Questions from a homeowner...

[therlinger]

Ok, we are making some upgrades to our home. CBS construction, central a/c is four years old. We are going to put in double glazed Low-e windows. My power bill was pretty high this last month. I live in Central Florida-hot and humid. A/C guy came today to look at unit. Said unit is too big for house (1266 SF - 3 ton unit). He says we will have mold problems behind the walls and suggests replacing everything with a 2.5 ton unit. Problem we were having was that air seems to kick on every ten to fifteen minutes and what we thought was leaking from the pan. Turns out the line is sweating really bad and leaking out thru a small cut in the line insulation. Air handler is in the laundry room which is not insulated and gets pretty warm. Also, they A/C guy said whoever installed this unit did a poor job as the box around the bottom is not plywood but a rigid type of insulation that is taped together to form a box. It should be a three sided box with the fourth side open to the return. It turns out the back side (against the wall) isn't actually boxed in and is open to the room, thereby sucking in the hot air from the laundry room. He says it should be a completely closed system. His company refuses to even attempt to fix the problem and will only work on it if we buy a whole new system and remove the one we have. It's only four years old and seems to keep the house cool, but I'd like to see my power bill not be the ridiculous price it was last month. Is my only option really to have a whole new system installed? Can't I just have the box enclosed? And what about the line sweating the way it is, it should sweat that much, should it? Also, will replacing the windows in the house help? I have terrible roll out awning style windows from the 60's. I'd like to thank everyone in advance for any help they can offer and hope that my post isn't too annoying to the pros.

[amd]

Replacing your windows will reduce heat gain (not sure by how much), but the A/C unit will run for a shorter period of time and not remove humidity very well.

It sounds like the guy doesn't want to be liable for potential mold and performance issues - quite understandable. However, I don't see how reducing the size by 1/2 ton will make a significant difference. Ask for a heat gain calculation.

A properly sized system will run continuously on the hottest day of the year.

Out of curiosity, how much energy is being consumed? (give in kWh, not cost)

[therlinger]

according to my bill total Kwh used for the month between May and June was 1533 approx. 51/day. If a properly sized unit will run continuously on the hottest days of the year and every day is 95 - 100 degrees then essentially my unit should be running constantly during the day from June thru September. Is that correct? How can that be efficient or affordable for anyone?

[markwolf]

Originally posted by therlinger
according to my bill total Kwh used for the month between May and June was 1533 approx. 51/day. If a properly sized unit will run continuously on the hottest days of the year and every day is 95 - 100 degrees then essentially my unit should be running constantly during the day from June thru September. Is that correct? How can that be efficient or affordable for anyone? Look at it like a car.stop & go traffic uses much more gas than the highway.It is the same way with ac.It takes three to five times more power to start an electric motor than it does to run one.Longer run times & less starts=money saved.

[acbyj208]

you have to do a load calc. then size it properly. i live in phx at 110 my two speed lennox runs 24/7 in low and shifts to high when needed, usaly at 3 o clock or so when its hot as hell. i have 1300 sq ft insulation and dual payne low e windows. without a load calc you are guessing.

[danglerb]

Replacing a less than 5 year old system due to "minor" size problems and major ductwork problems, sounds like you need more bids.

Now if the whole original installation is full of cheap equipment installed poorly, maybe the smart thing is to just replace the whole thing and fix everything at once. Just taking a wild guess, if the AC is a total hack job, you may have PLENTY of places to spend money around your house other than AC.

Sealing and insulating has to be done, otherwise its throwing money away. Proper repairs could require disconnecting the old system, and that could make replacement at the same time a "bargain" in the long run.

Now is a busy time of the year, contractors that might be willing to try and clean up a hacked in system when its slow, might be less flexible when they already have all the work they can handle.

You need more bids, plus tell us full model numbers, and maybe post some picts of the nasty stuff.

[browntigerus]

I would hAVE send him packing w/o pay. It is not your problem, if he is refusing to work on your system ( and may be he is right when doing so ).

Those sounds like minor problems, and replacing system cause 1/2 too large is absurd.

1/2 would make almost no difference on electric bill,
but fixing air leaks / insulation will.

> Problem we were having was that air seems to kick on
> every ten to fifteen minutes and what we thought was
> leaking from the pan.

Air leaks, location of the thermostat, anticipator will make more impact than 1/2t change.

Ask manufacture rep, if they could send someone to look at it...

[beenthere]

4 Years old. Don't want to change that out unless its a ton over sized.

Do your window upgrade first.
Then see if you can improve any other areas of the house, attic insulation, and weather stripping to minimize infiltration.

The suction line insulation can be repaired or peplace easly.

Have another company check it, and see if the blower can be slowed down, this will help with humidity.

Then go to this link, and do your own load calc, and if your oversized by a ton, then you should have the unit changed out.

http://hvaccomputer.com/talkref.asp