HVAC replacement question

[Texas Proud]

I would also say that if you replace a system, make sure the new equipment is properly sized for your house (insulation, window area, ceiling height, climate, orientation, etc) and that the system has a sufficient number of returns or it will never run properly.

I will agree... when they redid my ducts and added a split system.. they said my return was WAY too small... added three more in the upstairs game room... this created so much more airflow that when they were here fixing the motor we had the fan speed lowered...

 

[Texas Proud]

When I got a new unit in 2003, a 12 SEER, 3T unit cost $2700. A 14 SEER with two speed fan was $7000. Ignore the ROI? Not this guy...

That is the final info that I do not have yet.... costs... I would not pay that difference to go to the two speed... but the AC company said there are so many incentives right now for the more efficient unit that the cost is not supposed to be that big of a difference... I am thinking 20%.... but, we will see...

 

[Walt34]

But TexasProud lives in Texas, and I have never been hotter in my life than I was when living back in College Station, TX. I had my AC break there one summer, and believe me, it wasn't an experience I would ever want to repeat. With TexasProud's AC being as old as it is, it doesn't have many years left. I'd want to replace it proactively BEFORE it breaks down.

Ah. On this, I will yield to the voice of experience. I have never been in Texas, let alone in summer.

 

[davemartin88]

If the two stage unit pricing turns out to be as close as the AC people are telling you, then I'd go with that instead of a variable speed system. I'm assuming this is a heat pump and is also your heating? May not be as important in Texas as you'll be using the full capabilities more in the summer than we do here in WV but we liked the idea that sometimes the system is still cooling/heating as needed but doesn't always have to work at full capacity? During winter, the low stage may handle most of your needs?

Having said that, I'm not sure I'd replace anything right away if it was working now and hope it finally breaks during mild weather, lol.

 

[Texas Proud]

If the two stage unit pricing turns out to be as close as the AC people are telling you, then I'd go with that instead of a variable speed system. I'm assuming this is a heat pump and is also your heating? May not be as important in Texas as you'll be using the full capabilities more in the summer than we do here in WV but we liked the idea that sometimes the system is still cooling/heating as needed but doesn't always have to work at full capacity? During winter, the low stage may handle most of your needs?

Having said that, I'm not sure I'd replace anything right away if it was working now and hope it finally breaks during mild weather, lol.

No, not a heat pump. I would be replacing my heater also to get the two speed or variable speed which is why the cost will go up.

 

[travelover]

No, not a heat pump. I would be replacing my heater also to get the two speed or variable speed which is why the cost will go up.

I think that there is some confusion regarding a two stage AC compressor as opposed to a two speed or variable speed fan in the furnace.

For maximum dehumidification, you want the compressor to be as small as possible, yet still cool adequately under all heat conditions. A two stage compressor handles this nicely by running on low unless demand forces it to kick into the high range. A two stage compressor also is more energy efficient and provides more even temperatures. Down side is higher initial cost and higher repair costs.

 

[sengsational]

My units are 23 years old and I've kept them working through minimal investment in freon and capacitors.

Duke Energy sends me a graph that shows how I'm doing with my old "contractor grade" units, and frankly, I don't think it's too bad.

At 10.3 per kwh, I'm spending less than $150 a year over the average house in cooling season. Even if buying a new system puts me down at the green line (which it wouldn't because I still have the same insulation, windows, etc), it would take forEVer to payback...just a bad ROI.

So my system is going to have to die before it gets replaced. Unfortunately, on the upstairs unit, the condensate water started leaking out of the bottom of the evaporator coil box (instead of coming out of one of the two drain pipes). I guess that means the pan has rusted through, but haven't yanked it apart yet. Maybe a little silicone caulk once cooling season is over, hehe.

 

[Texas Proud]

I think that there is some confusion regarding a two stage AC compressor as opposed to a two speed or variable speed fan in the furnace.

For maximum dehumidification, you want the compressor to be as small as possible, yet still cool adequately under all heat conditions. A two stage compressor handles this nicely by running on low unless demand forces it to kick into the high range. A two stage compressor also is more energy efficient and provides more even temperatures. Down side is higher initial cost and higher repair costs.

Agree... and the variable stage (as I am told and read) is not just two compressors where you have X or Y running... you have anywhere between 30% to 100% working... so if the AC calculates you need 2 tons, it provides 2 tons... if you need 2.3, it provides 2.3.... if you need the full 5 tons... you got it....

 

[Texas Proud]

My units are 23 years old and I've kept them working through minimal investment in freon and capacitors.

Duke Energy sends me a graph that shows how I'm doing with my old "contractor grade" units, and frankly, I don't think it's too bad.

At 10.3 per kwh, I'm spending less than $150 a year over the average house in cooling season. Even if buying a new system puts me down at the green line (which it wouldn't because I still have the same insulation, windows, etc), it would take forEVer to payback...just a bad ROI.

So my system is going to have to die before it gets replaced. Unfortunately, on the upstairs unit, the condensate water started leaking out of the bottom of the evaporator coil box (instead of coming out of one of the two drain pipes). I guess that means the pan has rusted through, but haven't yanked it apart yet. Maybe a little silicone caulk once cooling season is over, hehe.

Not sure that the graph means anything... heck, you could be like my mom and love it hot!!! She lives in 78 or 79 all the time... we have it at 76...

The better question is how much would you save on your (lets just guess) 10 SEER unit vs a 16 SEER or even a 20 SEER..... add in a two stage system and the savings are even better....

But to your point... even the AC guy said that there is no ROI if all you are looking at are dollars.... he said the biggest benefit is comfort... these units control temp and humidity much better than a single stage...

And that is one of the problems.... our temp can be 76, but we still have too much humidity... so it is not as comfortable as we would like... so I have to put a value on that comfort...

 

[nash031]

Timely thread for me.

The recent heat wave and above average temperatures this summer have finally convinced me that people who live in Southern California and comment on how they "don't need A/C" are just willing to deal with months of 80 degree houses and 80% humidity. And that's in San Diego!

I have declared rolleyes to DW that we are getting A/C when my annual bonus hits, which coincides with the fall. According to a quick web search, several contractors recommended the fall as it is between the time when they are busy with HVAC repairs and the time when people figure out that their heat isn't working. I'm thinking October or early November here ought to provide whatever "deal" there is, or at least the most availability.

We live in a 1600 sqft, single-story home. I'm thinking we could probably get away with a 2 ton, maybe 3 ton unit, and given that we may only use it 3-4 months out of the year, that I don't think we need to break the bank for a top-of-the-line system. I admit I am not yet that familiar with two-stage vs. variable speed, etc.

We have existing ducting that our home inspector said was in good shape, as was the furnace, when we purchased the home 3.5 years ago. Unfortunately, the 30 year old house has never had A/C, so there will likely be more cost associated with a new install.

I'm interested in everyone's thoughts on my threadjack here... if you lived someplace like San Diego/Coronado where it gets hot but not HOT, humid but not HUMID, and lived in a house our size requiring cooling for 4 or so months each year, what type of system would you recommend?

(Note: NONE is no longer an option. )

 

[travelover]

.............
And that is one of the problems.... our temp can be 76, but we still have too much humidity... so it is not as comfortable as we would like... so I have to put a value on that comfort...

Have you considered also running a dehumidifier?

 

[JoeWras]

We live in a 1600 sqft, single-story home. I'm thinking we could probably get away with a 2 ton, maybe 3 ton unit, and given that we may only use it 3-4 months out of the year, that I don't think we need to break the bank for a top-of-the-line system. I admit I am not yet that familiar with two-stage vs. variable speed, etc.

We have existing ducting that our home inspector said was in good shape, as was the furnace, when we purchased the home 3.5 years ago. Unfortunately, the 30 year old house has never had A/C, so there will likely be more cost associated with a new install.

For San Diego, keep it simple. Earlier I waxed poetic about going all out. But I live in a very hot humid place in the summer, and still significantly cool in the winter. Our units get a real work out all year round.

If I lived in S.D., keep it simple. You only need a traditional unit that runs at a moderate speed. Done.

Since you have ducting, that's a plus. There are ducting retrofits that run like dryer hoses, but I don't think you need that.

Likely, your biggest extra surprise expense (aside from the unit) will be running some new electric for the outside compressor. Hopefully, you have a modern electric service. (I've seen too many "This Old House" kind of shows from California where people have these ancient electrical systems.) Assuming you have a modern 200 amp service, even the new electric run shouldn't be too bad. If you have to upgrade your service -- watch out.

The fact you have a furnace is big. Hopefully they can fit the new system in the footprint allocated. So, the furnace, fan and condenser fit right where your furnace is now. Then, they have to run the fridge line outside. You'll need room outside for the compressor. And then there is the electric to the compressor, which will be a heavy duty 240 service.

 

[springnr]

Timely thread for me.
I'm interested in everyone's thoughts on my threadjack here... if you lived someplace like San Diego/Coronado where it gets hot but not HOT, humid but not HUMID, and lived in a house our size requiring cooling for 4 or so months each year, what type of system would you recommend?

Take a look at Ductless Heatpump; AKA mini-split system. These units are great for retrofit installs and are actually more efficient than regular heat pumps. One outside compressor can run several indoor units.
Ductless Mini Split System Advantages

 

[Texas Proud]

Take a look at Ductless Heatpump; AKA mini-split system. These units are great for retrofit installs and are actually more efficient than regular heat pumps. One outside compressor can run several indoor of the units.
Ductless Mini Split System Advantages

Since he already has ducts, probably not a great fit for him... you do have to run the lines to all the outlets...

I have also not seen any outlet unit that is quiet enough.. our ducted system is pretty quiet... most places in the house you cannot even hear it running.... you can never say that about a ductless system...

 

[nash031]

Since he already has ducts, probably not a great fit for him...

Yeah, we'll go central based on what little research I've done. Pricing seems doable, expecting $2500-5000, but hopefully on the low end of that for what I think can be a simple install (at least as simple as can be).

If I lived in S.D., keep it simple. You only need a traditional unit that runs at a moderate speed. Done.

Since you have ducting, that's a plus. There are ducting retrofits that run like dryer hoses, but I don't think you need that.

Likely, your biggest extra surprise expense (aside from the unit) will be running some new electric for the outside compressor. Hopefully, you have a modern electric service.

The fact you have a furnace is big. Hopefully they can fit the new system in the footprint allocated. So, the furnace, fan and condenser fit right where your furnace is now. Then, they have to run the fridge line outside. You'll need room outside for the compressor. And then there is the electric to the compressor, which will be a heavy duty 240 service.

Our house is fairly modern, and we recently had some significant electrical work done before we moved in. No inspector or the two electricians that have worked here mentioned anything about it being old (just some bad series wiring in one room). I don't expect a huge electric modification, but of course we'll see.

When you say "fit the new system in the footprint allocated," I'm wondering if I haven't communicated properly. Our "furnace" (maybe more accurately a heat pump - though we run gas... I should check this) is located in the attic. I assume the compressor would be laid outside, so I think they would have to put down a foundation for it. I don't expect a super-simple installation, but nothing to blow the wallet either.

Anything I should look for with respect to the heat pump/furnace in the attic to determine if our installation is going to be more complex?

As previously mentioned, the home inspector three-plus years ago did specifically mention that our ducting was in good shape in the event that we did choose to install A/C, so that's good.

Thanks for the feedback thus far!

 

[Texas Proud]

Yeah, we'll go central based on what little research I've done. Pricing seems doable, expecting $2500-5000, but hopefully on the low end of that for what I think can be a simple install (at least as simple as can be).



Our house is fairly modern, and we recently had some significant electrical work done before we moved in. No inspector or the two electricians that have worked here mentioned anything about it being old (just some bad series wiring in one room). I don't expect a huge electric modification, but of course we'll see.

When you say "fit the new system in the footprint allocated," I'm wondering if I haven't communicated properly. Our "furnace" (maybe more accurately a heat pump - though we run gas... I should check this) is located in the attic. I assume the compressor would be laid outside, so I think they would have to put down a foundation for it. I don't expect a super-simple installation, but nothing to blow the wallet either.

Anything I should look for with respect to the heat pump/furnace in the attic to determine if our installation is going to be more complex?

As previously mentioned, the home inspector three-plus years ago did specifically mention that our ducting was in good shape in the event that we did choose to install A/C, so that's good.

Thanks for the feedback thus far!

If you have a heat pump that should work as the AC unit also... so I doubt you have one...

You probably just have a gas fired furnace.... they will need to add the condenser upstairs in that unit and then run the high and low pressure hoses along with some wire to the outside.... hopefully the furnace is close to a place where you can put the outside unit...

 

[JoeWras]

Yeah, we'll go central based on what little research I've done. Pricing seems doable, expecting $2500-5000, but hopefully on the low end of that for what I think can be a simple install (at least as simple as can be).



Our house is fairly modern, and we recently had some significant electrical work done before we moved in. No inspector or the two electricians that have worked here mentioned anything about it being old (just some bad series wiring in one room). I don't expect a huge electric modification, but of course we'll see.

When you say "fit the new system in the footprint allocated," I'm wondering if I haven't communicated properly. Our "furnace" (maybe more accurately a heat pump - though we run gas... I should check this) is located in the attic. I assume the compressor would be laid outside, so I think they would have to put down a foundation for it. I don't expect a super-simple installation, but nothing to blow the wallet either.

Anything I should look for with respect to the heat pump/furnace in the attic to determine if our installation is going to be more complex?

As previously mentioned, the home inspector three-plus years ago did specifically mention that our ducting was in good shape in the event that we did choose to install A/C, so that's good.

Thanks for the feedback thus far!

Hey nash, great questions.

First, I agree about your choice to use the ducting you have now. The mini-split ductless systems are awesome for certain retrofits, or even new work, in specific circumstances. But you don't sound like a candidate. The biggest downside of those is the system you have to mount on the wall. But anyway, onto your other questions...

When I said "footprint", here were my thoughts... You currently only have a furnace. I'm a bit confused since you say it is gas and and a heat pump? A little confusing. Anyway, a gas only, or electric resistance only furnace has a very small footprint. A heat pump or gas furnace with A/C has an extra footprint to hold the condenser coils. So, it is typically slightly larger. However, in the last 30 years, they've made improvements in size and could probably fit in the space if necessary.

The outside compressor just needs a pad. Most installers can actually just place a simple precast pad for you. This is much easier than pouring a custom pad.

So... What do you have? Do you have a heat pump today? If you did, you'd have an outside compressor already and really it would be simple for an AC conversion.

Finally, I love gas heat. But in Southern California, a heat pump should be pretty darn efficient. The upside is that the installation is simpler (no gas, no flue). The downside is there's no substitute for gas on those few cold days you do get. A heat pump in the attic is fairly safe and easy to maintain. Gas in the attic is possible, but you need to keep a little bit more of an eye on it. It probably also means an extra roof penetration. This is all do-able, but the electric heat pump only installation will be simpler.

 

[nash031]

You currently only have a furnace. I'm a bit confused since you say it is gas and and a heat pump? ... Anyway, a gas only, or electric resistance only furnace has a very small footprint. A ... gas furnace with A/C has an extra footprint to hold the condenser coils. So, it is typically slightly larger. However, in the last 30 years, they've made improvements in size and could probably fit in the space if necessary.

The outside compressor just needs a pad. Most installers can actually just place a simple precast pad for you. This is much easier than pouring a custom pad.

So... What do you have? Do you have a heat pump today? If you did, you'd have an outside compressor already and really it would be simple for an AC conversion.

Finally, I love gas heat. But in Southern California, a heat pump should be pretty darn efficient. The upside is that the installation is simpler (no gas, no flue). The downside is there's no substitute for gas on those few cold days you do get. A heat pump in the attic is fairly safe and easy to maintain. Gas in the attic is possible, but you need to keep a little bit more of an eye on it. It probably also means an extra roof penetration. This is all do-able, but the electric heat pump only installation will be simpler.

So, you're confused because my knowledge of such things is limited, at best. We have a gas water heater, gas grill connection outside, just last year installed gas appliances in the kitchen... I can only assume this means we have a gas furnace and I do know that it's in the attic. Coupled with your statement that we'd already have a compressor outside (we don't) this leads me to the obvious conclusion that we simply have a furnace up there. So I confused you by not know what the heck I'm talking about!

Thanks for clarifying all of that.

Based on what I've seen up there in my trips into that part of the attic, there's some pretty good space, and I do believe it's directly ventilated (as I would assume it must be. Fortunately, it is close to some outside access, including one place I think they would want to put the pad for the compressor.

Again - thanks for that feedback!

Any ideas as to the size for my application (~1600sq ft, single story, relatively mild heat/humidity 80/80% on avg in the summer)? I can't see going over 3 tons, and wondering if I can get away with 2?

Just want to be armed as well as possible before going into "estimate mode."

 

[meierlde]

Actually a simple test, does a pipe go from the furnace thru the roof or outside thru the walls? (a couple of inches in size). Do you have to light a pilot or is the furnace new enough to not have one, so when the furnace comes on you hear a fan start a bit the main fan comes on. When I had a gas furnace in the attic in Houston you could hear the gas come on. See also if a black pipe or a flexible coupling like used on the water heater goes to the furnace.

 

[aja8888]

Any ideas as to the size for my application (~1600sq ft, single story, relatively mild heat/humidity 80/80% on avg in the summer)? I can't see going over 3 tons, and wondering if I can get away with 2?

That's the trickiest part of a new installation. Making the CORRECT calculations to get the load and size the unit. Call an A/C specialist and ask if they can do the load calculations (professionally) It (the specification calcs) takes into consideration a lot of variables and physical attributed about the house.

A lot of A/C contractors just do repair and replacement since, hopefully, the specs were chosen correctly when the General Contractor built the house. If you don't do this sizing correctly, you can end up with an inefficient disaster.

 

[meierlde]

That's the trickiest part of a new installation. Making the CORRECT calculations to get the load and size the unit. Call an A/C specialist and ask if they can do the load calculations (professionally) It (the specification calcs) takes into consideration a lot of variables and physical attributed about the house.

A lot of A/C contractors just do repair and replacement since, hopefully, the specs were chosen correctly when the General Contractor built the house. If you don't do this sizing correctly, you can end up with an inefficient disaster.

Issues you need to address is the window to wall ratio and which side of the house the windows are on, the amount of insulation in the walls and ceiling as well as just the square footage.
There are two calculations manual j and manual d. But you will likely have to pay to have them done, as the installers tend to run by rule of thumb, such as houses in this area of about this size tend to have about x btu of capacity.

 

[springnr]

I did this upgrade three years ago, added a heat pump to an existing gas furnace, also added a new duct run to the far end of the house for balance.

Yep, the sizing can be fun, a little bit of a learning curve, but important as are some of the other details. The contractor I worked with was good, we did have some go arounds on sizing, as the whole front of my house is basically a window looking out over the sound. The install was worth it though for the comfort and reduced conditioning cost.

 

[nash031]

Just poked around upstairs: definitely a gas furnace, in fact a Rheem Criterion II. Nice, clean looking installation, too. Properly ventilated and gas line looks well done. Furnace looks relatively new. Ample space, it would seem, for an install in that area. Not sure where the easiest place would be to run the condenser line, but I have an idea...

 

[JoeWras]

Just poked around upstairs: definitely a gas furnace, in fact a Rheem Criterion II. Nice, clean looking installation, too. Properly ventilated and gas line looks well done. Furnace looks relatively new. Ample space, it would seem, for an install in that area. Not sure where the easiest place would be to run the condenser line, but I have an idea...

Great. You'll be good to go. Might as well stay with gas and just add the cooling. Sounds like you have the room.

Not sure how high your house is (1 story, 2 story?), but what a lot of guys do for retrofits is they mount a "box" which looks a bit like a downspout on the wall and then run both the condensate pipe AND the refrigerant line through this. This is very common on 2 stories. Just another thing to think about... i.e. the fridge line.

What I did on my retrofit is I worked with the installers and opened up a few walls for them (small holes for them to thread things through). They ran the fridge pipe and condensate here. They were OK with this as long as I did the fixing of the drywall. In the end, it created a really nice hidden install, both inside and out. Not saying you should go here, but just mentioning it.

 

[Texas Proud]

Well, the quotes are in....

Top variable speed system... $12,300
Lower rated variable speed... $10,900
Two stage..... $9,700

And to replace the AC unit (replaces the coil inside and a few other things inside)... $5,400...