heat an air operation

[dmccarty]

....

Short cycling hurts todays equipment more than helps.
...

Please define short cycling.

During the afternoon our AC can turn on for 15-20 minutes, turn off for 5-10 minutes and then turn back on so the cycle repeats. This happens on VERY hot days at the end of the day. We can get quite a bit of solar heat gain from the west side of the house and of course it is just HOT outside so the AC is needed.

Later,
Dan

 

[Sigarms]

Please define short cycling.

An example would be...

During the afternoon our AC can turn on for 15-20 minutes, turn off for 5-10 minutes and then turn back on so the cycle repeats. This happens on VERY hot days at the end of the day.

Interesting per the only time it happens.

 

[dmccarty]

An example would be...

...

Interesting per the only time it happens.

That was NOT the answer I wanted.

The solar heat gain on the west side of the house drives up the temperature in the house on hot days. One of the mistakes I made was to put the thermostat in the living room. It is right above the TV set. So the TV helps heat up the thermostat. Most of the time is does not really matter. But in the afternoon with the heat gain from the west and the TV running the AC will run for 20ish minutes and turn off. It does not take long for the temp to go back up to turning the AC back on again.

It only happens in the afternoon on hots days. I don't think the AC has been on since at least 9:00-10:00pm last night.

Later,
Dan

 

[Sigarms]

Dan, for what it's worth, I stayed awake in bed actually thinking about your situation and why it happens

 

[heehaw]

i have seen several thermostats recently that have a remote sensor: the actual thermostat can be mounted anywhere you want it: then the remote unit is portable an you can put it where you actually would like the thermostat to be: Sams club had them for about $50 about a year ago: years ago, knew some folks that would go outside and water down the west side of their house at dusk: if they didn't do that, the house would heat up from the heat gain of the brick an the ac would run constantly:
heehaw

 

[heehaw]

if it were me: i'd rather have 3 separate units than put in a 5ton to take the place of two: less complicated duct work, an almost everyone i have talked to recommends not going with a zoned system: they say they have way more trouble with them than its worth.
heehaw

 

[tulenutn2o]

I would go with separate units. Almost all 2 story homes in this area get the 2 unit treatment. I would definately do a load calculation and size the a/c's accordingly. 5ton is a big unit. I cool 2100ft ranch with 3ton and no shade. I would definately get with your HVAC guy and have him give you several options.

 

[heehaw]

they are having a separate unit for the upstairs: but the ground level is about double what it was: an the existing very old resistance heat system is a 3 ton: hence the talk of a 5 ton..but as i mentioned i would rather put in two 2.5 ton units an have 3 units instead of a 5 ton...
heehaw

 

[BobRip]

they are having a separate unit for the upstairs: but the ground level is about double what it was: an the existing very old resistance heat system is a 3 ton: hence the talk of a 5 ton..but as i mentioned i would rather put in two 2.5 ton units an have 3 units instead of a 5 ton...
heehaw

Can you insulate better and keep the size of the unit down?

 

[heehaw]

i think 5 tons is way overkill: but they are going by the heat/air folks recommendation:
heehaw

 

[eepete]

If you go with the 5 ton unit, I think you must be sure it has a two speed compressor on it. The vast majority of the time it will be running at the lower speed. This will also help with humidity control when cooling.

It's hard to know who to listen to and believe when dealing with all the trades. With this size unit, putting your foot down and requiring a two speed compressor helps to hedge your bet.

Pete

 

[BobRip]

If you go with the 5 ton unit, I think you must be sure it has a two speed compressor on it. The vast majority of the time it will be running at the lower speed. This will also help with humidity control when cooling.

It's hard to know who to listen to and believe when dealing with all the trades. With this size unit, putting your foot down and requiring a two speed compressor helps to hedge your bet.

Pete

I have a two speed compressor with variable speed fan in my house. It rarely goes to high speed during cooling except when I change to a lower temperature. The two speed aids in de-humidification. My cooling cost for a hot summer month run about $20. The house is ICF and well insulated.
Without two speeds, the humidity would be very high except on really hot days.

 

[Sigarms]

Without two speeds, the humidity would be very high except on really hot days.

Although a two stage compressor helps with dehumidification, just as important (if not more) is having a variable speed air handler which can reduce the airflow across your coil.

I'm a big proponent of variable speed, but any major brand HVAC manufacturer will tell you that you sell 2 stage equipment on comfort, NOT on return on investment.

That said, if dehumidifcation is what really is important to you, a 13 SEER variable speed system with a whole house dehumidifier will remove more moisture than an 18 SEER 2 stage system (less overall cost as well, but in the humid months, the dehumidifier pulling 14 amps will not save you more on your energy bill compared to the 16 or 18 SEER system). But then the question is, what would a 16 or 18 SEER system cost compared to the 13 SEER system with dehumidifier? Usually MUCH more.

 

[BobRip]

Although a two stage compressor helps with dehumidification, just as important (if not more) is having a variable speed air handler which can reduce the airflow across your coil.
.

You're right. My system has a variable speed air handler as well. It stays in low speed most of the time. My house is so well insulated that without the advanced system it would have terrible humidity control.