[A_DAB_will_do]

My home currently has a Bard oil fired furnace and Goodman forced air central AC system. The Bard furnace is about 25 years old and the AC system is 20 years old.

I just had a tech from a local Trane dealer out to give the system a preventative maintenance checkout prior to the start of summer in a couple months. During his visit we discussed a new HVAC system.

The furnace works well for it's age. The blower motor needs a new capactitor; a $20 part that I will replace if needed. The AC system is 2.5 tonnes and the outdoor compressor motor(not the fan motor) makes a noticeable bearing noise in operation.

The house is 2800 square feet, 1.5 stories with lots of windows, and a finished basement. We have to operate a portable dehumidifier in the basement during the warm weather months. We also have to install a window AC unit (10K BTU) in the upstairs bedroom because the current system can't keep the upstairs cool if the outside temp is over 75F.

If the outdoor temp is over 90F, then the system won't hold temperature below 78F indoors in any part of the hourse. If I set the thermostat to 76 or less when it's really hot outside, the coil freezes because the compressor never cycles off. So in the peak of summer we've kept the thermostat at 78-90F during the afternoon. After sunset we can cool the house down to 76 or so.

It's $10K for a new 16 SEER Trane heat pump and oil fired backup furnace. 5 years zero percent financing. We don't have natural gas service available, propane is $$$, and I just spent $1000 to replace the outside oil tank because the old one sprung a leak last summer.

Am I smart to replace the current system before it fails? Or should I continue with what I have? I have to buy a new window AC unit($300) for upstairs if I keep what we have.

I'm trying to get a feeling for how much money a new 3.5-4 ton heat pump is going to save me over the current 10 SEER AC unit. Our electric bill runs $350 per month in the summer. But we have electric hot water and clothes dryer adding to the bill...

Any advice from others who have made this upgrade, or professionals who have seen the before and after from this type of upgrade, is welcome.

 

[SeniorSitizen]

Quote: If I set the thermostat to 76 or less when it's really hot outside, the coil freezes because the compressor never cycles off.

Mine doesn't and yours should not.

 

[A_DAB_will_do]

Quote: If I set the thermostat to 76 or less when it's really hot outside, the coil freezes because the compressor never cycles off.

Mine doesn't and yours should not.

Oh, I know it shouldn't. That, and the window AC the the previous owner suggested we use, were good clues that the current system is too small.

 

[Technow]

"too small" systems NEVER freeze. Its a different issue.

 

[beenthere]

Your 2.5 ton A/C probably is a bit small. But that isn't why it freezes when you set the thermostat to 76 or lower. Not enough air flow is the problem. And in reality, you may have a dirty evap coil causing much of your cooling issues.

Can you post some picks of your duct work at the furnace, the trunk line, and the supply runs to some of the supply registers. Along with listing the size of the ducts.

Reason I ask for this is because if your duct system is under sized for 2.5 tons. You won't be able to set the thermostat lower then 80 with a 3.5 ton. And I don't want to see you waste money on a new system that performs worse then your current/old system.

 

[user_12345a]

If you have a reasonable, stable electricity rate, you should ditch the oil and put in a straight heatpump.

Lower maintenance and the heatpump can supply heat when it can't keep up on it's own. With oil backup the heatpump has to be shut down when it can still provide heat.

2.5 or 3 ton heatpump in 2800 sq ft may only keep up down to 30-40f. Duct modifications permitting, would have it sized in the 3 to 4 ton range - can get 2-stage to not be terribly oversized for cooling.

 

[user_12345a]

Oh, I know it shouldn't. That, and the window AC the the previous owner suggested we use, were good clues that the current system is too small.

The current system is probably not delivering its rated capacity based on your description.

Bad ductwork in an attic, incorrect charge, dirty coils, etc will kill capacity.

Upsizing due to poor performance is a mistake; in fact if the air ducts are undersized for the 2.5 ton, the bigger unit will have a worse problem.

I'm sure the 2.5 may be a little small; however, not keeping up when it's over 75 indicates that something's up.

You need a load calculation done especially for a heatpump.

 

[roughneck]

Don't be fooled into thinking the system is dramatically undersized when a duct issue is causing your problems. Your new system will perform worse then the existing one with inadequate duct. Bigger tonnage isn't better.
Be sure to have a manual j performed for equipment sizing. Don't guess.
Your unit has a problem if it's freezing up.

 

[A_DAB_will_do]

I'll snap some photos from the mechanical room and post them tomorrow. in the meantime, here is some information on duct sizing that the contractor put into the quotation for the system. These are taken at the location the furnace and blower connect to the main trunk lines for the house.

Supply ductwork is 20.5" wide 22" deep and 39.5" tall

Return ductwork 22.25" wide by 16.25" deep and 33"

There were photos of the system in the quote too. But they're too grainy and difficult to extract. I'll add some new photos tomorrow.

For now, here's what I can tell you in addition to the info above. There is a return duct in most rooms on the first floor. Most are approximately 8x12" at the grate; and all are in the floor. Supply ducts for the first floor are 4x10" registers and in the floor as well. The ductwork I've seen in the basement ceiling feeding the first floor looks like 6" round for the most part.

The second floor bedroom has a very small(6x8"?) return duct in the floor. The supply upstairs is a single 8" round insulated flex duct that feeds 3 knee wall mounted registers in series. That round ductwork is fed by a rectangular section of ductwork that passes up from the main supply in the basement through a first floor closet. The ductwork behind the kneewall is buried in blown-in cellulose insulation, but not completely covered

I've looked at the evaporator coil and it's clean. The blower motor squirrel cage fan is clean. I've cleaned the radiator fins on the outside unit and trimmed back all the undergrowth at least 3 ft away from the outside unit. It's been this way since the first summer we've moved in. I've had all the equipment inspected and the refrigerant charge checked every summer for the past 4 years.

 

[A_DAB_will_do]

My wife doesn't really care for the tepid feel of heat from a heat pump system. Neither do I. The oil furnace would be a backup for when outside temps drop below 34F.

We do not have stable electric supply; not enough that I trust it during storms, heavy snow, high winds etc. The oil furnace will operate from the power provided by a 10KW welder/generator I own. The heat pump with electric strip backup will not.

Call me an old fashioned paranoid, but I also have a wood burning insert in one of our fireplaces; just in case. Wood, at least for the moment happens to be cheaper than home heating oil or electricity....

If you have a reasonable, stable electricity rate, you should ditch the oil and put in a straight heatpump.

Lower maintenance and the heatpump can supply heat when it can't keep up on it's own. With oil backup the heatpump has to be shut down when it can still provide heat.

2.5 or 3 ton heatpump in 2800 sq ft may only keep up down to 30-40f. Duct modifications permitting, would have it sized in the 3 to 4 ton range - can get 2-stage to not be terribly oversized for cooling.

 

[beenthere]

The evap coil is clean on both sides of it? Or just the top. often its hard to see the side that the air enters.

A single 8" for 3 rooms upstairs is too small. Unless all 3 rooms are average size bathrooms.

 

[user_12345a]

We do not have stable electric supply; not enough that I trust it during storms, heavy snow, high winds etc. The oil furnace will operate from the power provided by a 10KW welder/generator I own. The heat pump with electric strip backup will not.

Call me an old fashioned paranoid, but I also have a wood burning insert in one of our fireplaces; just in case. Wood, at least for the moment happens to be cheaper than home heating oil or electricity....

You aren't paranoid, you're smart to have multiple sources of heat.

Most aren't - power goes out and you lose everything, even the gas fired appliances. Most people won't spend money on emergency prep - they just assume that the grid will always be there.

It's getting worse and worse with the use of power vent water heaters, electric stoves.

 

[DOUG1111]

IMO - Best to buy when you don't need it right away. SEER different areas & prices elect & equipment install prices. from a 10 SEER to a 14 Seer in my area app $600.00 in savings on elect per year ($50.00 a month). In my area central Fl - the new installs from 10 SEER to 14 SEER after the HO gets a lower elect bill - most lower target temp after they pay the first elect bill. Elect Co = set temp @ 78° and have average bill= for every degree below 78° will rise your elect bill 8% to 10% for every 1 degree lower than 78°- If installer wants $1100.00 more for 16 SEER VS 14 SEER equipment will not last long enough to get to the break even $$$ point. The new systems do not last as long as the older systems. Also most of the high SEER units need major duct mods (more $$$) I am NOT a fan of angie but good read http://www.angieslist.com/articles/difference-between-best-hvac-brands.htm also check out www.loadcalc.net - Hope this helps!! Best of luck!!

 

[A_DAB_will_do]

The evap coil is clean on both sides of it? Or just the top. often its hard to see the side that the air enters.

A single 8" for 3 rooms upstairs is too small. Unless all 3 rooms are average size bathrooms.

Oops, a slight mis-understanding here. The upstairs is one large open room with 3 supply vents along one wall; about 6' apart. The house is a cape cod with a bedroom in the 1/2 story attic. The space is about 450 sq ft.

 

[A_DAB_will_do]

Lo res pictures of the furnace and system. Will shoot some better shots tonight if these don't suffice.

 

[A_DAB_will_do]

Note, we don't use the fancy electrostatic air cleaner shown in the photos. Just an ordinary 1" 20x25 filter made by 3M; about $15 at the big box store. I replace it every 3 months. It slides into the bottom of the electrostatic filter housing and fits snug.

 

[A_DAB_will_do]

Thanks for the angie's list article. Thanks also for the answer to my original question. The quote I have from the HVAC contractor is for an (up to)18 SEER heat pump at the high end, and a 16 SEER AC unit for the economical option. Both would be paired with an oil fired furnace for heat(emergency backup in the case of the heat pump).

The price differential in the quote is about $1400.

BBB and local reviews on google seem to give high marks to the contractor I'm talking to. I have one other quote from a couple years ago that is substantially higher.

IMO - Best to buy when you don't need it right away. SEER different areas & prices elect & equipment install prices. from a 10 SEER to a 14 Seer in my area app $600.00 in savings on elect per year ($50.00 a month). In my area central Fl - the new installs from 10 SEER to 14 SEER after the HO gets a lower elect bill - most lower target temp after they pay the first elect bill. Elect Co = set temp @ 78° and have average bill= for every degree below 78° will rise your elect bill 8% to 10% for every 1 degree lower than 78°- If installer wants $1100.00 more for 16 SEER VS 14 SEER equipment will not last long enough to get to the break even $$$ point. The new systems do not last as long as the older systems. Also most of the high SEER units need major duct mods (more $$$) I am NOT a fan of angie but good read http://www.angieslist.com/articles/difference-between-best-hvac-brands.htm also check out www.loadcalc.net - Hope this helps!! Best of luck!!

 

[roughneck]

Your first issue is likely with the $15 1" pleated 3M filter. Don't use those, instead use the cheap fiberglass filters. Those 3M filters are horribly restrictive, and block airflow.

 

[user_12345a]

One of your problems could be is that the evaporator coil is too close to the furnace.

The heat exchanger in an oil furnace is a large drum and the sides of the coil are blocked off by the drain pan. There's little airflow in the middle of the coil when there needs to be unless there's sufficient space.

I'm betting this a/c is crippled by low airflow. A good quality tech can measure airflow, static pressure and tell you where the problem actually is.

When you get a new system, make sure they put the coil high in the plenum. New oil furnace has to have a large enough blower - minimum would be 1200 cfm for a 2.5 or 3 ton heatpump.

The 1" pleat filter isn't great either but shouldn't be enough to make a 2.5 ton a/c freeze up alone. 3.5+? sure.

 

[user_12345a]

IMO - Best to buy when you don't need it right away. SEER different areas & prices elect & equipment install prices. from a 10 SEER to a 14 Seer in my area app $600.00 in savings on elect per year ($50.00 a month). In my area central Fl - the new installs from 10 SEER to 14 SEER after the HO gets a lower elect bill - most lower target temp after they pay the first elect bill. Elect Co = set temp @ 78° and have average bill= for every degree below 78° will rise your elect bill 8% to 10% for every 1 degree lower than 78°- If installer wants $1100.00 more for 16 SEER VS 14 SEER equipment will not last long enough to get to the break even $$$ point. The new systems do not last as long as the older systems. Also most of the high SEER units need major duct mods (more $$$) I am NOT a fan of angie but good read http://www.angieslist.com/articles/difference-between-best-hvac-brands.htm also check out www.loadcalc.net - Hope this helps!! Best of luck!!

16+ SEER is never worth it imo.

Get a 14 paired with an ecm motor -> 15 seer/12 eer, 9 hspf, proper airflow, proper charge -> good to go.

CFM is the same - no duct mods aside from fitting the bigger coil in there.

Temperature setting preference will depend on climate.

If it's 90+f a lot and humid, 78 is okay. In a cooler climate 78 is hot and the machine won't run enough to remove moisture. Also people are more acclimatized.

Same thing in the south - I'm sure you guys wouldn't dream of setting the heat to 66 or 68f but when it's below freezing most of the winter, it's plenty warm.