OT - I need some home AC system advice...(long)

caliking · April 2015

Here's the scenario: 3700 sq ft house, built in 2003, 2.5 ton unit for the upstairs, 3 ton unit for the downstairs, both made by Amana, 14 SEER maybe. 95% efficiency ( I think that the right term) variable speed furnace. About 2 years ago, the upstairs wouldn't cool down, and I was told that there was a leak in the evaporator coil. Recharged with les than 1 lb of R22, so I figured I would let it ride and see what happened. About a month ago, I noticed that the upstairs unit was "short cycling" (the condenser's fan would start to spin and then shut off after a few seconds). This time it needed 6lbs to refill, and 2 weeks later it is now short cycling again.

So the options from the first vendor (American Standard) are:

1) replace the coil only for the upstairs for ~$2300 and see how long the condenser lasts.

2) replace condenser and coil for the upstairs ~$5000 for a 16 SEER system, ~$6200 for a 2-stage 17 SEER system

3) replace condenser, coil, and furnace for ~$7800 - 18SEER system American Standard Platinum XV Accucomfort variable speed system, Platinum SV variable speed furnace, Nexia Home Intelligence control.

2nd vendor:

Backed by Costco. I will get a 10% discount plus another 2-3% if I use my Costco AmEx. They will install Lennox systems.

1) Replace upstairs coil only for $2700

2) replace condenser and coil for ~$7000

3) the whole system for ~$11, 700. Model XC-21, Signature Series or something. Comes with IComfort tstat. 18.7 SEER. He only quoted me a solar-ready system, since I mentioned I may want to install solar panels at some point. Now that I think about it, we will probably be in this house for another 5 years or so, so I may not install the solar panels after all.

Part of me wants to just replace the evaporator coil and take a chance, part of me says that I'm just prolonging the agony by doing that, so go ahead and replace the whole upstairs system. The furnace is apparently a good one, so I kinda feel bad about replacing it if its still good. I will likely stick with the first vendor, since he came highly recommended. I was told that if I replace the condenser only, it will be charged with R22, but can be flushed and charged with R410A if I replace the furnace and condenser in the future. Yet another part of me says pick the middle ground and replace the condenser and coil, leaving the furnace in place. Hence, the cry for help.

If any pros out there what to throw their $0.02 in, or any homeowners who have been in this situation recently, or heck if you're bored this weekend... let me know what your thoughts are. caliprince sleeps upstairs, and Houston is starting to get warm, so I need to make a move on this soon.

Thanks!

nolaegghead · April 2015

No brainer to me. House fairly new, good insulation. Payback on the increase in SEER is not quick. Replace the evaporator. Leave the furnace if it works. 95% efficient are top of the line. You should have PVC ducting on the furnace if that's what you have, given the house age. You can get 15-20 years out of a system. All your components are modular. I would ask them to put a high efficiency evaporator in so when you do need the condenser, you'll have the high SEER system.

I put in my 14 seer system myself with a 95% furnace back in 2005. Not a single problem. The old system was almost 20 years old, and I was fixing it once or twice a year.

blasting · April 2015

I agree with @nolaegghead. SEER is less important than AC guys like to tell you. I'll add that I really like my variable speed, and living in AZ, where AC's are worked hard, I chose a Trane (American Standard is the same thing). I would also have been happy with a Carrier.

DoubleEgger · April 2015

Stay away from high SEER units unless it's new construction. Older existing ductwork generally can't handle the pressure of the new high SEER units. Bryant and Carrier are the same thing. Save yourself some cash if you go the full replacement route.

NPHuskerFL · April 2015

Reading each response. SEER less important than what "AC" guys say it is? That somebody would be the govt not AC guy. So the real big concern I see is repairing vs replacing you're still a slave to R22. R22 is beyond crazy expensive and likely makes up 40% of the repair total in option #1. That's a tough call but, personally I'd choose #2 which will get you a decent efficiency rating and refrigerant wise R410A vs R22.

tarheelmatt · April 2015

You plan to stay there, better replace now to get away from R22 and to have to increase SEERs later on and have replace duct work too.

tarheelmatt · April 2015

I was just faced with a similar situation. The unit wasn't cooling as well and not heating as well. HVAC guy said I could limp it for another year or so, but my energy bill was higher and just not as comfortable.

I decided to go new. Got a York heat pump with new air handler and UV light. Not planning to be here in 3-5 years but thought that would be a nice selling point to future buyers.

Got the unit, handler, UV light, digital tstat for $3k.

Was going to go with a NEST but guy actually didn't recommend with all electric heat pump.

NervousDad · April 2015

tarheelmatt said:

You plan to stay there, better replace now to get away from R22 and to have to increase SEERs later on and have replace duct work too.

Agree, R22 sucks, everything time I ever had work done on my unit they would tell me the need to collect it in a special way, which cost a fortune. I finally just had them replace my unit..

4Runner · April 2015

@tarheelmatt - strange. I have 2 Nest running my heat pumps. My brother went with the Ecobee. No issues. I think the guy wanted to sell you something else for some reason.

tarheelmatt · April 2015

4Runner said:

@tarheelmatt - strange. I have 2 Nest running my heat pumps. My brother went with the Ecobee. No issues. I think the guy wanted to sell you something else for some reason.

Actually, he could have upsold me to a Nest. He recommended the standard tstat that was included instead of a Nest.

What he explained to me was this. If I had natural gas heat instead of electric it would make sense to get a controller, however, with electric, if there's a difference of 3° the strip heaters will come on to get the temperature to the desired comfort. It's more efficient to just set the temp and leave the temp alone. As long as it's a temp that's not crazy you know. We set it to like 71-73°.

blasting · April 2015

NPHuskerFL said:

Reading each response. SEER less important than what "AC" guys say it is? That somebody would be the govt not AC guy.

Agreed, it is the government that pushes SEER, but a/c guys are to blame as well. Sizing a system properly is far more importaint than SEER, imho. If not sized correctly, the unit will short cycle and be inefficient - not to mention hard on the equipment. A/C salesman, in a lot of cases would rather blither on about SEER, instead of doing a proper load calc (required to properly size a system)

NPHuskerFL · April 2015

@blasting And that is precisely why, in FL at least, it is a requirement to have a Manual J preformed prior to changing out a residential HVAC system. + ductwork must be properly sized per spec too or a say a 4T 18 SEER system could very well only be performing to a 12 SEER at 3T capacity (this used to happen a lot). Glad I'm not a residential tech is all I can say.

nolaegghead · April 2015

What blasting said - sizing it is very important, esp with the older system. Oversizing will short cycle and it will be very hard on the equipment and humidity will be higher than you like. Undersizing will result wear out the equipment faster with long cycles.

The high SEER stuff is very advanced and deals with varying head loads better as it will unload tonnage through variable speed fans and high tech compressors, valves, etc.

You shouldn't have any leaks. R22 is expensive, costs your HVAC guy about $11/lb. You should never have to add any unless you have leaks. Fix the leaks. That's what the evaporator replacement should do for you.

caliking · April 2015

Thanks everyone for the input.

I will likely go with option 1 from the first vendor, and replace only the evaporator coil for the upstairs system. Will still give some thought to replacing the condenser, but I think its less likely. I am assuming that it will be okay to flush the evaporator coil and charge it with R410A in the future, if the condenser has to be replaced n a few years. I will ask for a higher efficiency coil to be installed.

chick533 · April 2015

How long do you paln on staying there? If moving in near future replace evaporator coil and be done with it. If you repalce the evaporator coil make sure a evaporator coil rated for R-410a is installed. That way when the condensing unit gives up the ghost they don't have to change out the coil for the new refirgerant.

Labor to install these units is the same if it's a 14 Seer or an 18 Seer. You are paying the higher price for the efficiency of the unit. Life cycle on this equipment is usually 20 years. Another question does you local utility offer any rebate money for higher effecent units. In my area the rebates will usually pay for the upgrade if you go 17 Seer or higher. Without a rebate I would not consider anything over 15 Seer.

On last thought there is a drop in replacement for R-22 that we have been using for several years with good results. It's called MO99, runs about 30% cheaper than R22.

4Runner · April 2015

tarheelmatt said:

4Runner said:

@tarheelmatt - strange. I have 2 Nest running my heat pumps. My brother went with the Ecobee. No issues. I think the guy wanted to sell you something else for some reason.

Actually, he could have upsold me to a Nest. He recommended the standard tstat that was included instead of a Nest.

What he explained to me was this. If I had natural gas heat instead of electric it would make sense to get a controller, however, with electric, if there's a difference of 3° the strip heaters will come on to get the temperature to the desired comfort. It's more efficient to just set the temp and leave the temp alone. As long as it's a temp that's not crazy you know. We set it to like 71-73°.

Understand all that...that is why the Nest knows what kind of system you have and adjusts accordingly.

lkapigian · April 2015

Man J S and D matter, proper sizing install and commissioning , select multi stage or VS as we size for a condition that only occurs 1 percent of the time

caliking · April 2015

@chick533 - I think we will be in this house for another 5 years or so. The utility company supposedly offers a $760 rebate, but only if the entire system is replaced. I was planning on installing a higher efficiency evaporator coil to make it "future-proof". Does that mean going with a higher SEER rating for the coil?

Does anyone know what a reasonable cost for replacing the evaporator coil would be? The interwebs says that it should run about $1000, maybe $1500 tops.

OT - I need some home AC system advice...(long)

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