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How low can indoor temp go
Residential Customer with 3 ton 13 seer split a/c system unit is properly charged and proper cfm
2 story home never is comfortable upstairs so runs thermostat at 65 degrees all the time unit occasionally
Freezes up how can this problem be fixed are air conditioners designed to cool this low ?
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Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.
Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
Sounds like they have humidity issues, and or their second fl is warmer than the 1st fl?
I bet it's freezing at night/morning
Is this a new system? New ducts? Is this a changeout? Did their "needs change", in other words.....when "were' they comfortable? Under what conditions were they comfortable before you entered their lives? You need to know those answers or you'll be an unhappy camper. You need to determine whether you're at fault or not
Increasing blower speed will help some if you're looking for more sensible and less latent.
Gary
Wilson Services, Inc
Northampton, MA
www.wilsonph.com
[email protected]
I keep my house at 70F, often 68F at night.
75F is too damn warm IMO.
At the same time, 65F seems a bit cold even for me. I guess my theory holds true, no matter how extreme you think you are at anything (good, bad, cold, hot etc), there's always someone out there that will go further.
Wilson Services, Inc
Northampton, MA
www.wilsonph.com
[email protected]
Just had a change out that is 6 months old, cooling not good. Air bear filter plugged. Usually get nearly a year out of those. But not the first year because of disrupting old dirt in RA panning.
Cool froze up in this case, young couple want 72 degrees.
I just added 15" insulation on top of my rafters and I put foil faced polyisocyanurate over all flooring and it is 1:15pm at 85 outside and my ac still is not required.
The house is part of the system.
ramermechanical.com
To learn more about this professional, click here to visit their ad in Find A Contractor.
For new T-stats I use the HW, even the 5000 series has programing for max and mini temp. The lowest cooling temp I program in might be 70 or 72. This gives the system some cycle off time and also try to set up the blower for long post cycle run on time. Or try to convince HO to let fan run continuously for AC season.
Some people see a digital number and it will control their desires. The upper end T-stats have a thermometer display that can be programmed to show an offset up to 5 degrees. ie. it could actually be 74 in the house but the T-stat tells them it is 69. Then they feel better and in control, the butter won't melt either.
I set all my stats up with 68 cooling/80 heating limits. Only had one complaint so far, & they were trying to get away without dehumidification in an exercise joint. @#%& injuhneers. The manager wanted to set the temp down to 66 to dry the place out. I don't think it works like that...
If your not getting 20° delta-T and its freezing up on you, with a clean air filter and coil, then I would say your under charged.
To be accurate about checking the delta-T, the temperature should be taken right at the equipment, in the return and supply plenum's.
If the humidity is high (around 80%) and it's 85°F in the return, you might see a 18-15 degree difference at first. As the humidity drops, so will the delta-T.
If you have a lot of return ducts work in the attic thats open or full of holes, you could be conditioning 120° air. That's why it's important to check temperature at the equipment, not in the space. Also if the return is full of holes, fix it.
Central air conditioning can't drop the indoor temperature more the 20° from the outdoor temperature. So if it's 90° outside and the thermostat is set to 68°, the system will never shuts off.
I can't say I've gotten a house down to 60° on a 80° day, but I've seen 64°.
More often I see inadequate return so that you can't get enough CFM no matter how hard you blow.
It took me all of 2 seconds to figure out what he was talking about.
I think it's because as you drop the pressure, there's less "stuff" for the blades to push.
When you restrict a vacuum cleaner, it's current draw drops big time. I assume a blower on a HVAC system is similar.
Curious, do normal air conditioners slowly drop power consumption as the evaporator drops temperature or does it remain fairly constant assuming the ambient conditions don't change?
We use 10x on all jobs. We don't do many but some 2 to 4 ton jobs here and there.
I don't get why people use 8x all the time. A round duct is best, a square duct is second best, a pancake is dog poo.
Basic rule of thumb don't exceed 50% of your duct height, but less is better.
10x is just a few bucks more.........
Gary
Wilson Services, Inc
Northampton, MA
www.wilsonph.com
[email protected]
I find 8x duct to be readily available, with more fittings on the shelf. 10x duct and fittings are less popular, so I can't always find what I need in the event my original master plan needs to change.
12x10, 16x8, 6x22, or 12" round, it's all the same when talking 100' of straight duct.
As the installer, you have to decide what makes the most sense to fit the home.
Round pipe is better for resistance around bends. But if I can save space with square duct, I'm sizing everything anyway, might as well make it look nice and tuck it in spots that can have a soffit easily built to hide it.
You need to do a new load calc and make sure the unit is sized right.
You need the total sq ft of the home and the sq ft of each room.
From the correct size of the unit figure 400cfm per ton and come up with the total cfm.
Then for each room
AREA OF ROOM DIVIDED BY THE TOTAL AREA X TOTAL CFM =
CFM FOR THIS ROOM
So for example if you had this unit as the right size and a 2000 sq ft house with a 12x14 master bedroom the numbers would look like this.
168 / 2000 x 1200 = 100.8
Then check your actual cfm for each room and see what you're really getting.
The other problem you're probably also having if the unit is in the basement is temp drop, see what your supply temp is on the 2nd floor compared to the first, my guess is you're losing big time, you might have 55 on the first and 67 on the second, you need a 20 degree drop.
good luck
phasers on stun
Wilson Services, Inc
Northampton, MA
www.wilsonph.com
[email protected]
I said " You need to do a new load calc and make sure the unit is sized right."
THEN
You need the total sq ft of the home and the sq ft of each room.
THEN
From the correct size of the unit figure 400cfm per ton and come up with the total cfm.
Then for each room............
it's quick and pretty accurate for splitting the cfm, some load programs will do each room for you some just do the whole house
but with this, 2 story, 3 tons?.........could be under sized, I have a raised ranch so my lower level is half in, no real cooling load, I'm doing just the upstairs with 3 tons and I'm tight, a home that isn't well insulated could be 4-5 tons or more, you really have to do that first or you're just chasing ghosts
Too much temp loss on the way, not to mention velocity. Many times it will work ok for heat but not cooling.