Has anyone updated to high efficiency gas furnace?

orange

I had a similar post that got no responses.
I'd like to know of questions to ask regarding upgrading a 20 yr old furnace to a new 90%+ efficient one.
Can anyone comment on what to watch out for/make sure you find out about...

Thanks.

related post is upgrading furnace and AC

Termite

You won't regret it. Replacing my old one with a high-efficiency unit cut my bills nearly in half.

Another benefit is that efficient units don't have combustion air requirements (like less efficient units) because their intake and exhaust is piped to outdoors.

I don't understand why anyone would install anthing under 90%.

orange

Thanks for the response, I appreciate it.
I'd like to request some quotes from different companies (see my other post upgrading furnace and AC).

Can you suggest anything else that I should be asking?
Thanks.

Termite

Just be sure that they're pricing the same thing when you compare bids. One guy might price a 120000 btu/h unit and a 3 ton AC, and the next guy might price something bigger or smaller, so you wouldn't be comparing apples to apples. Be sure that they're sizing the unit to your house, its insulating properties, fenestration, and duct system.

8 Ball

When you switch to a high efficiency furnace, there are codes and manufacturers recomendations, that MUST be complied with. Cant be vented above or below a deck or walkway etc.. Ask in advance for an I.O.M., Instalation Operation Manual, which describes the sequence of operation, manufacturers instalation requirements, and the manufacturers written warranty.

If you have a gas water heater, the chimney will need a stainless steel liner.

Most high efficiency furnaces are very similar and competitive. A 90+ with variable speed blowers are top of the line, and cost more than a 90+ with fixed speed blower.

Just because you purchase a high efficiency furnace, it does not mean that you need a smaller, B.T.U., unit. Avoid any major changes in size without a print out of the heat load calculation.

If you have central air, ask them to clean the evaporator (indoor Coil) while the furnace is out.

Good Luck.

angus242

I'll also endorse the HE unit. My neighbor and I had our houses built at the same time both with American Standard 3 ton furnaces. His was a Freedom 80 single stage, mine was Freedom 90 single stage. He actually had more insulation than me (he snuck it in during construction) and my bills were about 25-30% lower when we had our electronic thermostats set the same.
I paid $750 more for mine than he paid for his. I figured no more than 2 winters and I had 100% ROI!

Termite

That's a new one to me. Can you elaborate?

8 Ball

Sure.

Chimneys are sized by the amount of heat going into them, this heat rises, or vents at a specific rate. A draft guage will measure the amount of draft, crossreference to manufacturers recomendation...all is good.

A cold chimney will not vent properly, until it is warmed up. When the major source of heat has been removed, it takes a long time for a small heat generator to warm the same space. Heat + Cold = condensation.

That condensation is loaded with acids and byproducts of combustion that attack the bricks, tile and mortar, and eventualy crumble the chimney.

On a cold winter day, the furnace will cycle on many times, compared to the water heater with no usage, and keep the chimney warm, venting and almost condensation free, with the furnace vented elsewhere....

Our city has been requiring them by code for many years, not only for 90+ upgrdes, but also for 80+ upgrades.

delstu

Yes, 8ball is correct. It's just that most 90+ units in my area are usually vented using PVC pipe and exits the home some way other than through the chimney.

80+ furnaces also require a chimney liner due to condensation in the chimney containing acids which will eat the mortar.

orange

After reviewing products and talking with suppliers, we decided on a Bryant Evolution 90i with Humidifier, new thermostat and Bryant AC unit to replace our 20 year old Lennox products.

sweaty

I think the biggest advantage of the high efficiency unit is its sealed combustion chamber. Not only does it prevent CO problems, it draws combustion air from outside rather than from the house. So there's no vaccuum effect drawing cold air into the house through all the cracks.

I like the Carrier Infinity system.

Yoyizit

In principle it's a great idea, especially since energy saving are the buzzwords of the day.

My HVAC guy didn't recommend the high efficiency stuff, and I did ask him.
He seemed to say that they were touchy, the maintenance was frequent, etc. In other words, the "hidden cost of ownership", and maybe it cancels the gains from saving energy.
Maybe eating mortar is one of the least of these costs.

As an engineer, his answer sounded plausible to me, especially since he stood to gain financially if he recommended one of these.

They may not have all the bugs worked out, yet, from these hi tech marvels, but if the vendor provides you with reliability and cost-of-ownership data. . .why not?

JackA

I replaced a regular furnace with a high efficiency 20 years ago. If I had known what was to come, I would have stayed with a standard furnace. I had a high efficiency installed with the closed combustion air system (pvc in for air, pvc out for exhaust). That winter when I would come into the house, I could just feel the humidity in the air, we used bath exhaust fans, and range hood fans also. Then, one day while I was outside, on the north side of the house, I was seeing yellowish water streaks, coming from the siding laps running down the wall. I knew I had a serious problem. AND I had not had a humidifier on since putting in this high efficiency. ALSO, this house was a standard built, nothing "tight" about it (built late 70's). Never had this problem before. At that point I knew this closed combustion system was not pulling any new air into the house, had continual stagnent humid air. I knew of air exchangers, and talked to contractors on the issue, they agreed an exchanger should cure it. The BAD thing about it, they are only about 80% efficient. So, in the long run, I paid more for high efficiency, and then had to pay another $1500 or so to reduce that efficiency back to 80% or less, just to keep the excessively high humidity out of the house. In the long run, I would have been better off with a standard furnace.
And even with the new "tight" houses, they are still required to have the fresh air inlet duct. So I would find it hard to believe there is any advantage in a new home using high efficiency furnace/air-to-air exchanger other than to pay a lot more for your home, or to even retro-fit your home.

fireguy

Make a list of your concerns. What else needs to be replaced/upgraded in your HVAC system? How about a electro-static air cleaner, insultated ducts, new ducts? Talk to a couple of contractors in the phone book. pay to have a couple come to your home and do an energy audit. Ask them how they arrived at the BTU required. They should take into effect the number of windows and doors, insulation, condition of roof. Aslk them lots of questions. Then write your own specs, you want to know the size of the heater, efiency ratio, any upgrades needed to the house such as concrete pad, electrical upgrade, method of ducting, combustion air source. You want to see a copy of the contractor license, liability insurance, worker's comp, vehicle insurance. Ask about permits and inpsections. Then call your local building inspector and ask for the number of the state contractor board and make sure the contractor is licensed and insured. There is more, but you will soon add to the list. I did all of this when I had my furnace upgraded to a 97% unit. I added insulated duct, but not the floppy ducts that soon get occluded. I had 2 of my guys pour a slab and remove the old duct work. I took care of the old furnace and duct disposal. The job was permitted and inspected.

hvaclover

[quote=8 Ball;125412 If you have a gas water heater, the chimney will need a stainless steel liner.
.[/quote]


Excuse me 8 ball, not to step on your toes. Mi does not require stainless steel chimney liners. You are thinking oil or wood. Stainless Steel is cost prohbiitive.

All. liners in MI are aluminized steel and a lot less than Stainless

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