Very Short Run Times this morning

[rickytz7111]

Ok i'm back I had to go do some work. To answer some questions I live in Little Rock Arkansas. I have a family 400 American Standard stat with a allegiance AS 14 outside unit with comfort R 4 ton. The ac is single stage. Comfort R is seleced. The CFM is 350 I believe. They have it set to the lowest blower setting. My house is 1 story 2500 sq ft on a slab facing south. The RH in the house this morning was 52% and outside was 78%. The house stays very dehumidified. Do I have any other solutions other then to try and get a smaller unit??

[beenthere]

Unless your stat is defective, no.

[rickytz7111]

Is it possible for the stat to be deffective???

[beenthere]

Sure.
I'm not saying it is.
But its made in a factory that mass produces thermostats.

there will be defects from time to time.

[paul42]

Would a Honeywell IAQ thermostat have any settings that might help the OP?

Get a decent thermometer and verify the temperature readings of your thermostat. I have one that is just a few months old and the thermostat temperature readings are nowhere near accurate.

[beenthere]

The IAQ does CPH. And does have a setting for more aggressive cooling, which allows it to overshoot set point.

If he were to have it installed with it set to aggressive cooling, and also enable cool to dehumidify, it might get him longer run times.

But, From my side of the screen, I can't say it will for sure.

There is only so much you can do with some systems.

[mchild]

The IAQ does CPH. And does have a setting for more aggressive cooling, which allows it to overshoot set point.

If he were to have it installed with it set to aggressive cooling, and also enable cool to dehumidify, it might get him longer run times.

But, From my side of the screen, I can't say it will for sure.

There is only so much you can do with some systems.

Don't forget it will start his coffee in the morning too!

[rickytz7111]

Thanks for the info. I just read through the manual and didn't really see anything except for it cooling 3 degrees below the set point if the humidity is to high.

[BigJon3475]

Is the t-stat completely isolated from the wall cavity or is it mounted on a wall right next to a duct or the air handler,coil? Just thinking out loud.....no supplies blowing on it and what height did you say the stat was at?

[rickytz7111]

The stat is mounted next to one of the return ducts. No supply air is hitting it. The hole for the wires have been sealed. As far as height I would say 4-5 feet I think with out measuring

[Shophound]

Short of replacing the thermostat, you might try having it relocated. If that does not help, I would replace the thermostat and have the new one programmed for 3 CPH (typically default) in cooling, and then watch it from there.

As for your house staying dehumidified, you must be experiencing longer run times during the heat of the day, or your house is very tight and you don't generate much interior moisture (cooking, laundry, etc.). I think you mentioned you are seeing longer run times once the outdoor temperatures go up.

What Beenthere mentioned for the Honeywell IAQ is true for the other VisionPro thermostats as well, if you feel no need to purchase the IAQ package.

[rickytz7111]

Thanks Guys for all the info. I just got off the phone with one of the installers that I perfer to talk to. He said that I might have a 5 ton coil upstairs in the attic with the furnace would this make a diffrence? I don't know what that means but he said they do that for efficency. Could that be part of my problem?

[beenthere]

That would make a small difference in your run time. Not cause the times your posting.

[House]

Edit: Ignore the droop, I see you've tried it already. Seems like it had the opposite affect of what I expected.

Try changing the cooling droop(nice name!) in the stat to two degrees.

There any supply ducts in the wall cavity behind the stat?

[paul42]

2,500 sq. ft. with 8 foot ceilings is 20,000 cu. ft. of air

20,000 cu. ft. of air * .02 btu/deg * 2 degrees is 800 btu.

48,000btu/hr *1hr/60 min * .8 (sensible capacity) = 640 btu/min of sensible cooling capacity.

A two minute run time is barely enough to cool the air in the house, and won't have made a dent in changing the temperature of the house itself.

It sure sounds like there is something wrong with the thermostat to me.

[beenthere]

Very well could be.
i'd would also, recommend, using a piece of tissuue, and tapeing it above the thermostat, so its 1/2" above, and see it there are any slight breezes above it.
If so, you know whaere some of your trouble is. If not, have the stat changed.

[rickytz7111]

Thanks Guys they are coming to change the stat on monday. Thanks for the info on the 5 ton coil. That makes me feel better that has nothing to do with it. I spoke with one of the installers and they had set up this house for a 100 degree day at 74 degree stat setting. He said that since they have no idea who is going to buy the house they go with that setting. He also said if he would have know that we are use to keeping our stat at 78 that they would have gone with a 3.5 ton system instead of a 4 ton. He then said if someone would have bought this house wanting to keep it a 70 degrees they would never achieve that setting. I'm trying to lower my stat level down to 74 and see if I will get some longer run times once it reaches that temp. I had it set at 78 degrees and it has been running for almost an hour now trying to get the temp down to 74 degrees. I PRAY that the stat will fix our problem. Thanks again for all the help

[beenthere]

Most areas where they design for a 26° temp diff, the average temp is in the high 90s.
A/C sustems are to be designed to keep the home owner thats paying for it comfortable, not the next owner.(within reason)

Let us know how it works.

[rojacman]

ricky your'e getting good advice , i'd just like to add one thing. i suggest you get a data logger from Supco & put it on topof your stat for 24 hrs , then plug it in to your computer and print out your temp & humid. right at the stat. What a valuable tool this for those jobs with ambiguous complaints. The logger is inexpensive and comes with software , cord and the logger & u can set it for any interval of sampling for days and just do a printout and see where your'e at. Imho i'm also thinking oversize. regards..........Jack

[iraqveteran]

Ricky......

sounds like it could possibly be a couple different problems from oversized system, defective stat, breeze at stat location, stat being heated up by other means, air leaks......etc.


You questioned the load calc earlier in another thread. And it has been suggested that the installers have re-arranged some figures to put them in the clear.....



My opinion and advice would be to seek a professional opinion and diagnosis from another reputable contractor in your area. You will more than likely have to pay for their time but you may get the much valuable information you need.
If you've already had issues with this system and installer, I would also recommend you purchase the extended warranty for 10 yr parts and labor from the contrator. That is assuming that your going to keep your current system and contractor. I hate to see you get past your current labor warranty and start getting hammered with high repair bills.

We have offered as much help as we can without looking at the system. You are going to have to either trust your contractor or find another one to come give you a second opinion or other options.