Cycling times are these to short???
I timed my run and off times yesterday. I'm really concerned about the ones in the evening time. The contractor is telling me that everything is fine. I just don't see how a 2 minue run time is ok. I have a energy efficent I believe 2 stage compressor if that sounds right. It's a AS alegiance 14 The model #'s on the installers guide are 4a7a2018-060b1000aa. That is what is says under condensing units. The humidity inside is around 55-57%. Could this system be oversized? It's a 4 ton system on a 2500 sq ft house. What can be done to correct it without having to put a whole new system in? Thanks for any help.
11:06 Start – Went from 78 down 76 degrees 89 Degrees Outside
11:28 Stopped – 22 min run time
11:38 Start – 10 min off time
11:51 Stopped – 13 min run time
11:58 Start – 7 min off time
12:13 Stopped – 15 min on time
12:21 Start – 8 min off time
12:33 Stopped - 12 min on time
12:41 Start – 8 min off time
4:23 Stopped 91 Degrees Outside
4:32 Start – 9 min off time
4:41 Stopped – 9 min run time
4:47 Start – 6 min off time
4:55 Stopped – 8 min run time
8:15 Stopped 80 Degrees Outside
8:27 Start – 12 min off time
8:33 Stopped – 6 min run time
8:47 Start – 14 min off time
8:53 Stopped – 6 min run time
9:06 Start – 13 min off time
9:10 Stopped – 4 min on time
9:21 Start – 11 min off time
9:23 Stopped – 2 min run time
9:29 Start – 6 min off time
9:31 Stopped – 2 min run time
It would be very helpful to identify what city you are in or near. From that people can look up the "design temperature" for Manual J, which is intended to be hot but not the hottest you can reach. For example for Houston we have an outdoor design temperature of 94F, while it occasionallly can reach 100F we are not advised to design for that. I am a homeowner who has used Hvac-Calc software from this site to do Manual J a couple of times, I recommend it.
According to the principles of Manual J as I understand it, one sizing goal is to have long runtimes for humidity removal. If you size for the design temperature, it is said you should expect continuous running. I interpret that as 1-2 hour stretches with no shutoff, by that yardstick you are definitely oversized... if your test day resembles the design day. My 2 systems run such longer times.
I have A-S/Trane equipment too. Their "COMFORT-R" program cannot even complete its cycle with your short run times. I cannot tell you how to fix it, the pros go through some heavy duty training to get things right and to do no harm. But I definitely would advise him about slowing your fan speed to bias your cooling toward more latent (humidity) and less sensible capacity -- if I see things right you have a surplus of capacity and are short cycling. As a sporting bet just for entertainment, I wager your house could cool with only 3 tons capacity on days like you tested.
In cooler parts of the day, i.e. every evening, you will always be oversized. You would expect shorter runtimes but not as short as yours. Ask your pro if something cannot be done to at least get runtimes over 10 minutes.
Best of luck -- Pstu
I live close to Little Rock arkansas and it's noramlly really hot and humid here in the summer. We have not reached those days yet. It's been really windy here making it feel cooler then the 89-92 degree weather that we have been having. Is there a Thermostat that would give me a 2 degree offset? The one that I have right now is only set for 1 degree. I spoke to a AS distributor yesterday and he said there is a lot that goes into deciding what ton system to put in. He said that they might have designed it for the hotter summer days being in the mid to upper 90's. The contractor that installed it said that there is nothing wrong with the system and that i'm just worrying to much. They did a load on this house and he said that it was border line needing a 5 ton system. I don't see how that is possible unless they designed it for the hotter days. He said that I should just give it a little time because he said that I would be calling him back in mid july asking why the system is running for 45 minutes to 1 hour before it shuts off. If that is the case then do you guys feel everything seems normal? This is just a new system to me. Thanks for the help
Its suppose to run continuous when its at design temp outside.
Little Rocks design temp is 96*F. So when its 96 outside, it would be normal for it to run continuous during the day to maintain thermostat set point temp.
There is a chance you are over sized.
But first, where is your ductwork located. If its in an unconditioned area. Check for return air leaks, they can give you high humidity.
Although a little late now. Ask to see this load calc. if he can't show it to you. Good chance it wasn't done.
If you have a VS blower, comfort r can be enabled to help, but it may not be enough.
Also, the Allegience 14 is not 2 stage.
What interior temperature are you trying to maintain?
beenthere I have a couple of questions for you if you don't mind. Where would I check for return air leaks at? At the returns inside the house? One other thing how would I know if I had a VS Blower comfort R? MY ductwork is up in the attic. What can I do if it is oversized? On my test that I ran it was set at 76 I would be happy with temp between 76-78. We kept our old house at 78 and had to turn it down every now and then. So I would say somewhere in between there. Do you think this system is meant to keep the house colder then what I want it to achieve? Thanks
If you post the model number of the indoor unit, we can tell. Or if you want you can call your installer and ask him.
If Comfort r is enabled, the blower will slowly ramp up.
I think there is a good chance its over sized.
Turn your stat down 2 or 3 degrees lower then you normally would, and see if it gets the humidity out better.
Not a lot you can do about an over sized system. Except install a proper sized one.
The other possibility to replacing it, is to have a whole house dehumidifier installed.
Yesterday when I turned it down from 78 to 76 it took the humidity from 67% down to 55%. So it does take the humidity out when I lowered it 2 degrees. I was amazed on how it dropped it 12% in like 25 minutes. He said the system was fine because it was taking the humidity out of the air when I lowered it down and that the thermostat was getting satisfied. If the system has a one year builders warranty would that be covered if it was oversized? He said that it wasn't and they have done this exact house many times which I know that they really have done it, due to my builder, building this exact floorplan. I just want the system to work properly. If I had a whole house dehumidifier installed would that increase the run times? One last thing could they slow the fan speed down, would that help at all? Thanks again for all your help
Leave it set for 76* and see if it keeps the humidity 55% or less. If it soesn't, your at risk for mold.
Weather your builders 1 year will cover a unit swap out or not, I can't tell you that. You have to bring that to your builder to know.
Same with slowing the blower, they should be able to, but will it be enough?
I suggest you start keeping a log.
You can bring concerns about mold to the builders attention. That WILL give him motivation to have the HVAC contractor come out and recheck things.
that`s 5 ton unit
Originally Posted by rickytz7111
Generally speaking around here that would be too big for 2500sqtf home
Sorry - yesterday was the deadline for all complaints.
Thanks for all the info guys. So, according to the #'s I gave you it's a 5 ton unit? I was told it was a 4 ton unit. Thanks for the help. I started to keep run and off time logs. So you recommend me keeping a humidity log as well? Thanks. Do you feel that 78 would be to high to keep it set at? The one morning when I woke up like I said it was 67% humidity in here. Anything 55% and below is good I take it? It is 58% right now. If they end up changing the unit will it be the whole unit or are there just cretain items they can replace to bring it down to a 4 ton system? Thanks for all your help
Good chance, that they can just change the outdoor unit.
And yes, keep a log of the humidity too.
praha 99 do you mind if I ask where you found out it was a 5 ton system? I just tried to google it and I couldn't find anything on it. That is what the manual said on it. I will go outside tomorrow and look for #'s on the unit. I take it it should have a plate of some sort. Thanks Again guys for the help.