HVAC advice - ac or ac + furnace

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renegade06
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HVAC advice - ac or ac + furnace

Post by renegade06 » Mon Sep 30, 2019 5:03 pm

Hi everyone - just curious if there are any HVAC experts in Boglehead land. My ac system is 11 years old and the ac went out. I'm debating whether or not to just replace the ac unit and coil of if I should also replace the furnace as well. I do not want to repair the system since I will not be able to use freon after December 31, 2019. I'm also concerned about the efficiency by having a new ac and an old furnace. Not sure how long I will be in the current house (I'd say at least 3-4 years), but i would like to keep this as a rental property long term.

The Carrier coil and a/c unit (Carrier Infinity 19) would cost me $6,500. If I include the furnace, the total cost is $9,200 (after rebates).

Any thoughts/experiences from the group would be appreciated. Many thanks!

Big Dog
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Re: HVAC advice - ac or ac + furnace

Post by Big Dog » Mon Sep 30, 2019 5:09 pm

Just understand that freon is not going away; only manufacturing of the new stuff. It will be available, but in limited supply and therefore, the cost per unit will continue to increase.

Did your ac guy/gal say what the issue was? Is this a $750 repair, or a $2500 repair? A new coil should last at least 5+ years....

Personally, I would be reluctant to invest in an expensive ac unit for a rental in the next ~4 years.

lazydavid
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Re: HVAC advice - ac or ac + furnace

Post by lazydavid » Mon Sep 30, 2019 6:41 pm

Agreed with Big Dog, what is the nature of the repairs needed? 11 years is not that old for a good unit installed well, so it might be worth just fixing it.

Assuming replacement is warranted, there is no efficiency problem with a new condenser/new coil/old furnace combination, unless the condenser is a multi-stage or continuously variable, where a variable speed fan would be warranted. So the decision of whether or not to replace the furnace comes down to does it work well or does it seem tired and waiting to fail?

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JAZZISCOOL
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Re: HVAC advice - ac or ac + furnace

Post by JAZZISCOOL » Mon Sep 30, 2019 7:21 pm

I have a similar dilemma I have recently posted about (18 year old system with AC coil issues; basement flooded.) Will be interested to see this thread as well as I am still evaluating and gathering estimates. :happy

viewtopic.php?f=11&t=290924

Tjb
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Re: HVAC advice - ac or ac + furnace

Post by Tjb » Mon Sep 30, 2019 8:52 pm

If you have a gas furnace and a Separate AC system, both sharing the same blower, you only need to replace one, and maybe not the entire system, depending on whats bad. In the blower area is a coil for the AC, when the AC is on, that coil is cold and the fan blows hot air from your house over that coil to get cool. The hot refrigerant travels outside to the condenser where the heat is rejected and the cycle stats again. If the coil is leaking, then the coil can be replaced inexpensively if the condenser is bad, then that is usually the expensive part and your 6K number is about right, I just did the same thing. I replaced the entire AC system with the newer refrigerant. The blower and furnace were fine.

The old refrigerant will set you back a bit so if it is the condenser, you might as well replace it. If its only the cold coil, then the cost of the coil and old refrigerant could be less, but if your condenser has some age on it, it could be on it's last leg anyway, and when it goes, you will be changing refrigerant then anyway.

Mine was about $5500 but it was not a carrier, it was a Goodman, builders grade, but the last one I had lasted 20 years, so I went with the same brand.

Hope this helps

jharkin
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Re: HVAC advice - ac or ac + furnace

Post by jharkin » Tue Oct 01, 2019 6:58 am

Furnace is 11 years old? It shouldn't be anywhere near end of life, and a new one is not likely to be much more efficient. Total waste to replace.


For that matter are you sure your AC is not reparable?


*shakes my head* As I grew up with mechanical systems that lasted 20,30,40 years.. based on threads in this forum the life span of this new stuff appears to be truly poor (or for some reason normally frugal bogleheads love to spend money on mechanical systems...)

FederalFIRE
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Re: HVAC advice - ac or ac + furnace

Post by FederalFIRE » Tue Oct 01, 2019 7:34 am

Agree with several of the above comments. An 11 year old furnace should have 10-20 years of life left. Unless you're thinking about seriously upgrading your compressor - say from a single stage system to a variable drive system - a new AC unit without a new furnace probably won't matter. However, if you have a single stage blower on your furnace and put in a super high efficiency AC unit with variable drive, etc., then the kit will be mismatched and you'll be wasting money on the AC unit.

All that said, I would look into fixing it first. 11 years old is half (or less) of the life you should expect out of a AC system that was properly installed and is reasonably maintained.

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Watty
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Re: HVAC advice - ac or ac + furnace

Post by Watty » Tue Oct 01, 2019 8:47 am

A couple of things to consider.

1) What is your local climate like? If you are in some place like Phoenix and have been running the AC almost nonstop for 11 years then your AC could be about due for replacement, but your furnace would be almost like new. The opposite would be true in a colder climate like Maine.

2) Are you sure that your AC actually uses the R22 that is being discontinued? A/Cs that were installed after 2010 could not use it and if yours was installed in 2008 that might have been during a transition period. There should be a sticker on the side of the AC which says what type of refrigerant it uses. I would check that myself just in case they were trying to use scare tactics.

3) If you convert the house into a rental in a few years then you might wait to replace the furnace until then since the furnace might be deductible as a business expense. (Converting your house to a rental is usually a bad idea because of the taxes but that is the subject of another post.)

4) If you do decide to replace the AC and possibly the furnace then get at least four bids(more would be better). The last time I replaced them the bids varied dramatically for similar equipment. Now is a good time to do this because in most areas they are between the cooling and heating season so HVAC companies are not busy and may give good prices just to get the work.

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Watty
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Re: HVAC advice - ac or ac + furnace

Post by Watty » Tue Oct 01, 2019 8:53 am

One other thing to consider is the price level of the house. Replacing the systems in a million dollar home is easier to justify than in a $150K home.

brianH
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Re: HVAC advice - ac or ac + furnace

Post by brianH » Tue Oct 01, 2019 2:42 pm

jharkin wrote:
Tue Oct 01, 2019 6:58 am
*shakes my head* As I grew up with mechanical systems that lasted 20,30,40 years.. based on threads in this forum the life span of this new stuff appears to be truly poor (or for some reason normally frugal bogleheads love to spend money on mechanical systems...)
The units themselves are generally more reliable than ever, and parts are fairly cheap. The problem, however, is the labor rates for the HVAC companies. Two of the most frequent issues: a blown capacitor or blower motor can be replaced with a $30 or $300 part (respectively) and in less than a half-hour. However, you're likely to get a quote of hundreds of dollars to replace a capacitor or close to a thousand for a fan motor. If one has no choice but to accept these rates, the math for when to replace an older (but still young) unit changes dramatically in favor of replacing it rather than paying the inflated fix-it prices: exactly what the HVAC companies are trying to encourage. Throw in the sense of urgency/fear created by having a unit fail at the worst time of a season, and it's easy to see how convincing it is to replace.

Big Dog
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Re: HVAC advice - ac or ac + furnace

Post by Big Dog » Tue Oct 01, 2019 2:50 pm

dupe post, sry
Last edited by Big Dog on Tue Oct 01, 2019 2:51 pm, edited 1 time in total.

Big Dog
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Re: HVAC advice - ac or ac + furnace

Post by Big Dog » Tue Oct 01, 2019 2:50 pm

re: variable drive. Unless you have a variable speed now, I would not recommend putting one into a house that will become a rental. (According too hvac-talk.com, variable drives are expensive to repair.)

full disclosure: we put in a two-stage system last fall and love how it keeps the temp more consistent and is more efficient. But we plan to be here awhile, and have no plans to turn the house into a rental (where a single speed would be less expensive).

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