trying to decide on new Central A/C unit: SEER rating and +/- Heat pump

[someguy]

There is a lot of information out there and I'm looking for, as much as possible, unbiased information to educate myself before buying new units.  I appreciate any help.

[MrBill]

for the SEER rating generally pick the highest number you can find.

As for the heat pump question, it depends greatly on what your climate is, and what the price of natural gas is (or if you even have natural gas available).  it's pretty hard to predict if a heat pump is smart without more information.  My Electric company advertises that you'll save money with a heat pump, but what they mean is if you have an All Electric home and no natural gas available, then you will heat for less if you use a heat pump.  On the other hand, my gas company suggests if you have a heat pump with gas furnace backup you can save money on energy if you select a higher cut-over temp because in our area it's less expensive to heat with gas than run a heat pump.

I did switch from conventional AC to heat pump this year, primarily because the Heat Pump had a higher SEER for the price paid than the conventional AC.   There was an installation issue tho.  We had conventional AC which has a 2 conductor low voltage control cable between the furnace and the outdoor unit.  The new heat pump required more conductors (5 if i recall, its also 2 stage).  Anyway the path from the indoor unit to the outdoor unit has a finished space in between.  There was literally no way for them to replace the 2 conductor low voltage control cable with a new cable.   They weren't very helpful, and suggested things i would not approve like wire on the outside of the house running a huge difference.  I found a solution for them, but it took them a few extra hours to route the cable.

[tlightne]

What does this have to do with Automation and ISY?????

[someguy]

2 minutes ago, tlightne said:

What does this have to do with Automation and ISY?????

well, this is the coffee shop forum, so I figure we can discuss most anything... 

[TheA2Z]

36 minutes ago, someguy said:

well, this is the coffee shop forum, so I figure we can discuss most anything... 

Well the definition of room is:

Quote

A place to discuss unrelated topics in a casual, friendly atmosphere.
Any "FOR SALE" or "Items Available" posts should be posted here.
Also, please post when items are spoken for so thread can be closed.

As for your question. I live in Georgia.  This past winter temps got down to 7 degrees. As Eyegore from Young Frankenstein would say that is "Abinormal" for us.   To you northerners you are thinking, "Ah, that is T-Shirt weather"

Many of the homes in our area that had heat pumps ended up with frozen ruptured pipes as the heat pumps couldnt keep up with the cold.  Probably not designed for that low a temp though.

My view is as more folks move off Nat Gas to heat pump and other electric devices, it will get cheaper.  I am staying with it for heating, stove, hot water, and dryer.  At least until the Govt bans it and you cant buy anymore.

As for Seer, just had that conversation with an HVAC guy.  Really came down to 1) Estimated savings of higher SEER per month.  2) How long were you planning on being in house (Payback time) and 3) how much more the higher SEER device is going to cost.  Then you just run the numbers and make the call.

[tazman]

Unfortunately I don't have any good advice for you but I'm struggling with the same thoughts. I'm in Arizona so I know the heat pump will do well but I would like to keep the gas furnace and run it at night when the solar is not producing. An HVAC guy who was giving me a price told me it's not worth the money to get a high seer unit since I have solar to offset the electric cost. I work as an electrician for a school district and the HVAC guys there don't like the inverter unit's because they say they have more failures but I think they don't like that they are more complicated and they don't want to deal with them on their side jobs. 

[MrBill]

3 hours ago, tlightne said:

What does this have to do with Automation and ISY?????

 

3 hours ago, someguy said:

well, this is the coffee shop forum, so I figure we can discuss most anything... 

Correct!

[IndyMike]

On 7/22/2023 at 8:02 AM, someguy said:

There is a lot of information out there and I'm looking for, as much as possible, unbiased information to educate myself before buying new units.  I appreciate any help.

Hello someguy,

It's a bit difficult to provide information/recommendations without understanding your goals - comfort, efficiency, low out of pocket, lifecycle costs, reliability.

Beyond that, not knowing your home construction (frame, block, 1 story/2 story) and insulation make it tough. 

For reference, I recently updated my 23 years old Armstrong 2zone HVAC system with a American Standard Gas Furnace + A/C Variable speed compressor.  For reference, my house is 3500 sq feet (walkout), 2 story in northern Indiana.  I have 6 inch stud walls with foam/batt insulation.   My old A/C compressor was R22 and was no longer economically viable.

The new system with the variable speed blower is saving me ~$45 a month in ELECTRIC costs.  Gas savings is nil.  The variable speed compressor (essentially a heat pump) is saving ~$80 - $100 a month on electric (seer 19 vs seer 10 on it's last legs).    With the variable speed blower, multistage heat, and variable speed compressor, things are also far more comfortable and drier (much better de-humidification).  That's the good news.  That bad news is that at $19K, the system won't be paying for itself unless gas/electric prices go through the roof.  

I ran numbers for Kansas City MO. (not sure if you're in KA, or MO) and can see that you are pretty comparable in winter but warmer in summer than I am.  Cooling degree days (CDD) and  Heating degree days (HDD) are shown for our locations in the table below.  KSBN is my location and KMKC is your location. 

Comparing Gas/Electric.  Your gas rates are listed at $16.99/1k Ft^3 wile mine are at $9.91/1k Ft^3 (71% higher)

Electric is listed at 10.93¢/kWh at your location vs 8.5¢/kWh at mine (28% higher).

While it is true that older heat pumps were incapable of operating in cold temperatures, they have improved a lot.  Efficiency does drop off below freezing since the pumps must enter a defrost mode, but they are generally rated to temps below zero.   Given those numbers, I still elected to go with a gas furnace.  Your winter temps are similar to mine, but your gas prices are 70% higher.  Not sure if that changes the calculus.  You will likely need some sort of backup heat for the -20 days.

There is a lot of good weather information out there for computing efficiencies.  I used the degreedays.net site.

I also have a lot of information on HVAC manufacturers, ratings, system comparisons and the likes.  Not sure what you are looking for.

Here's a decent review/comparison site that runs through some of the options: https://highperformancehvac.com/

 

At the end of the day, when you think you've decided on the type of system you want, invest a LOT of time in picking an Installer.  A good installer can overcome a lot of system/home issues.  With a bad installer, the best system will be problematic.

I spent 2 months getting estimates from 7 installers across 4 different brands.  I chose an installer that I trusted and that didn't simply parrot the company propaganda (he was also the owner).  Not the cheapest, but far from the most expensive.

You may also want to wait until fall when many manufacturers run specials on their HVAC.  It's tough sinking a lot of money into a Air conditional without being able to evaluate it (until next year), but that's where your trust in your installer comes in.

Best of luck - let us know if you need specific information.

 

	KSBN	KMKC	KSBN	KMKC
	CDD 65	CDD 65	HDD 65	HDD 65
Jan	0	0	1214.2	1027.9
Feb	0	0.8	1066.5	938
Mar	1.5	9.9	832	574.2
Apr	12.5	48.9	574.9	353.1
May	101.4	174.3	223.4	103.1
Jun	225.9	422.3	44.2	4.9
Jul	305.5	500.1	13.3	0.1
Aug	263.3	446.9	24.5	1.2
Sep	142.7	292.2	96.3	38.6
Oct	33.8	65.6	402.4	314.1
Nov	4.8	8.4	767.7	630.4
Dec	0	1.4	973.3	846.5

Edited July 23, 2023 by IndyMike

[vbPhil]

9 hours ago, IndyMike said:

I used the degreedays.net site.

Thanks for the cool link! I’m replacing a gas furnace and your discussion is fueling my analysis. I’m cooling with a swamp cooler which is great on days below 15% humidity. Albuquerque NM

[IndyMike]

On 7/23/2023 at 9:21 PM, vbPhil said:

Thanks for the cool link! I’m replacing a gas furnace and your discussion is fueling my analysis. I’m cooling with a swamp cooler which is great on days below 15% humidity. Albuquerque NM

Hello vbPhil,

Your location is pretty much ideal for a swamp cooler.  Very efficient and low cost for your low humidity.  I have many work friends in the Tucson area that use them.  They do start to cry when humidity hits 25%.

Your choice of a gas furnace makes sense as well.  If you are interested in checking out Heat Pumps, there are a number of Gas VS Heat Pump calculators available (https://www.pickhvac.com/hvac/furnace-vs-heat-pump-cost/).  These are simple calculators, but they do take into account regional climate and electric/gas costs.  A heat pump will be more expensive to install and maintain.  Life expectancy is also not as good - through in your area it will probably be under utilized.  It can save money on heating depending on your gas/electric costs.  While it can also cool, your swamp cooler is already very efficient.  Not sure there is anything to be gained there.

Happy researching

[BigMojo]

@vbPhil you might find this helpful:

https://products.z-wavealliance.org/regions/2/categories/10/products

I would caution that whichever direction you go, you should verify that the thermostat will indeed meet your use case needs.

I fell into the Trane/American Standard zWave tstat trap myself with the XL1050 stat. Sure it’s zwave certified, has what appears to be the correct command classes but…

Other than static controller functions, none of the system controls or parameters are exposed via zWave rendering automation impossible without an Asairhome/Nexia cloud subscription.  It is zWave but crippled to drive revenue to their cloud service.

I’m running 12 tons on 3 systems (2 fully variable, 1 std), great equipment, huge run cost savings but a giant disappointment as far as automation capabilities with or without their cloud service.

[Hoosier Daddy]

FWIW, I wouldn’t consider a heat pump in Kansas City. They need to switch to aux heat at around 15F, and put out uncomfortably cool air even when it’s not that cold outside. I’m in Indianapolis and have used heat pumps, gas with standard a/c, and hybrid systems (gas combined with a heat pump). I have 2 systems, one up and one down.

For me, the flexibility of hybrid where I could change the aux heat cut-in temperature depending on gas and electric prices sounded great but wasn’t worth the extra cost of a heat pump. Upstairs, I switched from a heat pump only (with resistance aux heat $$$) to gas heat and it made the upstairs comfortable last winter for the first time in 31 years. A heat pump will never put out air that feels warm in this climate and I find that not worth maybe saving a few bucks.

Best kept secret in HVAC is AeroSeal. Night & Day difference in air flow and comfort, especially upstairs where my ducting is in an attic. It stops leakage that was leaving my building envelope up there.

[someguy]

3 hours ago, Hoosier Daddy said:

Best kept secret in HVAC is AeroSeal. Night & Day difference in air flow and comfort, especially upstairs where my ducting is in an attic. It stops leakage that was leaving my building envelope up there.

do you work for AeroSeal?  I'm curious because of the "best kept secret" sounds like a sales pitch. 

the system I was considering was one that uses the heat pump for temperatures from roughly 30 degrees to 70 degrees outside and a gas furnace for colder than 30 degrees.  but because of what i've learned about heat pumps here and elsewhere, it doesnt seem worth the extra money for three reasons: 

1) the heat pump costs more (but I'd get most of this back in a tax credit.

2)I am told that heat pumps only last 10-15 years whereas A/C units last 15-10 years (mostly because the heat pump is running more than the A/C)

3) heat pumps (supposedly) cost more to repair.

[Hoosier Daddy]

Haha, no involvement with that company at all. My neighbor was an executive at Carrier Corp and told me about them years ago. I finally decided to spend the cash last year and was blown away by the improvement. There are several rooms where I can now feel air circulation for the first time. That’s how much loss I had. I’ve never seen them advertise or reviewed. I’d be interested if anyone else reading this has heard of them.

As I wrote earlier, my attic supply and return ducts were so poorly installed that the aeroseal was a huge difference maker. A decent installation probably wouldn’t have the dramatic result that I got.

I think your assessment of the heat pump with gas aux is spot on. I had that configuration for about 12 years. It worked OK and I could have kept it going but I needed a new system upstairs and had a lot of other work done so they gave me a great price to replace the downstairs unit too with gas and regular a/c.


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[apostolakisl]

I haven't read all of these posts but I have maintained some 25 year old systems, keeping them tuned up great and have installed multiple new systems.  There are lots of options depending on your needs and how much money you want to spend.  The cost of your electricity is important when you look at it from an roi point of view.  Generally, the highest end equipment does not make financial sense.  Usually the upper mid grade stuff is best at that.

1) Builder grade heat pump.  Cheapest, lowest allowable SEER.  Single stage so you have to size it just right and it won't have flexibility for running nicely at the extremes.  Parts will probably be generic and cheaper to repair.  For example, the blower motor will like be a single speed device vs a variable speed.  Cost for variable speed will be maybe $1000 to replace vs $200. 

2)Upgraded heat pump systems.  I feel like a 2 stage unit is best for the money.  With 2 stage you can put in a larger system to handle worst case scenarios (you have 20 people in your house on a 100 degree day), but yet still run efficiently without cycling on normal days.  Most of these now can run efficiently down to single digit temps on heat mode.  You will now have variable speed fans and will have to endure the high cost of replacing these ECM motors should you have failure.  ECM (electronically commutated motor) circuit board may fail and then the whole motor needs to be pitched.  My outdoor unit fan motor on one unit failed and I think it was like $1200 (that was with me replacing it).  Really doubt it saved me $1000 in electricity before burning out.  It is a Carrier Infinity and was about 10 years old.

3) Super upgraded heat pump.  Now you have a continuously variable compressor and fans.  These are designed to run constantly just hard enough to maintain temp.  They will tend to be very comfortable because there are no swings in temp.  Of course your insulation and windows will play a huge role in this.  Good insulation and windows can make most systems very comfortable.  These are pricey and very proprietary.  Hard and expensive to service.   They also tend to have the flat vertical outdoor condensing unit which tend to be very quiet and smaller.

4) Geothermal.  Can be great.  It really is a cost thing.  If you have a lake in your backyard or shallow well or plenty of yard that you can easily trench, then it may be cost effective.  The condensing unit is typically inside and they are very quiet.  They can also make hot water.  Usually need special people to service them.  Theoretically with the condensing unit inside in a nice climate controlled space you would say it should last longer . . . theoretically.

5) Mini-split style.  There are versions of these where you have as few as a single outdoor condensing unit that feeds freon directly to multiple air handlers throughout your home that hang on the wall or are built into the ceiling.  Tend to be very efficient and you can have great control of each room.  These can be nice when retro-fitting an old home that never had an HVAC system since you only need to plumb the small copper lines and not big air vents.  Also used in new construction on high end stuff.  Rarely a retrofit to a house that already has forced air.

 

Other thoughts. 

1) Many of the fancy units will have proprietary thermostats and, being a HA forum and all, you may find issue with since they may not seamlessly integrate.  

2) FIX YOUR INSULATION!!!  I highly recommend this.  Spray foam insulation on the bottom of your roof deck which will seal in your attic.  You will dramatically cut air losses through all the holes in your ceiling to attic.  If your air handler and ducts are in the attic, you will no longer be losing air to the "outside".  Also, your losses across the walls of your ducts won't matter any more.  Consider that in the summer your attic might be 140 or 150 degrees and inside your ducts you have 45 degree air.  You are trying to hold a 100 degree delta across that thinly insulated duct wall.  Similar backwards in winter.  Plus now your attic is a reasonable place to be.  I keep my server in my attic and have lots of storage.  Temp is only about 10 degrees different from inside the house.  Also helps to turn away rodents when they don't "smell" the attic from outside.  One of my rental properties had issues with the hvac not maintaining temp on hot days.  The hvac system was old but working correctly.  I could have spent a bunch of money just powering through with a bigger unit, but instead insulated the attic roof deck.  That was 8 years ago, still using the same old hvac that is now 30 years old.  Cost half of what a new hvac would have cost.

[BigMojo]

You might look for a local provider to perform a Blower Door Test.  There's two basic flavors, Whole House and Differential.

The basic concept is:

Seal off the HVAC ducts (notoriously leaky as mentioned above)
An airtight fabric "door" with a big fan is hung in a doorway, window or whatever penetration you can use
Using a manometer (measures differential pressure between two points) tune the fan speed to de/pressurize the space to 50 pascals.
This will give you the ability to calculate the industry standardized ACH (air changes per hour) value which is the definition of how "leaky" a space is.

This test is actually mandated on new home construction in many jurisdictions so it's likely you have vendors nearby.

All credit on this to Matt Risinger of the Build Channel (highly recommend)

Build Channel - Blower Door Intro

[apostolakisl]

1 hour ago, BigMojo said:

You might look for a local provider to perform a Blower Door Test.  There's two basic flavors, Whole House and Differential.

The basic concept is:

Seal off the HVAC ducts (notoriously leaky as mentioned above)
An airtight fabric "door" with a big fan is hung in a doorway, window or whatever penetration you can use
Using a manometer (measures differential pressure between two points) tune the fan speed to de/pressurize the space to 50 pascals.
This will give you the ability to calculate the industry standardized ACH (air changes per hour) value which is the definition of how "leaky" a space is.

This test is actually mandated on new home construction in many jurisdictions so it's likely you have vendors nearby.

All credit on this to Matt Risinger of the Build Channel (highly recommend)

Build Channel - Blower Door Intro

Blower door test on an older home will probably be abysmal!  But likely will point you to the worst culprits as well as some low hanging fruit corrections.  You can use a thermal flir camera if you do it on a cold day and see where some of your worst leaks are.  Losses through the attic tend to be some of the biggest especially during heating season when air wants to rise.  I did not do a blower test on my house 15 years ago when I built it, but I did take advantage of the crazy cold we had 2 winters ago and took my flir camera to the attic and discovered a pretty large hole in the spray foam.  They totally missed between two joists where it meets the ceiling in one spot.  

Spray foaming the roof deck is also very helpful even if your house doesn't leak.  I took a flir reading on my roof on a 100 degree day with the sun beating down on my roof both of the roof from the outside, and then from the inside.  The reading on the outside surface of the roof was 145, the reading on the same spot on the inside was 88 and my attic air was 80.  I do not have vents in my attic, but I also do not have insulation between the house and the attic, so some seeps through . . . about just the right amount really in my opinion.  Climate controlled enough to make it useful storage space and to keep electronics safely operating.  I didn't measure the air at the peak of the gables, likely hotter up there, but I don't store things up there.

In Summary, better insulation will make your house more comfortable, save you money in HVAC electrical use, and also mean you can downsize your HVAC and save money there too.  Depending on how bad things are to start with, it very well may be that it doesn't hardly cost any more to do insulation plus smaller hvac system.

Edited August 10, 2023 by apostolakisl