Air conditioning for my house

[AlbertaNerd]

Originally Posted by -JR-

One think you will notice is all the cold air will sink to your basement if you do not have a way to close it off , like a door or a curtain .
If you don't close it off your A/C unit will run all day and never shut off. $$$

We put a bottom seal on the basement door, and a separate sensor down there (We have an Ecobee thermostat).

The only problem we've found is that the Ecobee says it measures the temperature of occupied rooms, but it seems pretty slow to respond to that. We've got it on "Maximum savings" too though, so that probably doesn't help.

Generally I'd recommend the Ecobee or something similar though. You can set it to switch off the heating or cooling when you go out. Nobody seems to agree whether that's a good or bad thing though.

[-JR-]

Originally Posted by flydude

Good point, another trick is to block off any return air grilles in the basement during the summer. This should only be done if your furnace will handle the extra pressure drop in the system.

Why would you block those ,i can understand closing the vents so cold air does not enter the basement but not the vents leaving .
Is it so the basement does not create negative pressure and draw air down from the basement

[Stinky Buffalo]

Originally Posted by -JR-

Why would you block those ,i can understand closing the vents so cold air does not enter the basement but not the vents leaving .
Is it so the basement does not create negative pressure and draw air down from the basement

I was wondering the same - my fan is set to run a certain amount of time per hour (regardless of whether the AC is on or not) to circulate the air around the house - the theory is that the cooler air from the basement is being blended with the warmer air from the upper levels... Or is that incorrect?

[Big Grey Wolf]

Stinky, you are correct, no use leaving All that nice cool air in the basement, when little fan time brings it where needed.

[Sundancefisher]

Important to put your ac unit where it will be exposed to less dust and debris like leaves and dryer vent exhaust and also get lots of unobstructed air flow.

Need to keep window shades down on the sunny side of the home.

Big swings in temp during the day like turning off and on… can really tax a unit.

I find it easier to maintain a temp throughout the day.

On cool evenings… opening a window and turning off the AC helps.

Also cold thunderstorms.

[flydude]

Originally Posted by -JR-

Why would you block those ,i can understand closing the vents so cold air does not enter the basement but not the vents leaving .
Is it so the basement does not create negative pressure and draw air down from the basement

If you block off the return air grille(s) in the basement this will produce a positive air pressure in the basement thus allowing the cooler air in the basement to flow upwards in the home. Keeping the doors to the basement shut will help limit the volume of air going upwards in the home. Blocking off the return air grille(s) in the basement will also cause the furnace to return more air from the upper levels which in most cases is hotter than that of the basement. There is no point in cooling the cold air in the basement. This also allows a higher temperature drop across the A/C coil because a warmer mix of air from the upper levels is being reintroduced back to the A/C coil. This equates to higher A/C system efficiency. Again, I do not recommend this unless you know your system will handle the added pressure drop as this could cause the A/C coil to freezer up due to lack of airflow during the cooling season, and if you forgot to open the return air grille(s) in the basement back up during the heating season the furnace could trip on high limits when on heating. Doors to the basement must be kept closed to limit the amount of air that will travel from the basement upwards. You could also close off the supply air registers in the basement but I don't suggest this as most systems wouldn't handle this amount of extra pressure drop in the system.

I have a variable speed system that speeds up to compensate for the increase in system pressure when I close the return air grille in my basement so this works very well in my home during the cooling season. I run the fan constantly and use an Ecobee thermostat that has 4 temperature sensors located throughout my home. I have programmed the system to run during the daytime from the temperature sensor located on the middle level of my home and at nightime from the temperature sensor located on the top level where the bedrooms are located. If I don't do this during the summer there is a huge difference in space temperatures between the lower and upper levels.

A couple other notes. I've only done this in homes with finished basements. In a home with an unfinished basement below grade sometimes it's better to return more air from the basement during the summer because the concrete floor and walls, if uninsulated, can act like an A/C system due to the temperature of the concrete floors and walls usually being quite cool compared to the air temperature in the basement. It's a form of free cooling. I used to remove the furnace door in the summer in a townhome I lived in that had an unfinished basement. It was unbelievable how well this worked during hot periods.

In case anyone is confused with what supply and return air ducting is here is a couple of examples of residential applications:

Standard supply air register:



Standard return air grille:




System examples:

[Big Grey Wolf]

Flydude, well presented guide on HVAC systems, you sound like a NAIT Instuctor, should help many understand their heating/cooling systems.

[Spidey]

We installed central air last summer and it's already paid for itself when we have to keep all the windows closed due to smoke in the air. Central air doesn't let any air in from the outside and is essentially, a heat exchanger. The heat from inside your home is absorbed and transported through the refrigerant line, then deposited outdoors.

Central air is actually a recommended strategy to keep the air in the home cleaner during periods of wildfire smoke. The level of furnace filter also comes into play, but you have to balance the MERV level with air flow so the coils don't freeze up due to restricted flow.

[tallieho]

I had a ac 2 ton unit installed,with new furnace & water heater.It's going to take me a bit to get used to the fan.Operating all the time.Set the ac at 19,heat at 22 .we'll see how that works.All new to this old fart...Programmable thermostat also. Any hints ,much thanks..

[jef612]

Originally Posted by tallieho

I had a ac 2 ton unit installed,with new furnace & water heater.It's going to take me a bit to get used to the fan.Operating all the time.Set the ac at 19,heat at 22 .we'll see how that works.All new to this old fart...Programmable thermostat also. Any hints ,much thanks..

Heat at 19 - A/C at 22. Hopefully that was just a typo.
Fan running all the time is good idea, especially with a new unit and a DC fan motor.
Enjoy the comfort!

[flydude]

Originally Posted by tallieho

I had a ac 2 ton unit installed,with new furnace & water heater.It's going to take me a bit to get used to the fan.Operating all the time.Set the ac at 19,heat at 22 .we'll see how that works.All new to this old fart...Programmable thermostat also. Any hints ,much thanks..

Is it possible you have the fan in manual ON? You should have an AUTO setting for the fan, use that if you don't want the fan running all the time. Also jef612 is correct, I think you may have stated the heat and cool settings backwards. The thermostat shouldn't allow a setting like that. When the room temperature is below 19 the system will HEAT up to the lower setting (19) and when the room temperature is above 22 the system will COOL down to the upper setting (22). In your case nothing should be running when the room temperature is between 19 and 22. Keep in mind there are some minimum equipment run times built in to thermostats so your system may not necessarily shut off at the exact temperature settings you set.

[tallieho]

Originally Posted by tallieho

I had a ac 2 ton unit installed,with new furnace & water heater.It's going to take me a bit to get used to the fan.Operating all the time.Set the ac at 19,heat at 22 .we'll see how that works.All new to this old fart...Programmable thermostat also. Any hints ,much thanks..

Good eye guys..Typo thanks