Time to replace HVAC - thoughts on options?

[stephenson]

Hi All,

So, been in house a year - knew HVAC was original - 20 yrs old, so obviously time for planning for replacement.

Location is Pensacola, FL ... hot summers and sometimes cold winters.

Current system is 10 SEER for cooling ... minimum replacement is 14 SEER cooling and around 9 for heat pump mode. Was gonna go this direction, but there are options:

- two speed, multi, or variable speed compressor vs single speed
- multi-speed fan unit (air handler) vs single
- ground source (geothermal) loop vs single
- marketed brands like Carrier vs lower cost, easy to repair brands like Ruud

Thoughts?

 

[FlaGator]

Hi All,

So, been in house a year - knew HVAC was original - 20 yrs old, so obviously time for planning for replacement.

Location is Pensacola, FL ... hot summers and sometimes cold winters.

Current system is 10 SEER for cooling ... minimum replacement is 14 SEER cooling and around 9 for heat pump mode. Was gonna go this direction, but there are options:

- two speed, multi, or variable speed compressor vs single speed
- multi-speed fan unit (air handler) vs single
- ground source (geothermal) loop vs single
- marketed brands like Carrier vs lower cost, easy to repair brands like Ruud

Thoughts?

Too many choices for me to consider......
Replaced my 20+ year old package unit when I lived in SoFla with a SEER 14 unit and saw electric bills drop by >30%.

Now living near you and haven't found the AC demand as high as I did down south. My highest electric bill in the last 2 years was with the cold weather last month. Expect this month's to be similar.

If I was in your shoes, I would go with the highest SEER unit (considering how long you expect to be in the house) from an installer you have reason to trust. Worked for me down south.

 

[Bamaman]

You don't say what type of unit. Natural gas furnace? Size of house? I assume it is a one storh house? Are the trunk lines and cold air returns properly sized or will you need some sheet metal work?

I have a lake house with 3 bedrooms upstairs and a greatroom/kitchen downstairs. Our premium Trane heat pump has been no better than lesser new brands. When it's life is up, I am going back with a minimalist unit with 3 heads upstairs and a separate minisplit for downstairs. You see them all over the world and they are twice as efficient as forced air systems.

 

[RobbieB]

He said he had a heat pump.

 

[travelover]

This has been discussed a number of times here - a site search will turn up previous conversations. It is unlikely that a ground loop system is cost effective unless you live near a lake or can install the loop yourself. Be sure to check with your local utility to see if they have any rebates for specific types of equipment.

 

[Senator]

Check out the cost of ordering and installing it yourself. You will find a unit that will be MUCH cheaper than any installers price, and save thousands.

Then, you can get all the options as they are only a few hundred more.

 

[Texas Proud]

I have two story.... got a variable with zone (upstairs and downstairs)... I had converted my old system to zoned and it made a huge difference... now the upstairs was cool in summer and downstairs warm in winter without the other being way too hot or too cold...


The rebate made a big difference... the cheapest would have been to just replace my outside AC unit but I was wanting a bit more comfort... I was going two stage but when they quoted me the variable it was not much more since the rebate was not quite double....

IMO, being in a place that has very hot summers but milder spring and fall the two stage or variable is the way to go...

 

[LOL!]

We have two separate HVAC setups, one for each floor of the house. We just replaced a 25-year-old gas furnace with a similar model. The old one had not worked for the last 2 winters, but the other floor of the house kept us warm enough.

We will replace the other 25-year-old unit and the AC, too, in a month or so. Original ACs were 13 SEER, so new ones will be at least that.

Our original systems were decent, so we just replaced with current models of the same systems. Cost was about $2500 for new furnace, so I am not sure about saving "thousands" because ours would be practically free if we knocked off $2000 in price. One could look up online the cost of the parts easily enough, too. We had American Standard / Trane and the new ones are American Standard.

We are not talking about changing ductwork, thermostats, or anything other than the heating unit. They are practically drop-in replacements for one's existing setup. The same will happen with our AC. Our thermostats were state-of-the-art in 1993 and seem to be state-of-art still today except for I cannot call them up on my cell phone and talk to them.

Lots of folks will talk about Manual J load calculation, but we didn't worry about it since what we had worked and got the same thing. We didn't get a variable fan or anything special either. The old fan was quiet and the new system is even quieter.

Our gas and electricity bills are about $1350 a year in the hot & humid Houston area for a 3100+ sq ft 4 br 3.5 ba McMansion which I don't think is bad at all, so we didn't need any special HVAC upgrades and didn't want to pay for them. I've seen some people say their utility bill dropped by more than $100 a month, but I don't see that happening for us no matter how fancy an HVAC is. Our home and ductwork are well-insulated already.

So it seems I'm different from Texas Proud when it comes to this. No variable fan, no two-stage. But since we have two separate units, we have redundancy and comfort.

Edit to add: I can estimate the cost of our AC electricity use by comparing summer and winter bills. Base rates come from looking at the electric bills in winter and the base cost of our furnace gas use by looking at our gas bills in the summer. Example: Last 12 months of gas cost $522.23 while minimum monthly gas bill is about $24. So $522.23 - (12 * $24) is $234.23 to heat the house in the past 12 months. A similar calculation for AC gives $424.44 to cool the house for the year. Water bill for the year is about $900 with a lawn irrigation system.

 

[target2019]

We went with Rheem/Ruud, two systems, kinda like LOL! Our furnaces were over 40 years old. Yes, I am slow moving forward.

Did not go with high efficiency furnace (we went 80%), but you may benefit from that.
16 SEER (I think)
variable speed furnace motor
ECONET thermostats

2-stage AC is good for humidity, if I remember correctly. We did not need that.

Overall, our bills dropped by 25-50%.

Our gas utility compares us to 100 efficient homes within 1 mile, and we are always on track with those owners.

 

[LOL!]

Did not go with high efficiency furnace (we went 80%), but you may benefit from that.

I think 80% is the lowest legally allowed and such a furnace is still called "high efficiency" by all the manufacturers. After all, no manufacturer would ever call their furnace "low efficiency." Our gas furnaces are 80%, too.

 

[target2019]

I think 80% is the lowest legally allowed and such a furnace is still called "high efficiency" by all the manufacturers. After all, no manufacturer would ever call their furnace "low efficiency." Our gas furnaces are 80%, too.

I call em "just-good-enough."

Even though the contractors said they could do high-efficiency, I found that salespeople really had no idea what was required, like installing additional venting. I took a hard look at my situation, and realized it would be very difficult to achieve all the venting requirements.

Also should have on my list:
- replace the line set

Some contractors insisted the old set would be good enough, when it wasn't. Contractor who got the job was knowledgeable, and had enough experience to know that some parts of the job could be difficult, so we discussed, and made sure it was part of the final price.

 

[sdtech]

We went to a variable speed fan on a high end unit. Really like how quiet the system comes on and turns off.

 

[CRLLS]

Check for Electric co. rebates. We replaced the A/C last year. 16 SEER qualified for rebates. The 14 SEER did not. We installed the 16 SEER for about $50 more than the 14. I know you are talking about heat pumps, but you may find close to the same deal where you are.

 

[stephenson]

Thanks, All!

The house is a smallish single floor 2200 SF, but cooling load is pretty high in the Florida panhandle - heating load can also be surprisingly high during cold years. House is pretty tight and built with relatively modern building techniques from 1997.

One major question - how large should the cooling solution be (in heat pumps, normally size for cooling load and use backup gas or electric).

Two secondary questions - single speed compressor or multi/variable, and single speed inside fan or multi/variable.

I don't mind paying for additional efficiency if it lowers bills enough to pay for itself over 5 yrs or so, or for substantive additional comfort (assuming this is possible given normal ops). I do think controlling moisture in the house is important - one reason for the different compressor and fan speeds, but many articles on experiences from folks have not always shown this to be the case.

BTW - my understanding is that 80% gas furnace is NOT considered high efficiency - the biggest difference is whether of not the furnace pulls out more heat with better heat exchangers - and, since this condenses moisture, it means they must be stainless steel - hence, more expensive - a positive however is that the exhaust can be handled with schedule 40 PVC pipe.

 

[W2R]

I have to admit that when I replaced my HVAC, I took a different approach. I called a local HVAC service that was unusually highly recommended by people who use that service. (I listen when people that I talk to IRL say they had good work done by local tradesmen, and keep notes on my laptop about who did it and their opinions). The HVAC pros recommended the size and so on, based on the layout of my house, and I told them to go ahead with the model they recommended. They replaced my entire HVAC system except for the ductwork (which they determined was still OK) in September of 2016.

They decided on a $7,200 (total) Trane system and I have been deleriously happy with it ever since. It was a big hit to the budget but now I know my HVAC will hold up for years to come. Meanwhile my bills are lower, so that's a nice minor consolation.

 

[RobbieB]

Seven grand, my magic number too.

Replaced mine in 2010 with a 95% efficient condensing nat gas furnace and a 14.5 SEER 3.5 ton AC. Single speed (nothing fancy) York system. Cost was seven grand but netted out to 4 grand with Federal tax credits and CA rebates.

Same deal, I didn't shop around, used an established firm in town, another 1 quote deal.

 

[Out of Steam]

Be careful not to oversize for cooling, because that reduces dehumidifying performance.

We've replaced our heating and cooling in the past 10 years, and I would go for the variable-speed fan if I had to do it over. I think that would apply even more with your high air conditioning demand.

A SEER of 14 for cooling is a little low for a new system in a house you plan to stay in. 16 is probably a good starting point.

Also, find out whether you need a heat pump designed for coastal areas that is more rust-resistant. Carrier recommends them within 10 miles of the seacoast.

https://www.carrier.com/residential/en/us/products/heat-pumps/25hnb6--c/

 

[Out of Steam]

Seven grand, my magic number too.

That number seems reasonable to me as well.

 

[Texas Proud]

Thanks, All!

The house is a smallish single floor 2200 SF, but cooling load is pretty high in the Florida panhandle - heating load can also be surprisingly high during cold years. House is pretty tight and built with relatively modern building techniques from 1997.

One major question - how large should the cooling solution be (in heat pumps, normally size for cooling load and use backup gas or electric).

Two secondary questions - single speed compressor or multi/variable, and single speed inside fan or multi/variable.

I don't mind paying for additional efficiency if it lowers bills enough to pay for itself over 5 yrs or so, or for substantive additional comfort (assuming this is possible given normal ops). I do think controlling moisture in the house is important - one reason for the different compressor and fan speeds, but many articles on experiences from folks have not always shown this to be the case.

BTW - my understanding is that 80% gas furnace is NOT considered high efficiency - the biggest difference is whether of not the furnace pulls out more heat with better heat exchangers - and, since this condenses moisture, it means they must be stainless steel - hence, more expensive - a positive however is that the exhaust can be handled with schedule 40 PVC pipe.

When I was talking to my HVAC guy he said there is no way that bills will be lower enough to pay for either 2 stage or variable.... ever... he said you do it for comfort, not cost savings...

If you have variable outside then you must have variable inside... it is an all or nothing decision...

As for LOL's comments.... I like the variable since it handles humidity much better than the single stage, especially in the milder months.... sure, you can change the temp to run it a bit longer, but the humidity will be higher with the single stage...

 

[LOL!]

Here is something I found by googling that might be helpful:

American Standard AC Reviews Prices & Buying Guide 2017

It looks like the previously mentioned "Manual J Load" calculation would answer the "how large" question. And you have answers for the single / variable question.

 

[travelover]

The two stage / variable speed compressor is nice for dehumidification. It solves the problem of the trade off for sizing for maximum load conditions vs maximum run time, which is good for dehumidifying. At my last home, the heavy tree coverage made humidity a priority over raw heat removal in the summer. The down side is initial cost and potential repair cost. It also makes the heating more even as the fan runs more, distributing the heat.

 

[stephenson]

Most Manual J Load Software is expensive, but I found a site that runs a basic heat-cool calc ... these used to be big spreadsheets, but now are likely more accurate with potentially more and more variables as the software model improves ... here's what my calc says.

I think one normally sizes for A/C load and uses the backup gas/electric for those few times (in our area) that the A/C running backwards in heat pump, won't keep up.

Load divided by 12K BTU gives the tonnage.

Texas Proud - I think you can have single speed compressor and option for multi speed fan, but if you have multi speed compressor, you must have multi speed fan?