Learn Me: Home HVAC

BLUF: I just don't want to be taken for a ride by some of these AC repair companies. 

The unt: My house is 17 years old and so is the AC unit. The air handler is located centrally in the home on a raised platform in it's own closet. Not my ideal design but hey it's literally "central A/C." It's a Carrier 10k BTU and the house is just under 2000sq ft with 15ft ceilings in 1500sq ft of the house. 

The problem(s): Recently the capacitor went out in the outside fan. Luckily I have a couple of spares so easy fix. It prompted me to do a thorough inspection of everything. I replaced the same capacitor about 2-3 years ago so I was curious what would cause the same thing (thinking strain at this point). I realize that the condensation drip pan/piping hasn't been doing its job and has been leaking all over the platform. This has also caused a spur of mold and mildew in the A/C closet as well as saturating some drywall that connects to the kitchen. The coils were somewhat dirty (had them thoroughly cleaned about 2-3 years ago), also had new freon put in after a snafu with the outside unit and a lawn mower blade, and kept the system fairly maintained. So maybe just a crappy capacitor....

My worries: The mold and mildew. It looks like black mold and its spotted throughout the air handler. Could it be in all the venting as well? I'm also worried that these guys are just trying to sell me a product. They all also quoted me $1200 in "system" cleaning. 

The A/C Repair Companies:  I've gotten three quotes from three separate A/C companies. They all recommend replacing the whole A/C system at a cost of $6500-7500. This doesn't include duct cleaning or fixing the platform and dry wall in the A/C closet. The system has been cooling the house pretty well and the power bill has been fairly reasonable for the summer months. They all said to go with a 14k BTU system since "No one makes 10k anymore!"

That seems to be somewhat on par with what I've experienced.  Mine was stoopid cheap because I already had the evap and ducting that the previous owner had installed with the forced air furnace.  Mine was just an installation of the compressor/condenser and some lines in to the evap.  I added my own service whip because it was just outside the breaker panel.  That was a $1400 job two years ago, and it was only a 1-ton unit.  A 1.5T would have been a bit more appropriate for the size of the house, but we were limited by the evap/duct size, but I'm incredibly happy with it.  835sf house with only 84" ceilings in PA.  Keeps it nice and cool, and it's cheap to run.

As far as the mold is concerned, easy fix.  Concrobium liquid and a mold fogger.  Easy to rent at most places.  Concrobium is an inert solution of salts.  When it dries, the crystals crush mold spores killing it.  Use the fogger on the closet for a while to kill it on the walls, then turn on the HVAC fan and point the fogger at the air return.  That will suck it through the whole system.

Concrobium won't take away stains like bleach, but it does kill the mold very effectively.  It's what pros use for mold remediation.  After the concrobium treatment you can use bleach on the walls to get rid of stains and then paint over it.... or just paint over it with Kilz and forget about it.

First question would be is it an old R-22 system?

Can the drywall be repaired without having to remove the air-handler?

I am always amazing how many jobs i get called to because condensate drains were poorly executed, and/or not serviced well.

Most newer systems have floats in the drain pan that turn off the system if the pan fills without draining.

10K btu for 2000 sq-ft? That seems small. Mine is 36k btu for 1800 sq-ft. Where are you located?

My unit is about the same age as yours. My plan is to run it until it has a catastrophic failure. 

In reply to DirtyBird222 :

Are those quotes for regular a/c or heat pump systems? Our house has two independent systems and we had those replaced last year with heat pumps for IIRC around 5k-6k each, without additional repairs though.

The heat pumps massively cut down on the amount of oil we needed to heat, so that might be something worth looking into.

Casa de DX has no central air but duct works in place so that is next house job. Have one window unit for bedroom and one for living/dining room but apparently its too small and can't keep up. I think its a 10k btu and recommendation was a 14k btu to keep up..

This seems crazy high - this is DC metro pricing and your profile says FL.

Need to know specifically what AC/heating components they're replacing as the "whole" - air handler too I guess?

Also ask for SEER ratings for efficiency. I targeted 16 as a sweet spot.

Agree you want more cooling, esp in FL - minimum 3 tons aka 36k BTU

Purple Frog (Forum Supporter) said:

First question would be is it an old R-22 system?

Can the drywall be repaired without having to remove the air-handler?

I am always amazing how many jobs i get called to because condensate drains were poorly executed, and/or not serviced well.

Most newer systems have floats in the drain pan that turn off the system if the pan fills without draining.

Sorry to hijack but its a/c related.   My system started shedding a lot of water last summer.  Drain is working but it was so bad the air plenum had water dripping from it and ruined the sheetrock ceiling below it..  I had an a/c guy check it out and they installed a splash shield just downstream of the cold coils before the plenum to get the air stream to shed the water droplets the fan was blowing into the plenum.  This solved some but not all of the problem.  

Its still blowing water into the ducting and I'm getting mold growth in the ducts.   What should I be considering is the issue?     I  had another a/c guy come out and he wanted me to rebuild my roof line because he said the unit was too close to the bottom side of the roof (about a foot, unit is horizontal and a duel heater & a/c 4.5 ton unit) and this was heating up the unit's sheet metal and causing excessive internal condensation.   (?)

Don't you want a smaller one in more humid climates? Idea is that it runs almost constantly and dehumidifies more effectively.  10k still sounds small but I'm no expert. 

So much goes into proper sizing of units:

Square footage of space.  Climate zone.  Amount of sun exposure.  Amount of insulation. Number of windows and placement.  Type of construction, yadda, yadda, yadda.

Many newer units have much better SEER ratings.

Too big of a unit can be a real problem for proper humidity control.

For units mounted in the attic space, many times we mount thermostat controlled fans in the gable ends to circulate air through the attic to try to lower attic temps.  and we insulate the outside of the metal ductwork in the attics.

OBTW, condensation should never being blown from the coils into the ducts.  Something seriously wrong there.

The house is in Central Florida. 
The front of the house faces East and the East and South facing walls have the biggest windows. It's nice for natural lighting but def heats up those rooms mid day as the sun beats on them throughout the course of the day.  Attic has about 30inches of that spray insulation that feels like wool ( don't know the appropriate name for it). Exterior walls are concrete block with insulation in the block. Open concept with 15ft ceilings in the living spaces, master bedroom, and den. 10ft ceilings in all other spaces. 

I may have misheard the quoting on the BTU rating incorrectly; however, IIRC from my research years ago, the humidity factor plays a part here. I'm sure someone else can explain that better. 

This unit does have a plunger for the condensation drip. The condensation was routing itself elsewhere.

All the quotes were to replace the outside fan component and the inside air handler. 

So I think time to fix the mold first for air quality, plus so the AC guys don't get the sense you want a new system ASAP from the mold.

So to be clear, 6.5-7.5k to replace #2-5 in the below diagram?  7.5k gets you the whole lot up here, and #1 is like a 1.5-2k job on its own.

I am skeptical that local market adjustments can offset what I assume are cheaper operating costs in Central FL (but learn me Florida) v DC.

I concede oversimplifying the sizing recommendations - thanks for the corrections.

zoomies - thanks for the diagram. They want to completely replace 1-5 with new units. I wouldn't mind paying the $6-7k if that including killing off the mold, fixing the drywall, and the platform as well. 

It's also peak A/C repair season in Florida due to it being well....summer time. 

I have no idea what type of freon the system uses. I'll have to look at that next time I'm back there (out for work travel). 

Other than ductless units no manufacturer has made less than 18,000 BTUH (1.5 ton) splits for years.   If you can get the manufacturer and the model number off the outdoor unit nameplate and post it I should be able to break it down.   A load calculation is really the answer to what’s required, as mentioned above the system needs to be sized correctly to dehumidify properly.  Oversized systems are terrible for comfort, the unit won’t run long enough in cooling to dry the air out and it will always feel clammy.

17 years old is probably getting long in the tooth for Florida, I got 23 years out my last system but I’m in the northeast.  Almost certainly an R22 system, it’s no longer in production so available stock is from reclaim / recycling programs.   It’s not hard to get but current prices for a 30 pound cylinder run close to $400.00 before any service company mark up. 

The mold issue sounds like it’s more related to the backed up drain pan.  Fix the drainage issue if you haven’t done so already. Spray and wipe down the insides of the air handler and keep an eye on things.  Chances are it’s only in the areas that stayed wet due to the clogged drain. 

Finally and as you noted it’s peak season for cooling work.   See if you can get it to go into the fall or winter. You should be able to get more competitive numbers when it’s not crazy busy. 

11GTCS said:

Other than ductless units no manufacturer has made less than 18,000 BTUH (1.5 ton) splits for years.   If you can get the manufacturer and the model number off the outdoor unit nameplate and post it I should be able to break it down.   A load calculation is really the answer to what’s required, as mentioned above the system needs to be sized correctly to dehumidify properly.  Oversized systems are terrible for comfort, the unit won’t run long enough in cooling to dry the air out and it will always feel clammy.

17 years old is probably getting long in the tooth for Florida, I got 23 years out my last system but I’m in the northeast.  Almost certainly an R22 system, it’s no longer in production so available stock is from reclaim / recycling programs.   It’s not hard to get but current prices for a 30 pound cylinder run close to $400.00 before any service company mark up. 

The mold issue sounds like it’s more related to the backed up drain pan.  Fix the drainage issue if you haven’t done so already. Spray and wipe down the insides of the air handler and keep an eye on things.  Chances are it’s only in the areas that stayed wet due to the clogged drain. 

Finally and as you noted it’s peak season for cooling work.   See if you can get it to go into the fall or winter. You should be able to get more competitive numbers when it’s not crazy busy. 

You guys are awesome. The drain/drip pan issue is fixed and will work on cleaning everything once I get back. I agree that 17 years in long in the tooth and most likely a necessity prior to selling the house. I have a lot of equity in it already; but, a few of these guys pulled a total scare tactic on the mom. She bought into the black mold/mildew sales pitch, which means I'm getting an earful for a remedy haha. 

I had her look at the unit and she said it's a 3.5 ton. 

Rates from the A/C company that came out the other day. 

In reply to DirtyBird222 :

Those are flat rate sheets, north of 60% margin in those numbers and generic “one size fits all” as if your installation is the same as every other.  (It isn’t ) Not that I don’t expect an installer to make a fair profit on a properly installed job (hint, this is what I do on the commercial side) but flat rate book pricing is absurd. 

3 1/2 tons sounds in the ballpark for that size house and where you’re located. Post the make and model of the outdoor unit and I’ll confirm if you like.   My suggestion is to spend the next few weeks researching your local contractors, I’m sure there’s a few that will stand out. Get several quotes, ask a lot of questions and don’t necessarily choose the lowest price.  Often it’s the one in the middle of the pack that has everything covered that will give you the best value.  

It sounds as if you’re selling this house, if that's not the case and you plan on staying long term I have a suggestion to discuss with whichever contractor you choose: Ask them to price upsizing the indoor unit (air handler) by 1/2 ton.  (4 ton inside if you have a 3.5 ton outdoor unit).  The larger indoor coil will improve dehumidification significantly because of the larger coil area and slightly increase system efficiency. There’s essentially no difference in price between a 3.5 and a 4 ton AHU, it should be a small increase.  I did this when we replaced our original units and it really improved comfort, getting moisture out of the air is what’s really important.

My only suggestion is go with the 14 SEER. 

When I considered building a new home before I bought this one, the builders all told me the upfront cost of the higher SEER ratings don't pay for themselves before they need to be replaced.

I'm surprised at the cost to install the unit.