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Questions for AC replacement
Old 06-21-2015, 04:45 PM   #1
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Questions for AC replacement

Time to utilize the collective wisdom of the group...

So our 25+ year old AC unit bit the dust last Thursday night (looks like a complete, sudden loss of freon). We have a person coming out tomorrow to give us the first of, I hope, three bids on a replacement. Our plan is to go ahead and replace the central air and the 20+ year old gas furnace at the same time. What are some key questions that I should be asking?

I will compile a summary list after the dust clears.

Thanks, everyone.
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Old 06-21-2015, 05:10 PM   #2
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Time to utilize the collective wisdom of the group...

So our 25+ year old AC unit bit the dust last Thursday night (looks like a complete, sudden loss of freon). We have a person coming out tomorrow to give us the first of, I hope, three bids on a replacement. Our plan is to go ahead and replace the central air and the 20+ year old gas furnace at the same time. What are some key questions that I should be asking?

I will compile a summary list after the dust clears.

Thanks, everyone.
You have it right that you will have to replace the indoor coil as well since you can't get new r22 ac units. Given the age of the furnace does it have a pilot light or an igniter. Also what part of the country are you in (this makes a difference between installing an 80 and a 90% efficient furnace. A 90 percent needs access to a drain line, but the Ac probably has one already. A 90% unit will require a new chimney liner as well. (the colder the climate the more the 90% unit makes economic sense)
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Old 06-21-2015, 05:14 PM   #3
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The single biggest problem I had when replacing both my furnace and my AC (sequentially) was that contractors refused to do a Manual J calculation to determine the right size. Instead they wanted to base it off the existing equipment or use a fudge factor based on square feet and install a much too large unit.

This is a big deal because a furnace that is too big cycles too often and does not maintain an even temperature, and is not as efficient as a properly sized one. An AC too large does not properly dehumidify the air , does not hold an even temperature and wastes energy.

I did my own calculations (on-line calculator) and had to sign a waiver basically stating I'd not taken their recommendations. I could not be happier. My two stage gas furnace keeps the house warm on subzero days on the 35,000 btu stage, only kicking into the 70,000 btu stage when switching from night time to daytime temperature. Similarly, the two ton AC works great and really cuts the humidity.

I found huge variation in prices for the same equipment between quotes.

Agree you'll need an inside coil and maybe a chimney liner.
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Old 06-21-2015, 05:58 PM   #4
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I would ask about a two stage or variable stage unit... they cost more upfront, but from what I hear you have better temp management and lower utility bills...


However, the cost for me to put in one was ridiculously high... so I just had them replace the outside motor on my old unit and keep using that...
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Old 06-21-2015, 06:16 PM   #5
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The furnace does have an igniter, but it is definitely showing its age, as well. Drain line is not a problem. One of my major concerns is that the recommendations for the AC will come in too large, although I suspect the current unit is too small, to tell you the truth.
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Old 06-21-2015, 08:57 PM   #6
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The single biggest problem I had when replacing both my furnace and my AC (sequentially) was that contractors refused to do a Manual J calculation to determine the right size. Instead they wanted to base it off the existing equipment or use a fudge factor based on square feet and install a much too large unit.

This is a big deal because a furnace that is too big cycles too often and does not maintain an even temperature, and is not as efficient as a properly sized one. An AC too large does not properly dehumidify the air , does not hold an even temperature and wastes energy. ...
I agree that you don't want either to be over-sized, for the reasons you mention.

I'm not sure I agree on the need for a Manual J calculation if you have history with the present equipment. I've made notes on the run time of our furnace on the coldest, windiest days, and I don't think I've ever caught it going over ~ 2/3rd on-time. Our A/C does a great job of getting the humidity out, but that makes it marginal for hot days when we have a crowd over - a two stage is probably the only real solution for that, or just live with it.


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The furnace does have an igniter, but it is definitely showing its age, as well. Drain line is not a problem. One of my major concerns is that the recommendations for the AC will come in too large, although I suspect the current unit is too small, to tell you the truth.
As I said above, I think your history is good guide. Taking any higher efficiency into account (I guess A/C is actually measured on cooling delivered, while furnaces are BTUs supplied - odd?).


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Old 06-21-2015, 10:06 PM   #7
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One of my major concerns is that the recommendations for the AC will come in too large, although I suspect the current unit is too small, to tell you the truth.
Yes, you don't want an AC unit that is too big (it doesn't adequately remove moisture in the air, even though the house will be cool enough.). If you think your old unit was too small (running very long on the very hottest days), then consider going up a small amount, but don't let them sell you a unit twice as big as your old one. Bigger equipment really doesn't cost them much more, they like to install more tonnage of AC so they don't get callbacks because the house doesn't cool.

It's summer and hot. This is obviously a bad time to shop for AC. Consider buying a window unit or a portable unit (about $300), it might be a good investment in mental health and marital bliss and give you time to sort through the options without a lot of pressure. You could very well end up saving several times the $300 by not rushing into this, taking the extra days it takes to get more quotes and find someone you trust and equipment/installation at the right price. And, you can sell the window/portable unit to someone or keep it handy for the next time the AC goes out. If it's not too noisy and you are a pennypincher, you can use it to cool just your bedroom at night even after your central unit is fixed, you could save enough to pay for the thing in a couple of years.

Brand recommendation: I have a Goodman furnace, I installed it myself. They also make AC units, and they are good. This equipment is made on the same assembly lines and using the same standardized components as many nationally advertised brands. It's frequently chosen by plant managers and industrial specifiers--no need to pay for an expensive dealer network and lots of advertising. An installer who handles just name brands (Carrier, Trane, etc) will not speak well of it--but it is good.

Here's a site (Alpine Home Air) that sells Goodman HVAC equipment directly to homeowners. It's where I bought my furnace. When you get some quotes for equipment, check against these prices and see if the quotes are reasonable. (I have no connection with the company, except as a customer). A 3 ton 14-15 SEER AC unit should run about $950, add another $300 to $350 for the evaporator coil. Obviously, other incidental supplies will be needed, too.

Good luck!
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Old 06-22-2015, 05:10 AM   #8
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We're getting quotes, but probably won't act on them until winter, when we'll get some other bids and work with our preferred supplier to bring his quote down to that of the competitors. What he's talking about now is about $4500 for a replacement for our 2.5 ton unit (including the coil), and $5500 for a replacement for our 3 ton unit (again including the coil), plus a bit to upgrade to a variable stage unit.
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Old 06-22-2015, 06:44 AM   #9
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buu: do those prices include the furnace? jjquantz: you should check with the power and gas companies local to you and see if any rebates for high efficiency are available in your area.
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Old 06-22-2015, 06:57 AM   #10
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Just the coil - not the whole furnace.
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Old 06-22-2015, 07:56 AM   #11
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Just the coil - not the whole furnace.
Sounds high. I had a two ton AC installed with new coil for about $2500, Two stage 95% furnace was about the same cost.
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Old 06-22-2015, 07:57 AM   #12
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I suspect the pricing is local. I'm sure it would have cost much more where we used to live.
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Old 06-22-2015, 09:47 AM   #13
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IMO, they should perform a sizing calc, and also make sure you have sufficient vents and returns for the system to cool all rooms in a balanced manner. Don't go for any older freon systems that could still be in inventory and sold at a low ball price.
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Old 06-22-2015, 10:04 AM   #14
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Samclem, I have considered getting a window unit, but DW works from home 2 days/week and it's hard to see how I could set things up for her to have a comfortable work area AND give us a cool bedroom. I have warned DW that this may be a protracted process - even if we were to jump at the first bid (not going to happen) then their crews might not be available for a week or two or more.

frank, a quick search shows no rebates for AC or furnace replacement from my service providers. I'll check more closely.

One other bit of information - our 12 month trailing total cost for gas and electricity is $1875, $1075 of that for electricity and $800 for gas (all heating). Taking out the base electric load to try to determine the total AC cost leaves about $350-$400/year in AC cost. Not sure how this is useful, but I am prepared to present this to the sales rep if he starts in on how we can save "hundreds of dollars per month" on heating and cooling.
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Old 06-23-2015, 08:17 AM   #15
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Sounds high. I had a two ton AC installed with new coil for about $2500, Two stage 95% furnace was about the same cost.
Travelover,

May I ask what brand and what state you are in? $2,500 sounds like a good price. I'm in eastern Pa. New heat pump / ac combo with new indoor coil goes for around $5,000 here, I think.
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Old 06-23-2015, 08:21 AM   #16
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Travelover,

May I ask what brand and what state you are in? $2,500 sounds like a good price. I'm in eastern Pa. New heat pump / ac combo with new indoor coil goes for around $5,000 here, I think.
SE Michigan. Furnace is a two stage 95% Lennox, AC is a mid range Carrier. My memory was incorrect, I paid $3400 for the furnace, 4 years ago.

If you look at the Alpine site that samclem linked, you can see what the hardware costs (retail).
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Old 06-23-2015, 11:43 AM   #17
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Samclem, I have considered getting a window unit, but DW works from home 2 days/week and it's hard to see how I could set things up for her to have a comfortable work area AND give us a cool bedroom. I have warned DW that this may be a protracted process - even if we were to jump at the first bid (not going to happen) then their crews might not be available for a week or two or more.
You might consider one of the roll-around portable units (something like this). They aren't too pricey, and you could put it where she is working during the day, move it to the den/LR after work, then to the BR at night. You just need a window within a few feet to vent the warm air from the condenser. Many now have technology that eliminates the need to empty out any condensate unless it is very humid--it gets sent out as vapor through the vent to the outside.
If my AC broke down, getting a window or portable unit as a stop-gap would be the cheapest answer, as I know DW would be spending every night at the Marriott until the thing was fixed..
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Old 06-23-2015, 12:13 PM   #18
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You might consider one of the roll-around portable units (something like this). .........
A good suggestion, but it is worth noting that these come in two flavors - one hose and two hose. The two hose units work much better, as the one hose units are constantly blowing cooled air out the window and sucking warm outside make-up air through the home's air leak passages.

Example: http://www.amazon.com/Whynter-ARC-11...oner+dual+hose
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Old 06-23-2015, 12:18 PM   #19
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A good suggestion, but it is worth noting that these come in two flavors - one hose and two hose. The two hose units work much better, as the one hose units are constantly blowing cooled air out the window and sucking warm outside make-up air through the home's air leak passages.
Thanks, I didn't know about the two-hose units. That does sound more efficient. I've got a one-hose model I use in an outbuilding, now I have a good DIY project to see if I can modify the source of air for the condenser cooling.
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Old 06-23-2015, 01:02 PM   #20
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Current units operate at higher pressures than decades-old ones. Typically this means they generate more noise, especially when operating as heat pumps during winter.
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