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I have a 5 ton Rheem and while it runs almost non stop to keep up, it does hold the temp at what I set it at (usually around 73). Nighttime it goes down to 68-69. The system is a horse and I might cry if it ever stops working in the middle of a heatwave.
How many square feet is your house? I have a 2400 square foot colonial so not a small house by any means. I think my CAC guy said we were "pushing it" for 5 tons when he installed without going for a 2 zone system which I didn't want.
You bring up an excellent point. Nowadays builders frequently install 2 units (one in attic and one in basement) on a colonial of that size. Even many retrofits have gone to this 2-system model. For some folks, 2 zones is an advantage. We have 2 AC units (attic and basement) and have had no issues this summer (of course the systems do run longer on the very hot days).
One suspects the 20-degree theory is one invented to explain the difficulty some systems have in keeping up with the very heavy load on very hot days.
The house is insulated well - at least R30 in the attic, good windows throughout and new exterior doors. We only use approx. 800 gallons of oil all year to heat and provide hot water for our 2600 sq ft (4 bedrooms) home, so I don't think insulation is a problem.
The ducts have not been cleaned but I do not consider that an issue, and they are not used for heat (baseboard recirculating hot water, not forced air).
I keep the bedroom doors open when cooling, but I tend to agree that when the heat index is over 100 degrees, the interior temp will only be 20 degrees less. The system is a 5 ton unit and I was told that is the largest residential system available. As the service visit is under contract (no cost), I will have the technician here tomorrow to check the system.
Some folks in houses of that size have two units. You may be slightly underpowered for the very few very hot days here on Long Island.
Thanks for the info everyone. I guess my unit is ok for now but will look for r410a in the future. I would still love it to be as cold as a grocery store frozen food aisle though.
Actually you dont. You wont get the dehumidification if you over sized the unit that big.
And just like that eveyones ac is working good again.
Quote:
Originally Posted by trusso11783
Thanks for the info everyone. I guess my unit is ok for now but will look for r410a in the future. I would still love it to be as cold as a grocery store frozen food aisle though.
Actually you dont. You wont get the dehumidification if you over sized the unit that big.
And just like that eveyones ac is working good again.
Lol so true my house cooled down much quicker today.
Yep oversizing can limit your dehumidification ability and increase wear and tear among other things, really oversized units can lead up to frozen coils because not enough warm air gets to the coils due to the short cooling cycles:
Technician was here today. Inspected the air handler in the attic as well as the compressor outside. Said the pressure in the compressor was perfect and the air handler was not frozen or dirty.
He also said that on extremely hot days, a 20 degree difference between outdoors and indoors is what to expect.
His suggestion was to change the filter once a month, set the thermostat lower and earlier on days where it is expected to be extremely hot, on extremely hot days spray the compressor with the garden hose, and to install shades on the skylights in our great room.
I am satisfied with his response.
BTW - no problems with maintaining the settings today as the temperature was not as extreme as last week.
This is another case where the mini-splits have been working great for us. We have control over individual rooms so don't need to cool a room unless we are using it. In the bedrooms I have one occupant who wants it cold and the occupant of the other room wants it warm, and we can accommodate the different preferences. I used to have CAC and closing the vents was never as effective. All without the bother and noise of window units, and on pleasant days we can actually use the window.
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