AC - possible problems

[Brian Dors]

Hi, I'll try and give as much info as possible, whether needed or not. 1250 sq ft, brick ranch, 1956 construction, original windows. Insulation - so/so. Cleveland, OH area - we'll see a few mid-90s days a year.

Had a Amana SV 80 furnace 70,000 BTU (maybe 75,000, whatever amana makes in that "size") put in in October. Worked great through the winter, though I wish it was quieter. We decided to have the installer wait and replace outdoor AC unit in spring. Indoor coil was a 2.5/3 Ton unit, he says he installed the 3 Ton valve in it. His plan was to have a 3 ton indoor setup paired to a 2.5 ton outdoor unit.

I just had the AC compressor put in this week. It's not cooling all that great. He said a 2.5 Ton was plenty big. I warned him that this house got hot easily (black roof) and that the previous AC had to literally run all day long on hot days just to keep the temp even. On hot days with the old unit, whatever temperature I turned the AC on at, was the temp it was able to simply "hold steady" during the day, only starting to drop after the sun went down.

The other day I turn on the new AC. Outdoor 85F. Indoor starts at 84F and hits 80.5F in 2 hours. Humidity drops 6% during this time, from 36% to 30%. So it's better than the old system but this still seems weak to me. I'm no expert but I would have thought more than 3.5 degrees in 2 hours. I measured the air coming from a medium-length duct run as 63 F.

I noticed he did NOT add any refrigerant to system. I realize it's pre-charged from factory but the manual says it's charged for up to 15' of pipe if I'm reading correctly. I have about 30' to the indoor coil.

Also, how do I set the blower speed of the SV 80 furnace during cooling? I found the diagram that shows which color wire to use for lo/med lo/med high/high during heat operation, but it just says "check installation instructions for setting blower for cooling operation". I didn't find the info in the installation instruction booklet. Isn't there a separate speed setting during cooling? I'm thinking going up one speed may help me out.

What should I do first? He did measure the pressure of charge at install. If it was near the min of the range and he added some would that help me noticeably? Can I bump up the blower speed? (I know the air won't dry as much, but I don't like very dry air, messes up my sinuses.) Should I bite the bullet and request he get rid of the 2.5 ton outdoor unit and put in a 3 ton?

THANKS!! Brian

[Noon-Air]

First off you really need to post this at alt.home.repair Second, I gotta ask 2 questions (pretty sure I already know the answer) 1) Did the contractor actually *do* a heat load/loss calculation?? 2) was your contractor the lowest bidder??

Now for a little information.... A correctly sized system is supposed to run constantly to maintain the design comfort levels (usually 70 - 72 for heating and 75-78 for cooling) at the design temperatures for your area. This should have been explained by your contractor. A correctly sized system will *maintain* the design comfort levels....not bring a really hot or really cold house to your comfort levels. Bigger is *not* better. A correctly sized system will be a whole lot more cost effective to operate. A correctly sized system with correctly sized ductwork will also be much quieter. BTW... a thermostat is a temperature controlled ON/OFF SWITCH...turning it up/down isn't gonna make the system work any harder. Set the thermostat and forget it.... the only time you should even need to touch it (other than switching from heat to cool) is if you are going to be gone for more than a day or 2...then set it back about 10 degrees.

[Brian Dors]

No he wasn't the lowest, he was the highest of 3, highly recommended by others.

Let me ask you this then. I am ABSOLUTELY sure he has the blower speed on either low or medium low. I know this because he had it on high temporarily when installing the furnace, and then he set it to the very lowest setting. When I switch between heat and AC, the blower works at the same speed.

Does the Amana SV 80 not have a separate cooling-mode blower speed setting? I have looked at the wiring diagram and there's just a box there saying See Installation Instructions. If someone could look up information on how to set the blower speed during AC operation I would be extremely greatful.

If you're posting a reply, please only reply to alt.home.repair. Thank you. I apologize for cluttering up the wrong group and I will use this message to move the thread over.

Thanks again. Brian

[Noon-Air]

The current blower speed setting *might* be the correct one for that particular system....A/C systems airflow is critical....400CFM per ton(plus or minus)...if you screw with the blower speed, you will be altering the entire system balance.

Yes the furnace will have multiple blower speed settings... keep in ming that your SV-80 may have a 4 ton blower drive in it...this means that the blower speed could most probably be varied from as low as 1000CFM (2 1/2 ton) to 1600CFM(4 ton). If it isn't broke, don't fix it.