Need New A/C Or Heat Pump

[minke]

We had a house built in Colorado Springs in '92 from 2,000 miles away. We were living near exceedingly hot
and muggy D.C. and chose no air conditioning for the new house. 33 years later things have changed!

We need advice. We've never hired a contractor (for anything large) and know nothing about HVAC.

Facts: house size is ~4,500 square feet, natural gas furnace says Trane XE 78, attic insulation said to be R-30,
and electrical panel has two (seemingly) spare 50 amp breakers with a plastic device so that they must be
switched simultaneously. Ducting is single zone. Many windows are new. NO, NO, NO, I'm not asking for a design!

What we think we want: air conditioning or heat pump, a new smaller natural gas furnace (or keep the old one),
or a heap pump with a gas furnace backup.

What I am looking for are 1) cautions, 2) what should my expectations be for the contractor to look at and ask us,
and 3) what do I need to understand to sniff-test any proposals. What am I not asking here that I should ask?
Said differently I need help with clarity of thought. I'm up for any reading suggestions but I don't learn well
from youtube.

My wife is up-tight about another winter with a 33 year old furnace. I'm just as up-tight about a new furnace
as an old one.

 

[danski0224]

You will need a load calculation.

Then you need to figure out the thermal balance point, and then the economic balance point. Those may not be the same.

Only then, and I do mean Only then, will you be able to know whether or not a heat pump is a viable option.

The economic balance point is needed for the thermostat.

The economic balance point will change with electric and gas costs.

Of course, if you have "free electricity" in the form of solar panels, then there is a wider range of opportunity.

I can also almost guarantee you that your ductwork is undersized.

 

[nadogail]

The Goodman brand has been acquired by another company, Diacon (sp?) and their quality seems to have improved.

 

[danski0224]

Daikin.

 

[minke]

Thanks!

Danski: I read what you have previously written here on GJ and I'll look for those results.
Enlarging ductwork sounds traumatic!

 

[Two Door]

Ask what refrigerant the proposed system will use. R410 is being phased out. Some people say the future availability isn't concerning, others say otherwise.

 

[danski0224]

Enlarging ductwork sounds traumatic!

Sometimes, if the equipment is sized properly (reduced in size), the ductwork issues can take care of themselves.

 

[danski0224]

R410 is being phased out.

Good luck getting any R410-A residential equipment at this point.

 

[Dagny]

The new refrigerants are flammable. And I hope the gas sensors work better than the ones on the water heaters.

 

[fitter30]

Call your electric provider / look on their web site see if they offer a energy audit that includes a blower door test. Might also consider breaking up the house with using two units. R 49 insulation is minimal code recommended up to R60.

 

[u3b3rg33k]

We had a house built in Colorado Springs in '92 from 2,000 miles away. We were living near exceedingly hot
and muggy D.C. and chose no air conditioning for the new house. 33 years later things have changed!

We need advice. We've never hired a contractor (for anything large) and know nothing about HVAC.

Facts: house size is ~4,500 square feet, natural gas furnace says Trane XE 78, attic insulation said to be R-30,
and electrical panel has two (seemingly) spare 50 amp breakers with a plastic device so that they must be
switched simultaneously. Ducting is single zone. Many windows are new. NO, NO, NO, I'm not asking for a design!

What we think we want: air conditioning or heat pump, a new smaller natural gas furnace (or keep the old one),
or a heap pump with a gas furnace backup.

What I am looking for are 1) cautions, 2) what should my expectations be for the contractor to look at and ask us,
and 3) what do I need to understand to sniff-test any proposals. What am I not asking here that I should ask?
Said differently I need help with clarity of thought. I'm up for any reading suggestions but I don't learn well
from youtube.

My wife is up-tight about another winter with a 33 year old furnace. I'm just as up-tight about a new furnace
as an old one.

Step one is figuring out what you actually want from a "new" system.

heat pumps are rarely cheaper to operate than a condensing gas furnace. there are reasons to put one in (my separate garage got a heat pump but it doesn't have a gas line), but rarely is operating cost the winning argument. this can depend heavily on where you live, and the heat pump you choose (they all have a COP curve that matters for OPEX)

so do you want new for the sake of new?
do you want quieter? better comfort?
do you want minimum CAPEX?

personally, I would do a dual fuel setup and just keep the heat pump as a backup - there SHOULDN'T be (but often is) a huge up charge to go from a straight cool unit to a heat pump unit, especially if it's an inverter unit, and that's assuming you can even buy a straight-cool inverter unit. if/when I replace my 20 year old AC that's what I'll do.

also note that you should size a new furnace on BTU OUTPUT not BTU INPUT. switching from an 80% 80k (64k output) to a 95% 80k (76k output) is a big upsize. If there's any rule of thumb I've seen, it's that the smallest furnace with a big enough drive for your AC is more than adequate to heat your house on the 99% design day (it's supposed to run non-stop on that day).

 

[minke]

Call your electric provider / look on their web site see if they offer a energy audit that includes a blower door test. Might also consider breaking up the house with using two units. R 49 insulation is minimal code recommended up to R60.

Good. I'll check that.

 

[minke]

Step one is figuring out what you actually want from a "new" system.

heat pumps are rarely cheaper to operate than a condensing gas furnace. there are reasons to put one in (my separate garage got a heat pump but it doesn't have a gas line), but rarely is operating cost the winning argument. this can depend heavily on where you live, and the heat pump you choose (they all have a COP curve that matters for OPEX)

so do you want new for the sake of new?
do you want quieter? better comfort?
do you want minimum CAPEX?

personally, I would do a dual fuel setup and just keep the heat pump as a backup - there SHOULDN'T be (but often is) a huge up charge to go from a straight cool unit to a heat pump unit, especially if it's an inverter unit, and that's assuming you can even buy a straight-cool inverter unit. if/when I replace my 20 year old AC that's what I'll do.

also note that you should size a new furnace on BTU OUTPUT not BTU INPUT. switching from an 80% 80k (64k output) to a 95% 80k (76k output) is a big upsize. If there's any rule of thumb I've seen, it's that the smallest furnace with a big enough drive for your AC is more than adequate to heat your house on the 99% design day (it's supposed to run non-stop on that day).

I'm disappointed in my writing. Our goal is 1) to get some kind of air conditioning, and
2) to minimize anxiety over the 33 year old furnace. Then I'll have some anxiety over the
new one!

 

[fitter30]

I'm disappointed in my writing. Our goal is 1) to get some kind of air conditioning, and
2) to minimize anxiety over the 33 year old furnace. Then I'll have some anxiety over the
new one!

33 year old furnace the heat exchanger needs to be looked at closely. I would want a flue gas analyzer used. Furnace is close to be total used up as far as the heat exchanger.

 

[minke]

33 year old furnace the heat exchanger needs to be looked at closely. I would want a flue gas analyzer used. Furnace is close to be total used up as far as the heat exchanger.

Thank you. Yet another thing for me to learn about.

 

[danski0224]

33 year old furnace the heat exchanger needs to be looked at closely.

Yes.

I would want a flue gas analyzer used.

Absolutely.

Furnace is close to be total used up as far as the heat exchanger.

The only way to know is with a combustion analysis.

The "gloom and doom" "15 year life expectancy" also includes all of the ****** installations out there that dramatically reduce equipment life. Manufacturers wouldn't have 20+ year warranties on the heat exchangers if they would not last, but the key problem is proper installation. Bad designs are the exception.

 

[danski0224]

Our goal is 1) to get some kind of air conditioning,

The fact the existing installation does NOT have AC means that the ductwork is likely undersized. Almost all residential work that I have seen is undersized more on the return side of the system.

and
2) to minimize anxiety over the 33 year old furnace.

If the existing furnace is intermittent ignition, 80% AFUE, replacing it with a 90+% AFUE model means that more airflow is required over the heat exchanger. Again, leading to undersized ductwork. Same rule applies if you have, for some reason, a standing pilot model and want to go to 80% AFUE.

Then I'll have some anxiety over the
new one!

There are tens of millions of people that are NOT on the internet complaining about how well their furnace is working. The piece of equipment is a commodity and the engineering is straightforward in a residential application. Even the "high end" models are no where near as complicated as high end commercial stuff.

Equipment life in a residential setting almost always comes down to proper installation, which is mainly about moving enough air through the equipment. Can't move enough air without "good enough" or proper ductwork... and the right air filter.

If the system has 1.0" wg (water gauge) TESP (Total External Static Pressure) on a fan rated at 0.5" wg, it isn't moving enough air, and the manufacturer charts will prove this. If that same system has a variable speed motor, the motor will ramp up in an attempt to deliver the set airflow, increasing current draw, eventually killing the motor. Bad ductwork and restrictive air filters drive up TESP, which kills airflow, which kills equipment. Following close behind is oversized equipment, which won't have proper airflow by design and it never runs long enough.

 

[brewchief]

When you say 4500 sq feet are you talking total living area including some finished basement space or is that all above grade living space?

Is ductwork located in an accessible basement space( non finished), a finished basement space or attic?

How does the current furnace vent? Does it go into a masonry chimney or into a metal B vent that goes up through the roof? Water heater(s) vented with it?

Is there a path to an outside wall that you can get one or two 3" pvc pipes out and maintain slope back to the furnace and have clearance to windows/doors? And not be in an area that vent pipes would be visually unacceptable ?

An energy audit is a great idea, if you can find an independent company that can follow that up with a manual J heat load calculation as well as a manual D and S you would be worlds ahead of 99% of people.

I almost always recommend a multi stage furnace, full modulating can be better but it's more about comfort .

A/C in a climate that is humid a multi stage or inverter unit makes a lot of sense but in a dryer climate a simple single stage unit can preform well.

Look into local energy company rebates as well as state and federal tax incentives, in some cases these will make the additional cost to go to a better more efficient unit practically nothing.

Many manufacturers offer warranties that may be 10 years, however these often start as a 5 year that gets extended if the equipment is registered within so many days of installation, make sure either you or the contractor registers it and if it's the contractor get proof that it was done. Also know what has to be done as far as maintenance to keep warranties in good standing .

 

[nadogail]

Our local Gas and Electric utility offered free audits as part of their Energy Conservation Program.
I have no idea if they are still doing that; and I am not interested enough to find out.

 

[ericm]

We had an energy audit done by a local firm. They found a bunch of issues and ranked them in terms of likely payback. One of them was duct resealing and fixing the duct insulation. The house was built in the late '80s. Standards were lower then and to be honest the house did not get the best workmanship in some areas. Another problem was poor return ducting for the HVAC system. Some crawlspace walls were not insulated properly.

Armed with this we went to some local HVAC companies. One wanted to cut a big hole in a wall and make an ugly wart on it to hold a second return. Another one figured out a way to run a return duct through a crawlspace and into the blower without hacking on the walls. They brought out their sheet metal wizard, who I think was also the owner of the company, and who spoke broken english. But he said "can do" and he made a very nice plenum for a limited space.

We had them address the top three issues on the audit, replace the furnace that failed just a couple weeks before the scheduled install, and replace the oversized 5 ton A/C unit with a 3 ton. It was about seven years ago but the insulation, duct resealing and new return only cost a few thousand above the furnace and the A/C. The house ended up being much more comfortable in winter and summer so it was worth it.

I agree with the other posters about finding an HVAC contractor who will run Manual J, S, etc and make their recommendations off that. Some want to just sell you what they have in stock or what has the best margin, or something oversized so they don't get callbacks when the customer turns the A/C down to 65 on the hottest day of the year.

Ducted heat pumps are less efficient than mini splits. But even with that you may find that it costs less to run a heat pump for heat than it does to burn fossil fuels. It all depends on your source of gas (piped or propane) and your local cost for gas and for electricity. If you're on propane then it's likely that a heat pump would cost less. Piped gas usually costs significantly less than propane so electric heat pumps are less likely to be cheaper there.

This spread sheet can be useful in figuring it out. Note that heat pump efficiency numbers have improved quite a bit since the sheet was made so be sure to adjust those to the equipment you're considering.

https://www.maine.gov/energy/sites/maine.gov.energy/files/inline-files/Home-Heating-Calculator.xls

 

[Vicdog]

I have a heat pump in Texas only because there is no natural gas in the neighborhood. Never again. If you have snow and ice, this will interfere with the fan and cause issues. You will also need a big generator to run heat vs a small one to run the gas furnace.

 

[Fabtechprerunner]

The new refrigerants are flammable. And I hope the gas sensors work better than the ones on the water heaters.

There not flammable as you think. They have a very small amount of propane in them. You can hold a open flame to R454B and it will not do anything, NOTHING. They legally have to put the flammability on the R454B jug for legal and environmental reasons. If there's a leak of R454B the alarms and sensors will go off so the home owner knows there's a leak. It will vent the leak through the duct.

Literally no different than R410, you're likely to suffocate or catch a illness the same way no matter what.

 

[bonneyman]

If the house (and unit) are from 1992 and you want to add A/C, you'll probably have to change the furnace out anyway. Most furnaces aren't rated to move the capacity of air that an A/C requires. Plus being 33 years old I'd say you're past the life of the thing anyway.

You might be able to find a suitable R410a unit hidden in inventory of a local warehouse. When I added A/C to my home, I grabbed the last R22 unit of the size I needed in the whole state! They sold out fast after the ban went into place but I found one. Had it shipped to my dealer and I bought it and it sat in the backyard till the spring when I installed it. I don't know how it works now but maybe you'll find a unit that the dealer is trying to get rid of. Do the furnace, evap coil, and condensing unit and be good to go.