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Old 07-18-2012, 05:18 PM   #21
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I would check you insulation level in the attic. I added R-30 to the existing R-12 and it helped reduce the 1st/2nd floor temp variations. Also, check if your system has a variable speed AC/DC motor. I was told by every estimator to run the fan 24/7 which would cost me very little in energy use and it would reduce the temp variations too. With both of these changes, there's a 4-6 degree difference compared to 5-9 degrees last year.

I did have 2 separate HVAC systems in my old house, but you'll need to pay for additional duct and install costs for 2 separate systems/maintenance. The advantage will be precise control of temps for each floor/area and overall lower utility costs.
We have lots of insulation.... my difference is about 4 or so degrees, but that is noticable when you have the downstairs at a higher level to save money...
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Old 07-18-2012, 06:34 PM   #22
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Ah, that's a component that helps protect the (expensive) compressor from getting fried by power flickers, surges and spikes. It's essentially the A/C equivalent of a surge protector "taking one for the team" and dying to protect the components plugged into it. It always sucks when A/C goes out this time of year, but at least the cheap part "did its job".
It's actually used to help create more of a rotating magnetic field by delaying one of the motor windings. Otherwise you can't turn a motor with single-phase AC power.
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Old 07-18-2012, 07:00 PM   #23
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We have lots of insulation.... my difference is about 4 or so degrees, but that is noticable when you have the downstairs at a higher level to save money...
The comfort of a split system will spoil you, I miss having it in our current house. It's best to do it when you need to replace your current setup unless cost isn't an issue. I went from hot water heat/cold water cooling all water pipes to gas/AC using duct.
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Old 07-18-2012, 08:20 PM   #24
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Just to clarify a few points:

1. As someone pointed out, it's a "start capacitor" which enables the compressor to get going. It has limited use as a surge protector. When the capacitor goes out, the compressor can't start. Most systems have the fan motor wired into the same capacitor for the same reason, so when the capacitor goes out the fan isn't running either. All you hear from the outdoor unit is a faint hum.

2. Many recommend a "boost" capacitor, which helps to lower the initial electrical current required to start the compressor.

3. The longer an AC unit runs, the more efficient it becomes. It is removing humidity from the interior air, and dry air is easier to cool than wet air. It also reduces the heavy electrical draw required to start the compressor each time. If you've got a system that can cool your home down to 78 when it's 105 outside and then cycles every hour or so, it's most likely oversized for your home.

4. Zoning one unit can provide the same efficiencies as two units at much lower costs - both initial and ongoing. Besides, seldom are any of us in all rooms of our homes at all times. Why heat/cool the entire space if we aren't using all of it?

5. The other old "rule of thumb" of 1 ton of AC for every 500sf of space has been replaced with much more exact science. For instance, I have a 3400sf two story in central Texas that has a single 5 ton unit. And when it's 110 degrees outside, it's 78 degrees on the inside with only a 2 degree differential between first and second story. Most would have thought this house would have required 2 systems. But a Manual J calculation of the heat load of the house works out to 5 tons with a bit of capacity left. And in practice, it's proven to be very efficient. This month, our electric bill was less than $190 and that's with the AC set to cool down to 70 from 6am-8am, up to 82 until 5p, down to 78 until 10p, and 74 from 10p-6a.
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Old 07-18-2012, 09:55 PM   #25
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Just to clarify a few points:

1. As someone pointed out, it's a "start capacitor" which enables the compressor to get going. It has limited use as a surge protector. When the capacitor goes out, the compressor can't start. Most systems have the fan motor wired into the same capacitor for the same reason, so when the capacitor goes out the fan isn't running either. All you hear from the outdoor unit is a faint hum.

2. Many recommend a "boost" capacitor, which helps to lower the initial electrical current required to start the compressor.

3. The longer an AC unit runs, the more efficient it becomes. It is removing humidity from the interior air, and dry air is easier to cool than wet air. It also reduces the heavy electrical draw required to start the compressor each time. If you've got a system that can cool your home down to 78 when it's 105 outside and then cycles every hour or so, it's most likely oversized for your home.

4. Zoning one unit can provide the same efficiencies as two units at much lower costs - both initial and ongoing. Besides, seldom are any of us in all rooms of our homes at all times. Why heat/cool the entire space if we aren't using all of it?

5. The other old "rule of thumb" of 1 ton of AC for every 500sf of space has been replaced with much more exact science. For instance, I have a 3400sf two story in central Texas that has a single 5 ton unit. And when it's 110 degrees outside, it's 78 degrees on the inside with only a 2 degree differential between first and second story. Most would have thought this house would have required 2 systems. But a Manual J calculation of the heat load of the house works out to 5 tons with a bit of capacity left. And in practice, it's proven to be very efficient. This month, our electric bill was less than $190 and that's with the AC set to cool down to 70 from 6am-8am, up to 82 until 5p, down to 78 until 10p, and 74 from 10p-6a.

What do you mean by zoning one unit

How do you get the rest of the house cool when you need it? PS... we need it most of the time because my kids are in their rooms upstairs... my wife is in her studio upstairs, I am downstairs watching TV or in the bedroom...
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Old 07-19-2012, 12:07 AM   #26
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What do you mean by zoning one unit

How do you get the rest of the house cool when you need it? PS... we need it most of the time because my kids are in their rooms upstairs... my wife is in her studio upstairs, I am downstairs watching TV or in the bedroom...
I'm familiar with zone heating with a boiler. Each zone is controlled by a separate thermostat tied to a automatic damper and to one heating system. It can control zone 1 heat only, zone 2 heat only or both zones together.

Here's a link to one zone controller I found (there's a 4 zone unit too):

HVAC 2-Zone Controller - Smarthome
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Old 07-19-2012, 12:18 AM   #27
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I have my HVAC guys come twice a year for maintenance - once for AC and once for the furnace. Being on this plan bumps me up to the head of the line if I ever do need an urgent repair, which is the main reason I do it. When they did the AC check a couple of months ago they said the capacitor "would need replacing soon." In the real world this means that the AC would probably die on July 4th when it is 102 degrees (NC). I went ahead and had them replace the capacitor - $93 for peace of mind. We've just had a string of killer 100+ degree days, so it was money well spent.
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Old 07-19-2012, 10:11 AM   #28
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I'm familiar with zone heating with a boiler. Each zone is controlled by a separate thermostat tied to a automatic damper and to one heating system. It can control zone 1 heat only, zone 2 heat only or both zones together.

Here's a link to one zone controller I found (there's a 4 zone unit too):

HVAC 2-Zone Controller - Smarthome

Wow... interesting.... I know they had them on the water systems, but did not know they had them for forced air for the home...

I wonder if my ducts are set up separate enough to do this...
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Old 07-19-2012, 10:35 AM   #29
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Wow... interesting.... I know they had them on the water systems, but did not know they had them for forced air for the home...

I wonder if my ducts are set up separate enough to do this...
Yes, surprised me too but your comments made me curious, so I checked around. Makes me want to look into this setup. It's a lot cheaper than adding another HVAC system. I talked to 4 companies when I replaced my AC unit and mentioned the temp change issue between the 2 floors and none of the installers ever brought something like this up.

Check your ducts on your system. If the installers did it correctly, your duct would be have two main trunks that separate the floors. You may have manual dampers so you can limit air flow, tweaking the dampers may provide the adjustments you need. My dampers are setup this way and most room have dampers too. As I mentioned before they don't shut off flow 100%.

I had an auto damper setup on my exhaust from the boiler when I replaced it back in the early 90's. This supposedly made it more efficient reducing heat loss, worked for 2 years then started having problems and triggered the safety limit switch multiple times preventing the boiler from heating and it had to be replaced at my cost since it wasn't covered by the boiler warranty. I ended up not replacing it when told these items break down frequently. Maybe they've improved since then.
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Old 07-19-2012, 12:54 PM   #30
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Zoning is such an inexpensive yet effective solution that most HVAC companies would prefer NOT to talk about it.
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Old 07-19-2012, 01:44 PM   #31
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Zoning is such an inexpensive yet effective solution that most HVAC companies would prefer NOT to talk about it.

I did some research and found 3 firms that are advertising it near me.... they all seem to be using the same web format, so they are probably linked by some major distributor....
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