. Keep one thing in mind, the best equipment improperly installed is worse than the worst equipment properly installed. Choose your contractor carefully. I would pick a brand first then go to the distributor and ask them which contractor selling their equipment does the best work. And I don't mean ask the guy working the counter but ask the general manager.
Click to expand...

I'd actually suggest doing it the other way around. Choose the company that you're going to have servicing the unit over the long term. Choose the unit based on their recommendations, including their ability/willingness to service and the availability of parts. The contractor is much more important to the process than the equipment.
 
wsuffa said:
The contractor is much more important to the process than the equipment.
Click to expand...
I'll agree with that. Most likely a good contractor is going to represent good products. I'm in the business and I can't tell you the times I've been hired to go out and straighten up a hack job. Usually the installing contractor won't return phone calls or the homeowner is fed up with them and doesn't want them back. I wish more people would do their homework before hiring a contractor but far too many people make their decision based on price alone. Georgia is very lax in enforcing codes. There are far too many crooks in this business, at least in Georgia there is.
 
Richard O said:
There are far too many crooks in this business, at least in Georgia there is.
Click to expand...

Amen to that.....
A co-worker just had a big name outfit here in Atlanta come out to do the "thrice yearly" checkup. The tech pulls the capacitor of of the outdoor condenser/compressor motor to "test" it. Slaps it on and skeedaddles.
4 hours later the house is getting warmer fast. Co-worker gets home to find the outdooe unit is starting, runs 5 or 10 minutes, then slooowwwwllllyyy stalls. Then repeats the process. So a call to the contractor. He now sez a new fan motor and assembly is needed. $450.00. And he doesn't have one on the truck, and that'll be $90 for an after hours callout. Next day I go over and look at it. Off to Grainger, got a new motor and capacitor for $76 total, and when re-installing noticed the tech had the compressor side of the cap wired to the fan and vice-versa. A frank conversation with the service manager did straighten out the charges and further they did refund the cost of the motor (which we installed anyway).

At my house a "checkup" 5 years ago the tech told my wife we needed a whole new furnace/air handler, (multiple K$) as ours had a dangerous crack in the fan housing! (the unit was 4 years old at the time) Turned out to be a plastic cover over the pulley shaft. A little JB Weld and it isn't a danger at all.
I'm beginning to think these guys went to the AAMCO Transmission/Just Brakes school of business ethics.
Not a cut at you, Richard. Just my experiences of late. I know there are good, honest HVAC guys out there. I just haven't had any dealing with them yet.
 
I have a client in the AC/Plbg service side, the stories he tells.

From time to time, he gets complaints, most are utter bunk (like the person who called 'em out to charge up their unit, tech told them it was ancient and near death, instructed to charge it anyway; 3 months later, unit fails, demand letter from homeowner's lawyer demanding a new ac unit be installed, gratis).

But occasionally, the call comes in and he tells me, "I got a complaint from a homeowner. investigated it and my tech royally screwed-up, it's all our doing. Call their lawyer and ask them what they want us to do to make it right." And anything in the realm of reasonable, they do with a smile.
 
Well, the installer that I've chosen has glowing reports on ServiceMagic, and one negative report on Angies List. In that negative listing, the home owner sounds somewhat unbelievable, but even so, admits that in the end, my installer came back and took out the equipment and refunded his money.

SO I asked my installer about it, and the installer's story, which certainly seemed credible, was that the guy in question had an unfinished 2nd floor, insisted on the install anyway knowing it wouldn't work right while leaky and uninsulated, then proceeded to run window units on the 1st floor, tinker with the equipment (putting it out of balance and making leaks), etc. and then complain that it didn't work right.

Reading between the lines on both sides, I'm ... reasonably confident that we're making the right choice. :)
 
Chuck, ask for other references.

I bungled our first service call in our new house. Went with someone high in the alphabet who returned our call. While I think the ultimate decision to replace the unit was sound, I don't think my choice of contractor was. I was in a tough place (no A/C, summer heat and humidity, new to the area). Had I been operating normally, I'd have looked around more carefully.

Once I did, I found a smaller local op that REALLY knows customer service. They will come back months later with encyclopedic recall of previous visits (without fancy touchpad computers), and stay until the job is done.

Ask around the neighborhood. It's the only way to be sure. Good luck.
 
You must log in or register to reply here.
Back
Top